Introduction to Human Anatomy

Introduction to Human Anatomy
Nawfal K. Al-Hadithi, Chairman, Anatomy Dept., College of Medicine, University of Baghdad

ANATOMY ?
Anatomy is one of the cornerstones of a doctor’s medical education.
What is being taught today may differ in content significantly from the past but the methods used to teach this have not really changed that much
It includes the study of those structures that can be seen grossly (without the aid of magnification) and microscopically (with the aid of magnification).
Typically, when used by itself, the term 'anatomy' tends to mean gross or macroscopic anatomy.
Microscopic anatomy, also called 'histology', is the study of cells and tissues using a microscope
Embryology, Molecular Biology, Histochemistry … were included
Sectional Anatomy, Radiologic Anatomy, Surgical Anatomy … are evolving
How can gross anatomy be studied?
Prosection:
A prosection is the dissection of a cadaver (human or animal) or part of a cadaver by an experienced anatomist in order to demonstrate for students anatomic structure
Dissection:
Dissection (also called anatomization) is usually the process of disassembling and observing something to determine its internal structure and as an aid to discerning the functions and relationships of its components.
The anatomical position:
This position is the standard reference position of the body used to describe the location of structures
Standing upright
Feet together
Hands by the side
Face looking forward
Mouth is closed
Facial expression is neutral
Palms face forward with the fingers straight and together and with the pad of the thumb turned 90° to others
Toes point forward
Anatomical planes:
1- Coronal planes are oriented vertically and divide the body into anterior and posterior parts.
2- Sagittal planes are oriented vertically and divide the body into right and left parts.
The plane that divides the body into equal right and left halves is termed the median plane.
3- Transverse, horizontal, or axial planes divide the body into superior and inferior parts.
Sections:
- Longitudinal sections: run parallel to the long axis of the body or of any of its parts regardless of the position of the body
- Transverse sections: or cross sections, are slices of the body or its parts that are cut at right angles to the longitudinal axis of the body or of any of its parts
- Oblique sections: are slices of the body or any of its parts that are not cut along the previously listed anatomical planes
Terminology:
Terms of relationship:
These are terms used to describe the location of structures relative to the body as a whole or to other structures
Anterior & posterior: describe the position of structures relative to the 'front' and 'back' of the body.
. Anterior; nearer to the front
. Posterior; nearer to the back
. Ventral Vs dorsal; in the trunk
. Palmar Vs dorsal ; in the palm
. Plantar Vs dorsal; in the foot
Medial and lateral: describe the position of structures relative to the median plane
. Medial; nearer to the median plane
. Lateral; away from the median plane
Superior and inferior: describe structures in reference to the vertical axis of the body.
. Superior; nearer to the vertex
. Inferior; nearer to the sole
Proximal & distal: used with reference to the origin or attachment of a structure, particularly in the limbs.
Proximal; nearer to origin
Distal; away from origin
Superficial & deep: used to describe the relative positions of structures with respect to the surface of the body.
Superficial; nearer to surface
Deep; away from surface
External & internal: used to describe the position in relation to the center
External; away from center
Internal; nearer to center
Terms of laterality:
Bilateral; paired strucures present on both sides (kidneys)
Unilateral; unpaired structure present on one side (spleen)
Ipsilateral; same thing present on the same side of the body (thumb & big toe)
Contralateral; same thing present on the other side of the body (Rt & Lt hands)


