THE FOREARM

FOREARM
Forearm is part of the upper limb lying between the elbow and the wrist. It takes the shape of a cone which is flattened anteroposteriorly, the transverse diameter is wider close to the elbow this is as a result of the mass of the muscle of the forearm. The transverse diameter increase towards the elbow and decreases downward due to decrease in the mass of muscles.

It is enclosed by a deep fascia which enclosed all the structures. In the elbow it is strengthened anteriorly by the biccipital aponeurosis, and towards the wrist, it forms the flexor and extensor rectinaculum. It sends septa to the bones of the forearm. It also gives attachment to some of the muscles of the forearm.
The muscles of the forearm are morphologically arranged into flexor compartment muscles and extensor compartment muscles. The flexor compartment is limited medially by the post subcutaneous border of the ulnar bone which is marked superficially by the ulnar artery. The extensor compartment is limited posteromedially by the posterior border of the ulnar and laterally by the extent of the radial artery.

FLEXOR COMPARTMENT
It is made up of muscles which are arranged in superficial and deep layers. The superficial layer muscles are five in number and they include:
· Pronator teres
· Flexor carpi radialis
· Flexor carpi ulnaris
· Flexor digitorum superficialis
· Palmaris longus
In the deep group they are three muscles which include:
· Flexor digitorum profundus
· Flexor pollisis longus
· Pronator quadratus.

PRONATOR TERES
Origin:
By means of 2 heads:
1. Common flexor origin at the medial epicondyle of the humerus.
2. The deep head from medial part of the coronoid process of ulnar bone. In between the two heads runs the median nerve which could be compressed resulting to pronator symdrome.

INSERTION: Middle 1/3rd of the lateral surface of the radius.
ACTION: Pronates the forearm and also acts as a weak flexor of the elbow joint.
NERVE SUPPLY: Median nerve

FLEXOR CARPI RADIALIS
ORIGIN: Common flexor origin which is at the medial epicondyle.
INSERTION: Towards its medial half the muscle gives its tendon which passes beneath the flexor retinaculum of the forearm and get attached to the 2nd and 3rd metarcarpal bones
Action:
* Flexes the elbow joint
* With other muscle its flexes the wrist
* With radial extensors it abducts the hand.
Nerve supply: Median nerve.

PALMARIS LONGUS
Origin: Common flexor origin
Insertion: Distal part of the flexor retinaculum and apex of the palmar aponeurosis.
Action: With other muscles it flexes the wrist, it also helps to stretches the palmar aponeurosis.
Nerve Supply: Median nerve

FLEXOR CARPI ULNARIS
Two heads through which the ulnar nerve passes
Origin: Medial epicondyle, and from a wide aponeurosis arising from the upper three-fourths of the posteromedial surface of the ulna and the olecranon.
Insertion: It gets attached into the base of the fifth metacarpal but towards its insertion the pisiform bone lies within its tendon as a sesamoid bone.
Action: It is a flexor of the wrist it also act with ulna extensors to adduct the hand.
Nerve Supply: It is supplied by the ulnar nerve.

FLEXOR DIGITORUM SUPERFICIALIS
ORIGIN: It takes origin from a wider area:
· From the common flexor origin
· Medial ligament of the elbow joint
· Medial border of coronoid process
· From a fibrous arch connecting radius and ulnar
· From the whole length of the anterior oblique line of the radius.
Insertion: Towards the distal half of the arm it gives 4 tendons which are arranged two superficial for the middle and ring fingers and two deep for the index and little finger. These tendons pass beneath the flexor retinaculum and spread out in the palm, at the base of proximal phalanx each of the tendons enters the fibrous flexor sheath and then splits into two and sends decussating fibers which form a tunnel through which the tendon flexor digitorum profundus passes. The split parts unite again but at the base of the middle phalanx it separates and inserts at the shaft of the middle phalanx.
Action: It flexes the proximal interphallangeal joint and the metacarpophallangeal joint indirectly as it passes the joints. It is a weak flexor of the elbow and wrist joints.
Nerve Supply: Median nerve.



DEEP MUSCLE OF THE FLEXOR COMPARTMENT OF THE FOREARM:
FLEXOR DIGITORUM PROFUNDUS
Origin: From the medial surface of the olecranon. From the upper three – fourth of the medial and anterior surfaces of the ulnar and from the ulnar half of the interosseous membrane. It gives up four tendons which passes beneath the flexor retinaculum at the palm they separate and go to the medial four digits.
Insertion: It passes deep to the tube formed by the decussating fibers and get attached to the base of the distal phalanx.
Action: Directly it flexes the distal interphallangeal joint. Indirectly it flexes the distal interphallengeal joints.
Nerve Supply: It is supplied by both the ulnar nerve and median nerve. The ulnar nerve supply the part of the muscle fibers that go to the little and ring fingers

FLEXOR POLLICIS LONGUS
Origin: From the anterior surface of radial bone between the area of attachment of pronator teres and the area of attachment of pronator quadratus. Sometimes it extends upward to the radial tuberosity and from the radial half of the interosseous membrane.
Insertion: It passes beneath the flexor retinaculum and inserts at the base of the distal phalanx of the thumb.
Action: Directly it flexes the distal interphallangeal joint of the thumb. It is also involved in other pollicis movement.
PRONATOR QUADRATUS:
ORIGIN: Arises from the distal ¼ of the antero-lateral aspect of the ulnar at the pronator ridge.
Insertion: Distal ¼ anterior border and surface of the radius. It extends deeper into a triangular area above the ulnar notch and the styliod process.
Action: Principal pronator muscle of the forearm while the deeper fibers help to maintain the apposition of the lower ends of the radius and ulna.
Nerve Supply: Median nerve.


EXTENSOR COMPARTMENT
It is limited medially by the posterior border of the subcutaneous part of ulnar bone and laterally by the course of the radial artery. It contains 12 muscles which are arranged into superficial and deep groups. The superficial group is further subdivided into a lateral group and a posterior group. Some of the superficial group muscles which are about seven in number share a common extensor tendon which is attached anterior to the lateral epicondyle, others originate from the lateral supracondylar ridge and from the lateral intermuscular septum. The lateral group of superficial extensor muscles include:
1. Brachioradialis
2. Extensor carpi radialis longus
3. Extensor carpi radialis brevis
POSTERIOR SUPERFICIAL MUSCLE
1. Extensor Digitorum
2. Extensor Digiti minimi
3. Extensor Carpi Ulnaris
4. Anconeus
Deep group of extensor muscles include:
1. Abductor pollicis longus
2. Extensor Pollicis longus
3. Extensor pollicis brevis
4. Extensor indicis
5. Supinator muscle.

BRACHIORADIALIS
Origin: It is an extensor muscle with extensor nerve developmentally; it is an extensor compartment muscle but acts as a flexor muscle. It takes origin from the upper lateral 2/3rd of the supracondylar ridge. It passes down overlying the radial nerve.
Insertion: It gets attached at the base of the styloid process of the radial bone.
Action: Flexes the elbow joint though it can act in active extension and active flexion of the elbow joint.
Nerve Supply: Radial nerve.

EXTENSOR CARPI RADIALIS LONGUS
Origin: From the lower 1/3rd of the supracondylar ridge. And from the lateral intermuscular septum.
Insertion: It forms a flat tendon which is attached to the dorsal surface of the base of the 2nd metacarpal bone.
Action: It acts as a wrist extensor and its very important in the making of a fist.
Nerve supply: It is supplied by the radial nerve.

