What is the main function of the triceps brachii muscle?

The triceps brachii is the primary extensor of the forearm at the elbow joint. Its long head also helps stabilize the humerus during certain arm movements.

What are the three heads of the triceps brachii and where do they originate?

The triceps brachii has three heads: the long head originates from the infraglenoid tubercle of the scapula, the lateral head from the humerus above the spiral groove, and the medial head from the humerus below the spiral groove.

Where does the triceps brachii insert?

The triceps brachii inserts via a common tendon into the posterior superior surface of the olecranon process of the ulna. Some fibers also attach to the elbow joint capsule.

What nerve supplies the triceps brachii?

All three heads of the triceps brachii are supplied by the radial nerve (C7, C8). The long head is innervated in the axilla, while the lateral and medial heads receive branches in the spiral groove.

Why might elbow extension be preserved after a radial nerve injury in the spiral groove?

Elbow extension can remain intact because the nerve to the long head of the triceps brachii branches off the radial nerve proximally in the axilla, before the injury site in the spiral groove.

What is a common cause of radial nerve injury affecting the triceps brachii?

A midshaft humerus fracture is a common cause of radial nerve injury in the spiral groove, which can impact the lateral and medial heads of the triceps.

Posterior Arm Muscles – Triceps Brachii Anatomy