Lecture 3

1. Lecture 3 Axilla, Brachial Plexus, Subscapular Regions

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

3. 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)

5. Axillary artery • continuation of subclavian artery. • segment in between 1st rib and teres major

7. 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

8. 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

9. 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

11. 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

14. 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

15. 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

18. 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

19. 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

21. 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

22. 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

24. 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

25. 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

27. 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)