OSTEOLOGY OF THE HEAD AND NECK THE SKULL

OSTEOLOGY OF THE HEAD AND NECK

THE SKULL

NORMA VERTICALIS:

• The skull is oval in shape broadened posteriorly by the parietal eminences.
• In children the prominent frontal eminences together with the parietal give the skull a square shape.

Visible bones:

1-The frontal bone anteriorly

2-The occipital bone posteriorly

3-The two parietals in between

4-The upper part of squamous temporal laterally

5-The zygomatic arch (zygomatic process of the temporal & temporal process of the zygomatic bones).

Visible sutures:

1-The coronal suture:

- Across the skull

- Between the frontal & parietal bones

2-The sagittal suture:

- Between the two parietals in the midline plane

- It meets the coronal suture anteriorly & the lambdoid posteriorly

3-The lambdoid suture:

- Very coarse, tortuous, inverted-V like suture whose apex meets the posterior end of the sagittal suture

• Its diverging two limbs descend in the direction of the mastoid process to meet the occipito-temporal suture
• Separates the occipital from the parietal bones
• Frequently contains sutural bones.

4-Metopic suture:

• Is a vertical suture that separates the frontal bone into two bones
• Usually obliterated but may persist in 8% of adults

Stigmata:

1-The superciliary ridges:

- form the anterior limit of this view.

2-The lambda "posterior fontanelle":

• The meeting point between the sagittal & lambdoid sutures
• It is a triangular opening in neonates & closes in the very early few months of life

3-The bregma "anterior fontanelle":

• Is the meeting point between the sagittal & coronal sutures
• It is a star-shape opening in neonates whose closure is delayed to 1.5 years of life

4-The parietal foramina:

• Two small foramina, one in each parietal bone near the sagittal suture
• They transmit parietal emissary veins
• They are nearer to the posterior pole

NORMA FRONTALIS:

Visible bones:

1-The frontal bone.

2-The bones of the nose:

• Nasal bones
• Vomer
• Ethmoid
• Inferior turbinates

3-The bones of the orbit:

• Lacrimal
• Sphenoid
• Ethmoid
• Other facial bones

4-The maxillae.

5-The zygomatic bones.

6-The mandible.

Visible sutures:

1- The fronto-nasal suture, between the nasal bones & the nasal process of the frontal bone.

2- The internasal suture, between the two nasal bones.

3- The fronto-zygomatic suture: between the zygomatic process of the frontal bone & the frontal process of the zygomatic bone lateral to the orbit.

4- The zygomatico-maxillary suture: oblique suture between the zygomatic bone laterally & maxilla medially.

5- Inconstant sutures: sometimes seen as the metopic & the intermaxillary sutures.

Stigmata:

1-Superciliary arches: are two blunt elevations in the frontal bone overlying the medial ends of both orbits

2-The glabella; is the depression between the two superciliary arches

3-The supra-orbital foramina: are located at the junction of the medial & middle thirds of each superior orbital margin & transmit the vessels & nerves of its own name.

4-The nasion: is the cross point between the fronto-nasal & internasal sutures

5-The orbit: will be discussed later

6-The anterior nasal aperture: an oval opening narrower above than below from which the cavity of the bony nose is seen

7-The anterior nasal spine: is a sharp spine in the inferior border of the anterior nasal aperture in the midline

8-The canine eminence: is an elevation surrounding the root of the canine tooth

9-The incisive fossa: a light depression in the maxilla medial to the canine eminence

10-The canine fossa: a more deep depression lateral to the eminence

11-The infra-orbital foramina: well defined rounded foramina in the maxillae just below the inferior orbital margin, they transmit the nerves & vessels carrying its own name

12-The symphysis menti: is a midline ridge in the body of the mandible

13-The mental protuberance: enlarged triangular lower end of the symphysis

14-Mental foramina: small foramina in the mandible, one below each second lower premolar tooth & transmit the mental vessels & nerves

NORMA OCCIPITALIS:

Visible bones:

1-The occipital bone

2-The parietal bones

3-The temporal bones

Visible sutures:

1-Sagittal suture

2-Lambdoidal suture

3-Occipito-temporal (occipito-mastoid) suture

4-Parieto-mastoid suture.

Stigmata:

1-The lambda.

2-The mastoid foramen: adjacent to the occipito-mastoid suture, transmits the mastoid emissary vein

3-The external occipital protuberance (EOP): a marked rounded process in the occipital bone in the midline easily felt through the skin

4-The external occipital crest: a well-defined midline ridge extending between the EOP & the foramen magnum

5-The highest nuchal line: faint line starts from the EOP & extends laterally in an upward curve in the direction of the mastoid process

6-The superior nuchal line: just below the highest one & more marked than it

7-The inferior nuchal line: between the superior one & foramen magnum, it is also a well defined line.

NORMA LATERALIS:

Visible bones:

1-The frontal bone.

2-The parietal bone.

3-The occipital bone.

4-The temporal bone.

5-The sphenoid.

6-The zygomatic bone.

7-The nasal bone.

8-The maxilla.

9-The lacrimal bone.

10-The mandible.

Visible sutures:

1- The coronal suture.

2-Temporo-parietal (squamosal) suture.

3- The occipito-mastoid suture.

4- Temporo-zygomatic suture.

5- Zygomatico-maxillary suture.

6- The fronto-nasal suture.

7- The spheno-frontal suture.

8- The spheno-parietal suture.

9- Spheno-squamosal suture.

Stigmata:

1-The temporal lines:

• Two lines (superior & inferior)
• Start at the root of the zygomatic process of the frontal bone & diverge as they go posteriorly curving upward, then inferiorly & then anteriorly completing the circle by joining the posterior root of the zygomatic arch.

2-The infratemporal crest:

• The rough lower free edge of the greater wing of the sphenoid bone
• Usually hidden by the zygomatic arch
• It separates the temporal fossa above from the infratemporal fossa below

3-The pterygo-maxillary fissure:

• A vertical slit exists between the posterior border of the maxilla & the anterior border of the pterygoid plate
• This fissure connects the infratemporal with the sphenopalatine fossae & transmits the posterior superior alveolar vessels & nerves

4-The temporal fossa: is the area bounded by the superior temporal line & infratemporal crest.

5-The zygomatic arch: formed by the zygomatic process of the temporal bone (posterior ¾) & the temporal process of the zygomatic bine (anterior ¼)

6-The pterion:

• Is the point where the coronal suture meets the spheno-parietal suture in the floor of the temporal fossa
• It represents the lateral fontanelle
• 7-The asterion: is the meeting point between the temporo-parietal & lambdoid sutures

8-The temporo-mandibular joint:

• Seen at the inferior aspect of the posterior root of the zygomatic arch
• Eminentia articularis lies in front of it.

9-The external acoustic meatus.

10-The suprameatal triangle:

• Lies postero-superior to the meatus
• Is an important surgical landmark in ear surgery

11-The mastoid process: is the downward projecting mamillary process of the temporal bone lies behind the external acoustic meatus

12-The styloid process:

• Sometimes seen projecting down deep to the external acoustic meatus
• Is a part of the temporal bone

NORMA BASALIS:

Visible bones:

1-The maxilla.

2-The horizontal plate of the palatine bone.

3-The pterygoid processes & greater wing of sphenoid.

4-The vomer.

5-The temporal bone.

6-The zygomatic bones.

7-The occipital bones.

8- Parietal bone (sometimes).

Visible sutures:

1-The intermaxillary suture.

2-The palato-maxillary sutures.

3-The zygomatico-maxillary suture

4-The temporo-zygomatic suture

5-The spheno-squamosal suture.

6-The squamo-tympanic suture.

7-The petro-squamous suture.

8-The petro-tympanic suture.

9-The occipito-mastoid suture.

Stigmata:

1-The alveolar process of the maxilla:

- The curved, teeth-carrying bone which bounds the skull anteriorly in this view

2-The hard palate:

• Lies in the concavity of the alveolar process
• Formed by the palatal processes of both maxillae (anterior 2/3) and the horizontal plates of the palatine bones (posterior 1/3)
• Represents the roof of the mouth & floor of the nasal cavity

3-The incisive fossa:

• Anterior depression in the midline of the hard palate in which lies the incisive foramen which connects the oral to the nasal cavities
• Transmits the long spheno-palatine vessels & nerves

4-The maxillary tuberosity:

• The non tooth-bearing part of the alveolar process behind the last molar tooth
• Gives attachment to the pterygomaxillary ligament

5-The posterior nasal spine:

• The midline spine projecting from the back of the hard palate
• Gives attachment to musculus uvulae

6-Posterior nasal apearture:

• The posterior opening of the nasal cavity
• The vomer divides it into two openings (the choanae)

7-The pharyngeal canal:

• Lies just above the junction between the vomer & pterygoid plates
• Transmits the pharyngeal branch of the spheno-palatine ganglion

8-The pharyngeal tubercle:

• A midline tubercle on the undersurface of the occipital bone anterior to foramen magnum
• From this tubercle shallow ridges pass laterally for the attachment of the pharyngo-basilar fascia

9-The pterygoid plates:

• Two downward projecting processes related to the sphenoid
• They bound the posterior nasal apearture on each side
• Each one diverge posteriorly into two plates:

a)The medial pterygoid plate;

• Long & narrow with a hook in its lower end called "pterygoid hamulus"
• High up, the base of this plate is hollowed laterally forming the "scaphoid fossa"
• The posterior border of this plate is sharp & shows a spur above which lies the cartilaginous part of auditory tube as it enters the nasopharynx

b)The lateral pterygoid plate;

• Broader than the medial
• This plate gives attachment to the pterygoid muscles on each side

*Pterygoid fossa; is the deep fossa between the two pterygoid plates & is almost filled by medial pterygoid muscle

10-The pterygoid canal:

Situated high up in the root of the pterygoid plate

It leads from the base of the skull to the pterygo-palatine fossa & transmits the nerve of pterygoid canal

11-The spine of sphenoid:

The greater wing of sphenoid extends laterally where it shows a sharp spine projecting inferiorly from its posterolateral aspect

Gives attachment to the sphenomandibular ligament

12-The foramen ovale:

• An oval foramen perforates the greater wing of sphenoid near the root of the lateral pterygoid plate
• It connects the infratemporal fossa with the middle cranial fossa
• Transmits; mandibular nerve, accessory meningeal artery, emissary vein between the cavernous sinus & pterygoid plexus and the lesser petrosal nerve

13-Foramen spinosum:

• A small, rounded foramen which perforates the spine of sphenoid
• Transmits the middle meningeal artery & the meningeal branch of mandibular nerve

14-The mandibular fossa:

• A depression in the squamous temporal in which the head of mandible rests to form the TM joint
• It is bounded posteriorly by the tympanic plate & anteriorly by the articular eminence which provides anterior stability for the joint

15-Foramen lacerum:

• The petrous part of temporal bone is wedged in 45O antero-medially between the temporal & sphenoid anteriorly and the occipital posteriorly
• The apex of the petrous bone ends short of the way to the occipital bone leaving a gap between its apex, the occipital bone & the root of pterygoid plate
• This irregular gap is called foramen lacerum which is closed from below during life but its upper part remains patent to transmit the ICA as it emerges from the medial end of the carotid canal

16-The carotid canal:

• A circular opening in the undersurface of the petrous bone through which the ICA enters the bone
• The carotid sheath is applied at its margins

17-The tympanic plate:

• V-shape plate which is applied to the undersurface of the temporal bone forming the external auditory canal
• Its lower free edge is sharp & gives attachment to the deep layer of parotid fascia
• The plate is pushed slightly ateriorly by the position of the styloid process
• At this curved part the parotid fascia is thickened from the styloid process down to the mandible forming the stylomandibular ligament

18-The styloid process:

• A hook-like process projects downward & anteriorly from behind the tympanic plate
• Its ossification is variable & consequently its length is variable too
• It gives attachment to three muscles & a ligament, the muscles are; stylopharyngeus, styloglossus & stylohyoid, the ligament is the stylohyoid ligament

19-The stylomastoid foramen:

• Lies behind the styloid process between it & the mastoid process
• It transmits the facial nerve & stylomastoid branch of the posterior auricular artery

20-The jugular foramen:

- Between a notch in the petrous bone & a notch of the occipital bone

- Transmits; IJV, inferior petrosal sinus, IX, X, & XI nerves.

21-The mastoid process: discussed.

22-The digastric notch: Deep to the mastoid process lies a deep elongated notch for the origin of the posterior belly of digastric muscle

23-The occipital condyles:

• A pair of oval articulating surfaces convex downward to fit the superior articular facets of C1
• They are applied in an anteromedial obliquity to the anterior ½ of foramen magnum.

24-Anterior condylar canal: perforates the root of the occipital condyle & transmits the hypoglossal nerve

25-Posterior condylar canal: smaller than (24) & transmits emissary veins

26-Foramen magnum:

• The largest foramen in the skull, lies in the occipital bone
• Transmits; medulla & its meninges, the anterior & posterior spinal arteries, spinal accessory nerve, vertebral arteries, articular structures.

27-The mandible: bounds the anterior ½ of the skull & shows the following landmarks:

a)The head:

• A rounded condaloid process
• Articulates with the temporal bone at the mandibular fossa

b)The neck: is the thin part of the bone which lies below the head

c)The coronoid process: is the upward projection which lies anterior to the head

d)The mandibular notch:

• Between the head & neck behind and the coronoid process in front
• Structures pass through this notch in their way to & from the infratemporal fossa

e)The ramus: is the part of the bone which lies vertical between the body below & the processes above

f)The mandibular foramen:

• Lies on the medial side of the ramus
• Bony spine protects its inlet called the lingula for the attachment of the sphenomandibular ligament
• Transmits the inferior alveolar vessels & nerves

g)The body: is the anteriorly curved horizontal part of the bone which carries the alveolar process & teeth.

h)The myelohyoid line:

• Long line on the inner aspect of the body reaches back near the mandibular foramen
• Gives attachment to myelohyoid.

i)The superior & inferior genial tubercles:

• Lie anteriorly on each side of the symphysis menti
• For the attachment of genioglossus & geniohyoid respectively

j)The digastric fossa:

• A light depression in the lower border of the mandible near the chin
• Gives attachment of the anterior bellies of digastric

THE CRANIUM:

The calvaria:

Is the inside of the vault of the skull, it shows some landmarks:

1-The groove for superior sagittal sinus:

This long depression grooves the sagittal suture from its inside & broadens as it goes backward ending on the internal occipital protuberance.

2-The lateral blood lakes:

On each side of the above sinus near the vertex lie a variable-size depression which marks the lateral blood lakes.

The anterior cranial fossa:

The floor:

• Formed by the orbital plate of the frontal bone (anterior 2/3) completed posteriorly by the lesser wing of sphenoid
• A gap in the midline between the two orbital plates is closed by the cribriform plate of the ethmoid bone & crista galli
• The floor of this fossa forms the roof of the orbit (laterally), the ethmoidal air cells (intermediate) & the nasal cavity (in the midline)

Boundaries:

• Anteriorly & laterally: the frontal bone
• Posteriorly: Body & the free edge of the lesser wing of sphenoid

Stigmata:

1-The frontal crest:

• A midline sharp ridge between the cribriform plate & the anterior wall of the fossa
• It gives attachment to the falx cerebri

2-The crista galli:

• The midline ridge which is centered on the cribriform plate
• It represents the upper part of the vertical plate of the ethmoid
• Gives attachment for the falx cerebri

3-The cribriform plate:

• Is the horizontal plate of the ethmoid which roofs the nasal cavity
• It is perforated by many foramina for the passage of the olfactory rootlets
• The ethmoidal foramina also lie in this plate laterally

4-The anterior clinoid process:

• As the posterior free border of this fossa curves medially, it will end in a sharp projection faces posteriorly called the ACP
• For the attachment of the tentorium cerebelli

The middle cranial fossa:

The floor:

• Formed anteriorly by the greater wing of sphenoid completed laterally by the squamous temporal & posteriorly by the petrous temporal
• The narrow midline part of the floor which connects the two fossae is formed by the body of sphenoid
• The floor of the fossa roofs the infratemporal fossa laterally & the sphenoidal air cells in the midline

Boundaries:

• Anteriorly: sphenoidal wings separated from each other by the superior orbital fissure
• Laterally: the greater wing of sphenoid & squamous temporal bones curves from the floor upward to form the lateral wall of the fossa
• Posteriorly the petrous bone closes it.

Stigmata:

1-The hypophyseal fossa:

• The midline deep notch in the sphenoid body to lodge the pituitary gland
• The fossa with its anterior wall (tuberculum sellae) & posterior wall (dorsum sellae) look like the Turkish saddle & therefore this complex is called the sella turcica

2-The middle clinoid processes: Two shallow projections anterior to the pituitary fossa & posterior to the optic sulcus

3-The dorsum sellae: is the back of the pituitary fossa.

4-The posterior clinoid processes: are the two projections that project from each side of the dorsum sellae.

5-The optic canal:

• A rounded foramen medial to the anterior clinoid process leads from the MCF to the orbit
• Transmits the optic nerve & the ophthalmic artery

6-The optic sulcus (groove): The shallow sulcus which connects the the two optic canals.

7-The foramen rotundum:

• A rounded foramen in the anterior wall of the fossa
• Transmits the maxillary nerve from the MCF to the spheno-palatine fossa

8-The superior orbital fissure:

• The elongated gap between the two wings of the sphenoid in the anterior wall of the fossa
• It leads to the orbit & transmits the III, IV, VI nerves & the ophthalmic division of V nerve with the superior orbital veins.

9-Foramina ovale, spinosum & lacerum: discussed.

10-The groove for the middle meningeal artery:

• A clear groove starts in the floor of the fossa from foramen spinosum
• Divides into anterior & posterior grooves according to the branches of the middle meningeal artery

11-The arcuate eminence:

• A laterally placed shallow eminence in the anterior wall of the petrous bone
• It is produced by the underlying superior semicircular canal of the internal ear

The posterior cranial fossa:

The floor:

- Formed mainly by the occipital bone completed laterally by the temporal bone.

Boundaries:

• Anteriorly: the occipital bone as it forms the dorsum sellae in the midline and petrous temporal bone lateral to it
• Laterally: the mastoid part of the temporal
• Posteriorly: the occipital bone

Stigmata:

1-Foramina magnum, jugular & hypoglossal: discussed.

2-The internal acoustic meatus:

• An oval foramen located in the anterior wall of the fossa
• Transmits the facial, vestibulo-cochlear nerves & nervus intermedius together with the labyrinthine artery

3-The vestibular aqueduct:

• Very small slit lies postero-lateral to the internal acoustic meatus
• Transmits the endolymphatic duct of the membranous labyrinth

4-Internal occipital protuberance: lies opposite to the external one on the inner aspect of the occipital bone.

5-Grooves for the transverse sinuses: From the internal occipital protuberance two grooves pass one to each side of the protuberance representing the transverse sinuses

6-Grooves for the sigmoid sinuses:

• Start at the root of the petrous bone laterally
• Groove the deep surface of the mastoid bone
• Descend down in an S-shape deep groove to end in the jugular foramen

7-The internal occipital crest:

• A blunt crest from the internal occipital protuberance to the foramen magnum in the midline
• For the attachment of the falx cerebelli

8-The cerebellar fossae:

• Lie on each side of the internal occipital crest
• They lodge cerebellar hemispheres

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

ANATOMY OF THE VERTEBRA

The vertebra is composed of the following parts:

1- The body:

• Has the shape of a short cylinder with rough upper & lower surfaces except for the smooth rounded circumference
• Bodies are separated & bound to each other by the intervertebral discs at the upper & lower surfaces
• They are also connected to each other by the anterior & posterior longitudinal ligaments at the anterior & posterior surfaces respectively

2- The pedicles:

• The short processes that project from the posterolateral aspect of the body
• Vertebral notches indent the upper & lower parts of the pedicle so when vertebrae articulate with each other these notches will produce the intervertebral foramina for passage of the spinal nerves

3- The laminae:

• The broad flat bony blades that converge posteomedially from the pedicles to meet at the root of the spinous process
• They are connected to each other along their upper & lower surfaces by ligamenta flava

4- The spine:

• Slopes posteroinferiorly from the junction of the two laminae in the midline
• They are connected with each other along their upper & lower borders by the interspinous ligaments & at their tips by the supraspinous ligaments which are deficient in the cervical region (ligamentum nuchae replaces them).

5- The transverse processes:

• Two processes project laterally from the junction of the pedicle & lamina between the articular processes
• They are connected with each other along their upper & lower borders by the weak intertransverse ligaments

6- The articular processes:

• Two superior & two inferior projections from the roots of the transverse processes
• Their shape and direction govern thetype of movement in the region

　

　

　

　

　

　

　

　

　

THE CERVICAL REGION

Atypical cervical vertebrae are the 1st (atlas), 2nd (axis) & 7th (vertebra prominence), all the remaining are typical.

The anatomy of the TYPICAL cervical vertebra:

A typical cervical vertebra has the following characteristics:

1- Bodies:

• Small, rectangular & have superior surfaces which are concave transversely with projecting lips on either side
• These lips articulate with a corresponding convexity in the inferior border of the vertebra above forming the joints of Lushka
• There is no vertebral region in the column which has direct articulation between vertebral bodies but the cervical region.

2- Pedicles:

• Project from the vertebral bodies midway between the superior & inferior surfaces so that the superior & inferior notches are equal in size
• In the other regions the pedicle is nearer to the superior than inferior surface
• This modification is to fit the extra spinal nerve in the region

3- Vertebral foramina are large & triangular in shape.

4- Spines are short & bifid.

5- Transverse processes:

• Short with prominent tubercles
• Carry foramina transversaria which transmit vertebral vessels & vertebral nerve plexus except that of C7 which transmit vertebral veins only.

6- Articular surfaces:

- Flat & oval permitting free movement at these joints

Atypical cervical vertebrae:

The atlas (C1):

1- Because it has lost part of its body which fused with the axis as the odontoid process & has no spine it looks like an oval bony ring.

2- The atlas has a short anterior & a longer posterior arches with two lateral masses carrying superior & inferior articular processes.

3- The anterior arch carries an anterior tubercle in the midline at its anterior surface for the attachment of the anterior longitudinal ligament & a facet on its posterior surface for articulation with the anterior surface of the odontoid process of C2.

4- The posterior arch carries a groove on its superior surface immediately behind the lateral mass for passage of vertebra artery & C1.

5- Superior articular facet is large, kidney-shape & concave facing upward, medially & posteriorly.

6- Inferior articular facet is nearly flat & oval fitting the superior articular facet of C2.

　

The axis (C2):

1- *The part of the body of C1 which fused with the axis is represented by the odontoid process (dens) which rests on the anterior part of the atlantic body.

*This constitutes the pivot around which the skull & atlas rotate on the axis.

*For this reason, the anterior surface of the dens carries an oval facet which articulates with a corresponding facet on the back of the anterior arch of the body of atlas.

*Structures which hold the dens in position are the cruciate together with the apical & alar ligaments.

2- Pedicles & laminae are heavy & broad.

3- Spine is very broad, heavy & bifurcated.

4- Superior articular facet is large, flat & faces superolaterally, while the inferior resembles the inferior facets of other cervical vertebrae.

Vertebra prominence (C7):

1- Spine is long, prominent & not bifid.

2- Transverse processes are larger than other vertebrae.

3- Transverse foramina are smaller than other vertebrae & transmit vertebral veins only. Occasionally they are absent.

The atlanto-occipital joint:

• The two occipital condyles represent the two lateral parts of a single ellipsoid surface the transverse diameter of which is longer than the antero-posterior one.
• These articulate with the superior facets of atlas so the general shape of the joint looks like an egg lies on its side in an egg-saucer, so the only permitted movement for this egg is to rotate around the longer axis of the ellipse therefore the only permitted movement in this joint is head nodding (flexion – extension of the skull)

- The articulation between the superior articular facets of C1 & occipital condyles are synovial joints with strong lax capsules

- The anterior & posterior atlanto-occipital membranes close the gaps between the corresponding atlantic arches & the base of skull around foramen magnum

The atlanto-axial joint:

- This joint is formed of:

1- The lateral atlanto-axial joints: TWO joints between the superior articular facets of axis with the inferior of atlas. These are synovial joints with lax capsule to permit rotation of the atlas carrying the skull on them.

