Ulna

Ulna
Position of ulna (shown in red)
Shown is the right hand, palm down (left) and palm up (right). Ulna is #2
Details
Identifiers
Latin	Ulna
MeSH	A02.835.232.087.090.850
TA	A02.4.06.001
FMA	23466
Anatomical terms of bone []

The ulna (/ˈʌlnə/) is one of the two long bones in the forearm (the other is the radius). It is on the side opposite the thumb, extends from the elbow to the wrist, and runs parallel to the radius, which it exceeds in length and size. In anatomical position, when the arms are down at the sides of the body and the palms of the hands face forward, the ulna is located at the side of the forearm closest to the body (the medial side). The bone may break due to excessive weight or impact.

The ulna is broader close to the elbow, and narrows as it approaches the wrist.

Close to the elbow, the ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge joint with the trochlea of the humerus. There is also a radial notch for the head of the radius, and the ulnar tuberosity to which muscles attach.

Close to the wrist, the ulna has a styloid process.