Lecture 3 Axilla, Brachial Plexus, Subscapular Regions
Jan 16, 2016
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)