Ulnar nerve

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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.)
Latinnervus ulnaris
Gray'ssubject #210 939
Innervatesflexor carpi ulnaris
flexor digitorum profundis
lumbrical muscles
opponens digiti minimi
flexor digiti minimi
abductor digiti minimi
interossei
adductor pollicis
FromC8, T1 (branch from Medial cord)
MeSHUlnar+nerve
 
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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.)
Latinnervus ulnaris
Gray'ssubject #210 939
Innervatesflexor carpi ulnaris
flexor digitorum profundis
lumbrical muscles
opponens digiti minimi
flexor digiti minimi
abductor digiti minimi
interossei
adductor pollicis
FromC8, T1 (branch from Medial cord)
MeSHUlnar+nerve

In human anatomy, the ulnar nerve is a nerve which 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, supplying the palmar side of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.

One method of injuring the nerve is to strike 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".[1] Alternatively, according to the Oxford English Dictionary it may refer to "the peculiar sensation experienced when it is struck".[2]

Arm[edit]

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.

Forearm[edit]

It enters the anterior (flexor) compartment of the forearm between the humeral and ulnar heads, 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.

In the forearm it gives off the following branches:[3]

Hand[edit]

After it travels down the ulna, the ulnar nerve enters the palm of the hand through the Guyon's Canal. The ulnar nerve and artery pass superficial to the flexor retinaculum, via the ulnar canal.

The course of the ulnar nerve through the wrist contrasts with that of the median nerve, which travels deep to the flexor retinaculum of the hand.

Here it gives off the following branches:[3]

Branches and innervation[edit]

Muscular[edit]

Dissection of ulnar nerve

The ulnar nerve and its branches innervate the following muscles in the forearm and hand:

An Articular branch that passes to the elbow joint while the ulnar nerve is passing between the olecranon and medial epicondyle of the humerus.

Cutaneous[edit]

The ulnar nerve also provides sensory innervation to the fifth digit and the medial half of the fourth digit, and the corresponding part of the palm:

Ulnar nerve

Ulnar nerve entrapment[edit]

The ulnar nerve can be trapped or pinched as it proceeds from the brachial plexus to the fingertips. One common cause is cubital tunnel syndrome. In this syndrome, a tunnel on the medial side of the elbow traps the nerve.

Pinching of the ulnar nerve often causes paraesthesiae (tingling) in the fourth and fifth digits. Temporary paraesthesiae can be caused by sleeping or poor posture while awkwardly placing weight on one's arm, or by cycling for extended periods of time. In severe cases, surgery is performed to move the nerve.

Severe entrapment or complete severing of the ulnar nerve can present clinically as an ulnar claw.

Injury[edit]

Cutaneous innervation of the right upper extremity. Areas innervated by the radial nerve are colored in pink.

Injury of the ulnar nerve at different levels causes varying motor and sensory deficits.

At the elbow

At the wrist

See also[edit]

Additional images[edit]

References[edit]

  1. ^ Hendrickson, Robert A. The Facts on File Encyclopedia of Word and Phrase Origins (Facts on File Writer's Library). New York: Checkmark Books. p. 281. ISBN 0-8160-5992-6. 
  2. ^ "Welcome to the new OED Online : Oxford English Dictionary". Dictionary.oed.com. Retrieved 2012-03-20. 
  3. ^ a b Ellis, Harold; Susan Standring; Gray, Henry David (2005). Gray's anatomy: the anatomical basis of clinical practice. St. Louis, Mo: Elsevier Churchill Livingstone. p. 700. ISBN 0-443-07168-3. 

External links[edit]