EXTENSOR CARPI RADIALIS BREVIS:
Origin: From the common extensors origin and run beneath the extensor carpi radialis longus.
Insertion: It forms a flat tendon which is attached to the 3rd metacarpal bone, It has a bursa on its superior and inferior ends. The inflammation of the superior end is referred to as tennis elbow.
Action: Extension of the wrist joint and it is also important in fist formation.
Nerve supply: It is supplied by the radial nerve.
EXTENSOR DIGITORUM:
Origin: It arises from the common extensor origin which is the anterior surface of the lateral epicondyle of the humerus.
Insertion: It gives rise to four tendons for each medial four digits which passes beneath the extensor retinaculum. On getting to the base of the corresponding proximal phalanx, each of the tendon divides into three slips the central slip get inserted into the middle phalanx, the other slips will diverge along the central slip, each will accept attachment of the interosseous and lumbrical muscles. This is referred to as dorsal extensor expansion. Towards the middle phalanx they converge and get attached to the base of the distal phalanx.
Action: Extends the interphallangeal joints.
EXTENSOR DIGITI MINIMI
Origin: It takes origin from the common extensor origin.
Insertion: It becomes tendinous passing beneath the extensor retinaculum up to the base of the 5th metacarpal bone, where it divides into two as it pass to the digiti minimi to join the dorsal expansion of the digit.
Action: extension of the little finger.
Nerve Supply: It is supplied by the radial nerve.
EXTENSOR CARPI ULNARIS
Origin: It takes origin from the common extensor tendon and from a common aponeurosis which it shares with the flexor carpi ulnaris.
Insertion: It is inserted into the base of the 5th metacarpal bone.
Action: Adduction of the wrist. It is also important in making a fist.
Nerve supply: It is supplied by the radial nerve.

ANCONEUS
Origin: Arises from the lowest part of the lateral epicondyle and is inserted in to the proximal part of the lateral side of the olecranon.
Action: Weak cubital extensor. (weak extensor). It is very minute in action. It is supplied by the radial nerve.




DEEP GROUP OF MUSCLES:

ABDUCTOR POLLICIS LONGUS
Origin: It takes origin from an oblique area on the radius and ulna and from the intervening interosseous membrane.
Insertion: It is inserted into the dorsal aspect of the base of the 1st metacarpal bone by means of a round tendon which splits into three separate bands. One of the bands extends beyond the metacarpal bone and then gives attachment to the abductor pollicis brevis.
Action: It helps in abducting and flexing the wrist joint it also abducts the thumb.
Nerve supply: It is supplied by the radial nerve.

EXTENSOR POLLICIS BREVIS
Origin: From the radial bone below the origin of the abductor pollicis longus and the adjoining interosseous membrane.
Insertion: It is inserted into the base of the thumb’s proximal phalanx by means of a slender tendon.
Action: It helps to extend the thumb’s proximal phalanx.
Nerve supply: It is supplied by the radial nerve.

EXTENSOR POLLICIS LONGUS
Origin: It originated from the ulnar bone also distal to the origin of the abductor pollicis longus and the adjoining interosseous membrane.
Insertion: It is inserted at the base of the distal phalanx.
Action: It extends the terminal phalanx of the thumb



EXTENSOR INDICIS
Origin: From the ulnar bone just distal to the origin of the extensor pollicis longus and the adjoining interosseous membrane and it passes through the extensor retinaculum beneath the extensor digitorum tendon.
Insertion: Its tendon joins the dorsal expansion of the index finger.
SUPINATOR
Origin: Arises by means of two heads in which the posterior interosseous nerve passes. The superficial head arises from the distal part of the lateral epicondyle and from the anterior part of the radial collateral ligament while the deep head arises from the supinator crest and fossa of the ulna.
Insertion: From the ulnar the fibers meet to be inserted in the radius between the anterior and lateral oblique line.
Action: It supinates the forearm especially when the elbow is extended.

CUBITAL FOSSA
It is an intermuscular space which is a depressed area found anterior to the elbow. It has a lateral and medial border, apex, base, a roof and floor and content.
· The medial boundary is formed by the lateral border of pronator teres.
· The lateral boundary is formed by the medial border of brachioradialis muscle
· The apex lies inferior and corresponds to the point where the brachioradialis over lap the pronator teres.
· The base lies superiorly and corresponds to an imaginary line passing between the lateral epicondyle and medial epicondyle. It is referred to as intercondylar line.
· The floor is formed superiorly by the brachialis and supinator muscle.
· Roof is formed by the deep fascia which is straightened medially by lacerta fibrosus (biccipital aponeurosis).
CONTENTS
Superficial to the roof runs the median cubital vein, the deep contents include from medial to lateral; the median nerve, brachial artery and its terminal branch the ulnar and radial artery, the tendon of biceps and radial nerve.
APPLIED ANATOMY
· It is the most convenient site for measuring blood pressure.
· The median cubital vein is the vein of choice for intravenous infussion

FLEXOR RETINACULUM
The flexor retinaculum is a tough fibrous band which is the condensed part of the deep fascia of the forearm which is found uniting the lateral and medial aspect of the carpal bones. It acts as a restraining band preventing the bowing out of the long flexor tendons around the wrist joint. Flexor retinaculum is attached medially to the pisiform bone and hook of hammate while laterally it is separated into two laminae; a superficial lamina which attaches to the tubercle of the scaphoid and trapezium and a deep lamina which attaches into the groove formed by the trapezius. This deep lamina and the groove formed by the trapezium form a separate tunnel for the tendon of flexor carpi radialis and its synovial sheath. Superiorly the retinaculum is continuous with the deep fascia of the forearm while inferiorly it is continuous with the deep fascia of the palm and the centrally placed palmar aponeurosis.
The flexor retinaculum is about 2 – 3cm in length and width. The bridging of the flexor retinaculum over the carpal bones gives rise to an osteofibrous tunnel which is known as the carpal tunnel. Through this tunnel passes the tendon of flexor digitorum profundus and superficialis, flexor pollicis longus and the median nerve while superficial to the flexor retinaculum passes the tendon of palmaris longus which is inserted into its distal half and the apex of the palmar aponeurosis. The tendon of flexor carpi ulnaris which is inserted into the base of the fifth metacarpal bone via the pisiform bone, the ulnar nerve and ulnar artery which lie lateral to the tendon of flexor carpi ulnaris and the palmar cutaneous branch of ulnar nerve and median nerve all run superficially over the flexor retinaculum.

APPLIED ANATOMY
CARPAL TUNNEL SYNDROME:
The inflammation of the synovial membrane which accompanies the long flexor tendons through the flexor retinaculum leads to compression of the median nerve within the carpal tunnel; this is known as carpal tunnel syndrome. The carpal tunnel is well crowded and the median nerve could easily be compressed in infections involving the synovial sheaths as a result of this compression on the median nerve there will be weakness in the action and wasting of the thenar muscles, there will also be loss of sensation around the radial two-third digits. The pressure caused by inflammation of the synovial sheaths can be relieved by incision of the flexor retinaculum. It should be noted that during carpal tunnel syndrome there is no loss of sensation over the skin of the thenar eminence, this is due to the fact that the median nerve has already given off a palmar cutaneous branch before entering the carpal tunnel.

EXTENSOR RETINACULUM
This is a broad band of condense part of the deep fascia of the forearm. It is about 2.5cm wide and lies obliquely across the extensor surface of the wrist joint.
ANATOMICAL SNUFF BOX
It is a depression found at the root of the thumb especially when the thumb is fully extended. It is bounded lateral by the extensor pollicis brevis and abductor pollicis longus and medial by the extensor pollicis longus, the floor is formed by the scaphoid and trapezium above is the styloid process of the radius and below is the base of the 1st metacarpal bone.
Contents:
Superficial radial artery
Cutaneous branch of the radial nerve

THE ARM

ARM
This is the part of the upper limb that lies between the shoulder and elbow joints. The bone of the arm is the humerus. The muscles of the arm are arranged in two compartments: The anterior and posterior compartments. The muscles present in the anterior compartment include:
· Bicep brachii
· Coracobrachialis
· Brachialis
In the posterior compartment is present one muscle known as the Tricep brachii.

