Ulnar nerve
Encyclopedia
In human anatomy
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...

, the ulnar nerve is a nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

 which runs near the ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...

 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
Medial epicondyle of the humerus
The medial epicondyle of the humerus, larger and more prominent than the lateral epicondyle, is directed a little backward. In birds, where the arm is somewhat rotated compared to other tetrapods, it is called ventral 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
Pun
The pun, also called paronomasia, is a form of word play which suggests two or more meanings, by exploiting multiple meanings of words, or of similar-sounding words, for an intended humorous or rhetorical effect. These ambiguities can arise from the intentional use and abuse of homophonic,...

, based on the sound resemblance
Homophone
A homophone is a word that is pronounced the same as another word but differs in meaning. The words may be spelled the same, such as rose and rose , or differently, such as carat, caret, and carrot, or to, two, and too. Homophones that are spelled the same are also both homographs and homonyms...

 between the name of the bone of the upper arm, the "humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

" and the word "humorous
Humour
Humour or humor is the tendency of particular cognitive experiences to provoke laughter and provide amusement...

". Alternatively, according to the OED
Oxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 it may refer to "the peculiar sensation experienced when it is struck".

Arm

The ulnar nerve originates from the C8-T1 nerve roots which form part of the medial cord of the brachial plexus
Brachial plexus
The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

, and descends on the posteromedial aspect of the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....


Forearm

It enters the anterior (flexor) compartment of the forearm through the two heads of flexor carpi ulnaris and runs alongside the ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...

. There it supplies one and a half muscles (flexor carpi ulnaris & medial half of flexor digitorum profundus). It soon joins with the ulnar artery
Ulnar artery
The ulnar artery is the main blood vessel, with oxygenated blood, of the medial aspect of the forearm. It arises from the brachial artery and terminates in the superficial palmar arch, which joins with the superficial branch of the radial artery...

, and the two travel inferiorly together, deep to the flexor carpi ulnaris muscle.

In the forearm it gives off the following branches:
  • Muscular branches of ulnar nerve
    Muscular branches of ulnar nerve
    The muscular branches of ulnar nerve, two in number, arise near the elbow: one supplies the Flexor carpi ulnaris; the other, the ulnar half of the Flexor digitorum profundus. ....

  • Palmar branch of ulnar nerve
    Palmar branch of ulnar nerve
    The palmar branch of the ulnar nerve arises about five cm above the wrist from where the ulnar nerve splits into palmar and dorsal branches.The palmar branch represents the continuation of the ulnar nerve as it crosses the flexor retinaculum of the hand on the lateral side of the pisiform bone,...

  • Dorsal branch of ulnar nerve
    Dorsal branch of ulnar nerve
    The dorsal branch of ulnar nerve arises about 5 cm. proximal to the wrist; it passes backward beneath the Flexor carpi ulnaris, perforates the deep fascia, and, running along the ulnar side of the back of the wrist and hand, divides into two dorsal digital branches; one supplies the ulnar side of...


Hand

After it travels down the ulna, the ulnar nerve enters the palm of the hand. The ulnar nerve and artery pass superficial to the flexor retinaculum
Flexor retinaculum of the hand
The flexor retinaculum is a strong, fibrous band that arches over the carpus, converting the deep groove on the front of the carpal bones into a tunnel, the carpal tunnel, through which the Flexor tendons of the digits and the median nerve pass.It is attached, medially, to the pisiform and the...

, via the ulnar canal
Ulnar canal
The ulnar canal or ulnar tunnel, also called Guyon's canal, is a space at the wrist between the pisiform bone and the hamate bone through which the ulnar artery and the ulnar nerve travel into the hand.-Eponym:...

.

The course of the ulnar nerve through the wrist contrasts with that of the median nerve
Median nerve
The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....

, which travels deep to the flexor retinaculum of the hand
Flexor retinaculum of the hand
The flexor retinaculum is a strong, fibrous band that arches over the carpus, converting the deep groove on the front of the carpal bones into a tunnel, the carpal tunnel, through which the Flexor tendons of the digits and the median nerve pass.It is attached, medially, to the pisiform and the...

 and therefore through the carpal tunnel
Carpal tunnel
In the human body, the carpal tunnel or carpal canal is the passageway on the palmar side of the wrist that connects the forearm to the middle compartment of the deep plane of the palm. The tunnel consists of bones and connective tissue...

.

Here it gives off the following branches:
  • Superficial branch of ulnar nerve
    Superficial branch of ulnar nerve
    The superficial branch of the ulnar nerve is a terminal branch of the ulnar nerve. It supplies the palmaris brevis and the skin on the ulnar side of the hand, and divides into a proper palmar digital nerve and a common palmar digital nerve....

