Download Tracing the Brachial Plexus

Tracing the Nerves through the Arm and Forearm

Musculocutaneous n.
o Branches off of the lateral chord of the brachial plexus
o Pierces the corachobrachialis
o Lies between the bicep brachii and brachialis moving medially to laterally.
o As it emerges beneath the bicep brachii, becomes the lateral cutaneous n. of the
forearm
o Terminal end of lateral cutaneous n. lies on the superior face of the brachioradialis
near the elbow

Ulnar n.
o After branching off medial chord, travel with the median n. in the medial neurovascular
bundle.
o Near the middle of the humerus, it begins to leave the medial neurovascular bundle
o Soon after, ulnar n. leaves the medial neurovascular bundle and pierces the medial
intermuscular septum moving posteriorly.
o Then passes posterior to the medial epicondyle of the humerus next to where the long
head of the tricep attaches to the olecranon (see Netter’s pdf pg 465)
o Ulnar n. enters forearm by passing between two heads of FCU (humeral head of FCU
above and ulnar head of FCU below the ulnar n.)
o Comes to lie between the FCU and FDP
o About 1/3 down the forearm, the ulnar artery joins the ulnar n.
o Gives off a dorsal branch of the ulnar n. and a palmar branch of the ulnar n. (see
course pack pg 65)

Median n.
o After formation via the lateral and medial chords, median n. travels in the medial
neurovascular bundle with the ulnar n.
o Note: medial neurovascular bundle starts off sandwiched between the coracobrachialis
and the latissimus dorsi/teres major  near mid humerus it then is sandwiched by the
bicep and tricep  near elbow it is sandwiched by bicep superiorly, tricep inferiorly,
and brachialis laterally (see Netters pdf pg 456)
o Proximally, the median n. lies lateral to the brachial artery while distally it lies medial to
the artery
o Median n. enters the cubital fossa anterior to brachioradialis and medial to insertion of
bicep brachii. (Note: there is a forearm fascia over the cubital fossa where the basilica
and cephalic veins reside see course pack pg 60)
o Near the apex of the cubital fossa, the median n. gives off the anterior interosseous n.
 The anterior interosseous n. accompanies the anterior interosseous a. (given off by
the ulnar a.) on the lateral border of the FDP inferior (below) the FDS (see Netter’s pdf
pg 469)
o The main branch of the median n. exits the cubital fossa between the two heads of the
pronator teres and continues distally to the wrist below the FDS
o

Eventually, median n. makes its way through the carpal tunnel  a palmar branch of
the median n. goes over the carpal tunnel and provides sensory information for the
palm
Radial n.
o Branches off of the posterior chord (so does the axillary n.)
o Goes through the triangular interval with the profunda brachii a
o Travels from medial to lateral while in the radial groove beneath the triceps
o Proximal to the lateral side of the elbow, the radial n. begins to move anteriorly and lies
between the brachialis and brachioradialis
o Adjacent to the cubital fossa, the radial n. branches into the superficial and deep
branches of the radial n.
o Superficial radial n. lies deep to the brachioradialis but above the supinator and
accompanies the radial a. (branch of the brachial artery)
o The deep branch of the radial n. enters between the two heads of the supinator
 When it emerges from the supinator, changes names to the posterior
interosseous n. and completes most of the posterior compartment innervation
 Accompanied by the posterior interosseous artery branches from the
common interosseous arterybranches from the ulnar a. part of the brachial
a.