BICEP BRACHII
ORIGIN: The bicep brachii arises by means of two heads as follows:
· Long head arises from supraglenoid tubercle forming its own belly
· Short head arises from the tip of coracoid process forming also its own belly
Both bellies will unite towards the lower aspect of the arm to become one and forms a tendon which passes through the cubital fossa to be inserted into the radial tubercle of the radius. It forms a though fascia known as bicipital aponeurosis which blends with the deep fascia of the upper medial aspect of the forearm.
Action: powerful supinator muscle of the forearm and flexor of the elbow joint.
Nerve supply: musculocutaneous nerve.

CORACOBRACHIALIS
Origin: Arises from the coracoid process.
Insertion: Medial part of the middle aspect of the humerus.
Nerve supply: Musculocutaneous nerve.
Action: Weak flexor of the shoulder joint, abductor muscle of the arm.


BRACHIALIS:
ORIGIN: Arises from the anterior surface of the lower half of the humerus.
Insertion: it is inserted into the ulnar tuberosity.
Nerve supply: Musculoctaneous nerve and radial nerve.
Action: It is the main flexor of the elbow joint. It is mainly used in smooth motions of the elbow joint like picking up a glass of wine or sipping a cup of hot tea.

TRICEP MUSCLE
It is the posterior compactment muscle which arises by means of three heads the long head, medial head and lateral head.
Origin:
Long head arises from infraglenoid tubercle; lateral head arises from the shaft above the upper lip of the radial groove while the medial head arises from the shaft of the humerus below the radial groove. In between the two origins along the spiral groove runs the radial nerve and profounda brachii artery.
The three muscle heads will later fuse to form one muscle belly at the lower 1/3rd of the humerus. Their common tendon is inserted into the tip of the olecranon process of the ulnar bone.
Nerve Supply: Radial nerve.
Action: Extension at the elbow joint and at the shoulder joint.

JOINTS OF THE SHOULDER REGION

JOINTS OF THE SHOULDER REGION
The joints of the shoulder region are of the synovial variety and to discuss synovial joints the following points should be kept in mind:
· The type of synovial joint.
· Bones and part of the bone that forms the joints
· Type of cartilage covering the articular surface.
· Attachment of fibrous capsule.
· Structures found within the capsules (Intracapsular structures).
· The attachment or lining of the synovial membrane.
· Extracapsular structures.
· Movement and muscle causing the movement.
· Blood and Nerve supply.
· Applied Anatomy.

Joints or the shoulder region include:
- Sternoclavicular joint.
- Acromioclavicular joint
- Shoulder joint

ACROMIOCLAVICILLAR JOINT
It is a synovial joint of the gliding type formed by lateral end of the clavicle and the medial margin of the acromion. The articular surface of the clavicle is convex while that of acromion is slightly concave. It is lined by a fibrocartilage. A tough fibrocapsule enclosed the joint cavity, it wrap around the articular margin of the joint. Within the capsule there is an articular disc which separates the articular surface. In most cases it does not divide the joint cavity into two, from the superior surface it extends downward. The acromioclavicular joint presents two ligaments;
Acromioclavilar ligament extends from the acromium to the clavicle. It is a very tough ligament. Coracoclavicular ligament extends from the lateral border of the coracoid process to the inferior border of the clavicle; it is strong and it is made up of two parts; trapezoid part with the shape of a trapezius and conoid part with the shape of an inverted cone. It holds into the scapular and the clavicle.
Movements that occur in this joint are passive and it is controlled by scapular rotation.
Blood supply: The joint is supplied by branches of the suprascapular artery, acromial branch of the lateral pectoral artery
Nerve supply: Suprascapular nerve, axillary Nerve, lateral branch of the supraclavicular Nerve.


Applied Anatomy:
It is prone to dislocation. It can involve the coracoclavicular ligament as a result the scapular will descend downwards while the acromium will ascend upwards. A simply test known as the piano keyboard sign is carried out to ascertain the dislocation of acromioclavicular joint. This is carried out by using the tip of the index finger to press down the tip of the acromium, this action reduces the pain immediately. The test is positive if as soon as the finger is released a sharp pain is felt.

SHOULDER JOINT (GLENOHUMERAL JOINT)
It is a synovial joint of the ball and socket variety. It permits a lot of movement. It is a multiaxial joint (3O freedom of movement) e.g. Abduction and adduction, circumduction, medial and lateral rotation making it a multiaxial joint. It sacrifices its bony stability for movement.
The hemispherical head of the humerus forms the ball which faces medially, upward and backward. The Socket is the shallow glenoid fossa or cavity and has tubercles above and below to give attachment to the long head of bicep and the long head of tricep respectively. The one above is the supraglenoid tubercle while below is the infraglenoid tubercle. The glenoid fossa is shallow and pear shaped.
The articular surface is lined by hyaline cartilage. The joint is enclosed by a tough but loose fibrous capsule which is attached medially to the margin of the glenoid fossa, it encloses the origin of the long head of biceps, and laterally it is attached to the anatomical neck of the humerus, inferomedial to the humerus it extends to enclosed upper 1cm of the shaft of the humerus. The long head of bicep is described as intracapsular but extrasynovial since it is not enclosed within the synovial cavity.
Intracapsular structure include: Glenoid labrum which is a fubrocartilage attach to the rim of the glenoid fossa increasing the concavity of the glenoid fossa and acting as a cushion to the head of the humerus; Long head of bicep which originated from the supraglenoid tubercle, traversing the cavity of the joint to pass through the intertubercular sulcus by passing beneath the transverse humeral ligament. It gives stability to the shoulder joint.
There are three glenohumeral ligaments, which extend from the superomedial margin of the glenoid fossa passing superiorly, medially and inferiorly. It is believed that these ligaments are the thickened part of the capsule.
The synovial membrane lines the internal surface of the capsule it also form a sleeve that enclosed the long head of biceps, it also lines the glenoid labrum and the part of the humerus that lies within, the joint cavity.
The sleeve also accompanies the long head of biceps into the tunnel created by the transverse humeral ligament and acts as a bursa.
The transverse humeral ligament bridges the gap between the greater and lesser tubercles of the humerus converting it into a tunnel through which the long head of biceps passes, this prevents it from springing out during humeral movement thereby helping in the stability of the joint.
A ligament attaching the head of humerus to the coracoid process known as the coracohumeral ligament also helps to stabilize the joint by preventing the downward dislocation of the humerus.
Within the intracapsular structure there are some bursae which include:
· Subscapularis bursa which protects the subcapularis tendon.
· The infraspinatus bursa which separates the muscle as it crosses the joint toward it’s insertion into the intermediate facet of the greater tubercle.
· Supraspinatus bursa which also separates the muscle from the joint as it crosses towards its insertion into the upper facet of the greater tubercle.
· Subacromial bursa is an extensive bursa which lies below the surpaspinatus and infraspinatus bursae. It also served as a cushion for the head of the humerus, as it extends above the greater and lesser tubercle beneath the deltoid muscle preventing the fleshy fibers of the deltoid from being irritated by the joint.
Another extracapsular structure is the rotator cuff muscles which include the subscapularis, supraspinatus, infraspinatus and teres minor. Their tendons blend towards their insertion and form a cuff which serve as accessory ligament of the shoulder joint.
The coracoacromial arch and the subacromial bursa provide a secondary socket for the head of the humerus which gives stability to the head and prevent upward dislocation of the humerus.
MOVEMENT OF THE SHOULDER JOINT.
FLEXION: Anterior fibers of deltoid, coracobrachialis, clavicular head of pectoralis major, tendon of long head of bicep.
EXTENSION: posterior fibers of deltoid.
ABDUCTION: Deltoid (Intermediate fiber) supraspinatus.
ADDUCTION: Pectoralis major, Teres major and latissimus dorsi.
LATERAL ROTATION: Teres minor and infraspinatus
MEDIAL ROTATION: Subcapularis, latissmus dorsi, Teres major and Pectoralis major.
CIRCUMDUCTION: This is a combination of the above six movements in sequence.
BLOOD SUPPLY: Posterior and Anterior circumflex humeral artery, suprascapular artery.
NERVE SUPPLY: Axillary Nerve, Suprascapular nerve, Lower and Upper subscapular nerve.


