Anatomy Tables - Axilla, Posterior Shoulder, & Arm

Osteology
Bone Structure Description Notes
scapula   the bone of the shoulder the scapula floats in a sea of muscles, so it is difficult to fracture; it articulates with the axial skeleton through only one bone - the clavicle at the coracoclavicular and acromioclavicular joints
scapular notch a notch on the superior border of the scapula located medial to the attachment of the coracoid process it is bridged by the superior transverse scapular ligament; the suprascapular a. passes superior to the superior transverse scapular ligament and the suprascapular n. passes inferior to it (Army goes over the bridge, Navy goes under the bridge)
acromion a broad, flat process located at the lateral end of the scapular spine it articulates with the clavicle through a synovial joint (acromioclavicular joint) (Latin, akron = tip + omos = shoulder, therefore the tip of the shoulder)
supraspinous fossa a broad depression located superior to the spine of the scapula it is the site of origin of the supraspinatus m.
infraspinous fossa a broad depression located inferior to the spine of the scapula it is the site of origin of the infraspinatus m.
humerus   the bone of the arm (brachium) the humerus articulates proximally with the scapula at the glenoid fossa; it articulates distally with the radius and ulna at the elbow joint
head the smooth, rounded proximal end of the humerus it articulates with the glenoid cavity of the scapula to form the shoulder joint
anatomical neck the constricted region located inferolateral to the head it is located at the circumference of the smooth articular surface of the head
surgical neck the proximal part of the shaft of the humerus it is located inferior to the greater and lesser tubercles; it is a site of frequent fracture; fractures of the surgical neck of the humerus endanger the axillary n. and the posterior circumflex humeral a.
greater tubercle the large projection located lateral to the head of the humerus it is the attachment site of the supraspinatus, infraspinatus & teres minor mm.
lesser tubercle the projection located lateral to the head of the humerus on the anterior surface it is the insertion site of the subscapularis m.
intertubercular groove the groove on the anterior surface of the humerus that is located between the crest of the greater tubercle and the crest of the lesser tubercle it is occupied by the tendon of the long head of the biceps brachii m.; the transverse humeral ligament spans the intertubercular groove and holds the biceps tendon in place; it is the attachment site for the tendon of the pectoralis major (lateral lip), teres major (medial lip), and latissimus dorsi (floor)
crest of the greater tubercle the ridge of bone on the anterior surface of the humerus extending inferiorly from the greater tubercle it forms the lateral lip of the intertubercular groove; it is the attachment site for the transverse humeral ligament and the pectoralis major m.
crest of the lesser tubercle the ridge of bone on the anterior surface of the humerus extending inferiorly from the lesser tubercle it forms the medial lip of the intertubercular groove; it is the attachment site for the transverse humeral ligament and the teres major m.
deltoid tuberosity the roughened process on the lateral surface of the mid-shaft of the humerus it is the insertion site of the deltoid m.
lateral epicondyle a knob-like projection on the lateral side of the humerus proximal to the capitulum it is the site of attachment of the common extensor tendon which is the origin of several forearm extensor muscles (extensor carpi radialis brevis m., extensor digitorum m., extensor digiti minimi m., extensor carpi ulnaris m. and supinator m.); inflammation of the attachment of the common extensor tendon is called lateral epicondylitis which is also known as "tennis elbow" (Greek, kondylos = the knob formed by the knuckle of any joint)
medial epicondyle a knob-like projection on the medial side of the humerus proximal to the trochlea it is the attachment site of the common flexor tendon which is the origin for the superficial group of forearm flexor muscles (pronator teres m., flexor carpi radialis m., palmaris longus m., flexor carpi ulnaris m. and flexor digitorum superficialis m.); inflammation of the attachment of the common flexor tendon is called medial epicondylitis which is also known as "tennis elbow"; the ulnar nerve is in contact with bone as it courses posterior to the medial epicondyle where it is susceptible to injury from blunt trauma or fracture Greek, kondylos = the knob formed by the knuckle of any joint)
radial groove the groove that spirals around the posterior surface of the shaft of the humerus it is a depression for the radial n. and the deep brachial vessels; fracture of the humerus at mid-shaft can injure the radial nerve and deep brachial vessels because they are in contact with bone at this location
ulna   the bone on the medial side of the forearm (antebrachium) the ulna articulates proximally with the trochlea of the humerus and the head of the radius; it articulates distally with the ulnar notch of the radius (Latin, ulna = elbow or arm)
  olecranon the proximal end of the ulna it is the insertion site of the tendon of the triceps brachii m.; when the elbow is extended, the olecranon of the ulna engages the olecranon fossa of the humerus (Greek, olecranon = the head or point of the elbow)
  coronoid process the anterior projection of bone located distal to the trochlear notch it is the insertion site of the brachialis m. (Greek, coronoid = resembles a crow)
styloid process a small projection from the distal surface of the head of the ulna it is the site of attachment of the articular disk of the distal radioulnar joint
radius   the bone on the lateral side of the forearm (antebrachium) the radius pivots on its long axis and crosses the ulna during pronation
  head the rounded proximal end of the radius it has a smooth, rounded surface for articulation with the ulna; the head of the radius is encircled by the annular ligament (4/5 of a circle) and the radial notch of the ulna (1/5 of a circle)
  neck the constricted area of the radius located distal to the head the annular ligament of the radius surrounds the head of the radius, not the neck of the radius
  radial tuberosity a roughened area on the anteromedial surface of the radius located just distal to the neck it is the insertion site of the tendon of the biceps brachii m.
