Anatomy of the Upper Extremity
ARM, AXILLA & BRACHIAL PLEXUS
I. Arm [N.402-3]
Aka. brachium
Extends from the gleno-humeral joint to the elbow (olecranon)
Types of movement
Flexion-extension
Pronation-supination
Contains:1 muscles
4 bones
terminal branches of brachial plexus
brachial artery and branches
facial septum divides arm into two compartments
See attached chart
1. Anterior Compartment (flexor)
Coracobrachialis
Biceps brachii
Brachialis
2. Posterior Compartment (extensor)
Triceps (long, lateral, medial heads)
Anconeus
3. Neurovascular Compartment
Medial aspect of arm
Contains median nerve and brachial artery
Brachial Artery
Principal arterial supply to arm
Continuation of axillary artery (brachial at inferior border of teres major)
Superficial, anterior to biceps and brachialis
Begins at inferior border of teres major
Runs medial to humerus then anterior to it
Accompanies median nerve (crosses br.art. anteriorly)
Main branches: deep brachial artery, superior and inferior ulnar collateral arteries
Ends opposite to neck of radius under bicipital aponeurosis
Divides into radial and ulnar arteries
Nerves
Musculocutaneous nerve: biceps brachii, brachialis, coracobrachialis (flexors)
Radial nerve: triceps brachii (extensor)
4 nerves pass through arm
median- descend onmedial side and enter forearm
ulnar- same as above
musculocutaneous
innervates flexors (anterior) of arm
begins at pectoralis minor, pierces coracobrachialis, continues between biceps brachii and brachialis
becomes the lateral antebrachial nerve (supplies skin on lat. Forearm)
radial
innervates extensors (posterior) of arm
enters arm post. To brachial artery, medial to humeral and ant. to long head of triceps
passes laterally with deep brachial art around body of humerous in radial groove
pierces lat. Intermuscular septum and cont. between brachialis and brachioradialis to lat. Epicondyle of humerus
divides into deep and superficial braches
deep- muscular and articular in distrib.
Superficial- sensory fibers to dorsum of and and digits
II. Cubital Fossa
1. Boundaries [N.417]
Medial- pronator teres
Lateral- brachioradialis
Base-epicondylar line of humerus
Floor- supinator and brachialis muscles
Roof- bicipital aponeurosis, skin, fascia
2. Contents [N.418]
Median nerve
Bifurcation of brachial artery and venae comitantes
Tendon of biceps
Radial nerve
Deep radial nerve
Crossed by medial cubital vein
Related to cephalic, basilic, and meidan antebrachial cutaneous veins
3. Olecranon (Elbow) Joint [N.407-408]
Hinge and pivot joint
Articulaion between arm and forearm
Proximal articulation between ulna and radius
Actions: flexion-extension of forearm
Pronation and supinatio of forearm
III. Axilla
1. Definition
Pyramidal shaped region between arm and body
Cervicoaxillary canal: bounded by clavical, first rib, scapula
Axillary sheath [M.295]
Axillary arter, veins, and cord of br.pl. enclosed in thin fascila sheath
Traced superiorly into the neck, continuous with prevertebral layer of cervical fascia
2. Boundaries [M.293]
Base- skin of axilla or armpit
Anterior- pectoral muscles
Lateral- bicipital groove, long head biceps, humerus
Posterior- latissimus dorsi, teres major, subscapularis
Medial- serratus anterior, ribs, intercostals m.
Apex- clavicle and 1st rib
3. Contents
Axillary artery [N.***]
Begins: lat. Border of 1st rib (continuation of subclavian artery)
Ends: inferior border of teres major (passes pect. Minoràbrachial artery)
First part:
Lat 1st rib à sup. Pect. Min.
Enclosed in axillary sheath with axillary vein and cord of br.pl.
Branch: superior thoracic artery
Second part:
Post. pect. Minor
Branches: thoracoacromial a.
Lateral thoracic a.
Third part:
Inf. Pect.min. -à inf. Teres major
Branches: subscapular a.
Anterior circumflex humeral
Posterior circumflex humeral a.