APPLIED ANATOMY:
It is the most easily dislocated joint of upper limb. Dislocation is mainly downwards. Upward dislocation is limited because of the thoracoaromial arch.

THE BRACHIAL PLEXUS

THE BRACHIAL PLEXUS
It is formed as a result of the union of the lower four cervical ventral rami and the greater part of the 1st throcacic ventral ramus. It develops as a result of somite migration as they move to form the upper limb. The somites are destined to from the muscles, skin and skeleton. When they migrate they drag along their original segmental nerve supply. As migration continues some of the nerves come into close proximity and then fused in a unique pattern to form the brachial plexus.
FORMATION OF THE BRACHIAL PLEXUS
The brachial plexus is formed as a result of the union of C5, C6, C7, C8 ventral rami and 1st thoracic ventral ramus with contribution sometimes from the 4th cervical ventral ramus and T2 ventral ramus. The participation of T2 & C4, gives the variations in the formation of brachial plexus in that when there is greater contribution from C4 and no contribution from T2 with little or no contribution from T1 such is referred to as prefix brachial plexus. When there is contribution from T2 no contribution from C4 and little or no contribution from C5 this formation is known as the post fixed brachial plexus. The normal configuration of the brachial plexus is C5-T1. It is divided into roots trunks, divisions and cords.
THE ROOT is formed by the ventral rami of C5, C6, C4 C8 and T1. The roots unite to form the trunks in the following manner:
-C5 accepts contribution from C4 and then unites with C6 to form the upper trunk.
- C7 will continue as the middle trunk.
-T1 accepts contribution From T2 and then unites with C8 to form the lower trunk.
The trunks desend laterally above the clavicle and bifurcate into anterior and posterior division. The divisions lie behind the clavicle and they emerge below it to form the cords in the following manner:
· The anterior division of the upper trunk and middle trunk will unite to form the lateral cord.
· The anterior division of the lower trunk continues as the medial cord.
· The posterior divisions of all the trunks will unite to form the posterior cord.
It should be noted that branches that arise from the union of the anterior division will supply the flexor compartment muscles of the upper limb while the branches that arise from the posterior divisions are destined to supply the posterior compartment muscles or extensor muscles.
The cords of the brachial plexus derived their names based on their relationship with the 2nd part of the axillary artery and they all lie in the axilla below the pectoralis minor.
RELATIONS OF THE BRACHIAL PLEXUS
IN THE NECK
It lies at the posterior triangle of the neck between the angle formed by the clavicle and the stenocleidomastoid muscle. It is found to emerge between the scalenus anterior and scalenus medius muscles. It is covered by the skin, deep fascia, and platysma muscle. It is also crossed by suprascapular nerve, external jugular vein, and inferior belle of Omohyoid muscle.
The roots and trunk lie in the posterior triangle but as the brachial plexus passes into the axilla it lies posterior to the clavicle and the subclavius muscle.
IN THE AXILLA
The lateral cord and posterior cord lie laterally to the 1st part of axillary artery while the medial cord lies posterior to it. They lie anterior to the subscapularis muscle.
Below the pectoralis minor the lateral cord lies lateral of the 2nd part of the axillary artery, posterior cord lies posteriorly while the medial cord lies medially to the 2nd part of axillary artery.
Below the p.minor the cords gives their terminal branches which lie in the same relation as their terminal cords.


BRANCHES OF THE BRACHIAL PLEXUS
There are a total of 17 branches arising from the brachial plexus that are destined to supply the upper limb. There are other branches that supplies structures within the neck, they include; nerve to scaleni and a branch that join the phrenic nerve to supply the diaphragm.
Of the seventeen branches of the brachial plexus, three of the branches arise from the root, one from the trunk, three from the lateral cord, five from the medial cord and five from the posterior cord.
BRANCHES FROM THE ROOT
1. Long thoracic nerve of bell (C5,C6,C7).
2. Dorsal scapular nerve (C5).
3. Nerve to subclavius (C5, C6).
BRANCH FROM THE TRUNK
1. Suprascapular Nerve.
BRANCEHS FROM THE LATERAL CORD
1. Lateral pectoral Nerve. ((C5, C6).
2. Musculocutaneous – (C5,C6, C7)
3. Lateral root of median nerve (C5, C6, C7).
BRANCHES FROM THE MEDIAL CORD
1. Medial pectoral nerve
2. Medial cutaneous nerve of arm
3. Medial cutaneous nerve of forearm
4. Ulnar nerve
5. Medial root of median nerve
POSTERIOR CORD BRANCHES
1. Axillary nerve (C5, C6)
2. Upper subscapular nerve (C5,C6)
3. Thoracodorsal nerve (C7,C8).
4. ower subscapular nerve (C5,C6)
5. Radial nerve (C5-T1).
DISTRIBUTION:-
Dorsal Scapular Nerve:-
It arises from the root, it has a root value of C5 it supplies the levator scapulae, rhombodieus major and minor. It accompanies the dorsal scapula-artery
Nerve to Subclavius:-
It is a small branch arising from the junction between C5 and C6 to supply the subclavius muscle; it is sometimes included as a branch from the trunk.

Long thoracic nerve
It arises from the root of C5, C6 and C7. It then descends posterior to the roots of the brachial plexus. It runs along the anterior surface of the serratus anterior muscle up to its lower border. It gives up branches to each digitation of the serratus anterior muscle. Sometimes the branch from the 7th root is absent and sometimes when present it joins the nerve at the surface to serratus anterior.
Suprascapular Nerve
This is the only branch from the upper trunk with root value of C5, C6. It is a large branch descending anterior to the brachial plexus. It enters the supraspinous fossa through the suprascapular notch which is converted to a canal by the transverse scapular ligament. It supplies the supraspinatus, and it is accompanied by the suprascapular artery through the spinoglenoid notch to enter the infraspinatus fossa to supply the infraspinatus muscle.
DISTRIBUTION OF THE BRANCHES OF THE LATERAL CORD
Lateral pectoral Nerve:-
It arises just above the pectoralis minor. It crosses the axillary artery and pierces the clavipectoral fascia to supply the clavicular head of the pectoralis major. It gives off a loop or ramus that passes across the axillary artery to the medial pectoral nerve. This ramus accompanies the medial pectoral nerve to supply the pectoral minor.
Musculocutaneous Nerve
It is the terminal branch of the lateral cord, arising just below the pectoralis minor lying laterally to the axillary artery. It pierces the coracobrachialis muscle which it supplies and then passes between the biceps brachii and brachialis muscles up to the lower lateral part of the arm, here it continue into the forearm as the lateral cutaneous nerve of forearm, it gives up muscular branches that supplies the bicep brachii and brachialis muscles, it also sends articular branches to the elbow joint and a small branch which accompanies a nutrient artery into the humerus.
Lateral root of median Nerve
This terminal branch joins with medial root of median nerve anterior or sometimes lateral to the axillary artery. The median nerve supplies most of the flexor muscle of the forearm and the muscles of the thenar compartment
DISTRIBUTION OF BRANCHES OF THE MEDIAL CORD
Medial pectoral nerve
It arises from the medial cord with root value (C8, T1) just behind the pectoral minor which it pierces and supplies and end up to supply the sternocostal head of pectoral major muscle.
MEDIAL CUTANEOUS NERVE OF ARM
It arises below the pectoralis minor and runs along the medial border of axillary vein and in the arm it runs along the medial border of the basillic vein up to the lower medial half of the arm, here it supplies the skin of that region.
Medial cutaneous nerve of forearm
It runs between the axillary artery and vein in the axilla and between the brachial artery and basillic vein in the arm. It passes into the forearm and gives off an anterior and posterior branch that supplies the anteromedial and posteromedial halves of the forearm.
Medial root of median nerve
This terminal branch joins with the lateral root of median nerve to form the median nerve.
Ulnar nerve
It is the terminal branch of the medial cord, root value C8, T1 but sometimes it is joined by fibers of C7 which arises from the lateral cord. It runs along the medial border of the axillary artery up to the medial aspect of the brachial artery to the middle of the arm were it pierces the medial intermuscular septum to enter the extensor compartment of the arm. It passes behind medial epicondyle of the humerus to enter the forearm where it supplies the flexor carpi ulnaris and the medial head of flexor digitorum profundus. It enters the hand to supply all the intrinsic muscle of the hand and the muscles of the hypothenar compartment.


