Anatomy of Brachial Plexus
 5 roots – may be
1. prefixed in which case cervical rib more common (C4-C8) – 25%
2. postfixed (C6-T2) – 2.5%
 5 Roots
1. Lie behind scalenius anterior, in front of medius
2. 3 branches
i. Dorsal scapular nerve (C5)
ii. Nerve to subclavious (C5,C6)
iii. Long thoracic nerve (C5,6,7)
 3 Trunks
1. Cross lower part of posterior triangle
2. 1 branch
i. Suprascapular nerve from upper trunk
 6 Divisions
1. Behind the clavicle
2. Each trunk has a anterior and posterior division
 3 cords (lateral, medial, posterior)
1. cords enter above the first part of the axillary artery, embrace the second part
and give off branches in the third part
2. lateral
i. lateral pectoral nerve (C5,6,7)
ii. musculocutaneous nerve (C5,6)
iii. lateral cord of median nerve (C5,6,7)
3. medial
i. medial cutaneous nerve of arm (C8, T1)
ii. medial cutaneous nerve of forearm (C8,t1)
iii. medial pectoral nerve (C8,T1)
iv. medial cord median nerve (C8,T1)
v. ulnar nerve (C7,8,T1)
4. posterior
i. upper subscapular (C5,6)
ii. thoracodorsal (C6,7,8)
iii. lower subscapular (C5,6)
iv. axillary (C5,6)
v. radial (C5-T1)
From Roots
Dorsal Scapular Nerve
i. levator scapulae
ii. rhomboid minor
iii. rhomboid major
Nerve to subclavius
i. subclavious
Long thoracic nerve
i. Serratus anterior
From Trunks
Suprascapular nerve
i. Supraspinatus
ii. Infraspinatus
o
Passes under border of trapezius
o
Passes thru the suprascapular foramen under the ligament
o
Descends lateral to the scapular spine to reach infraspinatus
From Cords
Lateral pectoral nerve
i. Pectoralis minor (via communication with medial pectoral nerve across the axillary
artery)
ii. Pectoralis major
iii. No cutaneous supply
iv. Emerges on the medial border of pectoralis minor
Musculocutaneous nerve
i. Sinks into coracobrachialis
ii. Coracobrachialis
iii. Biceps
iv. Most of brachialis
v. Sensation over lateral forearm (LCNA)
Medial pectoral nerve
i. Pectoralis minor
ii. Pectoralis major
iii. Pierces pectoralis minor lateral to lateral pectoral nerve
Medial cutaneous nerve of arm
i. Smallest and most medial nerve
ii. Runs on medial side of the axillary vein
iii. Emerges from fascia ½ way down humerius
Medial cutaneous nerve of forearm
i. Runs down between vein and artery on top of ulnar nerve
ii. Pierces fascia 2/3rd down humerus
iii. Divides into anterior and posterior branches
Ulnar nerve
i. Runs between nerve and artery under MCNF
ii. Most posterior structure in the flexor compartment
Median nerve
i.
Starts above and lateral to the artery, curves gently to be medial to it at the cubital
fossa
ii. Lies in the groove below coracobrachialis
Upper subscapular nerve
i. upper part of subscapularis
Lower subscapular nerve
i. lower part of subscapularis
ii. teres major
Thoracodorsal nerve
i. latissimus dorsi
Axillary nerve
ii. travels through quandragular space with posterior circumflex humeral artery
iii. anterior branch supplies deltoid
iv. posterior branch supplies teres minor and becomes upper lateral cutaneous
nerve of arm
Radial nerve
i. supplies long head and medial of triceps and gives off posterior cutaneous nerve of
arm before passes through the (lateral) triangular space with the profunda brachii
artery