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Portrait of Triceps brachii

Anatomy · Muscles

Triceps brachii

Three-headed extensor of the elbow

Upper limb · arm, posterior compartment

Triceps brachii is the three-headed muscle that fills the back of the upper arm and is the main extensor of the elbow. Its long head springs from the scapula and the lateral and medial heads from the back of the humerus, all converging on the olecranon of the ulna. It is supplied by the radial nerve.

How to spot them

  • ▸Fills the whole back of the arm, the only muscle of the posterior compartment
  • ▸Three heads: long, lateral and medial, with a shared flat tendon at the elbow
  • ▸Lateral and medial heads sit either side of the spiral groove that carries the radial nerve
  • ▸Tendon ends on the point of the elbow, the olecranon of the ulna

What to know

The single muscle of the back of the arm, the antagonist of the muscle that curls the forearm

Triceps brachii.

A muscle with three heads, one of them arising from the infraglenoid tubercle below the shoulder socket

Triceps brachii — the long head, the only one to cross the shoulder.

Its tendon ends on the olecranon, the point of the elbow

Triceps brachii — extends the elbow.

A muscle whose lateral and medial heads lie above and below the radial groove of the humerus

Triceps brachii.

A muscle supplied by the radial nerve, tested with a tendon tap just above the elbow (C7)

Triceps brachii — the triceps reflex.

The muscle that does most of the work in a press-up or a bench press, apart from the chest

Triceps brachii.

Key ideas

  • The long head crosses the shoulder joint as well as the elbow, so it also helps extend and adduct the arm.
  • Anconeus, a small muscle at the elbow, is often described as a continuation of the medial head.

Quick-fire facts

  • •Origin: long head from the infraglenoid tubercle; lateral head from the posterior humerus above the radial groove; medial head from the posterior humerus below it.
  • •Insertion: the olecranon of the ulna, via a common tendon.
  • •Nerve supply: radial nerve (C6–C8).
  • •Action: extends the elbow; the long head also extends and adducts the shoulder.
  • •It is the only muscle in the posterior compartment of the arm.
  • •The radial nerve and profunda brachii artery run in the radial groove between the lateral and medial heads.
  • •Triceps means 'three-headed'; the triceps reflex tests C7.

Drill it — 6 cards

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Sources