Radial & Ulnar Nerves

Question 1

What is the source of the radial nerve?

Answer 1

Posterior cord of brachial plexus (C5-T1)

Question 2

What is the path of the radial nerve in the arm?

Answer 2

Exits axilla
Enters posterior compartment of the arm

In the lateral triangular space of the posterior shoulder (with profunda brachii artery)

Travels in the radial groove between the medial and lateral head of the triceps (with profunda brachii artery)

At the lateral border of the humerus, crosses from the posterior compartment into the anterior compartment of the arm

Pierces lateral intermuscular septum of the arm (at lateral border of humerus)

Descends between brachialis and brachioradialis

Located in lateral aspect of cubital fossa

Question 3

What is the path of the radial nerve in the forearm?

Answer 3

Located in lateral aspect of cubital fossa

At the level of the lateral epicondyle, splits into deep and superficial branches

Question 4

What is the path of the deep branch of the radial nerve?

Answer 4

Stems from radial nerve at the level of the lateral epicondyle ( in cubital fossa)

enters forearm between two heads of the supinator muscle

runs around lateral aspect of radial neck into the posterior compartment of the forearm

becomes the posterior interosseous nerve

Question 5

What is the path of the superficial branch of the radial nerve?

Answer 5

Stems from the radial nerve at the level of the lateral epicondyle (in the cubital fossa)

Descends the forearm under the brachioradialis muscle

Emerges in the distal forearm

Crosses the wrist on the lateral side, superficial to the anatomical snuffbox

Question 6

What does the radial nerve innervate?

Answer 6

All posterior muscles of the arm

All posterior muscles of the forearm (as deep branch / posterior interosseous nerve)

Skin and joints of the hand (as the superficial branch)

Question 7

What is the source of the ulnar nerve?

Answer 7

Medial cord of brachial plexus (C8-T1)

Question 8

What is the path of the ulnar nerve in the arm?

Answer 8

Passes through anterior arm near brachial artery

Midway down arm, pierces medial intermuscular septum

Passes posterior to medial epicondyle (funny bone)

Question 9

What is the path of the ulnar nerve in the forearm?

Answer 9

Enters forearm medially between the two heads of the Flexor Carpi Ulnaris

Descends medially between the Flexor Carpi Ulnaris and Flexor Digitorum Profundus muscles

Passes into the wrist superficially to the flexor retinaculum

Passes through the Tunnel of Guyon into the hand

Question 10

What are the branches of the ulnar nerve?

Answer 10

No branches in the axilla or arm

Cutaneous branches arise in forearm (palmar and dorsal)

Deep branches supply the muscles in the hand

Question 11

What does the ulnar nerve innervate?

Answer 11

Flexor Carpi Ulnaris

Medial half of Flexor Digitorum Profundus

Deep branch:
Hypothenar eminance

Interossei muscles
Adductor Pollicis
Flexor Pollicis Brevis
Lumbricals 3-4