The skin (integumentum):
The largest body organ
Excellent indicator of the body health
Needs careful examination
Acts for:
Protection
Sensation
Cosmetic
Thermal regulation
Vit D sybthesis
Made of:
Epidermis
Dermis
Appendages:
Hair
Nails
Langer (cleavage) lines
Fasciae:
Fibro-areolar or aponeurotic laminæ, of variable thickness and strength
They act as wrapping, packing & insulating materials in the tissues
They have been subdivided into superficial and deep
Superficial fascia (subcutaneous tissue):
- Found immediately beneath the skin
Consists of fibroareolar tissue, containing in its meshes pellicles of fat in varying quantity.
Deep fascia:
- Is a dense, inelastic, fibrous membrane, forming sheaths for the muscles, and in some cases affording them broad surfaces for attachment.
They form compartments & intermuscular septa
Potential spaces are sometimes present between folds of deep fascia
Fascia is thick in unprotected situations, as on the lateral side of a limb
May assist muscle action by increasing the degree of tension
May surround special structures (carotid, parotid fascia…)
Muscles:
Classification:
1- Voluntary muscles (skeletal):
Parallel fibers with peripheral nuclei
Characteristic striation across fibers
Supplied by somatic nerves
Without motor supply they cannot contract
2- Involuntary muscles:
A) Cardiac muscles:
Fibers not parallel
Show striation
Usually have autonomic control
Contract automatically
B) Smooth muscles:
Fibers show no striation with big central nuclei
Supplied by autonomic system
Need autonomic supply to contract
C) Skeletal muscles:
Muscle is for movement
They are connected to bones, cartilages, ligaments, and skin
Muscle is composed of a belly & tendon
Muscles vary extremely in their shape:
Long muscles
Flat  muscles
Diaphragms
Fiber arrangement:
Flat muscles: have parallel fibers often with an aponeurosis
Fusiform muscles: spindle shaped with a round belly and tapered ends
Convergent muscles: from a broad origin fibers converge to a single tendon
Circular or sphincter muscles: surround a body opening or orifice, constricting it when contracted
Multi-headed muscles: have more than one head or more than one contractile belly
Quadrate muscles: have four equal sides
Pennate muscles: Oblique fibers converge to a tendon:
.Unipennate; fibers converge to one side of the tendon (FHL)
.Bipennate; fibers converge to both sides of a central tendon (tibialis posterior)
.Multipennate; fibers pass between septa within the muscle in 2 opposite directions, as in deltoid 
Muscle tendons:
White, glistening, inelastic fibrous cords
They consist almost entirely of collagen fibers
Their blood supply is very spares.
Their nerves have special modifications of their terminal fibers (organs of Golgi).
Aponeuroses:
The non fleshy part of flat muscles
They appear white color, iridescent, glistening, and similar in structure to the tendons.
They are only sparingly supplied with blood vessels
Muscle names, derived from:
(1) Situation, as tibialis, radialis ...
(2) Direction, as rectus, obliqus …
(3) Function, as flexor, supinator …
(4) Shape, as deltoid, rhomboid
(5) Number of heads, as biceps, triceps
(6) Points of attachment, as sternocleidomastoid
Terms related to muscles:
Origin: is meant to imply its more fixed or central attachment
Insertion: the movable point
* The origin is absolutely fixed in only a small number of muscles
* Accurate knowledge of these is of great importance in the understanding their mechanics
Muscle action:
Prime mover: direct action
Synergist: complemets the prime mover
Antagonist: opposes or inhibits the prime mover
Fixator; a muscle which fixes certain parts to promote the action of the acting muscle & reduce power loss
Bones:
206 named bines
Axial & appendicular skeleton
* Ossification:
1- O. in cartilage
2- O. in membrane
* Bone vasculature & nerve supply:
Periosteum
Nutrient arteries
Nerves
* Compact & spongy bones
Bone shapes:
1- Long bones: have shaft & 2 ends
2- Short bones: cube like
3- Flat bones: thin, flattened, with slight curvature
4- Irregular bone: complicated shapes
5- Sesamoid: within tendons
Ligaments:
A ligament is a cord of connective tissue uniting two structures
Usually associated with joints
Histologically divided into fibrous & elastic
Bursae:
A bursa is a lubricating device consisting of a closed fibrous sac lined with a delicate smooth membrane & filled with a jelly-like fluid
They are found where tendons rub against hard structures
Synovial Sheath:
A synovial sheath is a tubular bursa that surrounds a tendon
It is a lubricating & protective structure
Cartilage:
A type of elastic connective tissue of three main histological types:
1- Elastic:
Flexible, contains mainly elastic fibers
Never ossifies
Not seen in joints
2- Fibrocartilage:
Cartilage containing collagen fibers
It is very tough structure, never fracture
3- Hyaline:
Tough but brittle
May ossify with age
Is the most common type
Joints:
Joints are the meeting points between:
Two bones
Two cartilages
Bone & cartilage
Structural types:
1- Fibrous J.
2- Cartilagenous J.
3- Synovial J.
Morphological types:
1- Ball & socket J.
2- Condaloid J.
3- Gliding J.
4- Hinge J.
5- Pivot J.
6- Saddle J.
I) Fibrous joints:
Articulating surfaces are fastened together by dense connective tissue containing collagen:
  
