Ulna

The ulna is the bone of the forearm and functions as part of the elbow joint. It is a long bone, prismatic in form, placed at the medial side of the forearm, parallel with the radius.

Structure of the Ulna

The long, narrow medullary cavity is enclosed in a strong wall of compact tissue which is thickest along the interosseous border and dorsal surface.At the extremities the compact layer thins.

It articulates with the following:

• The humerus, at the right side elbow as a hinge joint.
• The radius, near the elbow as a pivot joint,
• The distal radius, where it fits into the ulna notch, and
• The radius along its length via the interosseous membrane that forms a syndesmoses joint.

Most people think it is the Ulna Bone when struck in that area that causes people to laugh or better known as the Funny Bone. When it is actually the Ulnar Nerve that causes one to laugh!

The ulnar nerve is a nerve which runs near the ulna bone. Aggravation of this nerve is commonly referred to as hitting one's "funny bone."

The ulnar nerve is the largest unprotected nerve in the human body (meaning, unprotected by muscle or bone), and the only unprotected nerve that does not serve a sensory function (those nerves specifically meant to perceive changes in the environment, such as nerves in the skin).

Conditions of the Ulna

Some of the problems that can affect the ulna include:

• Ulnar nerve dysfunction – impaired movement or sensation in the wrist and hand caused by damage to the ulnar nerve,
• Spondyloperipheral dysplasia - short ulna: A rare inherited disorder characterized by a short forearm bone (ulna) and other skeletal anomalies such as short hands and feet.
• Ulna fracture, and
• Other conditions that affect bones such as osteoporosis

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