styloid process the distal-most projection from the lateral side of the radius the radial styloid process projects lateral to the proximal row of carpal bones

Muscles
Muscle Origin Insertion Action Innervation Notes Image
deltoid lateral one-third of clavicle, acromion, lower lip of the crest of the spine of the scapula deltoid tuberosity of the humerus abducts arm; anterior fibers flex & medially rotate arm; posterior fibers extend & laterally rotate arm axillary nerve (C5,6) from posterior cord of brachial plexus deltoid is the principle abductor of the arm but due to poor mechanical advantage it cannot initiate this action; assisted by supraspinatus
teres major dorsum of the inferior angle of scapula crest of lesser tubercle of humerus adducts arm, medially rotates arm, assists in arm extension lower subscapular nerve (C5,6) from the posterior cord of the brachial plexus teres major inserts beside the tendon of latissimus dorsi, and assists latissimus in its actions (Latin, teres = round)
rotator cuff
supraspinatus supraspinatus fossa greater tubercle of humerus (highest facet) abduct arm (initiate abduction) suprascapular nerve (C5,6) from superior trunk of brachial plexus supraspinatus initiates abduction of the arm, then the deltoid muscle completes the action
infraspinatus infraspinatus fossa greater tubercle of humerus (middle facet) laterally rotate arm suprascapular nerve infraspinatus, supraspinatus, teres minor and subscapularis are the rotator cuff muscles Image Not Available
teres minor upper 2/3 of the lateral border of the scapula greater tubercle of humerus (lowest facet) laterally rotates arm axillary fixes head of humerus in glenoid fossa during abduction & flexion of arm
subscapularis medial two-thirds of costal surface of scapula (subscapular fossa) lesser tubercle of humerus medially rotates arm; assists extension of arm upper and lower subscapular nerves (C5,6) subscapularis, supraspinatus, infraspinatus, and teres minor are the rotator cuff muscles
biceps brachii short head: tip of coracoid process; long head: supraglenoid tubercle of scapula tuberosity of radius flexes forearm, flexes arm (long head), supinates musculocutaneous nerve (C5,6) a powerful supinator only if the elbow is flexed
brachialis anterior surface of lower one-half of humerus and intermuscular septa coronoid process of ulna flexes forearm musculocutaneous nerve (C5,6) powerful flexor
coracobrachialis coracoid process of scapula medial humerus at mid-shaft flexes and adducts arm musculocutaneous nerve (C5,6) musculocutaneous nerve passes through the coracobrachialis muscle to reach the other arm flexors (biceps brachii and brachialis)
serratus anterior ribs 1-8 or 9 medial border of the scapula on its costal (deep) surface it draws the scapula forward; the inferior fibers rotate the scapula superiorly long thoracic nerve (from ventral rami C5-C7) a lesion of long thoracic nerve will cause winging of the scapula (i.e., the medial border of the scapula falls away from the posterior chest wall and looks like an angel's wing) (Latin, serratus = to saw)
triceps brachii long head: infraglenoid tubercle of scapula; lateral head: posterolateral humerus & lateral intermuscular septum; medial head: posteromedial surface of inferior 1/2 of humerus olecranon process of the ulna extends forearm; long head extends and adducts arm radial nerve long head of triceps separates the triangular and quadrangular spaces (teres major, teres minor and the humerus are the other boundaries)
anconeus lateral epicondyle lateral side of olecranon and upper one-fourth of ulna extends forearm nerve to anconeus from radial nerve (Greek, ankon = elbow or a bend) Image Not Available

Nerves
Nerve Source Branches Motor Sensory Notes
brachial plexus ventral primary rami of C5-8 & T1 dorsal scapular, long thoracic, n. to subclavius, suprascapular, lateral & medial pectoral, medial brachial & antebrachial cutaneous, upper, middle & lower subscapular, musculocutaneous, ulnar, median, axillary, radial muscles of upper limb, excluding trapezius skin of upper limb axons from spinal cord levels C5-T1 are mixed (braided) in the brachial plexus and repackaged into terminal branches so that each branch contains axons from several spinal cord levels (Latin, plexus = a braid. A network of nerves, blood vessels, or lymphatic vessels)
