Triceps brachii muscle

Last revised by Assoc Prof Craig Hacking on 25 Aug 2021

The triceps brachii muscle, often referred to simply as the triceps, is a three-headed muscle in the posterior compartment of the arm.

  • origin
    • long head: infraglenoid tubercle of the scapula
    • medial head: posterior humerus inferior to the radial groove, both intermuscular septa
    • lateral head: posterior and lateral humerus superior and lateral to the radial groove, lateral intermuscular septum
  • insertion: proximal olecranon of the ulna and deep fascia of arm
  • innervation: radial nerve, branches of ulnar nerve
  • actions
  • long head: infraglenoid tubercle of the scapula
  • lateral head: posterior and lateral humerus from the surgical neck of humerus to the top of deltoid tuberosity (superior and lateral to radial groove), and lateral intermuscular septum
  • medial head: most of lower posterior humerus (inferomedial to radial groove), both intermuscular septa
  • long and lateral head converge into the distal triceps tendon that inserts into the proximal olecranon
  • medial head partly inserted into proximal olecranon, partly into deep surface of tendon, and also posterior elbow joint capsule
  • radial nerve and profunda brachii vessels run in radial groove in between origins of lateral and medial heads of triceps
  • medial head largely deep to lateral head of triceps
    • in between runs posterior antebrachial cutaneous nerve (branch from radial nerve)
  • posterior brachial cutaneous nerve (branch from radial nerve) emerges from around the front of the long head of triceps to become posterior near the intersection with teres major
  • posterior circumflex humeral artery and axillary nerve through quadrangular space lateral to the long head of triceps
  • teres major anterior to the long head of triceps
  • teres minor posterior to the long head of triceps near its origin
  • extension of the elbow joint
  • assists in extension of the shoulder joint (long head only)
  • long head of triceps is important for stabilizing the shoulder joint in abduction
  • medial head retracts capsule of the elbow joint on extension
  • patella cubiti may be present (very rare)
  • 4th head from the medial humerus
  • slip termed dorsoepitrochlearis extending between triceps and latissimus dorsi
  • long head of the triceps may be supplied by the axillary nerve 3

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Cases and figures

  • Figure 1: posterior shoulder muscles (Gray's illustration)
    Drag here to reorder.
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