Anatomy, Shoulder and Upper Limb, Triceps Muscle

Excerpt

The triceps brachii is a large, thick muscle on the dorsal part of the upper arm. It often appears in the shape of a horseshoe on the posterior aspect of the arm. The primary function of the triceps is the extension of the elbow joint. It is composed of three heads (tri = three, cep = head): a long head, a lateral head, and a medial head. The tendons all have different origins, but the three heads combine to form a single tendon distally.

The long head originates from the infraglenoid tubercle of the scapula, while both the lateral head and the medial head both originate from the humerus. The three heads converge into a single tendon, which attaches to the proximal portion of the olecranon process (the bony prominence of the elbow) located on the upper portion of the ulna.