Axillary vein [N.***]
Begins: inf. Teres major (continuationof basilic vein)
Ends: lat. 1st rib (subclavian vein)
Clavipectoral Fascia
Extends inferiorly from clavicle to skin
Creates depression called armpit
Pierved by nerves, vessels, and lymphatics
Fat, lymph nodes
Cords of brachial plexus
IV. Brachial Plexus [N.401]
1. Roots
Union of ventral rami of C5-C8 n. & T1 n.
2. Trunks ( rami enter neck, unite to form)
Superior trunk-C5, C6
Middle trunk- C7
Inferior trunk- C8, TI
3. Divisions (posterior and anterior)
Posterior cord- post. divisions of all three trunks
Lateral cord- ant. division of superior and middle trunks
Medial cord- ant. division of interior trunk
4. Cords (bear relationship to axillary artery)
Lateral cord- 3 branches
Medial cord- 5 branches
Posterior cord- 5 branches
5. Terminal Branches
L: Lateralpectoral n.*: pectoralis major
Musculocuataneous n.: pierces coracobrachialis, supplies biceps brachii & brachialis (term. as lateral antebrachial cutaneous n.)
Medial root of median n.: unites with medial root of median nerve = median n.-supplies flexor muscles in forearm, skin of hand, five muscles of hand
M: Medial pectoral n.* : pectoralis major and minor
Medial brachial cutaneious n.*: skin on med. of arm and sup. forearm
Medial antebrachial cutaneous n.*: skin on med.forearm
Ulnar n.: from arm and forearm- flexor carpi ulnairs, flex. Digitorum profundus, skin on med. hand
Lateral root of median n.: unites with medial root of median nerve = median n.- supplies flexor muscles in forearm, skin of hand, five muscles of hand
P: Upper subcapular n.*: subscapularis
Thoracodorsal n.*: latissimus dorsi
Lower subscapular n.*: teres major
Axillary n.**: deltoid, teres major, skin over inf. Delt.
Radial n.: larges branch, extensor m. of upper limb & skin on post. Arm and forearm
Divided into supraclavicular branches- from ventral rami and trunks
infraclavicular branches- cords to axilla
V. Clinical Correlates
It is uncommon for sternoclavicular joint to dislocate.
Dislocation of the acromioclavicular joint- result from hard fall on shoulder. Often called ‘shoulder separation’, is serious when both the acromioclavicular and coracoclavicular ligaments are torn. When the coracoclavicular lig. Rupture, the shoulder falls away from the clavicle because of the weight of the upper limb. If the fibrous capule of the joint also rupture, the acromion passes inferior to the acromial end of the clavicle. Dislocation of the acromoclavicular joint makes the acromion more prominent.
Anterior dislocation of the shoulder joint- caused by excessive extension and lateral rotation of the humerus. The head of the humerus is driven anteriorly and the fibrous capsule and glenoid labrum are usually stripped from the anterior aspect of the genoid cavity
A hardblow to the humerus when the shoulder joint is fully abducted tilts the head the humerus inferiorly onto the inf. Weak part of the articular capsule. This may tear the capule and dislocate the shoulder so that the humeral head comes to lie inferior to the glenoid cavity. Unable to use the arm, the patient commonly supports it with the other hand.
Avulsion of the medial epicondyle in children can result from fall that causes severe abduction of the extended elbow. Resulting traction on ulnar collateral ligament pulls the medial epicondyle distally. The anatomical basis of avulsion of the medial epicondyle is that the epiphysis for the medial epicondyle may not sue with the distal end of the humerus until up to age 20.
A traction injury of the ulnar nerve is a frequent complication of the abduction type of avulsion of the medial epicondyle. The anatomical basis for this stretching of the ulnar nerve is that it passes post. To the medial epicaondyle before entering the forearm.
Posterior dislocation of the elbow joint may occur when children fall on their hand swiththier elbows flexed. The distal end of the humerus is driven through the weak anterior portion of the fibrous capsule as the radius and ulna dislocate post.
Preschool children are partic. Vuln. To subluxation (incomplete dislocation) of the head of the radius (pulled elbow)the sudden pulling of the upper limb tears the attachment of the anular ligament, where it is loosely attached to the neck of the radius. The radial head then moves distally, partially out of the torn anular ligament. The proximal part of the ligament may become trapped between the head of the radius and the capitulum of the humerus.