  • Deep branch of ulnar nerve
    Deep branch of ulnar nerve
    The deep branch of the ulnar nerve is a terminal, primarily motor branch of the ulnar nerve.It is accompanied by the deep palmar branch of ulnar artery.-Path:It passes between the abductor digiti minimi and the flexor digiti minimi brevis....


Muscular

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.
  • In the forearm
    Forearm
    -See also:*Forearm flexors*Forearm muscles...

    , via the muscular branches of ulnar nerve
    Muscular branches of ulnar nerve
    The muscular branches of ulnar nerve, two in number, arise near the elbow: one supplies the Flexor carpi ulnaris; the other, the ulnar half of the Flexor digitorum profundus. ....

    :
    • Flexor carpi ulnaris
    • Flexor digitorum profundus (medial half)

  • In the hand
    Hand
    A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...

    , via the deep branch of ulnar nerve
    Deep branch of ulnar nerve
    The deep branch of the ulnar nerve is a terminal, primarily motor branch of the ulnar nerve.It is accompanied by the deep palmar branch of ulnar artery.-Path:It passes between the abductor digiti minimi and the flexor digiti minimi brevis....

    :
    • hypothenar muscles
    • The third and fourth lumbrical muscles
      Lumbricals of the hand
      The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints and extend the interphalangeal joints.-Structure:There are four of these small, worm-like muscles on each hand. These muscles are unusual in that they do not attach to bone...

    • Dorsal interossei
      Dorsal interossei of the hand
      The dorsal interossei of the hand are muscles that occupy the space between the metacarpals.-Structure:There are four dorsal interossei in each hand...

    • Palmar interossei
    • Adductor Pollicis
      Adductor pollicis muscle
      In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique....


  • In the hand, via the superficial branch of ulnar nerve
    Superficial branch of ulnar nerve
    The superficial branch of the ulnar nerve is a terminal branch of the ulnar nerve. It supplies the palmaris brevis and the skin on the ulnar side of the hand, and divides into a proper palmar digital nerve and a common palmar digital nerve....

    :
    • Palmaris brevis

Cutaneous

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:
  • Palmar branch of ulnar nerve
    Palmar branch of ulnar nerve
    The palmar branch of the ulnar nerve arises about five cm above the wrist from where the ulnar nerve splits into palmar and dorsal branches.The palmar branch represents the continuation of the ulnar nerve as it crosses the flexor retinaculum of the hand on the lateral side of the pisiform bone,...

     - supplies cutaneous innervation to the anterior skin and nails
  • Dorsal branch of ulnar nerve
    Dorsal branch of ulnar nerve
    The dorsal branch of ulnar nerve arises about 5 cm. proximal to the wrist; it passes backward beneath the Flexor carpi ulnaris, perforates the deep fascia, and, running along the ulnar side of the back of the wrist and hand, divides into two dorsal digital branches; one supplies the ulnar side of...

     - supplies cutaneous innervation to the posterior skin (except the nails)

Ulnar nerve entrapment

The ulnar nerve can be trapped or pinched as it proceeds from the brachial plexus to the fingertips. One common cause is cubital tunnel
Cubital tunnel
The cubital tunnel is a channel which allows the Ulnar nerve to travel over the elbow.Chronic compression of this nerve is known as Cubital Tunnel Syndrome, a form of Repetitive Strain Injury akin to Carpal Tunnel Syndrome .-See also:* Ulnar nerve...

 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
Cycling
Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...

 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
Ulnar claw
A hand imitating an ulnar claw created by distal ulnar lesion or papal hand of a proximal median nerve lesion. The metacarpophalangeal joints of the 4th and 5th fingers are extended and the Interphalangeal joints of the same fingers are flexed....

, or can be diagnosed by clinical tests, like card test, Froment's sign, and so on.

External links

  • Cubital Tunnel Support Forums - "The major subdivisions and terminal nerves of the brachial plexus
    Brachial plexus
    The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

    ." - "Anterior view of the nerves, vessels, and superficial tendons that cross the left wrist
    Wrist
    In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...

    ." - "Transverse section through the carpal tunnel
    Carpal tunnel
    In the human body, the carpal tunnel or carpal canal is the passageway on the palmar side of the wrist that connects the forearm to the middle compartment of the deep plane of the palm. The tunnel consists of bones and connective tissue...

     and distal row of the carpal bones." - "Axilla, dissection, anterior view"
  • Overview at neuro.wustl.edu
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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