Anatomically speaking, using the thumb side of the arm as the base for the lateral side, the antebrachium include the ulna (which rests on the medial side) and the radius on the lateral side.

The ulna is longer than the radius and is more concretely connected to the humerus than the radius. The radius does however create a stronger contribution to the movements associated at the articulation of the wrist joint.


The proximal end of the ulna is conjoined with both the humerus and the radius. The trochlear notch subsequently creates an amalgamation with the troclea of the humerus. This in fact creates a highly distinct impression. The anterior lip of the trochlear notch is formed by the coronoid process and the posterior lip is formed by the olecranon.


Image: Antebrachium

Accommodating the head of the radius is the radial notch which is positioned in the lateral and inferior portion of the coronoid process. The distal end of the ulna is tapered and on that end there is a portion that is knobby, the head, and a knob-shaped projection that is the styloid process. The ulna joins the radius at both ends.
Image: Ulna


The radius is composed of a smaller proximal end and a larger distal end with a body in between. The disk shaped proximal head meets up with the capitulum of the humerus as well as the radial notch that belongs to the ulna.

The radial tuberosity is quite prominent and is designed for the attachment of the biceps brachii. It is positioned just below the head on the medial side. A double faceted surface located on the distal end of the radius meets with the proximal carpal bones.

The styloid process rests on the distal end of the radius. It is located on the lateral tip with an ulna notch that rests on the medial side, which is responsible for receiving the distal side. The styloid processes of both the ulna and the radius are designed for lateral as well as medial stability for wrist movement.

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