2- The median atlanto-axial joint:

• TWO joints, the 1st between the anterior surface of the dens & the facet on the back of the anterior arch of atlas
• The 2nd between the back of the dens & the fibro-cartilagenous face of the transverse limb of the cruciate ligament
• These are synovial joints with thin capsules.

• The cruciate ligament:

1- The transverse limb:

• Is thick & strong band passes behind the dens
• It is attached between two tubercles located on the medial aspect of the lateral masses of atlas
• The part in relation to the dens is a fibro-cartilagenous face forming a joint with the back of the process

2- The longitudinal limb:

- From the back of the body of axis, a smaller band passes upward to be inserted in the anterior edge of foramen magnum

The apical ligament: is a single slender ligament passes from the apex of the dens to the anterior margin of foramen magnum.

- Alar ligaments: are two small but strong ligaments diverge superolaterally from each side of the apical ligament to be attached to the medial surface of the corresponding occipital condyles.

• Membrana tectoria:
• Is the upward extension of the posterior longitudinal ligament which broadens as it passes upward from the back of the body of axis to be attached within the anterior edge of foramen magnum, where it will be continuous with dura mater.
• It is the most posterior structure in this joint & its ligaments

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

THE NECK

SURFACE ANATOMY

Bony & cartilagenous landmarks:

1- Hyoid bone:

• Lies in the angle between the chin & the front of the neck
• Formed of body & two horns (greater & lesser)

2- Thyroid cartilage: Forms the midline prominence of the larynx 1-2 cm below the hyoid bone

3- Cricoid cartilage:Just below the thyroid cartilage separated from it by a sulcus

4- Tracheal rings: Frequently felt below the cricoid.

Muscular landmarks:

1- Sternocliedomastoid: Bisect the side of the neck into anterior & posterior triangles

2- Digastric: By its two bellies divide the suprahyoid compartment into submandibular & submental triangles

3- Omohyoid: Behind SCM divides the anterior & posterior triangles into further smaller ones.

SUPERFICIAL DISSECTION OF THE NECK:

The skin:

Langer lines "lines of cleavage":

• These lines represent the direction of arrangement of the collagen bands in the skin
• An incision along Langer lines heals with a minimum scar while an incision across them leaves
• an unfavorable scar tissue after healing Langer lines in the neck are arranged transversely along the circumference of the neck so incisions should be done in this direction unless contra-indicated

Subcutaneous conn. tissue:

• Formed of loose areolar & fatty tissues
• Replaced anteriorly by platysma
• Contains the cutaneous vessels & nerves which lie deep to platysma

Platysma:

Origin; Fascia covering pectoralis major & deltoid

Insertion; Lower border of the mandible & skin of lower part of the face & corners of the mouth

Nerve supply; Cervical branch of VII

Action; Depresses the corner of the mouth & lower border of the mandible

Superficial veins:

The External Jugular Vein:

• Formed behind the angle of the mandible by union of the posterior auricular v. & posterior division of retromandibular v.
• Descends vertically between platysma & SCM towards the middle of the clavicle
• 2 cm above the clavicle it pierces the neck fascia & drains into the subclavian vein
• Provided with 2 pairs of valves; one at its end in the subclavian v. & the other 4 cm above
• Tributaries:

• Posterior EJV from the back of neck
• Anterior JV from the anterior part of the neck
• Suprascapular & transverse cervical vv.

Clinical importance of the EJV:

1- Medical: as it is used sometimes as a sign of heart failure & to measure the central venous pressure ..

2- Surgical: sometimes used in cannulation & i.v therapy …

Anterior Jugular Vein:

• Formed near the hyoid bone by confluence of small submental vv.
• Descends vertically on each side of the midline (sometimes as a single vein in the midline)
• 3 cm above the manubrium, it perforates the superficial layer of deep cervical fascia & enters the suprasternal space
• In this space it communicates with its fellow be the jugular venous arch
• Then it turns laterally to empty in the EJV at its termination

Cutaneous nerves:

I )Nerves of the back:

- These are the Dorsal Primary Rami of Cervical Nerves

1- Greater Occipital Nerve: C2

Pierces semispinalis capitis & trapezius at their skull attachments and supplies the back of the scalp as high as the vertex.

2- Third Occipital Nerve: C3

Communicates with the great occipital n. & supplies the upper part of the back of the neck.

3- C4:

Supplies the reminder of the back of the neck.

II )Nerves of the front:

• These are the cutaneous branches of cervical plexus
• Nerves approach the surface near the midpoint of the posterior border of SCM where they diverge.

1- Lesser occipital Nerve: C2 & 3

• Ascends along the posterior border of SCM
• Supplies skin & subcutaneous tissue at the insertion of the muscle & behind & above the auricle.

2- Great auricular Nerve: C2 & 3

• Hooks below the posterior border of SCM
• Ascends in the direction of the auricle & angle of the mandible where it supplies:

Skin over the antero-inferior part of mastoid BY mastoid branches

Auricle, except the upper ½ of lateral surface BY auricular br.

Skin over parotid & angle of mandible BY facial br.

3- Anterior cutaneous nerve: C2 & 3

• Crosses SCM horizontally deep to platysma to reach the anterior triangle
• It divides into superior & inferior branches penetrating platysma & supplies skin & subcutaneous tissues of the cylinder of the neck
• Its block in local anaesthesia results in sensory loss in a wide area of the neck.

4- Supraclavicular nerves: C3 & 4

Descend toward the clavicle where they divide into 3 main groups:

- Medial; skin over manubrium sterni

- Intermediate; skin over the pectoral region down to the 3rd rib

- Lateral; skin over deltoid as far as the distal 1/3 of muscle

DEEP DISSECTION OF THE NECK:

Deep fascia:

FOUR entities of well defined deep fasciae are diagnosed in the neck:

1- The investing cervical fascia

2- The pretracheal fascia

3- The prevertebral fascia

4- The carotid sheath (one on each side)

The Investing Fascia:

• Double layered membrane encloses the whole structures of the neck like a collar
• It splits at certain areas to enclose 2 muscles & 2 glands on each side
• Upper attachment (to the skull base):

External occipital protuberance - superior nuchal line (splits for trapezius & SCM) - mastoid process - splits in 90 degrees:

- Superficial layer (covers the parotid gland); Lower border of zygomatic arch - lower border of mandible

- Deep layer (deep to the parotid gland); Lower border of tympanic plate - fuse with carotid sheath

Lower attachment:

To the pectoral girdle around the attachment of SCM & trapezius

Fixation points:

To the hyoid bone forming the angle between the chin & the neck

Special derivatives:

• Parotid fascia
• Submandibular fascia
• Stylomandibular ligament: thickening in the deep layer of parotid fascia between the styloid process & the angle of mandible

Enclosed structures:

• Parotid & submandibular glands
• SCM & trapezius
• Suprasternal space containing the JVA

The Prevertebral Fascia:

• Forms a smaller cylinder inside the large investing one enclosing the vertebral column & the surrounding muscles
• Superior attachment is to the base of the skull anterior to the attachments of the prevertebral muscles
• Laterally it is attached to the tips of transverse processes of the cervical spines
• Then extends laterally to cover the pre- & para-vertebral muscles reaching ligamentum nuchae & the vertebral spines
• Downward it reaches the lowest limit of longus colli (T4)
• Extends along the axillary artery as the axillary sheath

The Pretracheal Fascia:

• Attached superiorly to the hyoid bone & the oblique line of thyroid cartilage
• Encloses the thyroid gland forming its sheath
• It is responsible for the upward movement of the thyroid gland & any related swelling during deglutition
• Laterally it reaches the carotid sheath
• Inferiorly it blends with fascial coverings of the aortic arch
• It is pierced by the thyroid vessels

The Carotid Sheath:

• A dense cylindrical condensation of connective tissue surrounding the CCA, ICA, IJV & vagus nerve
• Attached superiorly at the margins of carotid canal
• Reaches downward to the aortic arch
• Its deficient around the IJV (for venous expansion)
• Fused laterally with the deep layer of investing fascia & antero-medially with the pretracheal fascia
• It is loosely attached to the anterior aspect of the prevertebral fascia along the tips of transverse processes of the cervical spines

Tissue spaces of the neck:

Behind the prevertebral fascia:

The space descend down to reach the lowest attachment of the fascia at T4, though an abscess there usually points in the posterior triangle by pathological walling off

In front of the prevertebral fascia (retropharyngeal space):

The space extends from the base of the skull down to the posterior mediastinum

Anterior to the pretracheal fascia:

The space reaches down through the superior to the anterior mediastinum

Between the pretracheal & prevertebral fasciae:

The space leads down through the superior to the posterior mediastinum

Posterior cervical triangle:

Is the triangular space which lies in a spiral fashion on the postero-lateral aspect of the neck.

Boundaries:

- Anterior; posterior border of SCM

- Posterior; anterior border of trapezius

- Inferior; middle 1/3 of clavicle

Roof:

Skin, subcutaneous tissue, platysma, investing fascia

Floor:

Scalene muscles, levator scapulae & splenius capitis covered by prevertebral fascia

Sternocliedomastoid:

Origin:

• Tendinous sternal head from the anterior surface of manubrium sterni
• Fleshy clavicular head from the upper surface of the medial 1/3 of clavicle

Insertion: Lateral side of mastoid process & lateral ½ of superior nuchal line

Nerve supply: Accessory nerve

Action:

• Unilateral contraction draws the mastoid process toward the shoulder (pushes the face to the opposite side)
• Bilateral contraction flexes the head over the neck
• With stabilization of the head, it is an accessory muscle of inspiration

Scalenus anterior:

Origin: Anterior tubercles of transverse processes of C3-C6

Insertion: Scalene tubercle on the upper surface of the 1st rib

Nerve supply: C5-C7 anterior primary rami

Scalenus medius:

Origin: Posterior tubercles of transverse processes of C2-C7

Insertion: Upper surface of the 1st rib behind subclavian artery groove

Nerve supply: C3-C8 anterior primary rami

Scalenus posterior:

Origin: Posterior tubercles of transverse processes of C5-C7

Insertion: Lateral surface of the 2nd rib rib

Nerve supply: C7 & C8 anterior primary rami

Contents of the posterior triangle:

I) In the roof (superficial to the investing fascia):

1-Platysma.

2-EJV.

3-EJ lymph nodes: 1-2 nodes along the EJV receive from the ear & parotid & send to the superior group of deep cervical nodes.

4-Cutaneous branches of cervical plexus, especially the lesser occipital & supraclavicular nerves.

II) In the triangle (between the investing & prevertebral fasciae):

Nerves;

1- The spinal root of accessory nerve:

• Crosses the triangle on the undersurface of investing fascia
• Is directed vertically toward the tip of the shoulder between the posterior border of SCM & anterior border of trapezius
• It supplies trapezius & SCM

Accessory nerve injury:

Unilateral injury of the accessory nerve results in paralysis of the SCM muscle on that side with the resultant unopposed action of the contralateral muscle so the face turns to the injured side & the mastoid process on the healthy side approaches the shoulder in a "wry neck" deformity.

2- The cervical plexus:

• Formed by the ventral primary rami of the upper four cervical nerves inside the substance of the prevertebral muscles.
• It gives 4 sensory & 4 motor branches.
• The sensory branches were discussed.
• The motor branches:

A) Direct muscular branches to prevertebral muscles:

• C1,2; longus capitis & the anterior & lateral recti
• C2,3,4; longus capitis & longus colli
• C3,4; levator scapulae & the scalene

B) Phrenic nerve: C3 & C4

• Descends vertically across the oblique course of scalenus anterior from its lateral to medial border
• Lies deep to the prevertebral fascia & crossed by the transverse cervical & suprascapular arteries
• Enters the thoracic inlet in a variable relation to the subclavian vein (usually behind it) & descends in the thorax to the diaphragm.

C) C1 fibers to hypoglossal nerve:

• XII nerve receives fibers from the C1 nerve at the anterior condylar canal
• These fibers leave XII as 4 branches:

1- Meningeal branch to the dura around foramen magnum

2- Superior ramus of ansa cervicalis (descendens hypoglossi)

3- Nerve to thyrohyoid

4- Nerve to geniohyoid

D) Inferior ramus of ansa cervicalis (descendens cervicalis): C2 & C3

• Descends behind the carotid sheath to join the superior ramus usually lateral to the IJV
• Ansa cervicalis, so formed around the IJV in a Y-shape or loop pattern, has a variable vertical position
• It supplies the infrahyoid muscles except thyrohyoid.
• Their supply is segmental (upper part of the muscle receives C1, middle part C2 & the lower part C3)

E) Proprioceptive fibers to SCM & trapezius (C2 & 3).

ARTERIES;

1- The transverse cervical & suprascapular arteries:

• Are branches of the thyrocervical trunk
• Crosses laterally in the base of the triangle above & parallel to the clavicle to hide underneath the anterior border of trapezius (TC) & behind the inferior belly of omohyoid (SS).
• The transverse cervical lies superior to the suprascapular.

2- The occipital artery:

Runs part of its course in the apex of the triangle in its way to the scalp

VEINS;

Similar to arteries.

LYMPH NODES;

1- The supraclavicular lymph nodes:

• Are extension from the postero-inferior group of the deep cervical nodes along the transverse cervical vessels.
• Receive lymph (in addition to the normal drainage of the postero-inferior nodes) from the apical axillary nodes, breast & sometimes from the upper limb & anterior chest wall.

2- The occipital lymph nodes:

• Situated along the occipital vessels in the apex of the triangle.
• Drains the back of the scalp upward to the vertex.

OTHERS;

The inferior belly of omohyoid:

• Emerges from behind the lower part of the posterior border of SCM & enters deep to trapezius.
• Divides the triangle into occipital & supraclavicular ones.

III) In the floor of the triangle (deep to the prevertebral fascia):

NERVES;

Brachial plexus:

Branches from the roots & trunks: these are branches have part of their course in the neck, though they are distributed to muscles in the upper limb:

1. Dorsal scapular nerve: passes over scalenus medius & posterior & hides deep to levator scapulae
2. Long thoracic nerve: leaves scalenus medius by two roots which unite down to form the nerve
3. Suprascapular nerve:passes above the plexus & hides under trapezius

VESSELS;

The subclavian artery:

• From the aortic arch (on the left) & brachioceohalic trunk (on the right), the artery leaves the back of the corresponding sternoclavicular joint & goes laterally in the root of the neck
• Crosses over the 1st rib behind scalenus anterior which divides it into 3 part (1st medial, 2nd behind & 3rd lateral to it)
• Around the 1st part of the right artery the right recurrent laryngeal nerve hooks
• It leaves the outer border of the 1st rib to the axilla as the axillary artery.

Branches:

I: From the 1st part:

1- Vertebral artery:

• Arises from the dorsosuperior aspect of the subclavian
• Enters the foramen transversarium of C6
• Ascends in the upper 6 cervical vertebrae in front of the emerging spinal nerves
• Arching behind the atlanto-occipital joint, it enters foramen magnum & unites with its fellow at the clivus forming the basilar artery

Branches;

* muscular (in the neck): to deep neck muscles

* spinal (in spinal canal): radicular arteries

2- Thyrocervical trunk:

• Short thick artery arises from the subclavian a. opposite to the internal thoracic a.
• Soon after its origin it divides into:

* Transverse cervical a.

* Suprascapular a.

* Ascending cervical a.: passes medial to the phrenic nerve anterior to scalenus anterior

* Inferior thyroid a.:

• Arches up as high as the cricoid cartilage where it pierces the prevertebral fascia & enters behind the thyroid gland
• The recurrent laryngeal nerve lies in between its 5-6 branches which pierce the pretracheal fascia separately & enters the thyroid gland
• It gives the inferior laryngeal a. to the lower part of the larynx.

3- Internal thoracic artery:

• Arises from the inferior aspect of the subclavian a.
• Descends behind the subclavian v. & phrenic nerve to enter the thorax
• It passes on each side of the sternum (1 cm away)
• Gives the anterior intercostal arteries
• Ends by dividing into superior epigastric & musculophrenic arteries.

II: From the 2nd part:

The costocervical trunk:

• Ascends on the back of cervical pleura & apex of the lung
• Passes between the trunks of brachial plexus
• On the neck of 1st rib it divides into highest intercostal & deep cervical artery

III: From the 3rd part:

• In 70% , the dorsal scapular a. leaves the 3rd part of the artery & follows the corresponding nerve after disappearing underneath the anterior border of trapezius
• In 30%, this artery arises from the transverse cervical artery

The subclavian vein:

• Lies in the root of the neck anterior to scalenus anterior crossing over the 1st rib & then grooves the apex of the corresponding lung & cervical pleura
• Joined by the IJV at the medial border of the muscle forming the brachiocephalic v.
• Receives only the EJV

The anterior cervical triangle:

• Is the area of the neck which lies between the anterior borders of the two SCM muscles & the lower border of the mandible.
• The anterior midline divides this area into two anterior cervical triangles.
• Digastric & the superior belly of omohyoid further divide each of the two triangles into carotid, muscular & submandibular triangles.
• The remaining area between the anterior bellies of both digastrics in the single submental triangle.

The carotid triangle:

Roof (lateral wall):

Skin, subcutaneous tissue, platysma and investing fascia

Floor (medial wall):

- Anteriorly: hyoglossus & thyrohyoid

- Posteriorly: middle and inferior constrictor muscles

Contents:

1- Carotid sheath & its contents.

2- Nerves; ansa cervicalis, hypoglossal nerve.

3- Deep cervical lymph nodes.

Contents of the carotid sheath:

The Common Carotid Artery (CCA):

• From behind the corresponding SCJ, the CCAs diverge as they ascend on each side of the neck separated by the larynx & thyroid gland
• Their course is in the carotid line (a vertical line midway between the angle of the mandible & the mastoid process)
• At the upper border of thyroid cartilage (C3-4) it divides into ECA & ICA
• The artery is crossed from below upward by the IJV, SCM, superior belly of omohyoid, superior laryngeal a. & thyroid veins

The carotid sinus:

• It is a dilatation at the bifurcation of the CCA especially around the origin of the ICA
• Its walls are especially elastic & contain baroreceptors responsible for regulation of blood pressure

The carotid body:

• A mass of cells in the posterior wall of the sinus
• Contains chemoreceptors for regulation of blood osmolarity

• BOTH carotid sinus & body are supplied by the sinu-carotid branch of IX nerve
• Carotid body tumor "Potato tumor":

A tumor affecting the carotid body resulting in a pulsetile swelling in the lateral aspect of the neck

The Internal Carotid Artery (ICA):

• At the bifurcation, the ICA is postero-lateral to the ECA, then it takes a medial relation alongside the pharynx.
• It passes upward with the IJV to reach the base of the skull where it enters the temporal bone through the carotid canal.
• It gives no branch in the neck.
• It supplies the brain & structures inside the orbit.

　

　

The External Carotid Artery (ECA):

• About equal in caliber to the ICA, the ECA extends between the upper border of thyroid cartilage & the neck of the mandible where it ends by dividing into its two terminal branches
• In the carotid triangle, the ECA lies superficial being covered directly by the investing fascia of the roof, it is crossed by the facial, lingual & sometimes the superior thyroid veins
• Leaving this triangle, the artery passes deep to the posterior belly of digastric & stylohyoid muscles separating them from stylopharyngeus
• Here, the ECA lies in the deep lobe of the parotid gland together with the retromandibular vein & facial nerve.

Branches of the ECA:

1. Anterior branches:

1- Superior thyroid a.

2- Lingual a.

3- Facial a.

B) Posterior branches:

4- Occipital a.

5- Posterior auricular a.

C) Medial branch:

6- Ascending pharyngeal a.

D) Terminal branches:

7- Maxillary a.

8- Superficial temporal a.

Superior thyroid artery:

- Given at the beginning of the ECA just below the tip of greater horn of the hyoid bone

- Descends downward towards the apex of the lateral lobe of the thyroid gland accompanied by the external laryngeal nerve

- Pierces the pretracheal fascia at the apex of the thyroid lobe & divides into anterior & posterior branches which descend on the corresponding surfaces of the gland & anastomose with the inferior thyroid branches

- Branches:

a) Superior laryngeal a.; pierces the thyrohyoid membrane together with the internal laryngeal n. & supplies the larynx above the level of vocal folds

b) Sternomastoid a.; to SCM

c)Muscular branches to the inferior constrictor muscle

Lingual artery:

- Arises opposite to the tip of the greater horn of hyoid bone.

- After an upward loop, the artery passes forward to disappear deep to hyoglossus.

- It is crossed laterally by the hypoglossal nerve, posterior belly of digastric & stylohyoid.

- Branches:

a) Dorsal lingual a.; given at the back of the tongue & supplies the tonsils, soft palate & epiglottis.

b) Sublingual a.; to the sublingual gland

Facial artery:

- Given just above the tip of greater horn of hyoid bone.

- Ascends up deep to the posterior belly of digastric in the submandibular triangle where it lies between the submandibular gland & myelohyoid.

- After an S-shape course in the triangle, the artery curves over the lower border of the mandible at the anterior edge of masseter to ascend in the face.

- Branches:

a) Ascending palatine a.; ascends between styloglossus & stylopharyngeus to lie on the superior constrictor muscle. It supplies the upper pharyngeal wall, soft palate, palatine tonsils & auditory tube

b) Tonsillar a.; to the palatine tonsils

c) Glandular branches to the submandibular gland

d) Submental a.; given before the facial a. curves on the mandible, it passes back between the anterior belly of digastric & myelohyoid with the nerve to myelohyoid in the submental triangle.

Occipital artery:

- Given from the back of the ECA at the level of the facial a.

- Ascends parallel to the lower border of the posterior belly of digastric to hide deep to SCM.

- It grooves the skull in the region of the occipito-mastoid suture to appear in the apex of the posterior triangle

- Pierces the fascia of the neck & ascends in the back of the scalp supplying it up to the vertex.

- Branches:

a) Muscular branches to digastric, stylohyoid & posterior cervical muscles.

b) Sternomastoid a.; to SCM

c) Meningeal, auricular & mastoid branches

Posterior auricular artery:

- Ascends parallel to the upper border of the posterior belly of digastric.

- Passes in the region of the parotid gland supplying it

- Crosses superficial to the mastoid process behind the auricle.

- Branches:

a) Stylomastoid a.; enters the corresponding foramen & gives stapedial arery to stapedius.

b) Auricular a.

c) Occipital arteries to the scalp

Ascending pharyngeal artery:

- From the medial aspect of the ECA, this long & slender branch ascends on the sidewall of the pharynx deep to the ICA.

- Branches:

a) Pharyngeal branches to the superior & middle constrictor muscles

b) Palatine a.; to the soft palate & palatine tonsils.

c) Inferior tympanic a.; to the middle ear

d) Meningeal branches to the dura mater after entering the hypoglossal canal or the jugular foramen.

Superficial temporal artery:

- The smaller of the 2 terminal branches of the ECA

- Given deep to the neck of the mandible

- Ascends in the temporal fossa

Maxillary artery:

- The larger of the 2 terminal branches of the ECA

- Given deep to the neck of the mandible

- Passes forward into the infratemporal fossa

The Internal Jugular Vein (IJV):

• It is the continuation of the dural sigmoid sinus in the posterior compartment of the jugular foramen.
• In the carotid sheath, the IJV is posterolateral to the artery in the upper part of the neck, then becomes lateral & in the root of the neck it is almost anterior
• Ansa cervicalis is usually formed around it
• Deep cervical L. N. lie around it
• At its beginning it has a dilatation called superior bulb, a similar (inferior) bulb lies at its termination

• Tributaries:

• Inferior petrosal sinus: just below the base of the skull.
• Thyro-glosso-facial confluence of v.: superior thyroid, lingual & facial vv. usually open in common or separately in the IJV at the level of the origin of lingual a. from the ECA.
• Pharyngeal veins: from the pharyngeal plexus, terminate in the IJV at the level of the angle of mandible.
• Middle thyroid v.

The Vagus Nerve:

• Leaves the skull with the IJV, IX & XI nerves through the jugular foramen.
• Descends in the neck inside the carotid sheath throughout which the nerve lies between the IJV & the carotids.
• In the neck it gives the following branches:

• Meningeal n.: to the dura of posterior cranial fossa
• Auricular n.: to the external acoustic meatus & tympanic membrane
• Pharyngeal n.: usually 2 in number to the pharyngeal plexus
• Superior laryngeal n.: divides into internal & external laryngeal nerves
• Cervical cardiac n.: usually 2 in number to the cardiac plexus
• Recurrent laryngeal n.

