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Triceps brachii (shoulder triceps)
Last reviewed: 07.07.2025
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The triceps brachii is thick, occupies the entire back surface of the shoulder, and has three heads. The lateral and medial heads originate on the humerus, and the long head originates on the scapula.
The lateral head (caput laterale) begins with tendon and muscle bundles on the outer surface of the humerus, between the attachment of the teres minor muscle proximally and the groove of the radial nerve distally, as well as on the posterior surface of the lateral intermuscular septum. The bundles of the lateral head pass downward and medially, covering the groove of the radial nerve with the nerve of the same name and deep vessels of the arm located in it.
The medial head (caput mediale) has a fleshy origin on the posterior surface of the arm between the attachment of the large teres muscle and the fossa of the olecranon; it also begins on the medial and lateral intermuscular septa below the groove of the radial nerve.
The long head (caput longum) begins with a strong tendon on the infraglenoid tubercle of the scapula and, continuing into the muscle belly, passes down between the small and large teres muscles to the middle of the back surface of the shoulder, where its bundles join with the bundles of the lateral and medial heads. The muscle formed as a result of the union of the three heads passes into a flat wide tendon, which is attached to the olecranon process of the ulna. Some of the bundles are woven into the capsule of the elbow joint and into the fascia of the forearm.
The function of the triceps brachii muscle (triceps pelvicis): extends the forearm at the elbow joint; the long head also acts on the shoulder joint, participating in the extension and adduction of the shoulder to the body.
Innervation of the triceps brachii muscle (triceps pelvic): radial nerve (CV-CVIII).
Blood supply of the triceps brachii muscle (triceps pelvic): deep brachial artery, posterior circumhumeral artery, superior and inferior collateral ulnar arteries.
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