Wrist fracture (colles’ fracture) involving the distal end of the radius when fall on outstretched had with forearm pronated. Threre is usually a complete transverse fracture of the distal 2-3 cm of the radusm, and the fragment is displaced proximally, causing shortening of the radius. The fragment is usually tilted posteriorly producing a chrac. Hump described as the ‘dinnerfork’ deformity because of the resemblance of the broken wrist to an upside-down dinner fork.
Damage to long thoracic nerve results in paralysis of serr. Ant. and is shown clinically by ‘winging of scapula’ (protrusion of the inf. Angle of scap) thus the phrase “C 5,6,7 keep your wings from heaven” The nerve may be injured by direct trauma or carrying heavy weights on shoulder or inadvertently transected in mastectomy.
Only supraspinatus, not deltoid, can initiate abduction. In paralysis of the supraspinatus, the individual may lean to the afflicted side or knock the upper extremity laterally with the hip to initiate abduction. Even the deltoid cannot abduct more than 90 degrees-rotation of scapula must assist
Bursitis is an inflammation of a bursa around the shoulder are several bursae, including the subdeltoid, supraspinatus, infraspinatus, and subscapularis bursae, which prevent fiction when a muscle or its tendon crosses a joint or protuberance.
A joint is innervated by the nerves which innervate the muscles that act on that joint. Muscles which cross more than one joint will act on more than one joint
Rotator cuff muscles are the main source of stability of the glenohumeral joint and maintains the head of the humerous in place. The capsule of the shoulder joint and the associated glenohumeral ligament also stabilize the joint.
Fracture of clavicle- lateral fragment of the clavicle dr0ps from the weight of the upper limb
Fracture of the surgical neck of humerus- common in elderly persona and usually result from falls on elbow when arm is abducted. The axillary, radial, media, and ulnar nerves may be injured.
Colles’ fracture- radius breaks proximal to wrist. The distal fragment is broken into pieces, and displaced, producing shortening of the radius.
Because of the prominence and accessibility of superficial veins, they are commonly used for venipuncture.
Subacromial bursitis- bursa that separates the tendon of the supraspinatus, the coraacromial lig, the acromion, and the deltoid, is inflamed, abduction of the arm is painful.
The supraspinatus tendon, part of the rotator cuff, is most likely to tear. Injury or disease may damage the rotator cuff and cause instability of the shoulder joint. Trauma may tear or rupture one or more of the tendons of the rotator cuff muscles (common with baseball pitchers).
Degenerative tendonitis of the rotator cuff is common in the elderly. To test for this injury, person is asked to lower the fully abducated limb slowly and smoothly. From about 90 degress the abduction of the limb will duddenly drop to the side in an uncontrolled manner if the rotator cuff (esp. supraspinatus portion) is torn.
Axillary nerve injury – displacement of humeral head in fracture of surgical neck or pressure on armpit.
Paralysis of deltois and teres minor – loss of sensation on lower deltoid skin. Abduction is reduced greatly (Atrophy of deltoid).
Radial nerve injury – pressure on armpit or by fracture/disc\location of proximal end of humerus (downward displacement).
Fracture of humerus at mid-shaft (spiral groove) – WRISTDROP, unopposed flexion of wrist injuries to deep bracnh will NOT cause wrist drop b/c brachioradialis and flexor carpi radialis still fn.
Median nerve injury – suprcondylar humeral fracture or flexor retinaculaum injury loss of flexion in wrist and hand w/o adduction & thumb opposition (APE HAND).
Ulnar nerve injury – CLAW deformity unopposed hypothenar extenstion.
Tennis elbow – tearing or degeneration of superficial extensor muscles from lateral epicondyle.
Mallet finger – insertion of an extensor tendon is avulsed, distal phalanx is flexed.
The clavicle most commonly fractured bone.
Smith’s fracture – reversed Colle’s fracture.
Tags: arm, axilla, brachial lexus, brachium, circumflex humeral, Clavipectoral Fascia, Cubital Fossa, facial septum, Flexion-extension, gleno-humeral, Lateralpectoral, medial epicondyle, Musculocuataneous, musculocutaneous, Musculocutaneous nerve, Neurovascular Compartment, Pronation-supination, thoracoacromial, Thoracodorsal