Hypoglossal Nerve:

• Descends in a downward curve on the lateral aspect of the ECA crossing it at the point of origin of the lingual artery.
• Enters the floor of the mouth lateral to hyoglossus.
• In the neck it gives the branches of C1 which hitch-hacked along it.

Deep Cervical Lymph Nodes

The muscular triangle:

Is the space between midline, superior belly of omohyoid & the anterior border of the lower part of SCM

Roof :

Skin, subcutaneous connective tissue, platysma and investing fascia.

Contents:

1- Infrahyoid (strap) muscles.

2- Thyroid gland.

3- Structures of the midline (pharynx, larynx, trachea & oesophagus).

Infrahyoid muscles:

1- Sternohyoid:

• This thin narrow muscle is the most medial of the infrahyoid muscles
• Separated from its fellow on the opposite side by the midline & Adam’s apple only

Origin; Posterior end of the sternal end of clavicle & back of manubrium sterni.

Insertion; The lower border of the body of hyoid bone.

N. supply; C1,2,3 by ansa cervicalis.

2- Omohyoid:

Formed of 2 bellies & lies lateral to sternoh.

Origin; Inferior belly arises from the scapular ligament & upper border of scapula

Insertion; Lying in the base of the posterior triangle, the inferior belly ends in an intermediate tendon behind SCM being held to this muscle by the deep layer of investing fascia. From this tendon the superior belly arises & ascends lateral to sternohyoid to the lower border of the body of the hyoid bone.

N. supply; Ansa cervicalis, C1 to the superior belly & C2,3 to the inferior one.

3- Sternothyroid:

Shorter, broader & deeper than sternohyoid.

Origin; Back of manubrium sterni reaching lower than sternohyoid, & 1st costalcartilage.

Insertion; oblique line of thyroid cartilage.

N. supply; By ansa cervicalis,C2 & 3.

4- Thyrohyoid:

Origin; Oblique line of thyroid cartilage as a continuation of sternothyroid.

Insertion; Lower aspect of greater horn of hyoid bone.

N. supply; Nerve to thyrohyoid, C1 fibers given as a branch from the XII nerve.

Action of infrahyoid muscles:

• Together with the suprahyoid muscles, these muscles move & regulate the movements of the hyoid bone, tongue & larynx
• They depress the hyoid bone either directly or by depressing the thyroid cartilage.
• Thyrohyoid could elevate the larynx to produce high notes if the hyoid bone is fixed from above
• Sternothyroid could depress the larynx to produce low notes if the hyoid bone is fixed from above

The Thyroid Gland:

Shape & position:

This H-shape gland has two lateral lobes connected in the midline by an isthmus:

The lateral lobe:

• Is a pyramidal shape lobe with an upward apex lying deep to thyrohyoid & a wide base reaches down to the level of the 6th tracheal ring
• The anterior border is thin & inclines inferomedially from the apex to reach the midline

- The rounded posterior border are separated from each other by the airway & foodway & touching the carotid sheaths posterolaterallly

The isthmus: Connects the two lateral lobes in the midline opposite to the 2nd, 3rd & 4th tracheal rings.

The pyramidal lobe:

• Sometimes arises from the isthmus & directed to one lobe (usually the left)
• Sometimes it is connected to the hyoid by levator glandulae thyroidae muscle

Fascia:

• The pretracheal fascia invests the gland within which lies free inside it except at the region of the isthmus
• The fascia is attached superiorly to the thyroid cartilage therefore the gland and any related swelling will move upward during deglutition

Capsule:

The gland has a histological fibrous capsule which sends septa into the gland dividing it into lobules

Relations:

* Antero-laterally: Infrahyoid muscles (except thyrohyoid).

* Posteriorly: Carotid sheath.

* Medially: Thyroid & cricoid cartilages & the upper 6 tracheal rings "anteriorly" and thyropharyngeus, cricopharyngeus & upper oesophagus " posteriorly".

Arteries:

1- Superior thyroid artery:

• Branch of ECA
• Pierces the fascia & distributed to the gland by an anterior & posterior branches.

2- Inferior thyroid artery:

• Branch of the thyrocervical trunk from the 1st part of subclavian a.
• Arches up then down behind the carotid sheath to reach behind the lower border of the gland where it divides into (5-6) branches which penetrate the fascia separately & distributed to the gland
• The recurrent laryngeal n. lies in between them.
• It gives tracheal, oesophageal, inferior laryngeal & pharyngeal branches

3- Thyroidea ima artery:

• Small branch arises from the brachiocephalic trunk or aortic arch & enters the lower pole
• They are seen n 10% of individuals.

Veins:

1- Superior thyroid vein:

• Formed on the anterolateral aspect of the lateral lobe of the gland
• Crosses in front of the CCA & receives tributaries corresponding to the branches of the superior thyroid a.
• It empties in the IJV separately or with the facio-lingual v.

2- Middle thyroid vein:

• Formed at the lateral surface of the gland
• This short wide v. courses laterally to empty in the lower part of the IJV

3- Inferior thyroid veins:

• Arise from the venous plexus which lies near the lower pole of the gland & communicates with the upper 2 veins
• They descend down receiving tributaries which correspond to the branches of the inferior thyroid a.
• Pass behind the manubrium to end in the corresponding brachiocephalic vein.
• Sometimes the 2 veins unite forming a single vein which empties in the left brachiocephalic v.

Nerves:

1- Sensory: Recurrent laryngeal n.

2- Sympathetic (vasomotor): Middle cervical sympathetic ganglion along the branches of the inferior thyroid a.

Lymph:

Along arteries:

• Superior thyroid: Anterosuperior group of deep cervical nodes
• Inferior thyroid: Posteroinferior group of deep cervical nodes

Applied anatomy:

• A midline neck swelling that moves with swallowing is related to the thyroid gland until proved otherwise.
• Incisions for thyroidectomy are made horizontally at the lower part of the neck.
• The recurrent laryngeal nerve is commonly injured during ligation of the inferior thyroid arteries in thyroid surgery

Pharynx & Larynx will be discussed later

Trachea:

• Begins at the cricoid cartilage (C6) & ends at the carinaT4 level, a 12 cm long tube ½ of which lies in the neck
• The CCA lie on each side of the trachea being separated from it above by the lateral lobes of the thyroid.
• The oesophagus lies behind it & the intervening groove is occupied by the recurrent laryngeal nerves
• Thyroid isthmus lies anterior to the rings 2-4
• Trachea is formed of C-shape cartilages opened behind & the opening is closed by trachealis muscle.
• Cervical trachea is supplied by the inferior thyroid a., drained by inferior thyroid v. , its nerve supply is similar to the thyroid gland & its lymph goes to the postero-inferior group of deep cervical nodes.

Applied anatomy:

• Tracheostomy is a life-saving operation to open the airway in acute & chronic airway obstruction.
• The incision is done below the cricoid cartilage & the trachea is exposed after dividing the successive layers in front of it
• A tube is inserted to keep the airway patent

Oesophagus:

• 25 cm tube begins at the level of C6 vertebra (cricopharyngeus) & ends at the cardiac opening of the stomach
• The carotid sheaths lie on each side being separated from it by the posterior part of the lateral lobe of the thyroid.
• The trachea lies anterior to it & the intervening groove is occupied by the recurrent laryngeal nerves
• The prevertebral muscles lie behind it with the sympathetic trunk on each side.
• Cervical oesophagus is supplied by the inferior thyroid a., drained by inferior thyroid v. , its nerve supply is similar to the thyroid gland & its lymph goes to the postero-inferior group of deep cervical nodes.

The submandibular triangle:

Is the space between the two bellies of digastric & the lower border of the mandible.

Roof :

Skin, subcutaneous connective tissue,

platysma and investing fascia.

Floor:

Myelohyoid "anteriorly"

Hyoglossus & part of the middle

constrictor "posteriorly"

Contents:

1- Suprahyoid muscles.

2- Submandibular gland.

3- Facial artery.

4- Common facial vein.

5- Submandibular lymph nodes.

6- Cervical branch of facial nerve.

Suprahyoid Muscles:

Digastric:

Origin:

• Anterior belly: From the digastric fossa at the lower border of the mandible on each side of symphysis menti
• Posterior belly: From the digastric notch on the medial aspect of the mastoid process.

Insertion:

The 2 bellies are directed to the body of the hyoid bone where they are united by an intermediate tendon which is held to the hyoid bone by a fibrous sling.

Nerve supply:

• Anterior belly: Nerve to myelohyoid (branch from the mandibular n. Vc)
• Posterior belly: Facial nerve

Action:

• Elevate the hyoid bone, larynx & pharynx during swallowing
• Opens the mouth widely

Stylohyoid:

Origin:

• From the posterior aspect of the styloid process near its root.

Insertion:

The muscle descends superomedial & parallel to the posterior belly of digastric to reach the intermediate tendon of digastric, here it divides into 2 slips which pass on each side of the intermediate tendon of digactric & inserted on the hyoid bone near the greater horn.

Nerve supply:

Facial nerve

Action:

• Pulls the hyoid backward & upward.

Myelohyoid:

Origin:

From the whole length of myelohyoid line on the inner surface of the mandible

Insertion:

• Fibers descend medially & backward
• Posterior part of it will reach the body of hyoid bone to which they are inserted
• Anterior fibers meet each other in a midline raphe which extends between the hyoid bone & the mandible

Nerve supply:

Nerve to myelohyoid (from

the mandibular nerve Vc)

Action:

• Forms the floor of the mouth

on which the tongue rests & move

• Plays a major role in swallowing.

Geniohyoid:

Origin:

Inferior genial tubercle.

Insertion:

The two ribbon like muscles descend side by side between myelohyoid & genioglossus to be inserted into the upper border of the body of hyoid bone.

Nerve supply:

C1 fibers from the XII nerve.

Action:

Pulls the hyoid anterosuperiorly.

Hyoglossus:

This is a tongue muscle & is an important key around which the structures of the floor of the mouth are distributed

Origin:

The upper border of the greater cornu of the hyoid.

Insertion:

The rectangular muscle ascends up to be inserted into the side of the tongue posteriorly

Nerve supply:

XII nerve.

Action:

• Pulls the hyoid up
• Depresses the side of the tongue
• Both retract the tongue

Submandibular gland:

Will be discussed later.

Facial artery:

Discussed.

Common facial vein:

• Formed at the lower border of the mandible by union of the anterior facial v. & anterior division of retromandibular v.
• Passes superficial to the submandibular gland in the direction of the carotid triangle of the neck
• Terminates in the IJV either separately or together with the superior thyroid & lingual veins
• It drains the structures in the submandibular triangle

Submandibular lymph nodes:

Will be discussed later.

Cervical branch of VII :

Descends vertically from behind the mastoid process to platysma.

The submental triangle:

Is the space between the anterior bellies of the 2 digastrics & the hyoid bone.

Roof :

Skin, subcutaneous connective tissue, platysma and investing fascia.

Floor:

Myelohyoid

Contents:

1- Submental branch of facial artery.

2- Nerve to myelohyoid.

3- beginning of AJV.

4- Submental lymph nodes.

Submental branch of facial artery:

Discussed.

AJV:

Discussed.

Submental lymph nodes:

Will be discussed later.

Myelohyoid nerve:

• Given from the inferior alveolar nerve at the mandibular foramen.
• Pierces the sphenomandibular ligament & passes forward in the floor of the submental triangle inferior to myelohyoid between it & the anterior belly of digastric supplying both.
• It is accompanied by the submental artery.

The prevertebral region:

Is the area which lies in front of the vertebral column & constitutes the prevertebral & paravertebral muscles covered by the prevertebral fascia.

Prevertebral Muscles:

Rectus capitis anterior:

Origin; lateral mass of atlas

Insertion; basi-occiput

Nerve supply; C1

Action; flexes the head

Rectus capitis lateralis:

Origin; transverse process of atlas

Insertion; jugular process of occipital bone

Nerve supply; C1

Action; laterally flexes the head

Longus capitis:

Origin; anterior tubercles of T.P of the 4 typical cervical vertebrae end-to-end with the tendons of scalenus anterior

Insertion; basi-occiput anterior to foramen magnum

Nerve supply; C1-C4

Action; flexes the head & neck

Longus colli:

This muscle extends on the anterior surface of the vertebral column from C1 to C4

Origin;

Vertical part: bodies of thoracic vertebrae

Superior oblique part: T.P of upper cervical vertebrae

Inferior oblique part: bodies of upper thoracic vertebrae

Insertion;

- Vertical part: bodies of cervical vertebrae

- Superior oblique part: anterior tubercle of C1

- Inferior oblique part: T.P of lower cervical vertebrae

Nerve supply; C1-T4

Action; flexes & rotates the neck

The Cervical Sympathetic Trunk:

• An upward extension of the thoracic S.T which is located behind the carotid sheath on the prevertebral fascia
• In a cord-like form or multiple strands, the S.T develops three ganglia in the neck; superior, middle & inferior
• Each one of the three has three sets of branches; somatic, vascular & visceral.
• The body of the cervical S.T is formed mainly of preganglionic fibers which traverse the white rami communicantes of the upper 5 thoracic segments
• Cervical S.T possesses no white rami communicantes attaching it to the spinal nerves since there is no lateral gray column in the cervical segments

Vascular br.	Visceral br.	Somatic br.	Position	Ganglion
-Carotid sympathetic plexus	-Superior cervical cardiac nerves -The left to the superficial cardiac plexus -The right to the deep C.P	-Gray rami communicants to C1-C4 spinal nerves	-Largest (2.5-3.5) cm long -C2 level	Superior C.G
-Inferior thyroid sym. Plexus	-Middle cervical cardiac nerves to the deep C.P	-Gray rami communicants to C5 & C6 spinal nerves	-Smallest (1.3 cm) long -C6 level	Middle C.G
-Vertebral sym. plexus	-Inferior cervical cardiac nerves to the deep C.P	-Gray rami communicants to C7 & C8 spinal nerves	-In 82% fused with the T1 ganglion to form the the stellate gan. on the neck of the 1st rib	Inferior C.G

　

　

Root of the neck:

• The root of the neck is based on the supra-pleural membrane which inclines downward & forward with the inclination of the first rib
• Behind & inferior to the membrane lies the lung apices with their cervical pleura
• In front & superior to the membrane lies structures of the root.
• The neck root is studied according to structure relation to scalenus anterior

The triangular space "of Chassaignac":

• It is the space bounded laterally by the medial border of scalenus anterior, medially by the sloping lateral border of longus colli & inferiorly by the neck of the 1st rib
• Its apex is the carotid tubercle (C6 T.P) against which the CCA can be compressed
• It contains the 1st part of subclavian artery & the 6th cervical sym. ganglion

Anterior relations:

1- Phrenic nerve: passes vertically across the obliquity of the muscle leaving its medial border inferiorly to pass to the thorax.

2- Vagus nerve: descends anterior & medial to the muscle to reach the front of the subclavian artery & gives the recurrent laryngeal n. around this vessel on the right side.

3- Ascending cervical artery: ascends from the inferior thyroid a. on the muscle medial to the phrenic nerve.

4- Transverse cervical & suprascapular arteries: cross anterior to the lower part of the muscle in their way to the posterior triangle.

5- IJV: lies anterior to the lower part of the muscle.

6- Subclavian vein: crosses the lower part of the muscle to meet the IJV medial to it in the pyramidal space.

7- Deep cervical L.N: around the IJV, inferior nodes lie especially in front of the muscle.

8- SCM: covers all the above structures.

Medial relations:

1- Vagus nerve.

2- Middle & inferior cervical sympathetic ganglia: lie in the pyramidal space on the medial side of scalenus anterior connected in front of the subclavian artery by the ansa subclavia.

3- First part of subclavian artery: with its three branches

4- Vertebral vein(s): leave the T.P of C7 & course forward to enter the confluence of the subclavian v. & IJV.

5- Thoracic duct (on the left) & right lymph duct (on the right): arch in the pyramidal space to enter the confluence of the subclavian v. & IJV.

Posterior relations:

1- Roots of brachial plexus: as they emerge from the intervertebral foramina to the posterior triangle, they lie superior to the subclavian artery.

2- Second part of subclavian artery: behind the muscle on the 1st rib, here it gives the costocervical axis.

Lateral relations:

1- Trunks of brachial plexus: in the posterior triangle.

2- Third part of subclavian artery: behind the prevertebral fascia in the floor of the posterior triangle.

• The muscles of the back of the neck are enclosed by the thoracolumbar fascia in the posterior compartment of which the postvertebral muscles lie
• Externally the investing fascia wraps the whole neck

Back of the neck:

Ligamentum nuchae:

A strong, triangular sheet of fibrous tissue dividing the back of the neck into two halves & provides an important origin for many muscles, it is attached by its three borders to:

1- The external occipital crest, superiorly.

2- Tips of cervical spines & supraspinous ligaments, anteriorly.

3- Posterior free border to which the investing fascia comes from either side of the neck to be attached.

Thoracolumbar fascia:

• A strong fascia attached to the spines & transverse processes of the vertebral column enclosing within its two compartments the muscles
• This arrangement persists in the the lumbar region, in the thoracic & cervical regions the anterior lamella of the fascia disappears leaving the middle & posterior lamellae only enclosing in between the postvertebral muscles

Muscles of the back of the neck:

Splenius:

• Its name in latin means "bandage" revealing its shape & function
• The muscle lies deep to trapezius & covers the deep muscles of the neck like a strap.

Origin: from ligamentum nuchae & spines of C6 & 7 with the supraspinous ligaments.

Insertion: The muscle is directed upward & laterally & divided into two parts:

- Splenius capitis; inserted into the deep part of mastoid & the lateral 1/3 of the superior nuchal line.

- Splenius cervicis; inserted into the posterior tubercles of T.P of the upper 3 cervical vertebrae.

Nerve supply: posterior rami of C2-C6.

Action: pulls the head back & laterally in the direction of the active muscle. Both extend the neck.

Erector spinae:

• This group of muscles extend from the sacrum to the skull in the form of three longitudinal parallel columns & occupy the posterior compartment of lumbar fascia
• Some of them are inserted into various regions (lumbar & thoracic) & some muscles belong to the head & neck.
• Their nerve supply is segmental

Longissimus:

• Is the intermediate column of E.S
• Has three parts (thoracis, cervicis & capitis).
• Arise from T.P of lower vertebrae.
• Inserted into T.P. of higher vertebrae.
• Capitis muscle is inserted into the back of the mastoid process deep to splenius & SCM.

Semispinalis:

• Occupy the medial column of the E.S
• Its limited to the thoracic (thoracis), cervical (cervicis) & head (capitis)regions
• S. cervicis & thoracis arise from the T.P of all thoracic vertebrae

They are inserted into the spines of 4-6 vertebrae above. The highest fibers of cervicis muscle are inserted into the undersurface of the spine of axis

They extend the upper vertebral column & rotate it to the opposite side

• S. capitis arises from T.P of C7-T6

It is the largest muscle in the back of the neck,being inserted into the occipital bone between the 2 nuchal lines medially

It is the most powerful skull extensor

The suboccipital muscles :

Rectus capitis posterior major:

• Origin: spine of C2
• Insertion: the area between inferior nuchal line & foramen magnum, laterally

Rectus capitis posterior minor:

• Origin: posterior tubercle of C1
• Insertion: the area between inferior nuchal line & foramen magnum, medially

Superior oblique:

• Origin: T.P of C1
• Insertion: the area between the two nuchal lines, lateral to semispinalis capitis

Inferior oblique:

• Origin: spine of C2
• Insertion: T. P of C1

The suboccipital triangle :

Is the triangle embraced by the supoccipital muscles except rectus capitis posterior minor which lies medial to it.

Floor: the posterio atlanto-occipital membrane & posterior arch of atlas

Contents:

1- Vertebral artery; in the floor.

2- Suboccipital nerve, C1.

3- Greater occipital nerve, C2: hooks below the inferior oblique & ascends in the roof of the triangle.

4- Occipital artery: ascends medially in the roof of the triangle in its way to the scalp together with the greater occipital nerve.

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

THE HEAD

The scalp:

Is a five-layered structure covering the vault of skull & bears the hair of the head, its name is derived from its 5 layers which are:

• Skin
• Connective tissue (subcutaneous connective tissue)
• Aponeurosis ( galea aponeurotica of occipito-frontalis muscle)
• Loose areolar tissue (subaponeu. space
• Periosteum (pericraneum)

Skin:

• Thin, hairy with generous amount of sweat & sebaceous glands
• Firmly adherent to the next layer

Subcutaneous connective tissue:

• Thick layer made of connective tissue septa in all directions to form a dense network enclosing fatty loculi
• Hair follicles pierce this layer
• Arteries, veins & nerves of the scalp lie in this layer and are held in position by the firm fibrous network
• Adheres to the layer deep & superficial to it, so the three layers could not be separated from each other & move together when moving the scalp

Epicranial aponeurosis:

• A musculo-aponeurotic layer formed by the 4 bellies of occipito-frontalis muscle connected by their galea aponeurotica
• Occipito-frontalis:

• The muscle arises by two bellies from the highest nuchal lines posteriorly
• The 2 bellies are inserted into the back of the aponeurosis which is formed of sagittally running fibers. From the anterior end of the aponeurosis the two frontal bellies arise and go forward to be inserted into the skin of eyebrows & root of the nose
• The muscle is innervated by facial nerve (posterior auricular branch to occipitalis & temporal branch to frontalis)
• It acts to pull the scalp backward & elevate the eyebrows as in surprise expression.

Subaponeurotic space:

• Extensive space lies beneath the galea & contains loose areolar tissue
• Movements of the superficial three layers take place in this plane
• It is only limited by the attachment of the galea
• anteriorly it is continuous with the eyelids & eyebrows
• Fluid accumulation in this space tend to go to the dependent areas, i.e; over the occipital bone posteriorly & in the eyelids anteriorly (if blood causes black eye)

Pericraneum:

• Is the periosteum of skull bones
• Is firmly adherent to the sutures
• Bleeding deep to this layer takes the shape of underlying bone

Arteries of the scalp:

• Branches from the ECA & ICA supply the scalp and anastomose freely with each other & with those of the opposite side
• Arteries are held by the fibrous septa of the 2nd layer which pull them & prevent their contraction when severed.

Branches of ECA:

1- Occipital a.;

• From the back of ECA goes deep to the posterior belly of digastric then in the apex of the posterior triangle grooving the occipito-mastoid suture on the skull then in the roof of the suboccipital triangle where it accompanies the greater occipital nerve to reach the scalp
• It divides into medial & lateral terminal branches which supply the scalp up to the vertex.

2- Posterior auricular a.;

• From the back of the ECA just above the posterior belly of digastric
• It passes superficial to the styloid process to lie in the groove between the mastoid process & the external auditory meatus
• Its branches are:

- Stylomastoid: enters the stylomastoid foramen & supplies the tympanic cavity, antrum & mastoid cavities.

- Auricular: supplies the auricle, posterior part of temporal area.

- Occipital: supplies the skin over the mastoid process & occipitalis.

3- Superficial temporal a.;

• The smallest of the 2 terminal branches of ECA
• From behind the neck of mandible the artery grooves the root of the zygomatic arch with the auriculotemporal nerve
• Ascends in the temporal fossa to end 5 cm above the zygomatic arch by dividing into frontal & parietal branches. Its branches are:

- Transverse facial: from its anterior aspect this artery passes over masseter between the parotid duct & zygomatic arch supplying all structures in the region.

- Middle temporal: arises above the root of the zygomatic arch & perforates the temporal fascia & muscle to lie directly on the squamous temporal bone grooving it with its accompanying vein.

- Zygomatico-orbital, anterior auricular & terminal branches supply muscles & skin in their regions.

Branches of ICA:

1- Supra-orbital a.;

• from the ophthalmic artery this branch leaves the supra-orbital notch to supply the scalp up to the vertex
• It anastomose with the termination of facial artery (angular a.) & the frontal branch of superficial temporal artery.

2- Supra-trochlear a.;

- From the ophthalmic artery this branch leaves the supra-orbital notch with the nerve of its name to supply the middle of the forehead.

