Long head of triceps brachii

At a glance

English

Long head of triceps brachii

Latin (TA2)

Caput longum musculi tricipitis brachii

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the long head of triceps brachii

Triceps brachii fills the back of the arm and straightens the elbow. Of its three heads, the long head is the most medial and the only one that begins on the scapula, so it acts on both the shoulder and the elbow. It lies superficial on the inner side of the back of the arm, with the lateral head beside it and the medial head deep to both.

The long head arises by a flattened tendon from the infraglenoid tubercle, just below the shoulder socket, with a few fibres blending into the joint capsule. Its belly descends between teres minor behind and teres major in front, and so divides the gap between those two muscles into separate spaces. Lower in the arm it joins the lateral head in a common tendon, which the medial head reinforces from beneath. This tendon attaches to the upper surface of the olecranon and to the deep fascia of the forearm.

At the elbow the long head adds to the force of extension, mainly in strong efforts. At the shoulder it helps extend the arm and draw it towards the trunk, and it supports the lower part of the joint when the arm hangs or carries a load. Its nerve is a radial nerve twig that usually leaves the main trunk in the axilla. Its blood comes from the deep artery of the arm and the posterior circumflex humeral artery.

This head is a key landmark of the back of the shoulder. The quadrangular space, which carries the axillary nerve and the posterior circumflex humeral vessels, lies lateral to it, and the triangular space, carrying the circumflex scapular artery, lies medial to it. Below teres major it also bounds the triangular interval used by the radial nerve.

Attachments, action and supply

Origin

Infraglenoid tubercle of the scapula, with some fibres from the shoulder joint capsule.

Insertion

Olecranon of the ulna through the common triceps tendon, with a slip to the antebrachial fascia.

Action

Extends the elbow; assists extension and adduction of the arm at the shoulder.

Nerve supply

Radial nerve (C6, C7, C8).

Blood supply

Deep artery of the arm and the posterior circumflex humeral artery.