Ulnar nerve

Ulnar nerve
Click image to enlarge - ulnar nerve is visible in lower left
Nerves of the left upper extremity. (Ulnar labeled at center left.)
Details
From	C8, T1 (branch from Medial cord)
Innervates	flexor carpi ulnaris flexor digitorum profundus lumbrical muscles opponens digiti minimi flexor digiti minimi abductor digiti minimi interossei adductor pollicis
Identifiers
Latin	nervus ulnaris
MeSH	A08.800.800.720.050.850
TA	A14.2.03.040
FMA	37319
Anatomical terms of neuroanatomy []

In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest unprotected nerve in the human body (meaning unprotected by muscle or bone), so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar side of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.

This nerve can cause an electric shock-like sensation by striking the medial epicondyle of the humerus from posteriorly, or inferiorly with the elbow flexed. The ulnar nerve is trapped between the bone and the overlying skin at this point. This is commonly referred to as bumping one's "funny bone". This name is thought to be a pun, based on the sound resemblance between the name of the bone of the upper arm, the "humerus" and the word "humorous". Alternatively, according to the Oxford English Dictionary it may refer to "the peculiar sensation experienced when it is struck".

The ulnar nerve originates from the C8-T1 nerve roots (and occasionally carries C7 fibres) which form part of the medial cord of the brachial plexus, and descends on the posteromedial aspect of the humerus. It runs inferior to the posteromedial aspects of the humerus, passing behind the medial epicondyle (in the cubital tunnel) at the elbow where it is exposed for several centimetres.

It enters the anterior (flexor) compartment of the forearm between the humeral and ulnar heads of flexor carpi ulnaris, lying under the aponeurosis of flexor carpi ulnaris alongside the ulna. There it supplies one and a half muscles (flexor carpi ulnaris and the medial half of flexor digitorum profundus) and courses with the ulnar artery, travelling inferiorly with it deep to the flexor carpi ulnaris muscle.