Veins of the scalp:

• Accompany the corresponding arteries
• Anastomose freely with their adjacent veins of the same side & of the opposite side.

1- Supratrochlear v.; unite at the medial canthus with the supra-orbital v. of its same side to form the angular v. which descends in the face as the facial vein.

2- Supra-orbital v.; is connected (before forming the angular v.) to the superior ophthalmic vein in the orbit which drains to the cavernous sinus.

3- Superficial temporal v.;

• Accompanies the artery & receives branches similar to those of the artery.
• Behind the neck of the mandible it receives the two maxillary veins to form the retromandibular v. which enters the parotid gland.

4- Posterior auricular v.; larger than the corresponding artery, it descends to meet the posterior division of retromandibular v. forming the EJV.

5- Occipital v.; accompanies the artery an ends in the deep cervical & vertebral venous plexus. Occasionally it ends in the IJV.

Nerves of the scalp:

Trigeminal nerve supplies the anterior part of the scalp up to the vertex by branches derived from its three divisions:

1- Ophthalmic division :

• Supratrochlear n.; supplies the middle of the forehead up to the hairline.
• Supra-orbital n.; supplies the lateral part of the forehead & meets its opposite fellow above the distribution of the supratrochlear n. to supply the scalp up to the vertex.

2- Maxillary division:

Zygomatico-temporal n.; supplies the non hairy part of the temple.

3- Mandibular division:

Auriculotemporal n.; from the infratemporal fossa this nerve accompanies the superficial temporal a. & crosses the root of the zygomatic arch to ascend in the temple. It supplies the upper half of the auricle externally, parotid gland & the hairy temple.

Posterior primary rami of C2 (greater occipital n.) and "to lesser amount" C3 supply the back of the scalp up to the vertex.

Lymph of the scalp:

• Anterior & lateral parts to the submandibular L.N
• Posterior part to the occipital L.N

Applied anatomy:

• Wounds of the scalp opens the 3 superficial layers therefore they have two main characteristics:

1- Open widely, due to the stretch effect of the aponeurosis.

2- Bleeds profusely, because the scalp is rich in blood vessels which lie in the second layer & this layer is stretches by the aponeurosis so the vessels tear more & hemostasis will be difficult.

• Because the scalp moves freely on the bone, the superficial injuries may not coincide with deep ones.
• Subaponeurotic hematoma will descend in the dependent areas leading to black eyes & posterior hematomas
• Subperiosteal hematomas take the shape of the underlying bone.
• Anastomosis between the ECA & ICA in the scalp is at a sagittal line which lies above the lateral end of the eyebrow, bleeding here is very profuse.

The face:

Muscles of Facial Expression:

• The face lacks deep fascia & its superficial fascia is modified into muscles whose one end is attached to bone "usually" & the other to the facial skin which they move producing various movements.
• The superficial muscles of the face are arranged around facial orifices (palpebral fissure, nostrils & oral fissure) as two groups around each orifice, dilator & constrictor.
• Man has trained himself to express & understand some facial movements produced by some of these muscles
• Many facial muscles produce no expression like buccinator, indeed a very meaningful expressions are produced by muscles not belonging to the face like genioglossus!!

I) Muscles of the palpebral fissure:

SPHINCTERS:

Orbicularis oculi:

• This muscle is formed of concentric fibers which are arranged circumferentially around the opening of the eyelid
• It is formed of three parts:

1- The orbital part:

• Arises from the medial orbital margin & the medial palpebral ligament
• Spreads onto the forehead & cheeks
• It is the most peripheral part of the muscle.

2- The palpebral part:

• Arises from the lateral end of the medial palpebral ligament
• Course in the subcutaneous connective tissue of the eyelids
• Interdigitate laterally forming the lateral palpebral raphe.

3- The lacrimal part:

• From the posterior part of the medial palperal lig. & psterior lacrimal crest
• These fine fibers are inserted into the lacrimal sac & tarsal plates

* The medial palpebral ligament:

• Is a strong band , 5 mm long
• Arises from the frontal process of the maxilla & extends laterally to divide into 2 slips each one is continuous with its corresponding tarsal plate

Nerve supply:

- Facial nerve supplies the muscle by its temporal & zygomatic branches

Action:

• Orbital part; depresses the eyebrows & protects from light as in looking from distance
• Palpebral part; closes the eyelids gently as in blinking
• Lacrimal part; squeezes the lacrimal sac
• ALL the parts; close the eyes forcibly as in protection from accidents

DILATORS:

Frontalis:

Discussed. It is the opponent of the orbital part of O. oculi.

Levator palpebrae superioris:

This muscle is the opponent of the palpebral part of O. oculi.

Origin; From the back of the orbit in front of the optic canal

Insertion;

• The muscle broadens as it traverses the uppermost part of the orbit forward to enter the upper eyelid
• It is inserted into the upper part of the orbital septum & O. oculi.

This muscle is formed of skeletal (voluntary component) & smooth muscle fibers (involuntary component), the latter is responsible for its unconscious prolonged & sustained contraction in opening the eyes for long time without fatigue.

Nerve supply:

• Skeletal part: superior division of oculomotor nerve
• Smooth muscle part: superior thoracic sympathetic ganglion (T1) whose injury in "Horner’s syndrome" is responsible for ptosis in this condition.

II) Muscles of the nose:

DILATORS:

Corrugator:

Origin; the superciliary arch

Insertion; medial half of the eyebrow skin

Action; pulls the eyebrows medially producing vertical wrinkles

Procerus:

Origin; lower part of nasal bone & alar cartilage

Insertion; skin between the eyebrows

Action; pulls the skin overlying the root of the nose downward

Alar part of nasalis:

Origin; canine eminence

Insertion; fibers ascend superomedially to meet its fellow on the nose

Action; depresses & dilate nostrils

SPHINCTERS:

Septal part of nasalis (depressor septi):

Origin; maxilla, near the anterior nasal spine

Insertion; lower part of the septum

Action; pulls the septum down & diminishes the openings of the nostrils

Nerve supply of nasal muscles:

Upper fibers: temporal branch of facial n.

Lower fibers: zygomatic & buccal branches of facial n.

III) Muscles of the oral fissure:

DILATORS:

Elevators of the upper lip:

Levator labii superioris alaeque nasi:

Origin; frontal process of maxilla

Insertion; partly in alar cartilage & partly in the lateral half of the upper lip

Action; elevates the angle of the mouth & dilates the nostril

Levator labii superioris:

Origin; inferior orbital margin above the infra-orbital foramen

Insertion; lateral half of the upper lip

Action; elevates the upper lip

Zygomaticus major:

Origin; zygomatic bone anterior to the zygomatico-temporal suture

Insertion; skin on the lateral side of the mouth & O. oris

Action; draws the mouth superolaterally

Zygomaticus minor:

Origin; lower part of zygomatic bone

Insertion; upper lip, medial to the mouth angle

Action; elevates the upper lip

Levator anguli oris:

Origin; from the canine fossa

Insertion; the muscle lies deep to LLS ends in the mouth angle

Action; elevates the angle of the mouth

Risorius:

Origin; parotid fascia

Insertion; skin of the angle of the mouth

The muscle is a contribution of many muscles& it is an important landmark for dentists.

Depressors of the lower lip:

Depressor labii inferioris:

Origin; mandible, medial to the mental foramen

Insertion; lateral side of the lower lip

Action; draws the lower lip downward & laterally

Depressor anguli oris:

Origin; oblique line of the mandible

Insertion; angle of the mouth

Action:depresses the mouth angle

Mentalis:

Origin; mandible, below the incisor teeth

Insertion; skin of the chin

Action; modifies the oral aperture indirectly by dimpling the skin of the chin.

SPHINCTERS:

Orbicularis oris:

Intrinsic part of O. oris (superficial part):

• Upper (maxillary) fibers from the alveolar process of the maxilla above the incisor teeth, these fibers go laterally & wind around the angle of the mouth to dip in the lower lip
• Lower (mandibular) fibers from the alveolar process of the mandible below the incisor teeth, these fibers go laterally to wind around the mouth angle & ascend in the upper lip

Extrinsic part of O. oris (deep part):

Formed by contributions from the dilators & buccinator

Action:

- Sphincter of the mouth

- Flattens the lip

- Protrudes the lip

Nerve supply of oral muscles:

- Above the mouth angle: zygomatic & buccal br. of VII

- Below the mouth angle: mandibular br. of VII

Buccinator:

This quadrilateral muscle lies in a deeper stratum than other muscles of the face & forms the main bulk of the cheeks.

Origin; from 3 lines forming & C-shape origin:

• Alveolar process of maxilla in a line which overlies the upper molar teeth (upper fibers)
• Alveolar process of the mandible in a line which lies parallel to the lower molar teeth (lower fibers)
• Pterygomandibular raphe which extends from the pterygoid hamulus to the deep surface of the mandibular angle (middle fibers) sharing this origin with the superior pharyngeal constrictor muscle

Insertion; the most peripheral fibers of buccinator (upper & lower) pass directly into the corresponding lip, while the middle fibers interlace at the angle of the mouth, the upper go to the lower lip & the lower to the upper lip.

Nerve supply; buccal branch of facial nerve

Action; compresses the cheek & increases the intra-oral pressure, its paralysis tend to accumulate food in the vestibule of the mouth.

• It is pierced by the parotid duct to which it gives a sphincter-like action
• The buccal branch of mandibular nerve is sensory to the muscle & ends in the skin overlying it

All facial muscles are supplied by proprioception from the sensory nerves supplying the overlying skin

Arteries of the face:

Arteries of the face lie in the subcutaneous tissue . The main artery of the face is the facial artery, other arteries which share in the supply of the face are:

1- Transverse facial artery.

2- Infraorbital artery.

3- Mental artery.

4- Buccal artery.

1- Facial artery:

• An anterior branch of the ECA leaving it deep to the posterior belly of digastric muscle & passes in the submandibular triangle to reach the lower border of the mandible where it curves up to the face.
• In the face the artery is superficial at its beginning being covered only by skin & platysma.
• The artery ascends in a very tortuous course towards the medial angle of the eye, its relation to the face muscles is variable but usually it is superficial to buccinator & levator anguli oris & deep to the zygomatic muscles.
• The facial vein lies lateral to the artery & its course is less tortuous.

Branches of the facial artery:

I ) In the neck (do not reach the face):

a- Ascending palatine a.

b- Tonsillar a.

c- Muscular branches

d- Glandular branches to the submandibular gland

e- Submental a.

II ) In the face:

a- Inferior labial a.

b- Superior labial a.

c- Lateral nasal a.

d- Angular a.

- The labial branches:

• Arise opposite to the angle of the mouth & enter the corresponding lips between O. oris & the mucous membrane
• Supply muscles, glands & mucous membranes of the lips
• Anastomose with labial branches of the opposite side

- Lateral nasal branch:

Arises alongside the nose

Supplies the ala & dorsum of the nose

Anastomose with the opposite artery, infraorbital a.

- Angular artery:

The terminal part of facial artery lies at the medial canthus

Supplies O. oculi & the lacrimal sac

Anastomoses with the infraorbital a.

2- Transverse facial artery. "discussed"

3- Infraorbital artery:

• One of the terminal branches of maxillary artery
• Leaves the infraorbital foramen & lies deep to lavator labii superioris
• Gives palpebral, nasal & labial branches

4- Mental artery:

• Is the terminal branch of the inferior alveolar artey
• Appears in the face from the mental foramen deep to depressor anguli oris
• Supplies the chin

5- Buccal artery:

• A branch of maxillary artery
• Accompanies its vein & the buccal branch of mandibular nerve to reach the area of buccinator
• Supplies buccinator & skin & m.m. of the cheek

Veins of the face:

1- Anterior facial vein:

• Begins at the medial canthus as the angular vein by confluence of supraorbital & supratrochlear veins
• Connected to the superior ophthalmic vein which joins it to the cavernous sinus
• Descends on the lateral side of the artery receiving corresponding tributaries
• Contains no valves so blood can go up to the cavernous sinus or down to the IJV
• At the angle of the mouth near buccinator, the anterior facial v. is connected to the pterygoid plexus (which is connected to the cavernous sinus) by the deep facial v.
• Dangerous zone: between the angular & the deep facial veins where facial venous blood can easily drains to the cavernous sinus transmitting infections resulting in sinus thrombosis
• In the submandibular triangle the vein lies superficial to the gland just deep to the roof of the triangle & receives veins from the gland
• It meets the anterior division of retromandibular v. forming the common facial v. which drains to the IJV

2- Transverse facial vein.

3- Infraorbital vein.

4- Mental vein.

5- Buccal vein.

Nerves of the face:

MOTOR:

Facial nerve:

• After leaving the stylomastoid foramen it gives muscular branches to occipitalis & to the posterior belly of digastric &stylohyoid
• In its way to the face this nerve enters the posterior surface of the parotid gland medially then passes very superficial in the gland dividing into:
• Temporofacial branch; the upper division which gives the temporal & zygomatic branches.
• Cervicofacial branch; the lower one which gives the buccal, mandibular & cervical branches
• Temporal br supplies muscles above the palpebral fissure
• Zygomatic br supplies muscles between the palpebral & oral fissures
• Buccal br is for buccinator
• Marginal mandibular br. supplies muscles of the lower lip
• Cervical br. is for platysma

SENSORY:

1 ) Trigeminal nerve:

Terminal branches of the three divisions of trigeminal nerve supply the face as follows:

I: Ophthalmic division:

Supraorbital n.: forehead up to the vertex

Supratrochlear n.: middle part of forehead up to hairline

Infratrochlear n.: medial ½ of the upper lid & bridge of the nose

Lacrimal n.: lateral ½ of the upper lid

External nasal n.: middle of external nose down to the tip

II: Maxillary division:

Zygomaticofacial n.: prominence of the cheek

Infraorbital n.:

Palpebral br.: lower lid

Nasal br.: lateral side of the external nose

Labial br.: upper lip

III: Mandibular division:

Buccal n.: skin over buccinator

Mental n.: chin & lower lip

2 ) Great auricular nerve:

Supplies skin over the angle of the mandible.

Applied anatomy of the face:

1- Cavernous sinus thrombosis could follow face infections especially with force manipulations, with the resultant ophthalmoplegia & high mortality rate.

2- Three branches of facial nerve could be easily injured in the face, the temporal & zygomatic as they pass over the z. arch could be injured in fractures of the arch producing dry eye & partial ptosis, the 3rd is the marginal nerve at the lower border of the mandible could be injured in abscess drainage producing drop lip.

3- Complete facial palsy is of two types:

1. Upper motor neuron; especially evident in the upper muscles
2. Lower motor neuron; clear paralysis seen affecting all ipsilateral facial muscles with its characteristic appearance.

The temporal fossa:

• Lies at the side of the head, being bounded by the temporal lines above, anteriorly & posteriorly and by the infratemporal crest of the sphenoid below.
• The floor of the fossa is formed by frontal, parietal, squamous temporal bones & greater wing of sphenoid.

Temporal fascia:

A strong membrane that arises from the area between the superior & inferior temporal lines and descends down covering temporalis muscle to be attaches to the upper border of the zygomatic arch & posterior border of the zygomatic bone.

Temporalis:

Origin; floor of the temporal fossa & temporal fascia.

Insertion; Fibers of this fan-shape muscle converge from this wide origin into a tringular tendon which slides in the gutter between the posterior root of the z. arch & the squamous temporal bone to be inserted in the coronoid process of the mandible

Nerve supply; anterior & posterior deep temporal branches from the anterior division of Vc.

Action;

• Anterior fibers (vertical): close the mouth
• Posterior fibers (horizontal): retract the mandible

Vessels of the fossa:

Superficial temporal vessels, discussed.

Sensory nerves of the fossa:

1- Zygomaticotemporal n. (branch of Vb): non-hairy part

2- Auriculotemporal n. (branch of Vc): hairy part

The fossa communicates inferiorly through the infratemporal crest with the infratemporal fossa.

The preauricular region:

Masseter:

• A thick quadrangular muscle that lies on the lateral side of the angle of the mandible partly covered by the anterior portion of the parotid gland & crossed by its duct
• It is one of the 4 muscles of mastication

Origin:

• The superficial part: anterior 2/3 of the zygomatic arch
• The deep part: posterior 1/3 & medial surface of the arch

Insertion: On the lateral aspect of the angle of the mandible

Nerve supply: Masseteric nerve, a branch of anterior division of Vc enters the deep surface of the muscle after passing through the mandibular notch from the ITF

Action: Closes the mouth.

The salivary glands:

-This is a group of glands that function as an initial digestion apparatus.

-They lubricate the mouth & partially digest some sorts of food.

-The main glands are three, parotid, submandibular & sublingual, though the mucous membranes of the oral cavity contains a lot of minute glands.

-Their secretion is a mixture of mucous & serous fluid called the saliva.

The parotid gland:

Is the largest of the salivary glands, almost totally serous in secretion.

Shape:

The gland is a pyramid with an irregular triangular base directed laterally

Position:

*The pyramid is wedged in the slit between the external auditory meatus posteriorly & the mandible anteriorly.

*The base of the pyramid lies laterally in the preauricular region, & the three borders are:

• Superior: along the zygomatic arch
• Posterior: anterior to the EOM & mastoid process
• Anterior: actually it is antero-inferior overlies the posterior part of masseter.

*The apex of the pyramid lies deep in the slit reaching the carotid sheath.

Relations:

* Superiorly: The zygomatic arch & the skull base above

* Posteriorly:

• Mastoid process sandwiched by the sternomastoid muscle & the posterior belly of digastric
• The EOM, styloid process & stylohyoid are also posterior relations.

* Antero-inferiorly: The angle of the mandible sandwiched between masseter & medial pterygoid muscles

* Laterally: The fatty tissue of the side of the face

* Medially: The carotid sheath & lateral pharyngeal space

The parotid duct:

• The duct leaves the anterior border of the gland 1 cm below the zygomatic arch.
• It courses over masseter in a horizontal line that could be marked on the surface as the middle 1/3 of a line passing from the intertragic notch to the point midway between the red margin of the lip & the lower border of the nose.
• At the anterior border of masseter, the duct dips medially piercing the buccal pad of fat & buccinator opposite to the last molar tooth.
• After a short course in buccinator (which acts as a valve), the duct opens in the vestibule of the mouth opposite to the upper second molar tooth.

The parotid isthmus:

• Is the thinnest portion of the gland that lies between the mandible & the mastoid process
• The part of the gland superficial to the isthmus is called (wrongly!) the superficial lobe & the part deep to it called the deep lobe.
• Actually, VII is the structure which separates the gland into its two lobes

The accessory parotid gland:

From the duct over masseter sometimes a piece of parotid tissue lies & may extend high up to the temporal fossa. This is the accessory parotid g. or sometimes named (glenoid lobe).

The parotid fascia:

Is derived from the investing cervical fascia which splits to enclose the gland.

The superficial layer of the fascia will be attached above to the zygomatic arch & after it crosses the gland it fuses with masseteric fascia.

The deep layer is attached above to the lower border of the tympanic plate & reaches medially the carotid sheath with which it fuses.

A thickening in the deep layer stretches between the styloid process & the angle of the mandible called the stylomandibular ligament which separates the gland from the submandibular gland.

The fascia is supplied by the great auricular nerve.

Contents of the gland:

Many important structures lie within or very near to the parotid gland, structures which lie within the substance of the gland are; from superficial to deep:

1-The facial nerve:

• After leaving the stylomastoid foramen in its way to the face this nerve enters the posterior surface of the gland medially then passes very superficial in its substance where it gives its terminal branches from the anterior border of the gland to the face.
• The facial branches are almost horizontal at their beginning and could be injured in parotid incisions.

2-The retromandibular vein:

• The two maxillary veins leave the ITF & go forward medial to the neck of the mandible to enter the parotid deep to the facial nerve
• After receiving the superficial temporal vein, the retromandibular vein is formed within the gland.
• It drains the parotid & divides into:

1. Anterior division: receives the anterior facial vein to form the common facial vein in the submandibular triangle.
2. Posterior division: receives the posterior auricular vein to form the EJV behind the angle of the mandible.

3-The external carotid artery:

• Enters the gland from below & ascends in it deep to the above two structures
• When reaches the neck of the mandible the ECA divides into its two terminal divisions which leave the gland from its anterior & superior borders.

4- The preauricular (parotid) lymph nodes:

1. Superficial nodes: between the gland & its fascia.
2. Deep nodes: embedded within the gland.

5- The auriculo-temporal nerve:

In its way from the ITF to the temporal fossa, it passes through the upper part of the gland to accompany the superficial temporal artery & go to the scalp.

Blood supply:

• Superficial temporal a.
• Posterior auricular a.

Venous drainage:

Retromandibular vein.

Lymphatic drainage:

The parotid lymph nodes.

Nerve supply:

1- Sensory & secretomotor: Lesser petrosal fibers from the otic ganglion via the auriculotemporal nerve.

2- Parotid fascia is supplied by the great auricular nerve.

Applied anatomy:

• Malignant tumors of the parotid sometimes involve the facial nerve forming lower motor facial palsy.
• Incisions in the substance of the gland should be horizontal along the facial nerve branches because they are superficial to the vessels of the gland & paralysis could occur by cutting the facial nerve before a serious bleeding is encountered.
• Inflammation of the parotid as in mumps usually obliterate the angle between the lobule of the auricle & the angle of the mandible.

　

　

The submandibular gland:

Shape & position:

- This mixed gland occupies most of the submandibular triangle

- It rests on the investing fascia while the latter is stretched between the mandible & the hyoid bone

- It leaves a smooth impression on the inside of the mandible below the mylohyoid line

- The gland goes posteriorly to reach the angle of the mandible near the parotid gland, here it turns up around the free posterior border of mylohyoid (which overlies it) & the remaining part of it will lie above this muscle in the floor of the mouth

- The part of the in the neck is called "superficial lobe" while the part in the floor of the mouth is called "deep lobe"

Relations:

- Anterolateral: mandible

- Below: investing fascia

- Above: mylohyoid

- Behind: parotid, digastric "post. belly" & stylohyoid

- Medial: digastric "ant. belly" & hyoid bone

Structures in close relation to the gland:

1- Facial artery: lies between the gland & mylohyoid then between it & the mandible where it enters the face.

2- Common facial vein: is formed in the triangle superficial to the gland.

3- Submandibular lymph nodes: in and around the gland.

The submandibular fascia:

• Like the parotid, this gland derives its fascia from the investing layer of deep cervical fascia on which the gland rests.
• The investing fascia encloses the gland by a superficial layer superficial to it & a deep layer between it & myelohyoid.
• Infection of the submandibular space causes Ludwig’s angina with increased pressure in the space pushing the tongue out of the mouth

The submandibular duct:

• A 5 cm duct leaves the anterior portion of the tongue-like deep lobe to pass in the floor of the mouth between mylohyoid & hyoglossus.
• On the lateral surface of hyoglossus the duct lies together with the lingual & hypoglossal nerves being crossed by the former twice.
• The duct then lies more anteriorly on the lateral surface of genioglossus & extends forward to open in the sublingual papilla on each side of the frenulum linguae.

Blood supply:

Facial artery.

Venous drainage:

Common facial vein.

Lymphatic drainage:

The submandibular lymph nodes.

Nerve supply:

1- Sensory & secretomotor (parasympathetic): chorda tympani fibers from the submandibular ganglion via the lingual nerve.

2- Submandibular fascia is supplied by the anterior cutaneous nerve of the neck.

The sublingual gland:

• The smallest of the three main salivary glands, almost totally mucous in secretion.
• An almond sized gland lies in the floor of the mouth being covered only with the mucous membrane of the floor of the mouth.
• It is bounded medially by the two genial muscles & laterally by the mandible on which it leaves a smaller impression than the submandibular one above the mylohyoid line.
• The gland opens by numerous duct onto the sublingual papilla & in the floor of the mouth.
• The gland has no fascia.
• It is supplied by the sublingual branch of the lingual artery & the submental branch of the facial artery.
• Veins are similar to arteries.
• Nerve supply is identical to the submandibular gland.