II) Cartilaginous joints:
Articulating bones are connected by hyaline cartilage or fibrocartilage:
 
III) Synovial (diarthrotic) joints:
Characterized by:
Surrounded by a joint capsule
Supported by ligaments
Lined with synovial membrane
Covered by hyaline cartilage
Contains synovial fluid
     
Joint movements:
Four types of movements are conducted on joints:
1- Gliding movement:
One surface glides over the other
It is common to all movable joints
This movement may exist between any two contiguous surfaces (not confined to joints)
2- Angular movement:
Occurs only between the long bones
The angle between the two bones is increased or diminished
It may take place:
(1) Forward and backward, constituting flexion and extension
(2) Toward and away from the median plane (or a specific axis), constituting adduction and abduction.
(3) Circumduction:
A combination of the four angular movements
Best seen in the shoulder and hip-joints
(4) Rotation:
Movement around a central axis without any displacement
The axis of rotation may lie in a separate bone or the bone itself
Rotation could be medial or lateral
* Special movements:
Inversion – eversion
Pronation – supination
Opposition

















The nervous system:
Division of the nervous system:
I- The somatic nervous system:
1- The central nervous system (CNS):
Brain
Spinal cord
2- The peripheral nervous system (PNS)
Cranial nerves
Spinal nerves
II- The autonomic nervous system
1- Sympathetic NS
2- Parasympathetic NS
Cells in the nervous system:
Neuron:
Are the nerve cells. They form the basic building unit in the NS
Parts:
1- The soma
2- The processes:
Dendrites: the short processes of the, usually bring impulses toward the soma
Axon: the longest process of the soma, usually takes impulses away from it
Schwann cells:
Form the myelin sheath envelop of the axon
Neuroglia:
Are the supporting cells of the NS
Gray & white matters:
The interior of the central nervous system is organized into gray and white matter
 Gray matter consists of nerve cells embedded in neuroglia
White matter consists of nerve fibers (axons) embedded in neuroglia
Schwann cells:
Large, flat cells wrap the nerve processes
They contain an insulating material, the myelin which preserves the nerve potential
The space between two adjacent Schwann cells is called the node of Ranveir
Electrical potentials travel from one node to another
Impulse passes in myelinated nerves faster than non-myelinated nerves
Neuroglia:
They are of four types:
1- Astrocytes
2- Oligodendrocytes
3- Microglia
4- Ependyma (lining brain ventricles)
Divisions of the CNS:
1- The Brain:
Forebrain:
Cerebrum
Diencephalon
B) Midbrain
C) Hindbrain:
Pons
Medulla oblongata
Cerebellum
2- The spinal cord
The brain:
The brain receives information from, and controls the activities of, the trunk and limbs through connection with spinal cord
It also possesses 12 pairs of cranial nerves through which it communicates mostly with structures of the head and neck.
In addition to sensory perception & issuing motor commands, the brain is responsible for maintaining visceral activities, & functions which characterizes human beings like thinking & personality
The spinal cord (medulla spinalis):
This long tubular structure is continuous with the brainstem
It is 45 cm long in mature male
Gray matter of the cord lies interior & arranged in an (H) shaped fashion:
. Anterior horn neurons are motor
. Posterior horn neurons are sensory
. Lateral horn is present in a part of the cord for sympathetic function
White matter constitutes bundles of fibers called (tracts) providing complex connections
Peripheral Nervous System:
Mainly formed of nerves (axons)
Collection of soma in the PNS form ganglia
The cranial nerves:
12 pairs of nerves arise from the brain or brain stem
May be sensory, motor or mixed
4 of them carry autonomic supply (III, VII, IX & X)
Their destination is variable & may reach as far as the colon
Collection of nerve cells outside the CNS is called ganglion

Modality    Name    Nerve number      
Sense of smell    Olfactory    I      
Sense of vision    Optic    II      
Motor to ocular muscles + parasympathetic    Oculomotor    III      
Motor to superior oblique    Trochlear    IV      
Sensory to face + motor    Trigeminal    V      
Motor to lateral rectus    Abducent    VI      
Motor to face muscles + parasympathetic    Facial    VII      
Sense of hearing & equilibrium    Vestibulocochlear    VIII      
Mixed    Glossopharyngeal    IX      
Motor + parasympathetic    Vagus    X      
Motor    Accessory    XI      
Motor to tongue muscle    Hypoglossal    XII   


