Forearm bones
Radius and ulna are the human forearm bones (lat. Ossa antebrachii) and are therefore located in the free upper extremity. They belong to the tubular bones. They are limited by the humerus and the carpal bones. The elbow joint and wrist are formed at these points.
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Anatomy
The forearm bones are formed from the parallel tubular bones: Ulna and radius. The ulna is located in the medial side of the forearm. The radius is parallel to the ulna and has a thicker diameter. The two bones are connected by the membrana interossea antebrachii. If the forearm is in supination position (palm of the hand points forward in hanging arm position), the forearm bones are parallel. In the pronation position (palm of the hand points backwards in the hanging arm position), however, the parallelism of the bones is no longer present. The ulna and the radius cross each other.
Function
The forearm bones create a connection between the upper arm and the hand. The two forearm bones form joints with the upper arm bone and the carpal bones. The ulna and the radius allow the rotation of the arm by crossing the bones when changing from supination to pronation position.
