Ulnar nerve

Ulnar nerve
File:Brachial plexus.JPG Click image to enlarge - ulnar nerve is visible in lower left
File:Gray816.png Nerves of the left upper extremity. (Ulnar labeled at center left.)
Details
From	Medial cord
Innervates	flexor carpi ulnaris flexor digitorum profundis lumbrical muscles opponens digiti minimi flexor digiti minimi abductor digiti minimi interossei adductor pollicis
Identifiers
Latin	nervus ulnaris
MeSH	D014459
TA98	A14.2.03.040
TA2	6449
FMA	37319
Anatomical terms of neuroanatomy

In human anatomy, the ulnar nerve is a nerve which runs from the shoulder to the hand, at one part running near the ulna bone. It is the only exposed nerve in the human body (it is unprotected for a few centimeters at the elbow).

Course

The ulnar nerve comes from the medial cord of the brachial plexus, and runs distally ant to the triceps medical to the brachial artery.Around the middle of the arm peirces the medical intermuscular septum and descends between it and the medical head of the triceps muscle. Then passes between the medial epicondyle of the humerus and the and the olecronon to enter the forearm. No branches in the arm.

After passing posterior to the medical epicondyle of the humerus the ulnar nerve enters the forearm by passing between the two heads of the flexor carpi ulnaris mm (FCU). The descend deep to this muscle on teh flexor digitorum profundus where it accompanies the ulnar artery neaar the middel of the forearm. Then it passes on the medial side of the ulnar artery and the lateral side of the tendon of the FCU. In the distal part of the forearm it is relatively superficial covered only by fascia and skin. It pierces the deep fascia and passes superficial to the flexor retinaculum with the ulnar artery, lateral to the pisiform and between it and the hook of the hamate. This passage for the ulnar nerve and artery covered by a slip of the flexor retincaculum is called the calnal of Guyton.

Branches and innervation

Muscular

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

• In the forearm, via the muscular branches of ulnar nerve:
  • Flexor carpi ulnaris
  • Flexor digitorum profundus (medial half)

• In the hand, via the deep branch of ulnar nerve:
  • hypothenar muscles
    • Opponens digiti minimi
    • Abductor digiti minimi
    • Flexor digiti minimi brevis
  • Adductor pollicis
  • The third and fourth lumbrical muscles
  • Dorsal interossei
  • Palmar interossei

• In the hand, via the superficial branch of ulnar nerve:
  • Palmaris brevis

Cutaneous

The ulnar nerve also provides sensory innervation to the part of the hand corresponding to the fourth and fifth digits:

• Palmar branch of ulnar nerve - anterior
• Dorsal branch of ulnar nerve - posterior

Ulnar nerve entrapment

Main article: Ulnar nerve entrapment

The Ulnar nerve can be trapped or pinched in various ways as it proceeds down the arm from the Brachial plexus to the ring and middle fingers. One common cause is cubital tunnel syndrome, where the tunnel runs the inner outside side of the elbow. Pinching of the nerve often causes tingling symptoms in the little and ring fingers. In some cases moderate to severe pain is experienced from pinching this nerve. Often such pins and needles sensations can be caused by sleeping wrong on your arm, but sometimes the problems last for days. In severe cases, surgery is performed.

See also

• Radial artery
• Axillary nerve
• Median nerve

Additional images

• 
  Brachial plexus
• 
  Cross-section through the middle of upper arm.
• 
  Cross-section through the middle of the forearm.
• 
  Transverse section across distal ends of radius and ulna.
• 
  Transverse section across the wrist and digits.
• 
  The palmar aponeurosis.
• 
  The axillary artery and its branches.
• 
  The brachial artery.
• 
  Ulnar and radial arteries. Deep view.
• 
  The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front.
• 
  Cutaneous nerves of right upper extremity. Anterior view.
• 
  Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Anterior view.
• 
  Cutaneous nerves of right upper extremity. Posterior view.
• 
  Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Posterior view.
• 
  Superficial palmar nerves.
• 
  Deep palmar nerves.
• 
  Front of right upper extremity, showing surface markings for bones, arteries, and nerves.
• 
  Back of right upper extremity, showing surface markings for bones and nerves.

External links

• Template:EMedicineDictionary
• Anatomy figure: 05:03-15 at Human Anatomy Online, SUNY Downstate Medical Center - "The major subdivisions and terminal nerves of the brachial plexus."
• Anatomy figure: 07:04-04 at Human Anatomy Online, SUNY Downstate Medical Center - "Anterior view of the nerves, vessels, and superficial tendons that cross the left wrist."
• Anatomy figure: 08:03-07 at Human Anatomy Online, SUNY Downstate Medical Center - "Transverse section through the carpal tunnel and distal row of the carpal bones."
• Ulnar nerve at the Duke University Health System's Orthopedics program
• Template:MUNAnatomy
• Hand kinesiology at the University of Kansas Medical Center
• Atlas image: hand_plexus at the University of Michigan Health System - "Axilla, dissection, anterior view"
• Overview at neuro.wustl.edu