The spinal nerves:
31 pairs of  nerves spring from the spinal cord, and are transmitted through the intervertebral foramina

Number of vertebrae    Number of nerves    Region      
7    8    Cervical      
12    12    Thoracic      
5    5    Lumbar      
5    5    Sacral      
1    1    Coccygeal   

Nerve Roots:
Each nerve is attached to the cord by two roots, an anterior & a posterior, the latter being characterized by the presence of a ganglion, the spinal ganglion
The anterior root (MOTOR): formed by axons of neurons in the anterior horn of gray matter
The posterior root (SENSORY): formed by axons of neurons in the spinal ganglion
Both roots unite in the intervertebral foramen to form the spinal nerve (mixed)
The spinal (dorsal root) ganglia:
Collections of nerve cells on the posterior roots of the spinal nerves.
Ganglia are usually placed in the intervertebral foramina
The ganglia contain unipolar neurons whose single process divides into two:
* Peripheral process, represents the dendrites & conveys information from the body to the nerve cell
* Central process, represents the axon & conveys these information into the posterior horn cells of S.C
Structure of the spinal nerve:
The spinal nerve contains:
Motor fibers
Sensory fibers
Sympathetic fibers; given to the nerve in the intervertebral foramen
 Immediately after its formation, the spinal nerve divides into anterior & posterior rami
Each ramus contains the three modalities
Dorsal rami supply skin & muscles of the back of trunk
Ventral rami supply the ventral side of trunk & limbs
Synapses:
The small cleft between 2 adjacent neurons which represents site of functional interneuronal communication
Most neurons may make synaptic connections to a 1000 or more other neurons and may receive up to 10,000 connections from other neurons
Synaptic transmission is a chemical process
The neurotransmitter passes across the synapse affecting the charge (potential) of the post-synaptic cell
This change will liberate neurotransmitter from the cell to affect the coming one & so on
The spinal reflex:
A sudden stimulation of the sensory nerve fiber is conveyed to the dorsal horn neurons
These neurons have a direct communication with their corresponding ventral horn neurons via a connector cell called interneurones
These interneurones will stimulate the ventral horn cells unconsciously
Involuntary movement of the injured area away from the stimulus will result
The higher centers will receive information about what happened later!
Terms related to spinal nerves:
The spinal segment:
It is the part of spinal cord which gives origin to a single pair of spinal nerves
The dermatome:
It is the amount of skin supplied by a single spinal nerve
The myotome:
Is the amount of muscle fibers supplied by a single spinal nerve
Autonomic N.S:
Sympathetic N.S:
All parts of the body needs sympathetic innervation
Therefore it is distributed widely through these ways:
1- With spinal nerves (somatic)
2- Directly to viscera (visceral)
3- With blood vessels (vascular)
Sympathetic ganglia are present on each side of the vertebral column & distribute these branches
This system is under control of the CNS through nerves called preganglionic nerves & enter sympathetic ganglia
Its direct branches to the target are called postganglionic nerves & leave these ganglia
The system provides motor & sensory functions
Functions of the sympathetic system:
The function of the sympathetic system is to prepare the body for an emergency.
The heart rate is increased, arterioles of the skin and intestine are constricted, arterioles of skeletal muscle are dilated, and the blood pressure is raised.
There is  redistribution of blood; thus, it leaves the skin and GIT to go to the brain, heart, and skeletal muscle.
- Sympathetic stimulation dilates the pupils; inhibit smooth muscle of the bronchi, intestine, and bladder wall; and close the sphincters.
The hair is made to stand on end, and sweating occurs.
Parasympathetic system:
Not all parts of the body needs this innervation
P.S system does not have the well defined structure like the S. system
Most of P.S innervation is distributed with cranial nerves & sacral spinal segment
Like S. system it is under control of the CSN by preganglionic nerves & its target branches are called postganglionic nerves
Like S. system, it provides sensory & motor functions
Functions of the P.S system:
The activities of the parasympathetic part of the autonomic system are directed toward conserving and restoring energy.
The heart rate is slowed
Pupils are constricted
Peristalsis and glandular activity is increased
Sphincters are opened
The bladder wall is contracted.