The infratemporal fossa:

• This is the space which lies between the pharynx medially & the angle of the mandible laterally.
• Boundaries:

-Anteriorly: the back of maxilla & pterygoid process

-Posteriorly: the styloid apparatus laterally & the carotid sheath medially

-Laterally: the ramus & angle of the mandible

-Medially: the wall of the pharynx & medial pterygoid plate

-Superiorly: the floor of the middle cranial fossa formed by the greater wing of sphenoid & squamous temporal, the roof ends laterally in the infratemporal crest which leads to the temporal fossa

-Inferiorly: the ITF is continuous with the neck at the retropharyngeal space which leads down through the superior into the posterior mediastinum.

Contents:

• Muscles:

1- Lateral pterygoid

2-Medial pterygoid

• Arteries:

Maxillary artery.

• Veins:

Pterygoid venous plexus.

• Nerves:

1- Mandibular nerve.

2- Otic ganglion.

The lateral pterygoid muscle:

• This muscle occupies the upper part of the ITF
• Its fibers are directed almost horizontally from the front backwards

Origin:

Upper head "small": infratemporal surface of the greater wing of sphenoid

Lower head "large": lateral surface of the lateral pterygoid plate

Insertion:

Upper head: Disc & capsule of TMJ

Lower head: Pterygoid pit

Nerve supply:

Nerve to lateral pterygoid, a branch of the anterior division of mandibular n.

Action:

• It is a masticatory muscle, it starts opening the mouth
• Lateral pterygoid is a protractor of the mandible too.

The upper head pulls the articular disc & anterior part of the capsule anteriorly preventing its nipping by the bone.

The medial pterygoid muscle:

• This muscle is seen at a lower level in the fossa
• Fibers are arranged in a posterior, inferior & lateral direction.

Origin:

Superficial head "small": maxillary tuberosity

Deep head "large": medial surface of lateral pterygoid plate

Insertion:

The two heads are inserted on the deep surface of the angle of the mandible almost almost alike the insertion of masseter on the lateral surface

Nerve supply:

Nerve to medial pterygoid, a direct branch from the main trunk of the mandibular nerve. This nerve has two main characteristics:

1-It enters the otic ganglion without relay of its fibers in it.

2-It supplies tensor palati & tensor tympani muscles too.

Action:

- Closes the mouth together with masseter.

- It is a grinding muscle, by the lateral orientation of its fibers the muscle pulls the mandible towards the opposite side

The maxillary artery:

• The larger of the two terminal branches of the ECA
• Enters the ITF by passing deep to the mandibular neck, between it & the sphenomandibular ligament, together with the maxillary veins & the auriculotemporal nerve
• It possesses a tortuous course passing usually (in 2/3 of individuals) lateral to lat. pterygoid according to which the artery is divided into three parts:

1- First "mandibular" part: before reaching the lateral pterygoid, it gives 5 branches each enters a bone.

2- Second "pterygoid" part: lies along (medial or lateral) to the lateral pterygoid, it gives 5 branches to soft tissue, 4 of them to the masticatory muscles & the 5th is the buccal.

3-Third "pterygopalatine" part: which enters the pterygopalatine fossa through the pterygomaxillary fissure & gives 5 branches that accompany those of the pterygopalatine ganglion & each branch of maxillary nerve.

Branches of the first part:

1- Deep auricular artery:

• Penetrates the external auditory meatus
• Gives a branch to the TM joint
• Supplies the skin of the meatus & outer surface of the tympanic membrane.

2- Anterior tympanic artery:

- Ascends parallel to the deep auricular artery

- Enters the tympanic cavity through petrotympanic fissure together with chorda tympani

- Supplies the tympanic cavity & the inner surface of the tympanic membrane

3- Middle meningeal artery:

- Is the prime artery of the cranial dura

- Ascends upward enclosed by the two roots of the auriculotemporal nerve, to enter the MCF through foramen spinosum

- At the floor of the MCF it lies between the greater wing of sphenoid & dura mater

- After a short course it divides into anterior & posterior divisions:

1-anterior; continues grooving the sphenoid then it reaches the parietal bone which it grooves near its anterior border as the artery ascends to the vertex.

2-posterior; goes back to groove the squamous temporal & ascends to the parietal bone near its posterior border, then along the superior sagittal sinus to reach the occipital bone.

4- Accessory meningeal artery:

• Frequently a branch of the middle meningeal
• Supplies some extracranial structures
• Enters foramen ovale to supply the trigeminal ganglion & adjacent dura mater

5- Inferior alveolar (dental) artery:

• Descends to the mandibular foramen behind the accompanying nerve
• Before it enters the foramen, the artery gives two branches:

1-lingual; with the lingual nerve

2-mylohoid; with mylohyoid nerve, piercing the sphenomandibular ligament & supplies the muscle

• In the bone, the artery supplies the teeth in a manner similar to nerve supply
• Terminates near the mental foramen by dividing into incisive & mental arteries

Branches from the second part:

1- Masseteric artery:

• Enters the mandibular notch
• Supplies masseter & anastomoses with the transverse facial artery

2- Anterior & posterior deep temporal arteries:

• Accompany the corresponding nerves to temporalis
• The accompanying veins impress the bone in the temporal fossa

3 & 4- Pterygoid branches:

- Supply the two pterygoids

5- Buccal artery:

• Accompanies the long buccal nerve
• Goes to the region of buccinator
• Supplies skin of the cheek & mucous membranes of the mouth

Branches from the third part:

A) Branches which accompany those of the pterygopaltine ganglion:

1-Posterior superior lateral nasal arteries.

2- Greater palatine artery.

3- Lesser palatine arteries.

4- Nasopalatine (anterior palatine) artery.

5- Pharyngeal artery.

B) Branches accompanying the maxillary nerve branches:

1- Posterior superior alveolar artery.

2- Infraorbital artery.

3- Anterior superior alveolar artery.

Pterygoid venous plexus:

• A plexus of veins which lie in & around the lateral pterygoid muscle
• It receives tributaries corresponding to those of the maxillary artery branches
• It is drained by two maxillary veins which leave the fossa deep to the neck of the mandible to the parotid in order to join the superficial temporal vein forming the retromandibular vein.

Applied anatomy:

*Stagnation of venous blood in the plexus initiates reflex contraction of lateral pterygoid muscle producing yawning.

*The plexus is connected to:

1-Anterior facial vein by two ways:

Via the infraorbital v. – supraorbital - angular

Via the deep facial v. which lies between masseter & buccinator.

2- Cavernous sinus by two ways:

1. Via the infraorbital – supraorbital - cavernous
2. Via an emissary vein which enters foramen ovale

These two connections of the anterior facial vein to the cavernous sinus facilitates transmission of infection from the face to the sinus therefore the area between these two connections (mask area) is regarded as dangerous area.

The Mandibular nerve:

*The largest of the 3 divisions of the trigeminal nerve

*It takes all the motor component of V nerve

*Enters the ITF from its roof through foramen ovale

*It lies very deep in the fossa near the medial wall (pharyngeal wall) on the lateral surface of tensor veli palatini

*It is closely related in this position to the otic ganglion

*It is divided into anterior & posterior divisions, the anterior is the smaller & is almost totally motor & the posterior is the larger & is almost completely sensory

　

*Branches:

A)From the trunk: - Meningeal n.

- Nerve to medial pterygoid

B)From the anterior division: - Masseteric n.

- Deep temporal nn. "MOTOR"

- Pterygoid n.

- Long buccal n. "SENSORY"

C)From the posterior division: - Auriculotemporal n.

- Lingual n. "SENSORY"

- Inferior alveolar n. "MIXED"

From the trunk:

1-Meningeal nerve:

• This branch is given just below the skull base
• Re-enters the cranium through foramen spinosum to supply dura mater in the floor of the MCF

2-Nerve to medial pterygoid:

• From the trunk of Vc, this nerve is given to medial pterygoid muscle
• It passes through the otic ganglion without functional relation to it
• It supplies also tensor veli palatini by a branch which enters it near its origin and tensor tympani by a branch which enters the cartilage of the auditory tube.

From the anterior division:

1-Masseteric nerve:

• This branch is given from the anterior division of Vc.
• Passes through the mandibular notch to enter the deep surface of masseter

2-Deep temporal nerves:

• 2-3 nerves arise from the anterior division of Vc
• After passing in the roof of ITF they enter the temporal fossa by passing over the infratemporal crest
• On the deep surface of temporalis, these nerves pass & supply the muscle

3-Lateral pterygoid nerve:

• This branch is given from the anterior division of Vc.
• Supplies lateral pterygoid muscle by entering its deep surface

4-Long buccal nerve:

• Is the only sensory branch in the anterior division
• Following temporalis tendon, the nerve passes in the direction of buccinator muscle accompanied by a branch from the maxillary artery
• Over buccinator it divides to supply the overlying skin of the cheek & undelying mucous membranes
• Should be differentiated from the buccal branch of facial nerve which comes from a more superficial plane but forms a plexus with this nerve over buccinator

From the posterior division:

1- Auriculotemporal nerve:

- Arises by two roots embracing the origin of the middle meningeal a.

-Passes deep to LPt. muscle in a posterior direction to leave the ITF between the neck of the mandible & sphenomandibular lig. with the maxillary vessels

-It passes in the upper part of the parotid gland

-It is accompanied by postganglionic fibers from the otic ganglion to supply the parotid gland with secretomotor supply, the preganglionic fibers are brought to the ganglion via the lesser petrosal branch of the IX nerve from the inferior salivatory nucleus.

-Branches:

1-Glandular; sensory fibers to the parotid

2-Auricular; to the external acoustic meatus & upper lateral ½ of the auricle

3-Articular; to the TM joint

4-Temporal; to the hairy part of the temple.

2- Lingual nerve:

-Passes on the lateral side of MPt. muscle anterior to the inferior alveolar nerve.

-Grooves the medial aspect of the mandible at the mandibular attachment of the pterygomanibular raphe just behind mylohyoid

-Passes forward on the lateral surface of hyoglossus in a curve which descends & then ascends across the submandibular duct

-In this region it hangs the submandibular ganglion from which it takes postganglionic secretomotor fibers to the submandibular & sublingual glands. The preganglionic of these came together with taste fibers by chorda tympani nerve which has joined the lingual nerve high in the ITF near the skull base.

-It supplies:

1-Ordinary sensation to the anterior 2/3 of the tongue, floor of the mouth & lingual aspect of the lower gingiva.

2-Secretomotor to submandibular & sublingual glands & minute glands of the floor of the mouth "chorda tympani".

3-Taste sensation to the anterior 2/3 of the tongue "chorda tympani".

3-Inferior alveolar nerve:

-Passes on the lateral side of MPt. muscle between it & the mandible behind the lingual nerve.

-It takes the whole remaining part of the motor component of the V nerve.

-Enters the mandibular foramen & passes in the inferior alveolar canal accompanied by the inferior alveolar vessels.

-Branches:

1-Nerve to mylohyoid; carries all the motor component of the posterior division, given just before the nerve enters the mandibular foramen, pierces the sphenomandibular ligament & passes forward between the anterior belly of digastric & mylohyoid supplying both.

2-Inferior dental branches; to the pulps of the lower canine, premolars & molars.

3-Terminal branches; at the mental foramen the nerve divides into:

a)Incisive branch; for the lower incisors.

b)Mental branch; exits from the mental foramen & supplies skin & m.m of the lower lip.

Structures related to the ITF:

1-Pterygomandibular raphe:

-Intermuscular raphe extending from the pterygoid hamulus to the mandible.

-It is the site where buccinator & superior constrictor muscles interdigitate, buccinator goes forward & superior constrictor backward.

2-Pterygomaxillary ligament:

-A short ligament extending between the pterygoid hamulus & the maxillary tuberosity

-It will form an osseo-ligamentous canal for the passage of the tendon of tensor palati muscle

3-Sphenomandibular ligament:

-A wide ligament lies superficial to medial pterygoid between it & the mandible, it extends between the spine of sphenoid & the lower border of the mandible near the angle

-It embraces the maxillary vessels & auriculotemporal nerve between it & the neck of the mandible

-It is pierced by nerve to mylohyoid & mylohoid artery

　

The orbit:

The bony orbit:

• The orbit is a four-sided pyramidal shape space whose base lies anterior & its apex posterior
• The base is almost 3.5 X 4 cm & the depth is about 5 cm
• Medial walls are parallel to each other with a 2 cm distance separating them
• Lateral walls diverge laterally at 45O from medial walls thus the lateral walls are 90O at each other
• Orbital axis lies along the center of the orbit & both will also be perpendicular on each other

Orbital margins:

The margins of the orbit are strong bones, they are even stronger than its four walls

• Superior: supraorbital arch of the frontal bone
• Lateral: frontal process of zygomatic bone & zygomatic process of frontal bone
• Inferior: zygomatic bone & maxilla
• Medial: frontal process of maxilla & maxillary process of frontal bone

Roof:

-Formed by orbital process of the frontal bone completed posteriorly by the lesser wing of sphenoid

-It is concave especially laterally where the lacrimal fossa which accomodates the lacrimal gland lies

Floor:

-Formed by the the orbital surface of the maxilla supplemented laterally by the zygomatic

-It slopes upward in the direction of the medial wall

-It contains the infraorbital groove which connects the inferior orbital fissure to the infraorbital canal

Lateral wall:

-Formed by the zygomatic bone in front & greater wing of sphenoid behind

Medial wall:

-Formed from in front backwards by: frontal process of maxilla, lacrimal bone, orbital lamina of ethmoid & near the apex by the body of sphenoid

-It is very thin & lies almost vertical

-It separates the orbit from the ethmoidal & spheboidal air cells

-It shows the site of the lacrimal sac which is bounded by anterior & posterior lacrimal crests

-It contains anterior & posterior ethmoidal foramina at its junction with the roof

Relations:

The orbit is bounded :

• Above: anterior cranial fossa & frequently the frontal air sinus
• Medially: sphenoidal & ethmoidal air cells
• Inferiorly: maxillay air sinus
• Laterally: temporal fossa

Anatomy of the eyelids:

The eyelid is composed of five layers:

1-Skin:

-very thin & moist

2-Subcutaneous tissue:

-lax, scanty & rarely contains any fat

-contains the roots of the eyelashes with the accompanying sebaceous glands "of Zeis" & modified sweat glands "of Moll".

-contains vessels & nerves of the lid

3-Muscular layer :

-consists of the palpebral & lacrimal parts of O. oculi

-palpebral part "discussed"

-lacrimal part connects the lacrimal sac & posterior lacrimal crest to the tarsus

-its posteromedial direction of contraction provides better contact between the eyeball & eyelid & consequently better distribution of tear film, also it dilates the lacrimal sac

4-Tarso-fascial layer:

-is the skeleton of the eyelid

-formed of two layers, the tarsal plate "tarsus" & orbital septum:

*Tarsal plate:

-tough fibrous layer extends between the medial & lateral palpebral ligaments

-2.5 X 1 cm in dimensions

-semilunar in shape with the straight edge at the lid margin

*Orbital septum:

-thin membrane which is continuous with the periosteum of the superior & inferior orbital margins

-the superior one is perforated by the levator palpebrae superioris

-away from this muscle, the tarso-fascial layer forms a complete septum between the superficial compartment of the eyelid which is continuous with the face & deep compartment which is continuous with the orbit

Tarsal glands:

Are modified sebaceous glands on the deep surface of the tarsus secrete an oily layer to prevent tear overflow at the lid margins

5- Conjunctiva:

-the transparent membrane which lines the lids (palpebral c.) & onto the eyeball (bulbar c.)

-the site of reflection is called the fornix, so we have superior & inferior fornices

-palpebral c. differs from the bulbar in being thicker, opaque & more vascular

-modifications in the conjunctiva:

1-lacrimal lake: a shallow bay on the medial angle of the eye bounded laterally by the semilunar fold, it acts as reservoir for lacrimal fluid.

2-semilunar fold: a rudimentary fold in the conjunctiva

3-lacrimal caruncle: a rounded elevation in the lacrimal lake formed of moist skin with fine hairs, sebaceous & sweat glands.

Contents of the orbit:

1-Eyeball.

2-Muscles: - LPS

- four recti

- two oblique

3-Nerves: - motor (III, IV & VI)

- sensory (Va)

4-Vessels: - ophthalmic artery

- ophthalmic veins

5-Fascial modifications: - periorbita

- muscular fasciae

- check & suspensory ligaments

- retrobulbar fat

6-Lacrimal apparatus: - lacrimal gland

- lacrimal sac

- nasolacrimal canal

Muscles o the orbit:

The recti are 4 in number:

• Superior rectus
• Medial rectus
• Inferior rectus
• Lateral rectus

Origin:

All the 4 recti arise from a tendinous ring surrounding the medial end of the SOF

Insertion:

The muscles, narrow at their origin broaden as they come forward to be inserted into the sclera anterior to the coronal equator forming a muscular cone around the eyeball

3- Oblique muscles:

a) Superior oblique:

Origin: from the bone just above the optic canal

Insertion:

• the muscle passes forward in the junction between the roof & medial wall of the orbit to reach the anterior part of the orbit as a thin tendon which hooks around the trochlea "pulley" which is attached in the roof of the orbit above the lacrimal crest.
• From this pulley the tendon returns postero-laterally to be inserted into the sclera deep to SR tendon behind the equator of the globe

b) Inferior oblique:

Origin: from the orbital surface of the maxilla lateral to the lacrimal groove

Insertion: the muscle is located below the eyeball, passes postero-laterally below IR to be inserted in the sclera beneath LR

* The recti will move the globe:

- SR superiorly + nasally (elevation + adduction)

- IR inferiorly + nasally (depression + adduction)

- MR nasally (adduction)

- LR temporally (abduction)

* The oblique muscles move the globe:

- SO inferiorly + temporally (depression + abduction)

- IO superiorly + temporally (elevation + abduction)

Nerve supply of ocular muscles:

LR 6 SO 4 Others 3

Motor nerves of the orbit:

1- Oculomotor n.:

-enters the orbit through the SOF as superior & inferior branches

-the superior branch crosses over the optic n. under SR supplying it & passes medial to it to terminate in the undersurface of LPS

-the inferior branch crosses below the optic n. to supply

GSE to MR, IR, & IO

GVE to sphincter pupillae & ciliary muscle "parasympathetic" with a relay in the ciliary ganglion, this component reaches the globe via branch to IO

2- Trochlear n.:

-the smallest of all cranial nerves, enters the orbit through the SOF being the highest of all nerves entering the orbit

-lies in the roof of the orbit medial to the frontal n.

-supplies SO at its posterior 1/3

3- Abducent n.:

-enters the orbit through the SOF inferior to all nerves

-enters the ocular surface of LR supplying it

N.B:

The above three motor nerves have a communication with Va in the cavernous sinus which make them able to carry the proprioceptive sensation from the muscles they supply.

Sensory nerves of the orbit:

-the ophthalmic division of trigeminal nerve "Va" is the smallest of the three divisions of V nerve, it is entirely sensory

-from the semilunar ganglion, Va leaves forward in the lateral wall of the cavernous sinus together with motor nerves of the orbit with which it forms some communication

-it divides into its three terminal division short of the way to the SOF after it gives the tentorial branch to the tentorial dura

-the three divisions of Va, namely the lacrimal, frontal & nasociliary nerves enter the orbit through the SOF to supply its contents

-in addition to the orbit & its contents, Va supplies:

*some skin of the face & scalp

*some mucous membranes of the nasal cavity & paranasal sinuses

-ALL STRUCTURES WHICH ENTER THROUGH THE S.O.F DO WITHIN THE CONE OF MUSCLES "THROUGH THE TENDINOUS RING" EXCEPT {LACRIMAL N., FRONTAL N., TROCHLEAR N. & THE OPHTHALMIC VEINS}

1-Lacrimal nerve:

-the smallest of Va branches, passes over the LR muscle

-half its way in the orbit it receives contribution from the zygomaticotemporal branch of Vb supplying it with parasympathetic component from the pterygopalatine ganglion to the lacrimal gland

-it supplies the gland with sensory & parasympathetic supply, together with the lateral ½ of the upper lid & its conjunctiva

2-Frontal nerve:

-the largest of Va branches, passes between LPS & the roof of the orbit

-in the middle of the orbit it divides into its terminal branches:

*the supraorbital n.; leaves the supraorbital notch (or foramen), supplies the lateral part of the skin of the forehead & the anterior ½ of the scalp up to the vertex

*the supratrochlear n.; lies medial to the former, it leaves the orbit above the trochlea of SO to supply skin of the middle of the forehead below the hairline

3-Nasociliary nerve:

-enters through the muscle cone & crosses the optic nerve from lateral to medial

-passes under the SR & LPS, the nerve is directed to the medial wall of the orbit where it divides into its principal branches; the posterior ethmoidal, anterior ethmoidal & infratrochlear nerves

Branches:

1-sensory root of ciliary ganglion; runs on the lateral aspect of the optic nerve to enter the ganglion

2-long ciliary nerves; pierce the sclaera to supply the eyeball with sensation

3-posterior ethmoidal nerve; enters the corresponding foramen to supply sensation to the posterior ethmoidal & sphenoidal air cells.

4-infratrochlear nerve; leaves the orbit below the trochlea of SO to supply the medial ½ of the upper lid & its conjunctiva together with the skin of the bridge of the nose

5-anterior ethmoidal nerve;

-leaves the orbit through the anterior ethmoidal foramen

-supplies the anterior & middle ethmoidal air sinuses

-enters the floor of ACF & courses over the cribriform plate

-enters the nasal cavity through the nasal slit on each side of crista galli

-supplies mucous membranes of the anterosuperior ¼ of the lateral wall of nasal cavity & upper part of nasal septum

-leaves the nasal cavity between the nasal bone & cartilage as the external nasal nerve which supplies the middle of the skin of external nose below the bridge

The optic nerve:

-is the 2nd cranial nerve

-wholly sensory

-enters the back of the eyeball just medial to its posterior pole

-its medial fibers transmit image from nasal side of the retina (temporal field)

-its lateral fibers transmit image from temporal side of the retina (nasal field)

-decussation of nasal fibers occur in optic chiasma so each eye will see the opposite ½ of visual field

-the nerve is crossed inside the orbit by many structures like the ophthalmic artery, nasociliary nerve, some motor nerves …

-ciliary ganglion lies on its lateral side

Arterial supply of the orbit:

-the ophthalmic artery, branch of ICA just after it leaves the cavernous sinus, enters the orbit through the optic canal

-it is directed in the orbit from lateral to medial across the optic nerve

Branches:

1-Branches to the eyeball:

- central artery of the retina

- long & short posterior ciliary branches

- anterior ciliary branches

2-Branch with each of the sensory nerves of the orbit; taking its course & destination

3-Muscular branches; with the motor nerves of the orbit supplying ocular muscles & give the anterior ciliary arteries

*The central artery of retina:

-pierces the optic n. near the middle of its intraorbital course

-supplies the distal 1/3 of the optic nerve & the whole retina

-its damage leads to total blindness of that eye with optic atrophy

*The short posterior ciliary arteries:

-pierce the back of sclera near the optic nerve

-supply the choroid

*The long posterior ciliary arteries:

-pierce the back of sclera near the optic nerve

-pass between the sclera & choroid to the iris

*Anterior ciliary arteries:

-branches of muscular arteries

-pierce the sclera near the cornea

-end in the greater arterial circle of the iris

Venous drainage of the orbit:

1-Superior ophthalmic vein:

-formed at the supraorbital foramen by union of the supraorbital & supratrochlear veins

-has the same course & branches of the ophthalmic artey

-joined by the inferior ophthalmic vein at the medial end of SOF

-enters the cavernous sinus after leaving the orbit

2-Inferior ophthalmic vein:

-formed in the floor of the orbit by union of muscular veins

-communicates with pterygoid venous plexus through the inferior orbital fissure

-empties in the SOV at the medial end of SOF

-sometimes empties directly in the cavernous sinus

Fasciae of the orbit:

1-Periorbita:

-the double-layered dura mater of the cranial cavity enters the orbit with the optic nerve

-the fibrous coat remains with the nerve & the endosteal layer leave the fibrous layer to form the periosteal layer of the orbit (periorbita)

-unlike in the cranial cavity, periorbita could be easily stripped from bones of the orbit

-the site where the two dural layers diverge in the orbit represents the site of complete separation of the orbital from cranial cavities

2-Muscular fasciae:

-fascia covering ocular muscles

-muscular fascia of MR thickened at certain site to be attached to the posterior lacrimal crest forming the "medial check ligament"

-the same thing occur in LR fascia & attaches it to the zygomatic bone forming the "lateral check ligament"

-these two thickenings fuse with fasciae of IO & IR to form the hammock-like sling on which the eyeball rests "suspensory ligament of the eyeball"

3- Retrobulbar (orbital) fat:

A fixed-sized cushion of fatty tissue on which the globe rests with a fixed position of its center.