dorsal scapular brachial plexus (C5)   rhomboid major & minor; levator scapulae   passes through scalenus medius
long thoracic brachial plexus (C5-C7)   serratus anterior   located on superficial surface of serratus anterior; lesion causes scapular winging, hence the saying "C5, 6, & 7 keep the wings from heaven"
lateral cord union of anterior divisions of upper & middle trunks lateral pectoral, lateral root of median n., musculocutaneous anterior arm; contributes to anterior forearm & thenar compartment lateral forearm; contributes to palmar hand  
medial cord anterior division of lower trunk medial pectoral, medial brachial cutaneous, medial antebrachial cutaneous, medial root of median n., ulnar fl. carpi ulnaris & medial half of fl. dig. profundus, contributes to other anterior forearm muscles; hand muscles medial forearm & hand  
posterior cord posterior divisions of upper, middle, & lower trunks upper, middle, & lower subscapular, axillary, radial deltoid, teres major & minor, subscapularis, posterior arm & forearm posterior arm & forearm, posterolateral hand  
suprascapular superior trunk of the brachial plexus (C5-C6) no named branches supraspinatus, infraspinatus no cutaneous branches passes through the suprascapular notch inferior to the superior transverse scapular ligament
lateral pectoral lateral cord of brachial plexus   pectoralis major   communicates with medial pectoral n. anterior to axillary a.; pierces clavipectoral fascia
musculocutaneous lateral cord of brachial plexus (C5,6) lateral antebrachial cutaneous coracobrachialis, biceps brachii, brachialis skin of lateral side of forearm pierces coracobrachialis
medial pectoral medial cord of the brachial plexus   pectoralis minor & major   communicates with lateral pectoral n. anterior to axillary a.; pierces pectoralis minor
medial brachial cutaneous medial cord of brachial plexus     skin of the medial side of the arm communicates with intercostobrachial n. (Latin, cutis = skin)
medial antebrachial cutaneous medial cord of brachial plexus     skin of medial side of forearm travels with basilic vein for part of course (Latin, cutis = skin)
ulnar medial cord of the brachial plexus palmar cutaneous br., dorsal br., superficial & deep br. flexor carpi ulnaris, flexor digitorum profundus (ulnar half), abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi, ulnar 2 lumbricals, palmar & dorsal interossei, adductor pollicis skin of medial side of wrist & hand & ulnar 1 1/2 digits on palmar side and 2 1/2 digits dorsally motor to most of the muscles of the hand (Latin, ulna = elbow or arm)
upper subscapular posterior cord of brachial plexus   subscapularis (superomedial part)    
thoracodorsal (middle subscapular) posterior cord of brachial plexus   latissimus dorsi    
lower subscapular posterior cord of brachial plexus   subscapularis (lateral part), teres major    
radial posterior cord of brachial plexus posterior brachial cutaneous, inferior lateral brachial cutaneous, posterior antebrachial cutaneous, superficial & deep br. triceps brachii, anconeus, brachioradialis, extensor carpi ulnaris, extensor carpi radialis longus & brevis, extensor digitorum, extensor digiti minimi, supinator, abductor pollicis longus, extensor pollicis longus & brevis, extensor indicis skin of posterior arm, forearm & hand motor to the extensor muscles of the arm and forearm
axillary posterior cord of brachial plexus superior lateral brachial cutaneous nerve deltoid, teres minor skin of upper lateral arm endangered by surgical neck fractures
median lateral & medial cords of brachial plexus anterior interosseous, palmar br., recurrent (motor) br., common palmar digital ns. (1st-3rd) pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus (radial half), flexor pollicis longus, pronator quadratus, abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, radial 2 lumbricals skin of radial half of palm & palmar side of radial 3 1/2 digits (and nail bed for these digits) motor to the flexor muscles of the forearm (except flexor carpi ulnaris and the medial 1/2 of the flexor digitorum profundus),the muscles of the thenar compartment and the lateral 2 lumbricals
intercostobrachial lateral cut. branch of 2nd intercostal     floor of axilla, medial and posterior surfaces of arm communicates with the medial brachial cutaneous n.

