Ulna

Definition

The ulna is one of the two long bones in the forearm, located on the side opposite to the thumb. It extends from the elbow to the smallest finger and runs parallel to the radius.

5 Must Know Facts For Your Next Test

1. The ulna forms a hinge joint with the humerus at the elbow, allowing for flexion and extension of the arm.
2. It is longer than the radius and primarily responsible for forming the elbow joint.
3. The ulna has three regions: proximal end (nearer to elbow), shaft, and distal end (nearer to wrist).
4. Its proximal end features structures such as the olecranon and trochlear notch which interact with other bones.
5. Fractures of the ulna are commonly referred to as 'nightstick fractures' due to their association with defensive injuries.

Review Questions

• What primary function does the ulna serve in relation to arm movement?
• Name two key anatomical features found at the proximal end of the ulna.
• Why are fractures of the ulna sometimes called 'nightstick fractures'?

Related terms

radius:

The second long bone in the forearm that runs parallel to the ulna and helps form part of both wrist and elbow joints

humerus:

The long bone in the upper arm that interacts with both radius and ulna at its lower end to form elbow joint

olecranon: The prominent bony projection on the proximal end of ulna which forms part of elbow joint