The lacrimal apparatus:

1- Lacrimal gland:

-an oval gland occupies the superolateral part of the orbit "lacrimal fossa"

-it is pierced by LPS muscle which incompletely divides it into orbital part which remains in the roof of the orbit partially invested by fascia of SR & LR muscles, & palpebral part which projects inside the upper eyelid with its deep surface in relation to the conjunctiva

-ducts of the gland are 6-10 in number, all empty in the superior fornix of conjunctiva

-supplied by lacrimal branch of ophthalmic artery

-drained by lacrimal v. which empties in the superior ophthalmic v.

-supplied by lacrimal nerve which carries autonomic component derived from the zygomaticotemporal branch of Vb

2- Lacrimal canaliculi:

-open in the eyelids as the lacrimal puncta whose openings are directed toward the lacrimal lake

-course over the corresponding eyelids, the puncta open in the lacrimal sac

-they collect tears from the lake to the sac

3- Lacrimal sac:

-it is the upper dilated end of nasolacimal duct

-measures 0.5 X 1 cm

-receives the lacrimal canaliculi separately

-lies in front of the lacrimal part of orbicularis oculi & behind the medial palpebral ligament

-contraction of the lacrimal part of O. oculi dilates the sac making negative pressure which sucks tears from the lake by the canaliculi

4- Nasolacrimal duct:

-extends from the lacrimal sac downward, backward & laterally towards the inferior nasal meatus

-transmits tears from the sac to the nasal cavity

-is about 2 cm long

The pterygo-palatine fossa:

• Apyramidal space located in the interval between the root of the pterygoid process posteriorly & the back of maxilla anteriorly.
• Boundaries:

-Anterior: back of maxilla

-Posterior: root of pterygoid process & body of sphenoid

-Lateral: ITF

-Medial: nasal cavity

-Superior: apex of the orbit

-Inferior: maxillary sinus

connections:

THROUGH	TO
Foramen Rotundum	MCF
Pterygomaxillary fissure	ITF
Inferior orbital fissure	Orbit
Sphenopalatine foramen	Nasal cavity
Pterygoid canal	Foramen lacerum
Palatine foramina	Oral cavity
Pharyngeal canal	Base of skull

Contents:

1- Pterygopalatine ganglion:

• Is one of the four cranial autonomic ganglia
• Is the ganglion of hay fever
• Supplies mucous membrane from the lower lid to the upper lip
• Gives five branches:

• Greater palatine n.
• Lesser palatine n.
• Posterior superior lateral nasal n.
• Nasopalatine n.
• Pharyngeal n.

2- Maxillary nerve:

-Is the 2nd branch of trigeminal nerve

-Enters the fossa through foramen rotundum

-Leaves the fossa through the inferior orbital fissure to pass in the floor of the orbit

• Gives the following branches

• Sensory root of pterygopalatine ganglion
• Posterior superior alveolar n. ; pierces the back of maxilla & supplies the molar teeth with adjacent gingiva & m.m.
• Middle superior alveolar n. ; given in the infraorbital canal to supply the bicuspid teeth of maxilla & adjacent gingiva & m.m.
• Anterior superior alveolar n. ; to the canine & incisors
• Terminal branches ; zygomatico-facial, zygomatico-temporal & infra-orbital nerves

3- Third part of maxillary artery:

- Enters the fossa through the pterygomaxillary fissure

-Gives a branch with each of maxillary nerve branches & PPG branches, these branches posses the same names of the corresponding nerves except the nasopalatine called long sphenopalatine artery & PSLN called short sphenopalatine arteries

Structures passing in & out:

THROUGH		STRUCTURE
Foramen Rotundum	in	Vb
Pterygomaxillary fissure	In	Maxillary artery
	out	Post. Sup. Alv. V.&N.
Inferior orbital fissure	In-out	Connection between IOV & pt. plexus
Sphenopalatine foramen	out	PSLN V.&N. Nasopalatine V.&N.
Pterygoid canal	in	Vidian nerve
Palatine foramina	out	Palatine V.&N.
Pharyngeal canal	out	Pharyngeal V.&N.

Applied anatomy:

The PPG is the ganglion of seasonal allergy.

Allergic rhinitis & conjunctivitis involve mainly m.m. supplied by this ganglion whose sensory root is derived from Vb.

The nose:

The External Nose:

Skeleton:

1-The bony part:

It is formed by the two nasal bones, it forms the upper part of the external nose.

2-The cartilagenous part:

• Formed by two lateral nasal & two alar cartilages
• Forms the lower part of the nose.
• Lateral nasal cartilage; is a triangle whose borders articulate with the nasal bone above, septal cartilage medially & alar catilage inferior ly.
• Alar cartilage; thin flexible cartilage, hooks around the nostrils from lateral rounded part to the medial hook-shaped part , the medial ends of the two cartilages are connected by loose tissue in the midline below the septum

Arterial supply:

1-Lateral nasal branch of facial artery.

2-Nasal branches of infraorbital artery.

3-Dorsal nasal branch of inferior ophthalmic artery.

Veins:

Accompany arteries.

Nerves:

1-Bridge; infratrochlear (Va)

2-Midline shin below the bridge; external nasal (Va)

3-Lateral side; infraorbital (Vb)

The Nasal Cavity:

Skeleton:

1- Lateral wall:

*Upper part: from before backward the bones are:

Nasal bone, frontal process of maxilla, lacrimal bone, ethmoid, body of sphenoid

*Lower part: from before backward the bones are:

Maxilla, inferior concha, palatine bone, pterygoid plate

2-Roof: cribriform plate of ethmoid.

3-Floor: hard palate (palatal process of maxilla & horizontal plate of palatine).

4-Medial wall (septum):

Posterosuperior; perpendicular plate of ethmoid

Posteroinferior; vomer

Anterior; septal cartilage

Parts of the nose:

• Vestibule; is the skinny part of the nasal cavity at the nostrils, it carries coarse hairs with other skin derivatives
• Choanae; are the posterior nasal apertures which open to the nasopharynx, they are 2 X 1.5 cm in dimensions & separated from each other by the posterior part of the septum

• Conchae:

• Are the three scroll-like projections in the lateral wall of the nose
• Their size increase as we descend downward
• The upper two are parts of the ethmoid while the lower is a separate bone
• Their medial ends almost reach the septum
• Their action is to increase surface area of m.m. to humidify & warm air
• They also act as shelves for the underlying meatuses
• Their covering m.m. is highly vascular & contain erectile tissue so their size may increase or decrease according to the situation

• Meatuses:

• Are the groove-like passages underneath the corresponding conchae
• The superior meatus receives the opening of the posterior ethmoidal air sinus
• The middle meatus show a bulging (bulla ethmoidalis) formed by the middle ethmoidal sinus on which opens the sinus itself.
• Below the bulla & parallel to it lies the uncinate process of the ethmoid converting the area between it & the bulla into a smilunar hiatus (hiatus semilunaris) into its anterior end opens the frontonasal duct (frontal sinus), just behind it opens the anterior ethmoidal sinus & in the posterior part of the hiatus opens the maxillary sinus.
• The inferior meatus receives the opening of the nasolacrimal duct.

• Spheno-ethmoidal recess:

Is the part of the lateral nasal wall between the superior concha & the body of sphenoid, it receives the sphenoidal ostia

Mucous membranes:

• The nasal cavity is lined with m.m. except for the vestibule
• m.m. of the nose is firmly bounded to the periosteum & perichondrium of the underlying structures (mucoperiosteum & mucoperichondrium)
• M.m. is continuous with other m.m. of the chambers with which the nasal cavity is continuous like the nasopharynx, paranasal sinuses, conjunctiva, ..

Nerve supply:

1- Lateral wall:

According to nerve supply the lateral wall of the nose could be divided into four quadrants:

• Anterosuperior: anterior ethmoidal n.
• Posterosuperior: posterior superior lateral nasal n.
• Anteroinferior: anterior superior alveolar n.
• Posteroinferior: greater & lesser palatine n.

2- The septum:

• The nasopalatine branch of the PPG (Vb) descends on each side of the nasal septum in an antero-inferiorly in the direction of the incisive foramen of the palate.
• The part below the course of this nerve is supplied by the same nerve
• The part above it is supplied by the medial nasal branches of the anterior ethmoidal n. (Va)

3- The roof:

The roof is lined by olfactore neroepithelium & is supplied by the olfactory nerve.

Arterial supply:

Follows the same way of nerve supply for both lateral wall & the septum.

Venous drainage:

• Starts in the cavernous plexus on the middle & inferior conchae & lower part of the septum
• From the lateral wall:

*Anterior ½; anterior facial vein

*Posterior ½; pterygoid venous plexus

• From the septum like lateral wall.
• connections:

*veins of the roof; superior sagittal sinus

*anterior ethmoidal; superior ophthalmic v.

Applied anatomy:

• Deviation of nasal septum is a common problem involving usually the septal cartilage commonly associated with part of the perpendicular plate of ethmoid & / or vomer.
• Epistaxis, bleeding from the nose most often takes place in Little’s area on the lower part of the septum where the cavernous venous plexus & capillaries often injured by the fingers & foreign bodies.

The paranasal sinuses:

• PNS are pneumatic areas in the frontal, ethmoidal, sphenoidal & maxillary bones.
• They are lined with m.m. which is continuous with that of the nasal cavity through the sinus apertures in the lateral wall of the nose.
• The maxillary sinus is well developed at birth, the frontal & sphenoidal exhibit a definite cavity at the 7th year of life while the ethmoidal develop late at puberty.
• The definite function of the PNS is not well known, theories about lightening the skull & resonating the voice exist but still there is more to be studied.

The frontal sinuses:

• These two sinuses are located on each side of the midline in the frontal bone behind the superciliary ridges.
• They are rarely symmetrical.
• They are roughly triangular in sagittal section with a maximum vertical length of 2.5 cm & maximum AP depth of 2 cm in the orbital plate of the frontal bone.
• It drains through the frontonasal duct to the lateral wall of the nose where its ostium opens in the most anterior part of the hiatus semilunaris.
• Supraorbita, supratrochlear & anterior ethmoidal nerves & vessels supply the sinus.

The ethmoidal sinuses:

• These three groups of sinuses are located in the lateral mass of the ethmoid in its labyrinth. They are named; anterior, middle & posterior sinuses (air cells).
• The walls of these spaces are very thin & completed by other bones like the lacrimal, sphenoid, palatine, frontal & maxillae.
• Medial to them lies the nasal cavity, laterally lies the orbit, superiorly the ACF & inferiorly the nasal cavity & maxillary antrum.
• The anterior opens in the anterior part of the hiatus, the middle in the summit of the bulla & the posterior in the superior meatus.
• The anterior & middle sinuses are supplied by anterior ethmoidal vessels & nerves while the posterior is supplied by the posterior ethmoidal vessels & nerves.

The sphenoidal sinuses:

• These two sinuses are located on each side of the midline in the body of sphenoid separated from each other by thin plate of bone.
• They lie behind the posterior ethmoidal cells, in front of the dorsum sellae, inferior to the hypophyseal fossa superior to the nasopharynx & bounded on each side by the MCF.
• Their ostia open in the spheno-ethmoidal recess.
• They are supplied by the posterior ethmoidal vessels & nerves & by the pharyngeal branch of the PPG.

The maxillary sinuses:

• These two sinuses occupy most of the maxillary body extending from the lateral nasal wall medially to the zygomatic process of the maxilla laterally & from the floor of the orbit superiorly to the alveolar process of maxilla inferiorly.
• They are pyramidal cavities with their bases open in the lateral nasal wall & apices in the direction of the zygomatic process.
• The big opening in the lateral nasal wall produced by the maxillary sinus is blocked for most of its size by the overlapping inferior concha.
• The sinus opens in the posterior part of hiatus semilunaris.
• It is supplied by vessels & nerves of the region, i.e; superior alveolar, infraorbital, zygomaticofacial …

Applied anatomy:

• Infection of nasal mucosa as in flu leads to blockage of the draining system of one or more of the PNS with the consequent accumulation of secretion in the sinus & superadded infection resulting in sinusitis. So this condition could not be treated unless the draining system is restored & normal physiology of its cilia is resumed either medically or surgically.
• Pain from sinusitis is usually referred to areas supplied by the same nerves & adjacent areas like the orbit, upper teeth, forehead & nose.
• The root of the upper second premolar tooth sometimes perforates the floor of the maxillary sinus & its extraction may lead to oro-antral fistula.

The oral cavity:

The lips:

• Are two muscular folds covered by skin, lined by m.m & formed mainly by muscles including the constrictors & dilators of the oral fissure
• The upper extends laterally to the nasolabial fold & the lower extend inferiorly to the mentolabial fold
• The philtrum are two skin ridges end below at the labial tubercle & above at the nasal septum
• The red margin (vemilion border) is covered by dry transparent m.m which give the underling red color of the highly vascular organ
• The upper lip is supplied by the infraorbital n. & the lower by the mental n., both are supplied by facial artery
• Labial glands are mucous gland in the submucosa & open by small individual ducts to the surface of m.m

The cheeks;

• Resemble the lips in structure but their main muscle is buccinator
• The fatty subcutaneous tissue (buccal pad of fat) is very loose & transmits the parotid duct
• The buccal glands simulate labial glands

The gingivae;

• Consist of dense fibrous connective tissue firmly attached to the underlying alveolar process
• Covered by smooth highly vascular m.m
• The gingivae also surround the necks of teeth
• The main blood supply to the upper gum are the palatine arteries & to the lower is the lingual artery

The oral cavity:

• The mouth consists of two parts:

1- The vestibule; is the narrow cavity in the interval between the gums & teeth on one side and the lips & cheeks on the other side.

2- The mouth proper; is the part of the cavity within the alveolar arches roofed by the palate, floored by the mylohyoid muscle & contains the tongue.

The roof of the mouth:

1- The hard palate;

• Forms the anterior 2/3 of the roof, it is formed in its anterior 2/3 by the palatal process of maxilla & in its posterior 1/3 by the horizontal plate of the palatine bone.
• The m.m is firmly bounded to the periosteum (mucoperiosteum) especially in the anterior part therefore any injection in this area is severely painful.
• It is supplied by the greater palatine & terminal parts of nasopalatine vessels & nerves.

2- The soft palate; will be discussed later.

The tongue:

- The tongue is a highly mobile muscular organ important for mastication, swallowing, taste & speech.

- At its root it is fixed by its connection to the palate (palatoglossus), pharynx (superior constrictor) & epiglottis (glosso-epiglottic folds), while its anterior part is free for movement

- It is partially separated into two symmetrical halves by a median septum of areolar tissue

- Tongue is composed embryologically of two different parts which possess different structure, appearance & in nerve supply & lymphatic drainage, they are the oral part (anterior 2/3) & pharyngeal part (posterior 1/3).

- The anterior 2/3 is separated from the posterior 1/3 by a v-shape sulcus terminalis whose apex is directed posteriorly at foramen caecum of the tongue

- The m.m of the anterior2/3 is fur-like & adheres to the underlying muscles, it is also characterized by the presence of the filiform, fungiform & vallate papillae, while m.m of the posterior 1/3 is smooth & movable over the muscle & shows multiple round elevations produced by the underlying lymphoid follicles (lingual tonsil).

- Frenulum linguae is a m.m fold in the midline connects the undersurface of the tongue to the floor of the mouth

Muscles of the tongue:

1. Intrinsic muscles;

• These are muscle fibers arranged within the tongue in three directions, antero-posterior (superior & inferior longitudinal), horizontal & vertical
• They are attached by their ends to the m.m. & to the midline lingual septum
• Their contraction changes the shape of the tongue, the size of the tongue mass is static, any change in one dimension affects other dimensions, e.g; flattening of the tongue (contraction of vertical group) is always associated with increase side to side length of it an d so on.

II) Extrinsic muscles;

There are three muscles which are related to the tongue, they connect the tongue to three different bones & their contraction alters the position & direction of the tongue. Palatoglossus, thogh it is a palatal muscle it will be discussed here for its important action.

Hyoglossus:

Origin; upper border of greater horn & body of hyoid

Insertion; fibers ascend anteosuperiorly to be inserted in the posterior part of the lateral border of the tongue intermingling with other muscles.

Action; retracts the tongue & depresses its sides. It also elevates the hyoid bone.

Genioglossus:

Origin; inferior genial tubercle

Insertion; fibers go back to enter the substance of the tongue contributing to its mass, the superior fibers are inserted into the tip of the tongue, middle fibers into the dorsum & the lowest fibers are inserted inferiorly.

Action; -protracts the tongue

-the superior fibers brings the tip of the tongue in contact with the floor of the mouth

-the dorsal fibers cause cupping of the tongue

Styloglossus;

Origin; lower part of styloid process anteriorly

Insertion; fibers descend anteroinferiorly & medialward to be inserted into the posterior part of hyoglossus, the fibers entr the tongue & pass forward along its side

Action; retracts the tongue & deviates it laterally

Palatoglossus:

Origin;-oral surface of the palatine aponeurosis

Insertion; fibers arch down under the m.m of the mouth raising the anterior pillar of the fauces (palatoglossal arch) to be inserted into the side of the tongue.

Action; It is the opponent of LVP:

-sphincter of the fauces

-depresses the soft palate

-raises the tongue

Nerve supply of lingual muscles:

All muscles of the tongue are supplied by the hypoglossal nerve except palatoglossus which is supplied (as a palatal muscle) by the pharyngeal plexus.

Sensory nerve supply of the tongue:

• Anterior 2/3;

-lingual n.; common sensation

-chorda tympani; taste sensation

Chorda tympani is an autonomic nerve derived from nervus intermedius (VII?), it joins the Vc just below the base of the skull in the ITF & runs in its lingual branch to supply parasympathetic power to the submandibular ganglion & give taste fibers to the anterior 2/3 of the tongue

• Posterior 1/3;

glossopharyngeal nerve supplies it with both types of senses

Arterial supply of the tongue:

Lingual artery:

This branch of ECA provides the tongue with all its blood, at its origin (level with the tip of grater horn of hyoid) it is crossed externally by the XII nerve & posterior belly of digastric & stylohyoid muscles. It passes forward to lie deep to hyoglossus between it & the septum of the tongue 5 mm deep to the inferior surface of the tongue, it gives:

1. Dorsal lingual branches to the tongue mass.
2. Sublingual branches to the sublingual gland & floor of the mouth

Veins of the tongue:

1- Deep lingual veins; two in number, accompany the lingual artery & receive similar tributaries, they empty in the IJV

2- Veni comitans nervi hypoglossi; accompany the XII, bring blood from the tip, they are larger than the deep veins & empty in the facial vein.

The floor of the mouth:

• The floor of the mouth is mylohyoid

Origin; mylohyoid line of the mandible

Insertion;

• The fibers descend downward & backward, those of anterior 2/3 interdigitate with the opposite one in a midline raphe which extends from the symphysis menti to the hyoid bone
• The posterior fibers reach the hyoid bone leaving a posterior free border for the muscle which connects the oral mouth to the submandibular triangle

Nerve supply; mylohyoid nerve, branch of the inferior alveolar nerve

Action;

1. An essential swallowing muscle, by wavy elevation of the tongue from anterior to posterior direction against the palate it compresses the bolus backward
2. Moves the tongue changing its position & direction
3. Elevates the hyoid & eventually the larynx

Structures in the floor of the mouth:

• A coronal section through the mid-mouth reveals a slit like cavity in the floor of the mouth between mylohyoid laterally & the side of the tongue (hyoglossus) medially.
• This cavity is covered with m.m of the floor of the mouth & contain important structures in relation to the lateral surface of hyoglossus, these are:

*Lingual nerve above (hooks around the submandibular duct)

*Submandibular duct in the middle

*XII nerve is the lowest

• Structures deep to hyoglossus are:

*Deep lingual artery

*Stylohyoid ligament

*IX nerve

The soft palate:

• Is a triangular fold of m.m containing aponeurosis of tensor palati, muscle fiber, mucous glands, vessels & nerves
• It hangs from the posterior border of the hard palate where its anterior surface will face forward to the oral cavity & its posterior surface faces backward
• The tip of the triangle contains a rounded mass of muscle fibers (musculus uvulae) with mucous glands it is called the uvula
• The main function of the soft palate is to act as policeman between the airway & foodway regulating swallowing in relation to berathing.
• Muscles of the soft palate are; tensor veli palatini, levator veli palatini, palatoglossus, palatopharyngeus & musculus uvulae

Tensor veli palatini:

• One should think of this muscle as two triangles, a muscular one lies in the ITF & an aponeurotic one in the oral cavity
• These two triangles are united to each other by a tendon which get access to the mouth through the fibro-osseous canal produced by attachment of the pterygomaxillary ligament between the pterygoid hamulus & maxillary tuberosity

Origin:

The muscular triangle in the ITF arises by two of its limbs;

- from the roof of ITF (from the spine of sphenoid to the scaphoid fossa)

-from the posterior border of medial pterygoid plate passing over the cartilagenous part of the auditory tube

The third border of the muscle is free

The muscle will lie in the fossa between the medial pterygoid plate & muscle to taper as it approaches the maxillary tuberosity into a slender tendon

Insertion:

The slender tendon after entering the fibro-osseous canal expands into aponeurotic triangle with three borders:

• One is attached to the posterior border of the hard palate
• The other will fuse with the opposite fellow
• The third will hang freely inside the oropharynx suspending the uvula

Action:

Contraction of TVP causes tension of the soft palate (aponeurosis of the muscle) which becomes straight & lower down to be elevated by the levator muscle to fit the Passavant ridge in the junction between the oro- & nasopharynx separating the two.

Levator veli palatini:

Origin: From the petrous apex & cartilagenous part of the auditory tube

Insertion: the pencil-like muscle descends deep to the m.m of the nasopharynx elevating a ridge near the tube orifice to be inserted into the dorsal surface of the palatine aponeurosis

Action: elevate the tense palatine aponeurosis closing the naso from oropharynx

Both TVP & LVP contraction opens the auditory tube since part of their origin is taken from it & since their contraction occurs mainly during swallowing this process will open the auditory tube equalizing pressure on both sides of the eardrum

Palatoglossus:"discussed"

Palatopharyngeus:

Origin:

- Nasal side of palatine aponeurosis

- Posterior part of the hard palate

Insertion: fibers arch down behind palatoglossal fibers to raise the posterior pillar of the fauces (palatopharyngeal fold) & inserted in the posterior border of the thyroid cartilage

Action: - depresses the soft palate

- elevates the larynx in the early stage of deglutition

Nerve supply of palatal muscles:

All palatal muscles are supplied by the pharyngeal branch of X nerve in the pharyngeal plexus except TVP which is supplied by nerve to medial pterygoid from the main trunk of Vc.

Arteries of the palate:

1- Greater palatine; hard palate

2- Long sphenopalatine; hard palate

3- Lesser palatine; soft palate

4- Ascending palatine br. of facial a.; soft palate

5- Palatine br. of ascending pharyngeal; soft palate

Veins of the palate:

Similar to arteries; pterygoid venous plexus

Nerves of the palate:

1- Greater palatine n.

2- Nasopalatine n.

3- Lesser palatine n.

4- Pharyngeal branch of PPG

5- IX nerve.