Axillary nerve
It arises from posterior cord, with root value C5 & C6. It passes posterior to the axillary artery running along the anterior surface of the subscapularis muscle. It accompanies the posterior circumflex humeral artery through the quadrangular space. It gives off a branch to the teres minor and continues round the surgical neck of the humerus to supply the deltoid muscle. It also gives off an articular branch to the shoulder joint and a cutaneous branch that supply the skin at the lower border of the deltoid. This branch is known as the lower lateral cutaneous nerve of arm.
Upper subscapular nerve
Sometimes it is double and passes to supply the upper fibers of the subscapularis muscle.
Lower subscapular nerve
It is larger than the upper subscapular nerve. It supplies the lower fibres of the subscapularis muscle and in addition, it supplies the teres major muscle.
Thoracodorsal nerve
This large branch arises between the upper and lower subscapular nerves and passes downward being accompanied by subscapular artery a branch of the axillary artery, along the posterior axillary fold to supply the latissimus dorsi muscle.
Radial nerve
It is the largest branch of the brachial plexus. It arises below the pectoralis minor posterior to the axillary artery. It runs posterior to the brachial artery. It then accompanies the profunda brachii artery through the spiral groove between the lateral and medial heads of tricep muscle. The radial nerve supplies all the extensor compartment muscles of the arm and forearm, it gives cutaneous branches to the skin of the arm and articular branch to the elbow joint.
APPLIED ANATOMY OF THE BRACHIAL PLEXUS
ERB’S PARALYSIS
This is the paralysis that occurs as a result of damage to the upper trunk of the brachial plexus. This area is referred to as Erb’s point which is marked by the convergence of two nerves (the C5 and C6 ventral rami) the divergence of two nerve ( the upper and lower divisions of the upper trunk) and the emergence of two nerves (the suprascapular nerve and nerve to subclavius). Injury to this area could be as a result of accidental fall from a bike where by the victim lands on the neck shoulder angle or cases of breech labor were the inexperience nurse try to pull the head of the emerging baby when the shoulder is fixed within the pelvic cavity. Erb’s paralysis can also be as a result to damage to the C5 and C6 ventral rami at its root. Erb’s paralysis results in damage to the nerves that have root value of C5 and C6 which include:
· Suprascapular nerve
· Nerve to subclavius
· Lateral pectoral nerve
· Axillary nerve
· Musculocutaneous nerve
The damage to these nerves results in the following defects:
1. Loss of abduction of the arm due to the damage to the suprascapular nerve which supply the supraspinatus muscle and the axillary nerve which supply the deltoid muscle.
2. The arm is medially rotated due to paralysis of the lateral rotator muscles of the arm which include the teres minor supplied by the axillary nerve and the infraspinatus muscle supplied by the suprascapular nerve.
3. Loss of flexion at the elbow joint due to paralysis of the biceps brachii muscle as a result of damage to the musculocutaneous nerve.
4. Forearm is pronated due to the unopposed action of pronator teres muscle as a result of paralysis of the biceps.
Due to these defects the arm is placed in an adducted position and medially rotated, the forearm pronated and the palm facing backwards presenting the classical waiters tip position.

KLUMPKE’S PARALYSIS
This is the paralysis that occurs due to the damage of the lower trunk of the brachial plexus. The lower trunk could be damaged when the victim tries to brake a fall with an out stretched arm, in so doing the weight of the falling body’s pull on the arm results to the tearing of the lower trunk. Lower trunk damage can also occur during breech delivery when the arm is unduly pulled. Damage to this trunk affects the following nerves:
· Medial pectoral nerve
· Medial cutaneous nerve of the arm
· Medial cutaneous nerve of the forearm
· Ulnar nerve
The defects that occur include:
1. Loss of skin sensation on the medial aspect of the arm and forearm.
2. Paralysis of the sternocostal head of pectoralis major muscle due to damage of the medial pectoral nerve.
3. Claw hand formation due to damage of the ulnar nerve.

SATURDAY NIGHT PALSY (SLEEP PARALYSIS)
This paralysis is related to Saturday’s weekend parties were the victim becomes drunk with too much wine so when he sits on a chair he sleeps off but with the arm thrown backwards over the chair’s back rest the undue pressure on the upper arm in that state of drunkenness does compress and damage the radial nerve as it passes through the spiral groove. This results to wrist drop.


CRUTCH PARALYSIS
This paralysis results due to damage to the radial nerve by ill-fitting crutches which how compress the nerve at the axilla. The effect is wrist drop.
WINGING OF THE SCAPULAR
This defect is as a result of damage to the long thoracic nerve mainly due to heavy weight carried on the shoulder. The long thoracic nerve supplies the serratus anterior muscle so when it is damage it results in the paralysis of the muscle which will result in retraction of the medial border of the scapular especially when the patient tends to push on a wall. The retracted scapular gives the presentation of a wing hence its name.
SCELENE SYNDROME
This syndrome is as a result of compression of the roots of the brachial plexus by the two heads of the scalene muscle as they emerge from the intervertebra foramen.
CERVICAL RIB SYNDROME
This syndrome is as a result of compression of the lower trunk by an abnormal presence of a cervical rib. The defect presents loss of sensation along the medial aspect of the arm and forearm in severe cases it might present the claw hand formation due to damage to the ulnar nerve

THE AXILLA

THE AXILLA
The Axilla is a pyramidal region which lies between the medial aspect of the upper arm and the lateral thoracic wall. It has the shape of a four sided pyramid with a blunt apex and a concave base. Its four walls included:
· Anterior wall
· Posterior wall
· Lateral wall
· Medial wall.
The Axilla is directed superomedially with its apex directed into the root of the neck while the base is facing downwards and outwards.
THE APEX
It is a blunt truncated space directed superomedially into the root of the neck. It has a triangular bony boundary which is formed anteriorly by the posterior surface of the clavicle, medially by the external surface of the 1st rib and posteriorly by the superior border of the scapular. Through this space the axillary vessels and the cords of the brachial plexus pass from the root of the neck into the axilla. This passage is referred to as the cervicoaxillary canal.
THE BASE
It is directed downward and it is convex inconformity with the concavity of the armpit. It is broader toward the chest wall and narrow towards the arm. It is formed by the skin, superficial fascia and a thick layer of the axillary fascia.
ANTERIOR WALL
It is formed by pectoralis major, pectoralis minor, the subclavius muscle and clavipectoral fascia. The pectoralis major forms the anterior axillary fold.
POSTERIOR WALL
It is formed above by the subscapularies muscle which overlies the scapular, below by the teres major and latissmus dorsi muscles. The teres major and the Latissimus dorsi form the posterior axillary fold.
MEDIA WALL
It is formed by the upper 4 ribs, upper four digitation of serratus anteror muscle and the intercostal muscles within the upper four intercostals space. The medial wall is convex.
LATERAL WALL
The anterior wall and posterior wall converge at the lateral wall thereby limiting the space of the lateral wall which now is formed by the humeral intertubercular sulcus which lodges the tendon of the long head of biceps.

