The Ulnar Nerve Explained

Nerves are cylindrical bundles of fibers that emanate in branches from the brain and spinal cord to every part of the body.  Nerves carry impulses that move muscles, receive sensory input, and control involuntary functions such as heartbeat.

The ulnar nerve is a nerve that runs near the ulna bone in the arm.  The ulnar nerve is the largest nerve in the human body unprotected by muscle or bone, so injury is common.

The ulnar nerve originates from the C8-T1 nerve roots in the spine.  This network of nerve fibers form part of the medial cord of the brachial plexus (network of nerve fibers).

Brachial Plexus. Adapted from Gray's Anatomy. Public domain illustration.

The ulnar proceeds through the neck, the axilla (armpit), and descends on the posteromedial aspect (in the back toward the middle) of the humerus (the large bone in the upper arm).

Nerves of left upper extremity. From Gray's Anatomy. Public domain illustration.

The ulnar nerve then runs in a groove (cubital tunnel) on the back the medial epicondyle (rounded knuckle on the end of a bone) of the humerus.  This is the most common location where the ulnar nerve becomes pinched, resulting in cubital tunnel syndrome.

Ulnar collateral ligament. From Gray's Anatomy. Public domain illustration.

The ulnar nerve then enters the anterior (flexor) compartment of the forearm through the two heads of the flexor carpi ulnaris (muscle).  It soon joins with the ulnar artery, and the two travel inferiorly together alongside the ulna bone in the forearm, between the flexor carpi ulnaris and flexor digitorum profundus (muscles).

Deep palmar nerves. From Gray's Anatomy. Public domain illustration.

The ulnar nerve then enters the hand, where it 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.

Cutaneous innervation of the right upper limb. From Gray's Anatomy. Public domain illustration.

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Related posts:

  1. Cubital Tunnel Diagram
  2. Nerve Compression Syndromes
  3. Cell Phone Elbow or “Cellbow” Damages the Nerve in Your Arm
  4. Severity Scale for Cubital Tunnel Syndrome
  5. Books About Cubital Tunnel Syndrome and the Ulnar Nerve

Important: This website is for information purposes only and does not constitute medical advice. The information on this website represents the personal experience of cubital tunnel patients and has not been certified by medical professionals. Each person and case is different. Be sure to seek medical advice from a doctor with experience treating cubital tunnel syndrome and get a second opinion if needed.

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