Arteries
Artery Source Branches Supply Notes
suprascapular thyrocervical trunk muscular supraspinatus & infraspinatus, shoulder joint anastomoses with the circumflex scapular a. and the dorsal scapular a. to form the scapular anastomosis
axillary subclavian (continuation of the subclavian lateral to the 1st rib) 1st part: superior thoracic; 2nd part: thoracoacromial, lateral thoracic; 3rd part: ant. & post. humeral circumflex, subscapular shoulder & upper limb pectoralis minor crosses the axillary artery anteriorly and is used to delineate the 3 parts mentioned at left (Latin, axillary = armpit)
superior thoracic axillary, 1st part muscular intercostal spaces 1 & 2 laterally  
thoracoacromial axillary, 2nd part pectoral br., clavicular br., acromial br., deltoid br. pectoralis major & minor, subclavius, deltoid, shoulder joint  
lateral thoracic axillary, 2nd part muscular serratus anterior & adjacent muscles, skin & fascia a rare artery in that it enters the serratus anterior from its superficial surface
subscapular axillary, 3rd part circumflex scapular, thoracodorsal subscapularis, teres major, teres minor, infraspinatus, latissimus dorsi anastomoses with suprascapular, dorsal scapular & deep br. of transverse cervical
circumflex scapular subscapular muscular teres major & minor, infraspinatus anastomoses with suprascapular & dorsal scapular branches (Latin, circum- = around + -flex = to bend)
thoracodorsal subscapular muscular latissimus dorsi  
anterior circumflex humeral axillary, 3rd part muscular arm muscles near surgical neck of humerus  (Latin, circum- = around + -flex = to bend)
posterior circumflex humeral axillary, 3rd part muscular arm muscles near surgical neck of humerus passes through quadrangular space with axillary nerve
brachial axillary (continuation distal to teres major m.) deep brachial, sup. ulnar collateral, nutrient, inf. ulnar collateral; terminal branches are the radial & ulnar arm, forearm & hand normally terminates at the level of the elbow, but high branching may occur
deep brachial brachial ascending br., terminal branches are the middle collateral & radial collateral post. arm  

Lymphatics of the Axillary Region
Structure Location Afferents from Efferents to Regions drained Notes
axillary nodes axilla   efferents form subclavian trunk upper limb, most of breast, some anterolateral chest wall axillary nodes are grouped as: 1) pectoral/anterior nodes, along lower border of pectoralis major; 2) lateral nodes, distal along axillary v.; 3) central nodes, centrally located along axillary v.; 4) subscapular/posterior nodes, along subscapular v. & tributaries; 5) apical nodes, at apex of axilla, receiving lymph from all other groups
pectoral nodes lateral border of pectoralis major most of breast, anterolateral chest wall & muscles central axillary nodes anterolateral thoracic wall and muscles, including most of the mammary gland also known as anterior axillary or level I nodes; an important group of nodes to examine during breast exam
lateral axillary along distal axillary v. small nodes in cubital fossa central axillary nodes upper limb
posterior axillary anterior to subscapularis m. central axillary nodes posterior shoulder a.k.a. subscapular nodes
central axillary along axillary v. posterior to pectoralis minor m. lateral, anterior & posterior axillary nodes apical axillary nodes upper limb, breast, posterior shoulder, lateral chest wall a.k.a. level II nodes
apical axillary along axillary v. medial to pectoralis minor m. at apex of axilla central axillary nodes subclavian lumph trunk upper limb, breast, posterior shoulder, lateral chest wall a.k.a. level III nodes

Topographic Anatomy
Structure/Space Boundaries Significance
quadrangular space boundaries: medial - long head triceps tendon, lateral - humerus, superior - teres minor, inferior - teres major significance: traversed by the axillary nerve & posterior humeral circumflex artery
subacromial/subdeltoid bursa between the deltoid, the supraspinatus tendon and the glenohumeral joint facilitates movement of the supraspinatus tendon and the deltoid
triangular space boundaries: lateral - long head triceps tendon, superior - teres minor, inferior - teres major significance: traversed by the circumflex scapular artery
anterior compartment separated from the posterior compartment by the medial and lateral intermuscular septa contains the biceps brachii, coracobrachialis, and brachialis mm. and musculocutaneous n.
