1. Axilla, Brachial Plexus, Subscapular Regions
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. acromial b. clavicular c. deltoid d. 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 subscapularis branches: a. circumflex scapular - to muscles of dorsal scapula b. 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+C6 b. middle trunk = C7 c. 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 flexors c. 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)