CONTENT OF THE AXILLA
1. Axillary vessels which include the axillary artery and vein.
2. The infraclavicular part of the brachial plexus.
3. The axillary group of lymph nodes and vessels.
4. Intercostobrachial nerve and some lateral branches of some intercostal nerves.
5. The axillary Adipose tissues & areolar tissue.
6. Axillary tail of Spence.
APPLIED ANATOMY:
The arrangement of the fascia in the axilla determines the spread of pus during axillary abscess. The clavipectoral fascia which attaches to the clavicle enclosing the subclavius and pectoralis minor and then attaches to the axillary fascia provide 2 routes of spread of suppuration during axillary abscess, therefore pus suppuration can spread above the pectoralis minor accumulating between it and pectoralis major, accumulation is felt at the margin of anterior axillary fold. Pus could also accumulate below the pectoralis minor before surrounding the axillary vessels. It can also spread upward into the root of the neck, this is an area of least resistance. Suppuration can also spread into the arm by tracking along the axillary vessels.
In surgical procedure involving axillary abscess, incisions are made mid way between the anterior and posterior axillary folds close to the medial wall this is to avoid the laceration of lateral pectoral nerve, the suprascapular N and the axillary vessels which lie on the anterior, posterior, and the lateral wall respectively.

SCAPULAR REGION

SCAPULAR REGION
This is the region that lies at the posterior thoracic wall. This region presents one bone known as the scapular which gives attachment to the following muscles:

TRAPEZIUS:
Origin:
It arises from the following areas:
· Medial 1/3rd of the superior nuchal line
· The external occipital protuberance
· -The ligamentum nuchea which extends from the 1st cervical vertebra to the spine of 7th cervical vertebra
· The spinous process of T1 – T12 and the supraspinous ligament.

Insertion:
Upper fibers are inserted into the lateral 1/3rd of the posterior surface of the clavicle.
Intermediate fibers into the medial and superior surface of the acromin, the upper lip of the crest of the spine it is also attached to the deltoid tubercle.
The inferior fibers ascend laterally to be inserted into the medial end of the spine of the scapular.


Nerve supply:
It is supplied by the spinal accessory nerve and branches from C3 and C4, (sensory supply).
Action: It stabilizes the shoulder with other muscles.
· With the levator scapulae muscle the upper fibers elevate the scapular.
· The intermediate fibers retract the scapular thereby squaring up the shoulder. With the Rhomboid muscles and pectoralis minor muscle it helps to rotate the scapular.
· With the serratus anterior muscle the inferior fibers helps to depress the scapular.

LEVATOR SCAPULAE
Origin:
From the transverse process of C1 – C4
Insertion: Medial border of the scapular between the superior angle and the upper base of the spine of the scapular.
Action: Elevation of the scapular
Nerve supply: Branch of the dorsal scapular nerve.



RHOMBOIDIUS MINOR
Origin:
From the spinous process of the 7th cervical and the 1st thoracic vertebrae.
Insertion:
It is attached to the medial border of the scapular at an angular area at the base of the spine.



RHOMBOIDIUS MAJOR
Origin:
It arises from the spinous process of the second to the fifth thoracic vertebrae
Insertion:
It is attached to the medial border of scapular below the base of the spine of the scapular up to the inferior angle.
Never supply: It is supplied by nerve to Rhomoboidus a branch of the dorsal scapular nerve.
Action: Both muscles retract the scapular.

LATISSIMUS DORSI
It is a triangular muscle or fan shaped muscle.
Origin:
It takes its origin from:
· The posterior 1/3rd of the outer lip of the iliac crest.
· The posterior layer of a though fascia known as the lumbar fascia which is attached to the spinous processes of the sacrum and lumbar vertebrae
· The spinous processes and supraspinous ligament of the lower five thoracic vertebra. Here it covers the lower fiber origin of trapezius (T7-T12).
· From the inferior angle of the scapular.
· From the lower 3-4 ribs.
It ascends to form the posterior axillary fold with the teres major. It is initially posterior to the teres major, twisting over the teres major muscles towards its point of insertion.
INSERTION:
It is inserted into the floor of intertubercular sulcus.
NEVER SUPPLY: Thoracodorsal nerve
ACTION:
· It adducts the arm
· Extension at the shoulder joint
· It functions in media rotation of the arm. All these actions are put into play in swimming, climbing, pushing, in pulling and in pushing.

SUPRASPINATUS
Origin:
Medial 2/3rd of the supraspinous fossa and from the fascia enclosing it.
INSERTION:
It is inserted at the supra facet of the greater lubercle of the humonis.
NEVER SUPPLY: Suprascapular nerve which is a branch arising from the upper trunk of the brachial plexus.
ACTION: It is said to be the initiator of Addiction, when acting alone it can adduct the arm up to 15O.

INFRASPINATUS
ORIGIN:
From the medial 2/3rd of the infraspinous fossa and it’s enclosing fascia.
INSERTION:
Intermediate facet at the greater tubercle of the humerus.
NERVE SUPPLY: Suprascapular Nerve.
ACTION: Lateral rotation of the humerus.

TERES MINOR
Origin: Lateral border of scapular close to the infraglenoid tubercle.
Insertion: Inferior facet of the greater tubercle
Nerve supply: Axillary nerve a branch from the lower trunk of the brachial plexus
Action: Lateral rotation of the humerus.

TERES MAJOR
Origin: Inferior angle of the scapular.
Insertion: Medial lip of intertubercular sulcus
Nerve Supply: Lower subscapular nerve a branch from the lower trunk of the brachial plexus.
Action: Adduction of the humerus medial rotation of the humerus

TRICEP
Origin: The long head of tricep originates from the infraglenoid tubercle. It is discuss under muscles of the arm.

SUBSCLAPULARIS
Origin: Medial 4/5th of the subscapular fossa.Insertion: lesser tubercle of the humerus.
Nerve supply: Upper and lower subscapular nerve.
Action: Medial rotation of the humerus

QUADRANGULAR SPACE
It is a four sided space lying within the scapular region. It bounded
laterally by the surgical neck of the humerus, medially by the long head of the tricep, superiorly by the teres minor and subscapularis, inferiorly by the teres major muscle
content: Axillary nerve and posterior circumflex humeral artery and vein. UPPER TRIANGULAR SPACE
It is bounded superiorly by the teres minor, inferiorly by the teres major and latissmus dorsi while laterally is the long head of tricep.
Content:
Circumftex scapular artery and vein
LOWER TRIANGULUR SPACE
It is bounded superiorly by the teres major, medially by the long head of tricep. Laterally by the shaft of the humerus
CONTENT
It transmits the radial nerve and the profund brachii artery and vein.

DELTOID MUSCLE:it is a triangular muscle both in origin and insertion.
ORIGIN: It takes origin from:
· The anterior fibers arises from the anterior surface of the lateral 1/3rd of the clavicle
· Intermediate fibers arise from the lateral border and surface of the acromion
· Posterior fibers arise from the lower lip of the crest of the spine of the scapular.
INSERTION:
It is attached to the deltoid tuberosity at the middle aspect of the lateral surface of the shaft of the humerus.
ACTION
· Anterior fiber causes flexion
· Posterior fiber causes extension
· Intermediate fiber causes abduction of the humerus. It abducts the humerus as the supraspinatus initiates abduction up to 90O after which it is assisted by the anterior and posterior fibers.
Nerve supply: Axillary nerve

SERRATUS ANTERIOR
Origin:
Upper 8th ribs and membrane of the corresponding intercostal spaces it may extend to the 9th or 10th rib.
Insertion:
It is inserted medial part of the costal surface of the scapular from the superior angle to the inferior angle where it is concentrated most.
Action: Protraction of the scapular.
Nerve supply: Long thoracic nerve of bell.

THE BREAST

THE BREAST
The breast is a modified sudoriferous gland of the apocrine variety which is found in both males and females as a paired gland. In males and immature females the breast is rudimentary but during puberty in females the breast undergoes developmental changes but it attains its final development in the final stages of pregnancy and during lactation.

