Long Head of Triceps Brachii
The structure indicated is the long head of the triceps brachii.
The triceps brachii is the sole muscle in the posterior compartment of the arm. As the name suggests, the triceps brachii has three heads:
- Long head
- Medial head
- Lateral head
These three heads converge to insert on the olecranon of the ulna.
- Long head – infraglenoid tubercle of scapula
- Medial head – posteriorly on the shaft of the humerus below the radial groove
- Lateral head – posteriorly on the humerus, above the radial groove
Insertion: Olecranon of the ulna
Action: Extension of the forearm at the elbow joint
Innervation: Radial nerve