The pharynx:

• Is a muscular tube common for airway & foodway extends from the base of the skull down to the level of cricoid cartilage (C6 vertebra) where both ways diverge from each other
• It is located behind & opens anteriorly into three openings, the nasal cavity, the oral cavity & the larynx from above downward, so its cavity is divided into the nasopharynx, oropharynx & laryngeal pharynx
• It is about 12 cm long, its widest diameter is 5 cm at the base of the skull, its narrowest diameter is 1.5 cm at the upper oesophagus, so it possesses a funnel shape

The wall of the pharynx:

• The structure of the pharyngeal wall looks like four cups one inside the other
• The highest & innermost is the pharyngobasilar fascia which is attached to the skull base.
• The next three are the pharyngeal constrictors
• Each constrictor muscle has an anterior small origin from which its fibers fan out posteriorly to meet its fellow in the posterior midline forming the pharyngeal ligament (the posterior pharyngeal raphe) which extends from the base of the skull to the lower border of thyroid cartilage
• Pharyngeal constrictors are the intrinsic muscles of the pharynx

The pharyngo-basilar fascia:

• This strong fascia lines the muscular layer of the nasopharynx & extends from the base of the skull to the hard palate (C1 vertebra)
• It is responsible for keeping the nasopharynx always open for respiration
• Origin;

• From the pharyngeal tubercle in the base of the skull the line of origin goes laterally in a forwrad convexity to reach the petrous apex which is involved by the origin of fascia
• Then it passes forward to reach the base of the medial pterygoid plate where the cartilagenous part of the auditory tube is lodged.
• It passes over the tube then takes origin from the posterior border of the medial pterygoid plate medial to the superior pharyngeal constrictor where its origin ends at the level of the pterygoid hamulus

The superior pharyngeal constrictor:

Origin: from the posterior border of the medial pterygoid plate below the cartilagenous part of the auditory tube - pterygoid hamulus - pterygomandibular raphe - posterior border of mylohyoid line

Insertion: fibers fan so that upper fibers ascend to reach the base of the skull in the midline, middle fibers go horizontally & lower fibers go down inside the middle constrictor to the level of the lower border of thyroid cartilage, all are inserted posteriorly in the pharyngeal raphe

The middle pharyngeal constrictor:

Origin: from the angle between the lesser & greater horns of the hyoid bone & lower part of stylohyoid ligament

Insertion: fibers fan so that upper fibers ascend to reach the base of the skull in the midline outside the superior constrictor, middle fibers go horizontally & lower fibers go down inside the inferior constrictor to the level of the lower border of thyroid cartilage, all are inserted posteriorly in the pharyngeal raphe

The inferior pharyngeal constrictor:

Thyropharyngeus;

• This is the largest portion of the ICM & the largest of all constrictors
• It arises from the oblique line of the thyroid cartilage & area above
• Fibers ascend up & go medially but not inferiorly to be inserted into the midline pharyngeal raphe

Cricopharyngeus;

• This circular muscle arises from the cricoid cartilage & is continuous with the upper part of the oesophagus
• It is continuous with its opposite fellow
• There is a gap between it & the thyropharyngeus part

The extrinsic muscles of the pharynx:

Stylopharyngeus;

• Origin; from the back of the root of styloid process
• Insertion; the slender muscle passes with IX & pharyngeal branch of X between the ICA & ECA to be inserted into the posterior border of thyroid cartilage in front of palatopharyngeus

Palatopharyngeus; "discussed"

Salpingopharyngeus;

• Origin; from the lower border of the auditory tube
• Insertion; fibers converge on palatopharyngeus with which it is inserted into the back of the thyroid cartilage

Relations of the pharynx:

* Upper part:

• Laterally; carotid sheath containing ICA, CCA, IJV& the last 4 cranial nerves
• Posteriorly; retropharyngeal space containing sympathetic trunk posterolaterally
• Anteriorly; nasal cavity

* Lower part:

• Laterally; carotid sheath containing CCA, IJV & X nerve
• Posteriorly; same relations
• Anteriorly; larynx

Nerve supply of the pharyngeal muscles:

All pharyngeal muscles are supplied by the pharyngeal branch of X through the pharyngeal plexus, except:

-Stylopharyngeus; glossopharyngeal n.

-Cricopharyngeus; external laryngeal n.

The pharyngeal plexus of nerves:

This plexus is formed on the lateral surface of the MCM, it is formed by:

1- Pharyngeal branch of X; motor

2- Pharyngeal branch of IX; sensory

3- Pharyngeal branch of superior cervical sympathetic ganglion vasomotor

Gaps in the pharyngeal wall:

1- Between the pharyngo-basilar fascia & base of the skull:

filled anteriorly by the cartilagenous part of Eustachian tube.

2- Between the SCM & MCM: enters stylopharyngeus & IX.

3- Between the MCM & ICM:

internal laryngeal nerve & superior laryngeal artery.

Arteries of the pharynx:

1- Ascending pharyngeal (ECA).

2- Ascending palatine (facial a.).

3- Descending palatine & pharyngeal aa. (3rd part of maxillary a.).

4- Muscular branches of superior thyroid artery

Veins of the pharynx:

• Accompany arteries
• Form two venous plexuses, one external & the other between the constrictors & pharyngobasilar fascia
• The upper part of the pharynx drains to the pterygoid plexus
• The lower part drains to the IJV

The interior of the pharynx:

The pharyngeal cavity is divided according to the part it lies behind into :

1- The nasopharynx; which lies behind the nasal cavity & extends from the base of the skull to the level of the hard palate (L1).

2- The oropharynx; which lies behind the oral cavity & extends from the level of the hard palate to the glosso-epiglottic folds.

3- The laryngeal pharynx; which lies behind the laryngeal orifice.

Each one of these parts possesses special stigmata, structure, arterial & nerve supply.

The nasopharynx:

• Is completely respiratory & opens anteriorly to the posterior nasal choana
• Its cross section simulates the origin of the pharyngobasilar fascia which strengthens its wall keeping it always patent
• Structures in this part are:

1- The nasopharyngeal tonsils "adenoids":

a collection of lymphatic tissue in the posterior wall of the nasopharynx near its roof.

2- The tubal tonsils: lymphatic tissue collections around the orifices of the auditory tubes.

3- The openings of Eustachian tubes:

on each side, near the roof connecting it to the tympanic cavity.

4- The salpingopharyngeal fold:

a mucosal fold produced by the underlying salpingopharyngeaus extending from the back of tubal orifice downward.

5- The pharyngeal recess (fossa of Rosenmuller):

lies posterolateral in the wall, it contains the levator palati muscle deep to its m.m. & immediately lateral to it lies the ICA.

The oropharynx:

• Is common respiratory & digestive path. Opens anteriorly to the oral cavity constituting the back of the tongue & superiorly to the nasopharynx.
• Structures in this part are:

1- The palatoglossal fold: a mucosal fold raised by the the underlying palatoglossus separating the oral cavity from the oropharynx.

2- The palatopharyngeal fold: a mucosal fild raised by the underlying palatopharyngeus muscle.

3- The palatine tonsils:

• Two big collections of lymphoid tissue lying between the palatoglossal & palatopharyngeal folds measuring 2cm in greatest dimension
• They don’t fill the area between the two arches but leave the supratonsillar recess above them
• Their free surface is characterized by the tonsillar crypts
• Their deep surface is covered by thin but firm capsule which is continuous above with the pharyngobasilar fascia & lies deep to the superior constrictor

4- Lingual tonsils: in the posterior 1/3 of the tongue.

The Waldeyer’s tonsillar ring:

The laryngopharynx:

• Lies opposite to the laryngeal inlet.
• Its anterior wall is characterized by:

1- The median glosso-epiglottic fold; a midline mucosal fold between the epiglottis & the posterior 1/3 of the tongue.

2- The lateral glosso-epiglottic fold; one on either side, connecting the lateral borders of the posterior 1/3 of the tongue to the epiglottis.

3- The valleculae; on each side of the medial GEF bounded by the median GEF & lateral GEF & the posterior 1/3 of the tongue.

4- The piriform recess; is part of the larynx between the quadrate membrane medially & thyrohyoid membrane laterally.

Nerve supply of the mucosa of the pharyngeal cavity:

*Nasopharynx; pharyngeal branch of PPG (Vb)

*Oropharynx; pharyngeal branch of IX nerve

*Laryngeal pharynx; superior laryngeal branch of X nerve

Applied anatomy:

*Enlarged adenoid - nasal blockage - block auditory tube - recurrent ear infections & reduced hearing.

*Pharyngeal diverticulum: herniation of food-containing mucosal pouch through the gap between the two parts of inferior constrictor seen as a swelling at the side of the neck.

The Larynx:

The larynx lies in the anterior part of the neck in the midline opposite to C4-C6 vertebrae forming the laryngeal prominence (Adam’s apple)

At this level the L. is triangular in cross section while lower down at the level of the cricoid cartilage it is circular in cross section

Relations:

- Anterolaterally; Thyroid gland & strap muscles

- Laterally; Carotid sheath

- Posteriorly; Pharynx

Skeleton:

The thyroid cartilage:

• This hyaline cartilage is composed of two quadrilateral laminae meet in the midline
• The meeting angle is 90O in male & 120O in female (therefore the L is more prominent in male)
• The superior thyroid notch is a V-shape notch just above the prominence
• The posterior border of the cartilage is thick & rounded & extends above & below the laminae as the superior & inferior horns
• The superior & inferior borders are characterized by superior & inferior tubercles between them the oblique line of the cartilage extends which gives attachment to thyrohyoid, sternothyroid & thyropharyngeus
• The upper border is attached to the thyrohyoid membrane which is thickened in the midline as the median thyrohyoid ligament & thickened laterally between the superior horn & tip of greater horn of the hyoid as the lateral thyrohyoid ligament
• The inferior thyroid notch lies opposite to the superior one, from its deep surface the root of the epiglottis arises

The cricoid cartilage:

• This signet ring-like cartilage is characterized by an anterior arch & posterior broad lamina
• It lies at the level of C6 vertebra & forms the foundation on which the rest of the larynx is built
• The posterior lamina is marked in the midline by a ridge on either side of which lies a shallow depression for the posterior crico-arytenoid muscle
• The arch which is 5 mm in vertical height gives attachment anterolaterally to crico-thyroid muscle & posteriorly to the cricopharyngeus just above which the lateral crico-arytenoid arises
• The upper border of the arch gives attachment to the conus elasticus
• The sloping shoulders of the lamina provides a synovial joint for the arytenoid cartilages
• At the junction of the arch & lamina is a synovial joint for articulation of the inferior horns of the thyroid cartilages

The arytenoid cartilage:

• This is a three sided pyramidal hyaline cartilage whose apex projects posteromedially & carries the corniculate cartilages
• The base of the pyramid carries three processes
• The anterior sharp process is the vocal process & to which the upper free end of the conus elasticus is attached as the vocal fold
• The lateral process is the muscular process to which the lateral & posterior crico-arytenoids are attached
• The medial surface of the pyramid is flat & faces the opposite one
• The anterolateral surface is curved & gives attachment for the thyro-arytenoid muscle
• The posterior surface is smooth & gives attachment for the transverse arytenoid muscle
• The arytenoid cartilage sits on the elongated facet on the sloping shoulder of the cricoid lamina forming the crico-arytenoid synovial joint

The corniculate cartilage:

• This small nodular elastic cartilage lies on the apex of the arytenoid to prolong it backward & medialward
• They are enclosed by the ary-epiglottic folds

The cuneiform cartilage:

• Are rod like elastic cartilages lies on the previous ones in the ary-epiglottic folds

The epiglottis:

• This elastic, leaf-like cartilage is attached by its lower 1/2 to the back of the thyroid cartilage by the thyro-epiglottic ligaments in the midline, its upper 1/2 stands erect behind the posterior 1/3 of the tongue & the hyoid bone
• The anterior surface of the epiglottis is attached to the hyoid bone by the hyo-epiglottic ligament
• The m.m of the E. is reflected on the posterior 1/3 of the tongue as three folds, the median & two lateral glosso-epiglottic folds which mark the division between the oro- & laryngo-pharynx, on each side of the median one lies a vallecula
• The cartilage is well pitted to receive the multiple mucous glands which cover it
• To the margins of the free upper ½ is attached the quadrate membrane

Laryngeal membranes:

1-Thyro-hyoid membrane:

• Suspends the thyroid cartilage to the hyoid bone
• It passes from the upper border of the thyroid cartilage to the upper border of the hyoid bone passing behind the bone separated from it by a bursa
• It shows one median & two lateral ligaments of the same name
• It is pierced by the superior laryngeal artery & internal laryngeal nerve.
• It forms the lateral boundary of the piriform recess

2- Conus elasticus:

• Is a half-circle ligament whose lower attachment is to the whole length of the upper border of the cricoid arch
• Its free upper border is attached on either side to the vocal process of the arytenoid cartilage forming the vocal fold (true vocal cord) which contains in its free border muscle fibers (vocalis)
• Anteriorly the membrane is attached to the back of the thyroid cartilage in the angle between the two laminae in the midline midway between the superior & inferior notches converting the curved membrane to V-shape membrane
• Its thickening in the midline anteriorly produces the median crico-thyroid ligament

3- Quadrate membrane:

• Is a weak membrane whose posterior border is attached to the anterior surface of the arytenoid cartilage & its anterior border is attached to the sides of the lower half of the epiglottis
• Its upper free border will extend between the epiglottis & the arytenoid cartilage forming the ary-epiglottic fold which involves in its substance the corniculate & cuneiform cartilages
• Its lower free border will be parallel to the upper free border of the conus (true vocal cords) forming the vestibular fold (false cords)
• It forms the medial boundary of the piriform recess

The interior of larynx:

The laryngeal inlet:

• Opens in the anterior wall of the pharynx in a vertical plane
• Is an inverted triangle whose base is formed by the epiglottis antero-superiorly & its apex is the narrow interval between the two arytenoids postero-inferiorly
• The sides of the triangle is the ary-epiglottic olds

The laryngeal vestibule:

• Is the triangular cavity beyond the laryngeal inlet until the rima glottidis
• It is bounded on each side by the quadrate membrane
• It shows three features:

1- The vestibular folds; are the lower free border of the quadrate membranes

2- The laryngeal ventricle; is a sac like mucosal herniation between the true & false vocal folds whose upper border extends up & may reach the

upper border of the thyroid cartilage, it is filled with mucosal glands for lubrication

3- The rima vestibuli; is the opening between the vestibular folds, it is wider than the rima glottidis.

The vocal folds:

• Are formed by the free upper border of the conus stretched between the thyroid cartilage anteriorly & the arytenoids posteriorly
• The anterior 3/5 are true components of the conus while the posterior 2/5 are formed by the vocal process of the arytenoids
• They contain in their free edge the vocalis muscle which increases the apposed surface area of the cords during phonation
• The opening between them is called the rima glottidis
• Glottis, is a term applied to the two vocal cords & the rima glottidis as they are the main structure involved in phonation

The rima glottidis:

• Is the interval between the two vocal cords
• Is 23 mm long in male & 17 mm in female
• It could be opened either in V-shape or diamond shape manner according to the type of movement of the arytenoid
• Downward movement of the arytenoid on the sloping shoulders of the cricoid lamina pulls the two ends of the conus downward separating them & opens the rima in a V-shape manner, here the vocal processes of the arytenoids are parallel to each other, this occurs in quite respiration
• Rotation of the arytenoids around their vertical axes pulls the free ends of the conus away & opens the rima in a diamond shape manner, the back of the diamond is formed by the vocal processes of the arytenoids which become perpendicular on each other, this occurs in forced respiration
• During phonation the folds come in contact with each other & the rima becomes slit like

Intrinsic muscles:

The ary-epiglottic muscle:

• Extends in the ary-epiglottic fold from the arytenoids to the lateral border of the epiglottis
• The oblique inter-arytenoids are regarded as the continuation of the muscle to the vocal process of the opposite arytenoid
• Contraction of both brings the arytenoids near each other & oppose the ary-epiglottic folds & pull the epiglottis as a shelf over the constricted laryngeal inlet producing an effective sphincteric action for the inlet

The posterior crico-arytenoid:

Origin; from the back of cricoid lamina from the fossa on each side of the midline ridge

Insertion; upper fibers go horizontally to the vocal process of the arytenoid while the lower fibers go vertically to the to the same process

Action; upper fibers rotate the arytenoids so they open the rima glottidis in a diamond shape while the lower fibers pull the arytenoids away from each other so they open the rima in a V-shape

The transverse arytenoid:

• This is a muscle formed of fine & short fibers stretched between the two arytenoids deep to the oblique one
• Its contraction opposes the vertical fibers of the posterior c-a muscle

The lateral crico-arytenoid:

• Arises from the posterior part of the cricoid arch
• Inserted into the vocal process of the arytenoid
• Its contraction opposes the horizontal fibers of the posterior c-a muscle

The crico-thyroid:

• This muscle arises from the anterolateral surface of the cricoid arch
• Its fibers radiate upward & backward to be inserted into the lower border & medial aspect of the thyroid cartilage
• Its contraction approximates the thyroid & cricoid cartilages diminishing the area between them, this will bring the thyroid cartilage away from the arytenoid increasing the length & hence tension of the vocal cords affecting consequently the type of the voice

The thyro-arytenoid:

• This muscle arises from the inner surface of the thyroid lamina
• Its fibers pass backward to be inserted into the muscular process of the arytenoid
• Its contraction approximates the thyroid & arytenoid cartilages diminishing the area between them, this will decrease the length & hence tension of the vocal cords affecting consequently the type of the voice, this movement also acts as a laryngeal sphincter

Arteries of the larynx:

1- Superior laryngeal artery;

• A branch of the superior thyroid a.
• pierces the thyrohyoid membrane together with the internal laryngeal nerve to lie underneath the m.m of the floor of the piriform recess
• supplies the larynx to supply mucosa down to the level of the vocal cords.

2- Inferior laryngeal artery;

• A branch of the inferior thyroid artery
• enters the lower part of the larynx deep to the inferior pharyngeal constrictor
• supplies it up to the vocal cords (vocal cords are supplied by the inferior one).

Nerves of the larynx:

Motor:

All muscles of the larynx are supplied by the recurrent laryngeal n. except cricothyroid which is supplied by the external laryngeal branch of the superior laryngeal nerve (X nerve).

Sensory:

• Above the vocal folds : internal laryngeal branch of superior laryngeal nerve (X nerve) accompanies the sup. laryngeal artery.
• Below the vocal folds: recurrent laryngeal nerve accompanies the inferior laryngeal artery

　

The ear:

The external ear constitutes:

1. The auricle (pinna).
2. The external auditory (acoustic) meatus.
3. The tympanic membrane (eardrum).

The auricle:

• Is an oval cartilage attached to the side of the skull by anterior & posterior auricular ligaments.
• The skin is thin & well attached to the underlying perichondrium & prolonged inward into the external auditory meatus as far as the tympanic membrane.
• The cartilage is prolonged inward to be continuous with the external 1/3 of the EAM.
• Three auricular muscles are present to move the auricle but their function is negligible in human.
• Vessels; posterior auricular & superficial temporal vessels.
• Nerves; great auricular, vagus and auriculotemporal nerves share the supply of the auricle as mentioned.

The eam:

• Is 24 mm in length
• Its lateral 1/3 is cartilagenous & directed upward & backward as it goes medially
• Its medial 2/3 is bony & directed downward & forward as it goes medially
• The bony canal is narrower than the cartilagenous
• The skin is adherent to the underlying bone & cartilage
• The narrowest part of the canal is the isthmus which is the junction between its two parts
• The skin of the cartilagenous part contains hair with sebaceous & ceruminous glands
• The EAM is bounded anteriorly by the TM joint & parotid gland & posteriorly by the mastoid process
• The inferior wall of the canal is 5 mm longer than the superior one due to the obliquity of the eardrum
• Vessels; as the auricle & deep auricular vessels.
• Nerves; auriculotemporal & auricular branch of the vagus nerves.

The eardrum:

• A nearly oval membrane 8X10 mm, set in a cone like shape whose concavity faces outward & its most concave point is its center "umbo"
• It is semitransparent, pearly grey in color
• It is applied in an oblique manner in the EAM so that its lateral surface faces downward, forward & laterally making 55O angle with the floor
• Its circumference is a fibrocartilagenous ring set in the tympanic sulcus
• It is composed of three layers:

1. Outer layer of modified skin continuous with that of the EAM
2. Inner layer of m.m continuous with that of the middle ear
3. Intermediate fibrous layer formed of circular & radial fibers which is responsible for the strength of the membrane

• The upper 1/6 of the membrane lacks the intermediate layer so it is lax & called pars flaccida, the rest of the membrane is called pars tensa
• The handle of the malleus is fused with the upper part of the membrane

Applied anatomy:

• In order to straighten the EAM in examination of the ear it should be pulled upward, backward & laterally in adults and downward, backward & laterally in children
• Wax of the external ear mostly affects the lateral 1/3 of the EAM
• In ear syringing, the nozzle should be directed forward at first then backward, upward & medially to avoid injury to the tympanic membrane
• Normal tympanic membrane is semitransparent & pearly grey with a cone of light in its antero-inferior part, a diseased membrane looses its shiny appearance & the cone of light`

The middle ear:

Is a small, six-walled cavity in the temporal bone where the sound waves are converted into mechanical waves

• The cavity is 15 mm in height, 15 mm in AP dimension but narrow from side to side where it is narrowest in the center (2 mm)but wider above & below (like a biconcave lens)
• The cavity communicates anteriorly with the nasopharynx via the Eustachian tube & posteriorly with the mastoid air cells through the aditus, their mucosal lining is continuous with each other & is respiratory in type

Parts:

1. Epitympanum "epitympanic recess OR attic"; the part of the cavity which extends above the level of the tympanic membrane
2. Mesotympanum; the part of the cavity opposite to the eardrum
3. Hypotympanum; the part below the level of the eardrum

• Contents:

1. ONE nerve; chorda tympani
2. TWO muscles; tensor tympani & stapedius
3. THREE bones; incus, malleus & stapes

Walls of the middle ear:

The roof:

The roof of the tympanic cavity is formed by the thin plate of tegmen tympani which separates the ear from the cranial cavity

The floor:

• The floor of the middle ear separates the ear from the jugular fossa
• It is perforated by the tympanic branch of glossopharyngeal nerve

The lateral wall:(discussed)

The medial wall:

* The most prominent feature of the medial wall is the promontory of the internal ear which is the basal turn of the cochlea

* The promontory is grooved by branches of the tympanic plexus

* The oval window "fenestra vestibuli": is an oval opening above the promontory whose long axis is horizontal & maximum convexity is superior, it is closed in life by the footplate of the stapes

* The round window "fenestra cochleae"; lies below & behind the promontory & closed in life by the secondary tympanic membrane

* The facial canal seen in the medial wall as a prominence of bone above the oval window which then curves inferiorly & nearly vertically behind the promontory, the bone may be so thin in this area

* The prominence of the lateral semicircular canal sometimes seen as a prominent ridge above the facial canal

The anterior wall:

• This wall separates the middle ear from the carotid canal
• It is perforated by the coraticotympanic nerves which leaves the carotid plexus around the ICA to enter the tympanic plexus over the promontory
• In the upper end of the anterior wall lies the opening of the Eustachian tube
• Above the auditory tube opening lies the semicanal for tensor tympani muscle
• Tensor tympani, a 2cm long muscle which arises from the septum between the auditory tube & its canal & from the cartilagenouos part of the tube gives rise to a slender tendon which hooks around the processus & then directed laterally to insert into the handle of the malleus, its contraction tenses the tympanic membrane by pulling the handle of the malleus medially resulting in dampening of its vibrations

The auditory (Eustachian) tube:

• This 3.5 cm long tube connects the cavities of the middle ear & nasopharynx
• Its tympanic 1/3 is osseous & pharyngeal 2/3 is cartilagenous
• The direction of the tube from the ear to the nasopharynx is downward, forward & medially making 45O angle with the sagittal plane & 35O angle with the horizontal plane
• The mucosa of the middle ear therefore is continuous with that of the nasopharynx through the tube
• Mucous glands are present in the cartilagenous part whose pharyngeal end is surrounded by the tubal tonsils
• The tube is shorter, wider & more horizontal in children

The posterior wall:

• The upper part of the posterior wall is open to the mastoid antrum through the aditus ad antrum which is a large irregular opening leading from the middle ear to the mastoid antrum
• Fossa incudis lies below the opening of the mastoid antrum, it lodges the short process of the incus
• The vertical facial canal lies medially in the posterior wall
• The pyramidal eminence projects from the posterior wall in front of the facial canal, it is hollow structure whose walls give rise to stapedius muscle
• Stapedius arises from the pyramidal eminence, its tendon is inserted into the posterior part of the neck of the stapes, its contraction tilts the footplate of the stapes resulting in dampening of its effect on the internal ears (protective function)

The mastoid air cells:

• These are small bony cavities communicating with each other located within the mastoid process
• The first cell is the largest & called mastoid antrum which lies immediately behind the attic with which it communicates through the aditus ad antrum
• The size & number of mastoid air cells vary considerably, sometimes only few small cells are present within the mastoid & called sclerotic mastoid
• The mastoid process develop into a definite elevation only at the age of 2 years
• The lining mucosa is continuous with that of the tympanic cavity

The auditory ossicles:

• Three bones, the incus, malleus & stapes united by true synovial joints form a lever system which convert the vibrations of the tympanic membrane into mechanical energy represented by the pressure of the footplate of stapes on the oval window
• The fixation of these bones in the tympanic cavity is provided by:

1. The attachment of the malleus handle to the eardrum
2. The attachment of the stapedial footplate to the oval window
3. The anterior & posterior ligaments of the bones

The malleus:

• The bone’s name is derived from its resemblance to a hammer
• The rounded head of the bone lies in the epitympanic recess
• The long handle is fused with the upper half of the tympanic membrane
• The head shows a posterior oval concavity which receives the incus in the incudo-mallear joint which is of the saddle variety
• The short anterior process is connected to the petro-tympanic fissure of the anterior wall by a ligament

The incus:

• The anterior part of the body of the incus has a concavo-convex facet for articulation with the mallear head
• The short process (posterior crus) extends posteriorly to lie in the fossa incudis
• The long process (inferior crus) descends vertically parallel to the handle of the malleus to end in a rounded structure, the lenticular process which is received by the head of stapes in the incudo-stapedial joint which is of ball & socket variety

The stapes:

- The head of stapes is hollowed for reception of the lenticular process of the incus

- The narrow neck receives posteriorly the insertion of stapedius

- Two crura diverge from the neck to attach the footplate

- The footplate closes the oval window to which it is attached by a ring like ligament

Blood supply of the middle ear:

The arterial supply:

• The main artery of the eardrum is the anterior tympanic branch of maxillary artery
• The main artery of the tympanic cavity, mastoid antrum & mastoid air cells is the stylomastoid branch of posterior auricular branch of the ECA together with the anterior tympanic branch of the maxillary artery
• Smaller branches from the ascending pharyngeal artery, middle meningeal artery, artery of pterygoid canal share in the supply of the middle ear

The veins:

• Are parallel to arteries & drain to:

1. Superior petrosal sinus
2. Pterygoid plexus

Nerve supply of the middle ear:

The tympanic cavity, the deep surface of the tympanic membrane & mastoid air cells are supplied by the tympanic plexus.

