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. 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
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
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+C6
b. middle trunk = C7
c. 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
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
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)