Lecture 3

Axilla, Brachial Plexus, Subscapular Regions

Axilla

• pyramid between arm and thorax – contains brachial plexus, axillary vessels and lymph node

Landmarks

• Apex: entrance to axilla, passage way from neck– superior convergence point of: clavicle, scapula, 1st rib

• Base: concave inferior border = fascia and skin• Anterior border: clavicle = pectoral muscles• Posterior border: subscapularis, teres major,

latissimus dorsi• Medial border: ribs, intercostal muscles, serratus

anterior• Lateral border: humerus – intertubercular groove

(holds long head of biceps brachii)

Axillary artery

• continuation of subclavian artery.

• segment in between 1st rib and teres major

Segments

• A. First part of axillary artery – between the lateral border of the 1st rib and

medial of pectoralis minor– inside axillary sheath, along with branch

plexus and axillary vein– superior thoracic artery = the only branch of

this section– supplies 1st, 2nd intercostal spaces; superior

part of serratus anterior

Segments

• Second part, deep to pectoralis minor• Branches:

– 1. thoracoacromial artery: goes through clavipectoral fascia and divides deep to pect major into a. acromialb. clavicularc. deltoidd. pectoral

– 2. lateral thoracic artery: to pectoral muscles and axillary lymph nodes; * esp. large in women provides blood to breasts

Segments

• Third part, axillary artery: from inferior edge of pectoralis minor to inferior edge of teres major

• 1. anterior humeral circumflex: – anastomoses with posterior circumflex around surgical neck of

humerus, can also supply biceps, coracobrachialis• 2. posterior humeral circumflex artery:

– travels with axillary nerve through quadrangular space to deltoid, triceps muscles

• 3. subscapular artery: – largest branch of axillary artery; along lateral edge of

subscapularisbranches: a. circumflex scapular - to muscles of dorsal scapulab. thoracodorsal - to latissimus dorsi

Axillary Vein

• Formed by the union of basilic vein and brachial vein, becomes subclavian vein after 1st rib

• receives tributaries corresponding to axillary artery branches 

• Joined by cephalic vein superior to pectoralis minor

Brachial Plexus

• Nerve network bundle from neck into axilla to arm (C 5, 6, 7, 8 & T1)

• Nerves - progress sequentially from ventral rami of spinal nerves

• Rami (anterior) > trunks > divisions > cords > branches

Trunk

• ventral rami - from C5-C8, T1 ( emerge between scalenus anterior and scalenus medius) a. superior(upper) trunk = C5+C6b. middle trunk = C7c. inferior(lower) trunk = C8+T1

Divisions

• each trunk splits to form anterior and posterior divisions

• a. anterior divisions - supply anterior, flexor of arm

• b. posterior divisions - supply posterior / extensors of arm

Cords

• anterior and posterior division combine to form cords: names refer to position relative to axillay artery

• a. posterior cord = all 3 posterior divisions (superior, middle, inferior)

• b. lateral cord = anterior divisions of superior, middle trunk

• c. medial cord = anterior of inferior (lower) division

Branches

• cord divide into terminal branches: ( each also has other, side branches, below)

• a. posterior cord– axillary nerve and radial nerve (three smaller

branches: upper, lower subscapular nerves, & throracodorsal nerve)

• b. lateral cord– musculocutaneous and lateral root of median nerve

(other branch: lateral pectoral nerve)

• c. medial cord:– ulnar nerve and medial root of median nerve

Supraclavicular Branches

• Supraclavicular Branches of brachial plexus: (from ventral rami and trunks)

• 1. dorsal scapular nerve - to rhomboideus major muscle, levator scapulae - from C5,C4

• 2. long thoracic nerve - to serratus anterior - from C5, C6, C7

• 3. nerve to the subclavius - from superior trunk, C5, C6 and C4

• 4. suprascapular nerve - to supra and infraspinatus - also from superior trunk, C5, C6 and C4

Infraclavicular branches

• 1.Lateral cord branches: a. lateral pectoral nerve (side branch)– to pectoralis major

* (named after lateral cord, actually sits medial to medial pectoral nerve )

– b. musculocutaneous (terminal) : to anterior arm - coracobrachialis, biceps, brachials( moves superficial at elbow, becomes lateral antebrachial cutaneous nerve in forearm)

– c. Lateral root of median nerve (=continuation of cord) join medial root to form median nerve to forearm flexors

Infraclavicular branches

• 2. Medial cord branches: (all from C8, T1) – a. ulnar nerve (terminal branch): to forearm, hand

(C8,T1, sometimes C7) – b. medial root of median nerve (terminal branch): joins

lateral root, forms median nerve to forearm flexorsc. medial pectoral nerve (side branch): to pectoralis minor (+part of major) * ( named after medial cord, actually sits lateral to lateral pectoral nerve )

– d. medial brachial cutaneous nerve (side branch): skin of medial arm

– e. medial antebrachial cutaneous nerve (side branch): skin of medial forearm

Infraclavicular branches

• 3. Posterior cord branches: to extensors, skin of upper limb– a. axillary nerve (a terminal branch): to teres minor, deltoid

(C5,C6)-- goes thru quadrangular space with post humeral circumflex artery, around neck of humerus-- ends as upper lateral brachial cutaneous to skin over inferior deltoid area

– b. radial nerve (terminal branch): to upper arm, forearm extensors and skin( triceps, anconeus, brachioradialis) -- goes between long and medial ticeps heads, sits in radial groove of humerus (C5-C8, T1)

– c. upper subscapualr nerve (side branch): to subscapularis (C5,C6)

– d. lower subscapular nerve (side branch): to subscapularis, teres major (C5,C6)

– e. thoracodorsal nerve (side branch): to latissimus dorsi(C6,C7,C8)