küünarluu

The küünarluu, known in English as the ulna, is one of the two long bones located in the forearm of the human body. It is situated on the medial side of the forearm, meaning it is closer to the midline of the body, and runs parallel to the radius. The ulna is the longer of the two forearm bones.

The ulna has several key features. Its proximal end (closest to the elbow) forms the olecranon, which is the bony prominence commonly referred to as the "elbow." This olecranon articulates with the humerus (upper arm bone) to form the elbow joint, allowing for flexion and extension of the arm. The distal end (closest to the wrist) of the ulna is smaller and articulates with the radius and carpal bones, contributing to the wrist joint.

The shaft of the ulna is roughly triangular in cross-section and serves as an attachment point for various muscles of the forearm, including those responsible for pronation (turning the palm downwards) and supination (turning the palm upwards) of the forearm, though the radius plays a more significant role in rotation. Fractures of the ulna can occur due to direct trauma or falls and may require medical intervention depending on the severity. The ulna plays a crucial role in the structure and function of the forearm and elbow.