anterior axillary fold anterior boundary of the axilla inferior border of the sternocostal head of the pectoralis major
bicipital aponeurosis a triangular membranous band that runs from the biceps tendon across the cubital fossa and merges with the antebrachial fascia passes obliquely over the brachial artery and median nerve (Greek, aponeurosis = a broad, flat nerve)
medial intermuscular septum extends from the deep surface of the brachial fascia to the medial supracondylar ridges of the humerus divides the arm into anterior and posterior compartments
lateral intermuscular septum extends from the deep surface of the brachial fascia to the lateral supracondylar ridges of the humerus divides the arm into anterior and posterior compartments
posterior axillary fold posterior border of the axilla composed of skin and muscular tissue of the latissimus dorsi and teres major
neurovascular compartment of arm formed by a split in the medial intermuscular septa contains the median & medial antebrachial cutaneous nn. and brachial vessels
posteror compartment of arm separated from the anterior compartment by the medial and lateral intermuscular septa contains triceps brachii, radial n., and deep brachial vessels, as well as ulnar n. in its distal, medial half
cubital fossa superior - line between humeral epicondyles, medial - pronator teres, lateral - brachioradialis site for phlebotomy

Clinical Terms
Term Definition
Erb-Duchenne palsy injury to the superior roots of the brachial plexus, C5 and C6, leads to paralysis of the supraspinatus and infraspinatus muscles, and in more severe forms may involve deltoid, biceps, brachialis, coracobrachialis, brachioradialis, teres minor, and subscapularis; the upper limb is adducted at the shoulder, medially rotated, and extended at the elbow. This type of injury can result from too much traction on the neck, or forcible lateral neck bending, as can occur during delivery. This should be suspected when the muscles of the hand are intact, but the Moro reflex is absent in an infant (Moro reflex is similar to the startle reflex, and involves abduction and then adduction of the arms).
Klumpke's palsy a lower brachial plexus injury; occurs when a person grabs something to break a fall or a baby's arm is pulled too much during delivery; the dorsal and ventral roots of the spinal nerves that form the inferior trunk of the brachial plexus (C8 and T1) may be avulsed; the short muscles of the hand are affected, and a clawhand results
radial nerve/Saturday night palsy The radial nerve is often injured when the humerus fractures at mid-shaft; wrist drop is a common clinical manifestation. The deep branch of the radial nerve can be injured by deep puncture wounds to the forearm. The deep branch of the radial nerve is responsible for extending the thumb and the MP joints. Neither deep nor superficial radial nerve injury causes much sensory loss, but cutting the superifical leaves a coin-shaped area distal to the bases of the 1st and 2nd metacarpals without sensation.
rotator cuff tear can lead to rupture of one or more of the tendons of the muscles forming the rotator cuff; acute tears may occur when the arm is violently pushed into abduction; a tear in the rotator cuff may present as pain in the anterosuperior part of the shoulder; tears also follow dislocation of the shoulder
subdeltoid/subacromial bursitis the tendon of the supraspinatus is separated from the coracoacromial ligament, acromion, and deltoid by the subacromial bursa; when this bursa is inflamed (subacromial bursitis), abduction of the arm is extremely painful during of the arc of 50 to 120 degrees (painful arc syndrome); pain may radiate as far distally as the hand, acute pain is also felt lateral to the acromion
painful arc syndrome pain caused by subacromial bursitis; felt during the arc of 50 to 120 degrees

The material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest & Jaye Schlesinger
Published by ILOC, Inc., New York
Copyright © 1995, unauthorized use prohibited.
 The excellent editorial assistance of
Dr. Pat Tank, UAMS
is gratefully acknowledged.
Copyright© 2000 The University of Michigan. Unauthorized use prohibited.
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