Tympanic plexus:

An autonomic plexus formed at the promontory of the internal ear by contribution of:

1. The tympanic branch of glossopharyngeal nerve
2. Coraticotympanic branches of the carotid sympathetic plexus

Nerves in the middle ear:

1. Facial nerve has part of its course in the medial & posterior walls of the tympanic cavity but this part does not contribute to ear supply
2. Chorda tympani traverses the tympanic cavity between its bones but also give no branch to the ear.

Applied anatomy:

• Communication between the nasopharynx & middle ear results in transmission of infections from the nose & pharynx to the ear so otitis media is one of the complications of upper respiratory tract infection which complicates children infections more than adults due to the shape of their tubes & the possibility of associated adenoids
• Communication between the middle ear & the mastoid air cells results in transmission of infection from the middle ear to the mastoid resulting in acute or chronic mastoiditis
• Facial nerve involvement may be associated with diseases of the middle ear (LMND), Bell’s palsy

The inner ear:

• The inner ear is the essential organ of hearing & equilibrium
• It consists of the membranous labyrinth which is filled with endolymph & located inside a similar bony structure, the bony labyrinth which is filled with perilymph
• The membranous labyrinth consists of the:

1. Cochlear duct; is the snail like part of the inner ear responsible for hearing
2. Interconnecting channels responsible for maintaining equilibrium:

1. The utricle & saccule; stimulated by linear acceleration
2. The semicircular ducts; stimulated by angular acceleration
3. The part of the bony labyrinth lodging the cochlear duct is named the cochlea
4. The part lodging the semicircular ducts is called the semicircular canals
5. The part lodging the utricle & saccule is called the vestibule

The bony labyrinth:

The Cochlea

• Resembles a snail shell formed of 2.5 turns & lies on its side
• It is the most anterior part of the bony labyrinth situated in front of the vestibule & internal acoustic meatus
• It is 0.5 cm in height & its basal turn measures 1 cm in diameter
• The central axis of it is called the modiolus from which the spiral lamina arises & projects inside the cochlear turns & partially divides the cavity of the cochlea into scala vestibuli above the lamina & scala tympani below it
• The oval window opens to scala vestibuli & the fluid surge made by the pressure of the footplate of stapes ascends to reach the summit of the cochlea (helicotrema) where it is transmitted to scala tympani which ends below in the secondary tympanic membrane occluding the round window
• Another opening in the basal turn of the cochlea opens to the inferior surface of the petrous bone called the cochlear aqueduct

The Vestibule:

• It is the middle part of the inner ear bounding the middle ear medially
• In its lateral wall the oval window opens to the tympanic cavity from which the stapedial footplate closes this window
• Vibration of the footplate of the stapes results in fluid surge in the perilymph of the vestibule

The Semicircular Canals:

• Are three, anterior (superior), posterior & lateral
• They lie above & behind the vestibule & behind the internal acoustic meatus
• Each canal describes a greater part of a circle whose diameter is 1 mm & has a dilatation in one end called the ampulla
• The canals are perpendicular to each other, the superior is vertical & lies transverse to the long axis of the petrous bone, the posterior, also vertical, lies in the long axis of the bone while the lateral lies horizontally so its convexity lies laterally making a bony bulge in the medial wall of the middle ear
• Only five opening of the SCC opens into the vestibule since the posterior end of the anterior canal opens in the posterior SCC in the crus commune

The membranous labyrinth:

- These channels contain the sensory organs of hearing & equilibrium swimming in the endolymph:

- The sensory organ of the cochlear duct is the spiral organ of Corti

- The sensory organ of the SCC is the crista

- The sensory organ of the utricle & saccule is the macula

- The specialized cells in each sensory organ are the hair cells

Arteries of the labyrinth:

• The main artery is the labyrinthine branch of the basilar artery
• The stylomastoid branch of the posterior auricular artery supplies some of the blood

Veins of the labyrinth:

Similar to arteries & drain to the inferior petrosal sinus

The cranial cavity:

The Cranial Meninges:

The brain & spinal cord are enveloped by three layers of meninges variable in consistency & arrangement, they are from within outward:

1. Pia mater.
2. Arachnoid mater.
3. Dura mater, which is divided into:

A; Inner fibrous layer, the dura proper or fibrous dura.

B; Outer membranous layer, the endosteal (periosteal) dura.

Pia mater:

• This is a delicate, intimate areolar investment which faithfully follows the contour of the brain & cannot be dissected from it.
• It is invaginated into the nervous tissue with blood vessels surrounded by a tubular prolongation of CSF-filled subarachnoid space named the perivascular space.
• It is evaginated with cranial (& spinal) nerves which leave the nervous tissue.
• It is meshed with blood vessels so it exhibits the name (vascular membrane).

Arachnoid mater:

• This is a delicate, transparent membrane made mainly of collagenous & elastic fibers & lined by squamous mesenchymal epithelium.
• It is separated from the pia by the CSF-filled subarachnoid space.
• It is loosely applied to the brain & don’t strictly follows its contour, so it approaches (& may come in touch with) the pia over brain gyri but diverge from it over the sulci.
• The only invagination of the arachnoid on the brain is into the longitudinal fissure of the brain.

The subarachnoid space:

• This CSF-filled space is crossed by trabeculae derived from the two bounding meninges.
• In regions where brain contour change markedly, the arachnoid mater bridges over wide intervals of pia-covered brain tissue resulting in large CSF lakes called subaracnoid cisterns.
• These cisterns are mainly located under the brain & they are traversed by cranial nerves & blood vessels in the region of the cistern. The main cisterns are four:

1. Cisterna cerebellomedullaris; between the undersurface of the cerebellum above & the roof of the fourth ventricle below.
2. Cisterna interpeduncularis; lies in front of the midbrain between the two cerebral peduncles.
3. Cisterna pontis; lies in front of the basilar part of the pons between it & the basilar part of the occipital bone.
4. Cisterna chiasmatica; lies just below the optic chiasma

• Arachnoid villi; finger-like projections of arachnoid through the fibrous dura into the superior sagittal sinus where CSF diffuses into the venous blood
• Arachnoid granulations; are the folded round ends of the villi which have special histological structure to permit CSF diffusion

Dura mater:

Endosteal layer:

• This is the periosteum of the undersurface of the cranial bones lies external to the fibrous layer.
• Because of its more intimate relation & fusion with the fibrous dura than cranial bones from which it can easily be pealed off, this layer is regarded as an external layer of cranial dura mater
• Venous sinuses are located in separations of the two layers of dura or between folds of the fibrous layer of dura mater

Fibrous layer "dura proper":

• This is a tough, dense, fibrous membrane which encloses & protects brain tissue
• Folds of this layer between various parts of brain tissue are responsible for preventing the effects of movements of the head on the floating brain
• Dural folds are four in number:

1. Falx cerebri
2. Tentorium cerebelli
3. Falx cerebelli
4. Diaphragma sellae

Falx cerebri:

• This is a sickle-shape dural fold which occupies the median longitudinal fissure of the brain
• It is attached anteriorly to crista galli & broadens as it goes backward to end by becoming continuous with the dorsal surface of the tentorium cerebelli
• Its upper convex border is attached to the midline of cranial bones & sagittal suture enclosing the superior sagittal sinus, it ends posteriorly at the internal occipital protuberance
• The inferior concave margin arches over corpus callosum of the brain to end posteriorly in the straight sinus

Tentorium cerebelli:

• This fold separates the cerebellum from the undersurface of occipital lobes of the cerebrum
• It is elevated in the midline like a tent where it meets the posterior end of falx cerebri
• Its attached posterior margin encloses the lateral (transverse) sinuses which diverge from the internal occipital protuberance on the occipital bone
• Its attached anterior margin encloses the superior petrosal sinuses along the top of the petrous bone
• The anterior concave free margin arches around the brainstem & is attached anteriorly to the anterior clinoid processes
• The straight sinus lies in the line of junction of the tentorium with the falx cerebri

Falx cerebelli:

• This shallow fold separates the two cerebellar hemispheres
• It is attached to the internal occipital crest
• It contains the occipital venous sinuses

Diaphragma sellae:

• This is a horizontal fold of dura projecting from the margins of sella turcica
• It roofs the sella leaving a midline opening for the pituitary stalk

Dural venous sinuses:

• These are endothelial-lined spaces between the two dural layers or between folds of fibrous dura
• They are the collecting channels of cerebral, meningeal & diploic veins
• They communicate with external veins by emissary veins
• They end in the IJV either directly or indirectly
• They are classified by many classifications, one of them is:

1- Midline unpaired sinuses

2- Paired sinuses

Unpaired sinuses:

1- Superior sagittal sinus:

• Begins at foramen caecum where it receives a vein from the roof of the nose
• Passes back in the root of the falx cerebri to the internal occipital protuberance being triangular in coronal section
• As it goes backward it becomes larger as it receives more blood
• The lateral blood lakes (lacunae) lie on each side of it at parietal level, into these lakes the arachnoid granulations bulge for diffusion of CSF
• It receives cerebral, diploic & emissary veins
• At the internal occipital protuberance it ends in the sinus confluence or bifurcates into right & left lateral sinuses or continues to one side "usually the right" as the lateral sinus

2- Inferior sagittal sinus:

• Begins one third the distance behind the attachment of the falx cerebri
• It occupies the inferior margin of the falx
• Ends posteriorly in the straight sinus
• It receives tributaries from the medial surface of the hemispheres & from the falx

3- Straight sinus "sinus rectus":

• It is the continuation of the inferior sagittal sinus in the tentorium cerebelli
• It lies in the line of junction of the falx cerebri & the tentorium
• It receives the great cerebral & superior cerebellar veins
• Ends as the superior sagittal sinus at the internal occipital protuberance buts it has the tendency to continue as the left transverse sinus

Paired sinuses :

1- Cavernous sinus:

• They lie in the MCF on either side of sella turcica extending from the superior orbital fissure anteriorly to the apex of petrous bone posteriorly
• They are trabeculated as to be given the name "cavernous"
• They begin anteriorly by union of the superiorophthalmic vein & sphenoparietal sinus
• They end posteriorly by division into the superior & inferior petrosal sinuses
• They communicate with the angular vein & pterygoid plexus

a) Contents of the lateral wall:

• Oculomotor nerve
• Trochlear nerve
• Ophthalmic & maxillary divisions of trigeminal nerve

b) Contents of the lumen:

• Abducent nerve
• ICA enters the sinus from below posteriorly at foramen lacerum & passes in its floor grooving the bone to pierce its roof anteriorly medial to the anterior clinoid process to the circle of Willis

2- Intercavernous sinuses:

• Connect the two cavernous sinuses
• Pass anterior & posterior to the stalk of the hypophysis

3- Sphenoparietal sinuses:

• Lie in the dural fold at the lesser wing of sphenoid
• Receive radicles from the midle meningeal veins
• End in the cavernous sinus

4- Superior petrosal sinus:

• Lie in the attached anterior margin of the tentorium at the top of the petrous bone
• They connect the cavernous with sigmoid sinuses
• They receive the cerebellar, inferior cerebral & tympanic veins

5- Inferior petrosal sinus:

• Arise from the postero-inferior part of cavernous sinus
• Groove the petro-occipital fissue
• Pass through the anterior compartment of jugular foramen
• End in the IJV
• Receive pontine, labyrinthine, medullary & cerebellar veins

6- Basilar plexus:

• Lie on the basilar part of the occipital bone
• Connect the two inferior petrosal sinuses
• Connected to the anterior vertebral venous plexus

7- Occipital sinuses:

• Arise from union of small veins near foramen magnum
• Pass through the root of falx cerebelli
• Ends at the internal occipital protuberance at the confluence of sinuses

8- Sphenoparietal sinuses:

• Arises by receiving a radical from the middle meningeal vein deep to the pterion
• Lies in dura on the undersurface of the lesser wing of sphenoid
• Ends in the anterior part of the cavernous sinus

9- Transverse (lateral) sinuses:

• Begin at the internal occipital protuberance
• They lie in the posterior attached margin of the tentorium cerebelli
• They extend laterally to reach the base of the petrous temporal where they receive the superior petrosal sinus & descend in the posterior cranial fossa the sigmoid sinuses
• They receive the inferior cerebral & superior cerebellar veins

10- Sigmoid sinuses:

• Are large S-shape sinuses formed at the root of the petrous bone by confluence of the lateral & superior petrosal sinuses
• They groove the deep surface of the mastoid process of temporal bones
• They continue on the occipital bone to reach the jugular foramen
• At the jugular foramen they continue as the IJV
• They receive the mastoid emissary veins & inferior cerebellar veins

Blood supply of cranial dura:

Arteries:

The endosyeal layer of dura is very richly supplied by blood, unlike the fibrous layer which needs little supply.

1- Supratentorial part is supplied by the middle meningeal artery, a branch of maxillary artery which enters the cranium through foramen spinosum & divides into anterior & posterior divisions.

The anterior division courses up passing over the precentral gyrus, haematoma in this region causes contralateral paralysis.

The posterior one passes back courses over the superior temporal gyrus, haematoma from this artery causes contralateral deafness.

2- Cranial fossae:

1. Anterior CF: ophthalmic & anterior ethmoidal arteries.
2. Middle CF: middle & accessory meningeal arteries.
3. Posterior CF: vertebral arteries.

Veins:

Blood is collected into two main sources:

1- Middle meningeal veins, accompany the arteries & leave the cranium through foramen spinosum to enter the pterygoid plexus.

2- Diploic veins, which drain either to the exterior or to dural venous sinuses especially the superior sagittal.

Nerves:

1- Supratentorial dura : tentorial branches of Va.

2- Cranial fossae:

1. ACF: Anterior & posterior ethmoidal n.
2. MCF: Vb & Vc.
3. PCF: meningeal branches of IX & X cranial nerves
4. The area around foramen magnum: the upper three cervical spinal nerves.

Lymphatic drainage of the head & neck:

• Lymph from H & N is collected into two major circles of lymph node chains, superficial & deep circles
• From both circles, lymph is eventually collected to the deep cervical lymph nodes which lie along the IJV between the two circles
• Deep CLN, as they lie along the IJV is roughly divided into superior & inferior groups, each of which is further divided into anterior & posterior
• Of the anterosuperior group, the jugulodigastric node is of special importance since it collects lymph from the tongue & palatine tonsils
• Of the posteroinferior group, the juguloomohyoid node is of special importance since all lymph from the tongue pass directly to it bilaterally before it is collected in the jugular lymph trunk
• From the deep CLN, lymph is collected into the jugular lymph trunk, then to the thoracic duct (left side) & right lymph duct

Superficial circle:

1- Submental LN

2- Submandibular LN

3- Preauricular (parotid) LN

4- Post (Retro) auricular (mastoid) LN

5- Occipital LN

6- Mandibular LN

7- Buccal LN

8- Anterior jugular LN

9- External jugular LN

Deep circle:

1- Pretracheal LN

2- Paratracheal LN

3- Retropharyngeal LN

(10): DEEP CERVICAL LN

Submental LN:

Position: Submental triangle between the two anterior bellies of digastric

Afferent: Wedge shape piece between the two lower canines including the lower incisors, their gum, lower lips, floor of the mouth & tip of the tongue

Efferent: Submandibular & anterosuperior group of DCLN

Submandibular LN:

Position: Submandibular triangle in & around the gland

Afferent: Area of the face anterior to the facial artery, anterior nose, gums, tongue, hard palate, submandibular gland & adjacent nodes (submental, buccal & mandibular)

Efferent: Anterosuperior group of DCLN

Preauricular LN:

Position: In & around the parotid gland

Afferent: Anterolateral part of the scalp, temporal fossa, part of the face lateral to facial arteries, external ear, lateral part of eyelids & parotid gland

Efferent: Anterosuperior group of DCLN

Retroauricular LN:

Position: On the mastoid process

Afferent: Posterolateral part of the scalp & external ear

Efferent: DCLN

Occipital LN:

Position: In the apex of posterior triangle along the occipital artery

Afferent: Back of the neck & posterior part of the scalp

Efferent: DCLN

Mandibular LN:

Position: At the lower border of the mandible as the facial artery enters the face

Afferent: Adjacent area of face & neck

Efferent: Submandibular LN

Buccal LN:

Position: On buccinator

Afferent: Adjacent area of the face, nose & lips

Efferent: Submandibular LN

Anterior jugular LN:

Position: Around the AJV

Afferent: Adjacent area of neck

Efferent: DCLN

External jugular LN:

Position: Around the EJV

Afferent: Adjacent area of the cervical skin, parotid region & lower lateral part of the external ear

Efferent: DCLN

Pretracheal & prelaryngeal LN:

Position: Anterior to trachea & larynx

Afferent: Trachea, larynx, adjacent parts of the thyroid gland

Efferent: DCLN

Paratracheal LN:

Position: Between the trachea & oesophagus near the recurrent laryngeal nerve

Afferent: Trachea, oesophagus & lateral part of the thyroid gland

Efferent: DCLN

Retropharyngeal LN:

Position: Anterior to the prevertebral fascia, behind the pharynx & oesophagus, its enlargement causes dysphagia

Afferent: Pharynx, oesophagus, posterior part of nasal cavity, paranasal sinuses, nasopharynx, oropharynx & back of the tongue

Efferent: DCLN

　

　

Parasympathetic ganglia in the head & neck:

• The parasympathetic system of the H & N is represented by FOUR cranial parasympathetic ganglia which share in the supply of structures recommending this type of autonomic supply
• These are: CILIARY, PTERYGOPALATINE, SUBMANDIBULAR & OTIC ganglia
• Each of the four possesses three roots:

1- Sensory: from the trigeminal nerve for common sensation

2- Sympathetic: Postganglionic branches from the superior cervical sympathetic ganglion reaching via a branch from the carotid system

3- Parasympathetic (motor): from parasympathetic nuclei in the brainstem

- Postganglionic branches of these ganglia contain fibers from all the three modalities are furnished to the specific areas

Ciliary G.:

Sensory root: Nasociliary n. (Va)

Sympathetic root: Along Ophthalmic branch of ICA

Parasympathetic root: E-W nucleus in the midbrain – III - N. to inferior oblique

Postganglionic branches (short ciliary n):

- Ciliary & sphincter pupillae muscles

Pterygopalatine G.:

Sensory root: Maxillay n. (Vb)

Sympathetic root: (Deep petrosal n) Along ICA

Parasympathetic root: Superior salivary nucleus - nervus intermedius - greater petrosal nerve

Greater + deep petrosal nerves = vidian nerve (n. of pterygoid canal)

Postganglionic branches:

- Lacrimal, nasal, nasopharyngeal & palatal glands

Submandibular G.:

Sensory root: Lingual n. (Vc)

Sympathetic root: Along facial branch of ECA

Parasympathetic root: Superior salivary nucleus - nervus intermedius - chorda tympani

Postganglionic branches:

- Submandibular & sublingual salivary glands

Otic G.:

Sensory root: Auriculotemporal n. (Vc)

Sympathetic root: Along middle meningeal branch of maxillary artery (ECA)

Parasympathetic root: Inferior salivary nucleus – IX - lesser petrosal nerve

Postganglionic branches:

- Parotid gland

The temporomandibular joint:

• This is an articulation between the mandibular head & the mandibular fossa on the undersurface of the squamous temporal bone.
• Since both heads of the mandible belong to one bone, movement of one TMJ will inevitably move the other one, therefore the TMJ is regarded as a bilateral components of one cranio-mandibular articulation.

The capsule:

The strong fibrous capsule is attached at the skull to:

• Eminentia articularis …… Anteriorly
• Squamotympanic fissure …… Posteriorly
• Margins of the articular surface …… on each side

The attachment on the mandible is around the articular surface except posteriorly where the capsular attachment is much lower than anterior level

The disc:

• The joint cavity is divided, by a fibrocartilagenous disc, into upper & lower compartments.
• The disc is attached at the periphery to the underside of the annular fibrous capsule.
• The disc concavoconvex anteroposterioly in the sagittal plane

Stability:

In addition to the bony contour & muscular attachment, stability of the TMJ is enhanced by three main ligaments:

1- Lateral lig.: From the undersurface of the zygomatic arch passes lateral to the neck of the mandible to be attached to the posterior part of the neck, it prevents forward dislocation.

2- Stylomandibular lig.: From the styloid process down to the back of the angle of the mandible.

3- Sphenomandibular lig.: From the spine of sphenoid to the lingula of mandibular foramen.

The latter two ligaments pass medial to the joint.

Anterior dislocation of the mandible:

*The TMJ is more stable in occlusion than open position since the teeth stabilize the mandible on the maxilla

*Articular eminence & tension of masticatory muscles (except lateral pterygoid) prevent open mouth from anterior dislocation

*Lax muscles & ligament with forced opening of the mouth will lead to anterior mandibular dislocation which will not return due to spasm of the three stabilizing muscles themselves

*In order to reduce this dislocation, downward push on the molar teeth for a moment before reducing the dislocation is mandatory to overcome muscular spasm

Movements of the TMJ:

*Elevation-depression, (open-close) mov.:

• Axis:rotation occurs around a horizontal axis passing through both mandibular heads
• Joint compartment: lower (below the disc)
• Main muscles:

Open: digastric & lateral pterygoid

Close: other three masticatory muscles

*Gliding (side-to-side) movement:

• Axis: Rotation of the mandible around axis which lies just behind the head on the other side
• Compartment: Upper (above the disc)
• Main muscles: Pterygoids on one side push the mandible to the other

*Protractio-retraction movement:

• Compartment: Upper
• Main muscles: All masticatory muscles protract & passive recoil retract

Blood & nerve supply:

• The joint is supplied by arteries & veins in the vicinity.
• Superficial temporal & maxillary arteries are the main distributors
• Auriculotemporal nerve is the main sensory nerve for the joint

Joint type:

TMJ is a typical synovial joint of ball & socket variety