Humerus

The humerus is the name given to the bone in the arm that runs from the shoulder[?] to the elbow[?]. On a skeleton, it fits between the scapula, and the radius and ulna.

Articulation

At the shoulder, there is a ball-and-socket joint, where the head of the humerus articulates with the glenoid fossa of the scapula. This type of joint allows a wide range of movement.

The distal end of the humerus (at the elbow) creates a hinge joint with the ulna, allowing only flexion and extension. This happens on the trochlea of the humerus. Two pits at this end of the humerus (the coronoid fossa and the olecranon fossa) allow the ulna room to move, but prevent it from over-flexing/extending.

There is also a pivot joint between the capitulum of the humerus, and the head of the radius. This allows the hand to pronate and supinate (turn to face downwards or upwards).

Muscle attachments

A variety of muscles attach to the humerus. These enable movement at the elbow and at the shoulder.

The rotator cuff muscles attach at the proximal humerus, and can rotate and abduct the arm at the shoulder.

Deltoid[?] has a variety of actions on the top of the arm. Pectoralis major[?], teres major[?] and latissimus dorsi, which all insert at the intertubercular groove of the humerus, adduct and medially rotate the humerus.

Biceps brachii, brachialis, coracobrachialis[?], and brachioradialis (which attaches very distally), act to flex the elbow. Biceps however does not attach to the humerus.

Triceps brachii[?] and anconeus[?] extend the elbow, and attach to the posterior side of the humerus.

Some of the forearm muscles, (such as pronator teres[?], and the flexors and extensors of the wrist) also attach to the distal humerus.