The triceps brachii is a muscle in the posterior compartment of the upper arm. It is a large horseshoe-shaped muscle, which forms the majority of the muscle bulk of the upper arm.
- Long head originates from the infraglenoid tubercle of the scapula.
- Lateral head originates from the humerus (superior to the radial groove).
- Medial head originates from the humerus (inferior to the radial groove).
- Distally, the heads converge into one tendon which inserts onto the olecranon of the ulna.
- Function: Extension of the arm at the elbow.
- Innervation: Radial nerve.