DEVELOPMENT OF THE BREAST
The breast development commences at the sixth week of intrauterine life as two vertical ridges extending from the area of the future axilla and to the inguinal region. This line is referred to as the mammary ridge or the milk line. In human the caudal 2/3rd of the milk line degenerates while the cranial 1/3rd is destined to form the rudiments of the mammary gland. At birth only the lactiferous ducts are present but in females during puberty branching of the lactiferous duct occurs and growth of adipose tissue and fibrous tissue occur thereby increasing the size of the breast, this continues in the nulliferous but during pregnancy the final development of the breast commences whereby the alveoli is formed so as to produce milk immediately after birth.

LOCATION
The female breast is a rounded eminence which is found situated at the superficial fascia of the anterior thoracic wall overlying the pectoralis major muscle, serratus anterior muscle and the aponeurosis of the external oblique abdominus muscle. Its upper lateral quadrant further extend into the axilla as the axillary tail of Spence which pierces the pectoralis fascia at the level of the third intercostal space creating an opening known as the foramen of Langer.

EXTENT OF THE BREAST
The breast has a nipple which corresponds to the apex and a base which is fairly constant in most females. The base extends vertically from the 2nd to the 6th rib taking orientation from the midclavicular line. Horizontally it extends from the lateral border of the sternum to almost close to the mid axillary line.

SIZES AND SHAPE OF THE BREAST
The size and shape of the breast varies among races and among individuals based on functional activities, it also varies with age. It is also anatomically common to find one breast larger than the other in the same individual The shape of the breast varies from hemispherical (globular), conical, various kinds of pendulum, piriform and flattened.. The size of the breast is determined by the fatty content but the size of the breast does not interfere with its milk producing capacity.

RELATIONS OF THE BREAST
The base of the breast is related to the pectoral fascia, the pectoralis major, the serratus anterior muscle, the aponeurosis of the external oblique abolominis muscle. It is separated from the pectoral fascia and the pectoralis major by an areolar space which is referred to as the submammary space or retromammary space. This space allows for an independent movement of breast over the pectoral fascia and the pectoralis major.

STRUCTURE OF THE BREAST
The structure of the breast is quite remarkable and complex, it is consfigured or designed to produce milk. The structure of the breast comprise of:
1. The skin
2. Parenchyma
3. The Stroma
The Skin
The skin just like in other part of the body enclose the breast but it present the following features:
1. The Nipple or Mammary Papilla: This is a cylindrical or conical projection which lies a little below the center of the breast. It forms the apex of the breast and sometimes in nulliferous females it over lies the 4th intercoastal space. It is traversed by 15-20 lactiferous duct through which milk is discharged to the surface. It also comprises of non-striated myocytes (smooth muscle cells), which are arranged circularly and longitudinally. The circular smooth muscle cells on stimulation either by sucking or by tactile stimulation contracts thereby causing erection of the nipple this serve the purpose of opening up that lactiferous duct in lactating mothers.

The longitudinal smooth muscle cells on contraction causes flattening of the nipple this also serve the function of closing up the lactiferous ducts thereby preventing the outflow of milk in lactating mother.
2. The Areolar: It is the highly pigmented area of the skin that surrounds the base of the nipple it is rose pink in Caucasian females while in blacks and other melanized races it is darker and highly pigmented. During the 2nd months of pregnancy the pigmentation increases thereby giving a darker colour of which after pregnancy it never returns to its original colour. This has a medicolegal importance among the Caucasians. In the areolar are found peripherally arranged, modified sebaceous gland referred to as the glands of Montgomery. At the onset of pregnancy the nipple and areolar become slightly swollen and also the glands of Montgomery form cyst like structures referred to as the tubercle of Montgomery. The secretions from this gland help to lubricate the areolar and the nipple preventing them from cracking in lactating mothers. The nipple and areolar are devoid of hair and there are no fat beneath them.

THE PARENCHYMA
The parenchyma is the milk producing tissue or the glandular tissue of the breast that is composed of about 15-20 lobes, each lobe is made up of clusters of lobules and each lobule is comprised of clusters of alveoli. The lobes are drained by lactiferous ducts which open into the rough ended tip of the nipple. At the base of the areolar the lactiferous ducts expand forming the lactiferous sinus which acts as a reservoir for milk during lactation.

THE STROMA
The stroma of the breast is the supporting tissue of the breast. It comprises of fibrous and adipose tissues, the stroma is enclosed by the subcutaneous tissue and from there septa emerge attaching the skin and the lobes to the pectoral fascia thereby forming the suspensory ligament of Cooper. The adipose tissue are the main determinants of the size of the breast and their presence gives the breast its smooth contour.

BLOOD SUPPLY OF THE BREAST
· The breast is supplied by the perforating branches of the internal thoracic artery.
· Pectoral branch of the thoracoacromial artery.
· Lateral branches of the posterior intercostal artery.
· Lateral thoracic artery.

VENOUS DRAINAGE
The breast is drained by veins that bear similar name with the corresponding artery. They first form anastomotic cycle around the base of the nipple this is referred to as circulus venosus. From the anastomotic cycle sets of vein emerge. The superficial varies drain into the internal thoracic vein and into some of the superficial veins of the lower part of the neck. The deep veins drain into the following veins: axillary vein, the anterior intercostal veins and posterior intercostal veins. In the resting state of the breast there is an avascular zone of fibroblast which is referred to as epitheliostromal junction which separates the epithelium of the glandular tissue and the stroma.

LYMPHATIC DRAINAGE
The knowledge of the pathway of the breast is of utmost importance for the perfect understanding of the spread of carcinoma of the breast. The lymphatic drainage of the breast runs in two sets.
1. Superficial set of lymphatic vessel drains the skins of the breast except the nipple and areolar.
2. Deep set of the lymphatic vessels drains the parenchyma, stroma the nipple and areolar of the breast.
About 75% of the lymph of the breast drains to the axillary group of lymph nodes, 20% drains into the parasternal group of lymph nodes while 5% drains into posterior intercostal nodes. The lymph of one breast can also drain to the opposite breast passing through the intermammary cleft.

The lymphatic vessels of the breast also form plexuses:
1. Subareolar plexus of Sarpy which main drains into axillary group of lymph nodes, it follows the axillary tail of Spence. The subareolar plexus of Sarpy lies beneath the areolar.
2. Submammary lymphatic plexus lies within the submammary space, though it is not involved with the normal lymphatic drainage of the breast unless there is obstruction of the normal pathway.

NERVE SUPPLY
It is supplied by the lateral and anterior cutaneous branches of the 4th – 6th intercostal nerves.

APPLIED ANATOMY
Cancer of the breast because of the excessive communication of the breast lymphatic vessels with other parts of the body, cancer of the breast can easily spread into regions like the brain through the posterior intercostal veins which communicates with the vertebral veins that drains the brain. Cancer of the breast can spread to the abdominal region affecting organs like liver through the parasternal group of lymph nodes which communicates with the subperitoneal group of lymph nodes. It can also spread to the pelvis affecting the uterus through a pathway which is referred to as the pathway of Gerota which is not well defined. It can spread from one breast to the other through the inter communicating lymphatic vessels. Cancer cells can infiltrate the lactiferous duct which later results to the inversion of the nipple. When it infiltrates the fibrous tissues (Suspensory ligament of Cooper) it causes retraction of the skin which results to pitting of the skin of the breast. Cancerous cells can also block superficial vessels draining the skin of the breast; this will lead to edema of the skin. As a result of this the skin will have the appearance of an orange skin or peel of orange a condition known as peau d orange. Cancer of the breast could also infiltrate the pectoralis major causing adhesion of the breast to the pectoralis major.
It can lead to abscess formation in the breast which can be drained by incision which could be done in a radial manner so as to avoid laceration of the lactiferous duct. In severe cases of cancer of the breast a radical mastectomy is carried out where the breast is completely removed including the pectoralis major and pectoralis minor. The axillary lymph nodes that are involved are also removed.


