Brachial Plexus: Mnemonic: Read The Damn Cadaver (Book) 656-665.

I. Roots (anterior rami): C5-8, most of T1.

A. branches of roots:.

1. dorsal scapular nerve:.

a. origin: C5 root of brachial plexus.

b. innervation: rhomboid major and minor.

c. location: passes posteriorly, piercing middle scalene muscle in neck, travels medial border of scapula.

2. long thoracic nerve:.

a. origin: anterior rami of C5 to C7.

b. innervates: serratus anterior muscle.

c. location: passes vertically down the neck, through axillary inlet, down the medial wall of axilla.

II. Trunks:.

A. superior: union of C5 and C6 roots.

1. branches of superior trunk:.

a. suprascapular nerve:.

i. origin: superior trunk of brachial plexus.

ii. innervation: supraspinatus and infraspinatus muscles.

iii. location: laterally through posterior triangle of neck, suprascapular foramen, posterior scapular region.

iv. suprascapular artery: accompanies the nerve in the lateral parts of neck and in posterior scapular region.

b. nerve to subclavius muscle:.

i. origin: superior trunk of brachial plexus.

ii. innervation: subclavius muscle.

iii. location: anteroinferiorly over the subclavian artery and vein.

B. middle: continuation of C7 root.

C. inferior: union of C8 and T1 roots.

III. Divisions: anterior (3), posterior (3).

IV. Cords:.

A. lateral: union of anterior divisions of superior and middle trunks (contributions from C5 and C7).

1. location: lateral to the second part of the axillary artery.

2. branches of lateral cord:.

a. lateral pectoral nerve:.

i. innervation: pectoralis major muscle.

ii. location: most proximal of lateral cord branches, runs anteriorly to penetrate clavipectoral fasia spanning the gap between subclavius and pectoralis minor muscles.

b. musculocutaneous nerve:.

i. innervation: all three flexor muscles of anterior compartment of arm.

ii. location: runs laterally to penetrate corachobrachialis muscle, between biceps brachii and brachialis muscles of arm.

c. lateral root of median nerve:.

i. location: runs medially to join branch from medial cord, forming medial nerve.

B. medial: continuation of the anterior division of the inferior trunk (contains contributions from C8 and T1).

1. location: medial to the second part of the axillary artery.

2. branches of medial cord:.

a. medial pectoral nerve:.

b. medial cutaneous nerve of arm (medial brachial cutaneous nerve):.

c. medial cutaneous nerve of forearm (medial antebrachail cutaneous nerve):.

d. medial root of median nerve:.

e. ulnar nerve:.

i. origin: medial cord (though often receives communicating branch from lateral root of medial nerve that carriers fibers from C7).

ii. innervation: intrinsic mucles of hand (except three thenar and 2 lateral lumbrical muscles), flexor carpi ulnaris muscle, medial half of flexor digitorum profundus muscle, skin of palmar surface of little finger, medial half of ring finger, palm and wrists, skin of dorsal surface of medial part of hand.

iii. location: runs through arm and forearm into the hand.

C. posterior: union of all three posterior divisions (contributions from all roots of brachial plexus).

1. location: posterior to second part of axillary artery.

2. branches of the posterior cord:.

a. superior subscapular nerve:.

b. thoracodorsal nerve:.

c. inferior subscapular nerve:.

d. axillary nerve:.

i. innervation: deltoid and teres minor muscles.

ii. location: from posterior cord, passes inferiorly and laterally along posterior wall to exit axilla through quadrangular space, posteriorly around surgical neck of humerus.

iii. posterior circumflux humeral artery: accompanies the axillary nerve.

e. radial nerve: largest terminal branch.

i. innervation of radial nerve:.

I. all muscles in posterior compartments of arm and forearm:.

II. skin on posterior aspect of arm and forearm, lower lateral surface of arm, dorsal lateral surface of hand:.

ii. location: out of the axilla into posterior compartment of arm through triangular interval between inferior border of teres major muscle, long head of triceps brachii muscle, and shaft of humerus.

iii. profunda brachii artery: accompanies radial nerve through the triangular interval.

D. branches of cords:.

1. median nerve: along with the musculocutaneous nerve, lateral & medial roots of median nerve, and ulnar nerve forms an 'M' over third part of axillary artery.

a. origin: (roots from) lateral and medial cords.

b. innervation of median nerve: branches innervate most muscles of the anterior compartment of the forearm (except for flexor carpi ulnaris muscle and medial half of flexor digitorum profundus muscle).

i. in the hand: 3 thenar muscles associated with thumb, 2 lateral lumbrical muscles associated with movement of index and middle fingers, skin over palmar surface of lateral 3 and 1/2 digits and over lateral side of palm and middle of wrist.

c. location: anterior to the third part of axillary artery, arm anterior to brachial artery, arm into the forearm.

Drake, Richard L., Wayne Vogl, and Adam W. M. Mitchell. Gray's Anatomy for Students. Philadelphia: Elsevier, 2005.