CONGENITAL MALFORMATION AND ABNORMALITIES OF THE BREAST
1. Polythelia: A condition where there is more than two nipples.
2. Athelia: A condition where there is absence of one or both nipples.
3. Polymastia: A condition where there is presence of more than 2 breasts.
4. Amastia: A condition where there is absence of one or both breast.
5. Gynaecomastia: A condition where there is development of breast in male
6. Inversion of the nipple: Is where the nipples fail to evect.

PECTORAL REGION

PECTORAL REGION
It is composed of muscles of the pectoral region which include: The Pectoralis major, Pectoralis minor and subclavius muscle.
The pectoralis major muscle is enclosed by a fascia known as pectoral fascia while the pectoralis minor and subclavius muscles are enclosed by a deep fascia known as clavipectoral fascia. The bone of the pectoral region is the clavicle. On the anterior aspect of the pectoral region is the breast.

PECTORALIS MAJOR MUSCLE
It is a thick triangular muscle, it is also fan shaped which arises by means of 2 heads that are continuous with each other, it is the most superficial muscle of the pectoral region.
ORIGIN
1. The clavicular head arises from the medial 2/3rd of the clavicle.
2. The sternocoastal head arises from the anterior half of the sternum, coastal cartilage of the upper six ribs and the aponeurosis of the external oblique abdominus muscle.

INSERTION
It is inserted into the lateral lip of the bicipital grove or intertubercular sulcus of the humerus by means of a thick bilaminar tendon which is about 5cm in length.
NERVE SUPPLY
Its nerve supply is derived from 2 sources.
1. lateral pectoral nerves a branch from the lateral cord of the brachial plexus
2. medial pectoral nerve a branch from the medial cord of the brachial plexus.
The Lateral pectoral nerve pierces the clavipectoral fascia to supply the clavicular head while the medial pectoral nerve pierces the pectoralis minor to supply sternocoastal head of the pectoralis major.

ACTION
1. Adduction {humeral}
2. medial rotation
3. Flexion at the shoulder joint
4. Extension at the shoulder joint
Flexion at the shoulder joint and ability to use the thumb to touch the tip of the shoulder is a function of the clavicular head while the Sternocoastal head extends the shoulder joint against resistance. The two heads of the pectoralis major acting together with other muscles of the scapular region causes humeral adduction and medial rotation of the humerus

PECTORALIS MINOR
It is a small muscle that lie posterior to the pectoralis major. The outline of the pectoralis minor is a very important landmark in the upper limb. The p. minor is synonymous to the piriformis muscle of the gluteal region.
ORIGIN
The pectoralis minor arises from the 3rd to 5th rib sometimes it can also arise from the 2nd rib or extend up to the 6th rib close to their costochondral junction.
INSERTION
It is inserted into the medial part of the superior Surface of the coracoid process but it is not uncommon to find the tendon passing the coracoid process to blend with the coracoclavicular ligament or even to the coracohumeral ligament.
Sometimes muscle fibers arising from the 1st rib to the coracoid process are referred to as pectoralis minimus.
NERVE SUPPLY
It is supplied by the
1. Medial pectoral nerve
2. Lateral pectoral nerve though this is not by a direct branch but a communicating branch sent as a loop to the medial pectoral nerve.
ACTION
1. Forward and downward pull of the scapular.
2. Serve as an accessory muscle of respiration.
3. Causes depression of the shoulder.

SUBCLAVIUS
It is a small triangular muscle lying between the clavicle and the 1st rib. It arises from the 1st rib, close to the costochondral junction it ascends laterally to be inserted into the medial 2/3rd of the inferior surface of the clavicle at the area known as the subclavian groove.

NERVE SUPPLY
Nerve to subclavius which is derived from the brachial plexus just before the upper trunk is formed
ACTION
The subclavius muscle stabilizes the clavicle at the stenoclavicular joint though the strength of the stenoclavicular ligament supersedes this role. Actually because it is difficult to palpate its action is more imagined than real.
In cases of fracture of the clavicle it serves as a cushion to prevent the jagged edge from lacerating the vessels (subclavian vessels) that pass below it.

CLAVIPECTORAL FASCIA
It is a thickened fascia that lies below the clavicular head of the pectoralis major. It fills in the space between the clavicle and the p. minor. It is attached laterally to the coracoid process and medially it fuses with the external intercostals membrane of the upper two intercostal spaces. It is also attached medially to the 1st rib, between the 1st rib and the coracoid process the fascia is thinckened to form the costocoracoid ligament. Superiorly the clavipectoral fascia split to enclose the subclavius muscle it then get attached to the anterior and posterior surface of the clavicle in relation to the subclavian groove. Inferiorly on getting to the superior border of the pectoralis minor it splits to enclose the pectoralis minor then on the lower border of pectoralis minor it fuses again descending to get attached to the axillary fascia forming the suspensory ligament of the axillary fascia. The clavipectoral fascia is pieced by the following structures:
1. The lateral pectoral nerve
2. The thoracoacomial artery
3. The cephalic vein
4. The lymphatic vessels.

THE PECTORALIS FASCIA
It is a deep fascia enclosing the pectoralis major muscle. Superiorly it is attached to the clavicle while posteroinferiorly it extends to the scapular region forming the axillary fascia. In the axilla it is pierced by the axillary tail of Spence of breast at the level of the 3rd intercostal space, the opening created there is referred as foramen of Langer

INTRODUCTION TO UPPER LIMB
The basic pattern of the upper limb is designed so as to create mobility in order for humans to manipulate there environment. The hand which is the major tactile organ of human beings is placed in such a way that it can reach every aspect of the body. It is mainly designed for apprehension.

REGIONS OF UPPER LIMB
The upper limb is divided into the following region
1. shoulder region
2. The arm.
3. The forearm
4. The wrist
5. The hand

SHOULDER REGIION
It is further subdivided into the pectoral region and the scapula region
In between the pectoral region and scapula region is the area known as the Axilla. The bone of the shoulder region is the scapular and clavicle they form the shoulder or pectoral girdle.
1. The joint between the scapular and humerus is the shoulder joint or scapulohumeral joint or glenohumeral joint.
2. Acromioclavicular joint between the economy claviate.
3. The sternoclavicular joint between the sternum and the clavicle.

THE ARM [BRACHIUM]

It is the part of the upper limb lying between the shoulder joint and the elbow joint. The bone of the arm is known as the humerus, its proximal part forms the shoulder joint with the scapular while its distal part with the radius and ulna bones form the elbow joint. The arm is divided into two compartments. The flexor compartment contain and the following muscles.
1. The bicep brachii
2. Brachialis
3. Coracobrachialis
They cause flexion at the shoulder and elbow joints.
The extensor compartment contains the tricep brachii muscle which extends the shoulder and elbow joints.

FOREARM (ANTEBRACHIUM).
It is the part of the upper limb that lies between the elbow and the wrist joints. The bones of the forearm include the radius and ulnar bone. The forearm is divided into the flexor compartment and the extensor compartment. The flexor compartment has eight muscles and the extensor compartment has 12 muscles.

THE WRIST
It is the transitional area between the forearm and hand, it is made up of eight carpal bones which include the scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate and hamate. The joint in relation to this area include. Inferior radiocarpal, intercarpal and carpometacarpal joint.

THE HAND
It is the main tactile and sensory organ of the upper limb. Its basic design is different from that of other primates and mammals in that it has an inherent ability to grasp object between the thumb and index finger (opposition). The hand comprises of 20 muscles that control the intrinsic movement of the hand, 5 metacarpal and 14 phalanges. It has 2 surfaces: palmer and dorsal surface, it also has 5 digits, which are named from lateral to medial the thumb (pollex), index finger (forefinger), middle finger, ring finger, little finger {digit minimi}. The joints that are in relations to the hand are
Carpometacarpal, metacarpophalangeal, interphallangeal (proximal middle and distal)