Triceps Brachii Muscle Anatomy

Location & Overview

The triceps brachii is a three headed muscle of the arm. It is a relatively large muscle which is located posterior to the humerus and is primarily responsible for flexion of the elbow. It often has a horseshoe like appearance. The Latin word ‘brachii’ is a reference to the muscle being located in the arm. The ‘tri’ in the word triceps is a reference to its three muscle heads (or points of origin). The word ‘ceps’ means head. The three heads of the triceps are: a long head, a lateral head, and a medial head ^{[1] [2]}.

Origin & Insertion

The long head originates from the infraglenoid tubercle of the scapula. The medial head originates just inferior to the radial groove, whereas the lateral head originates superior to the radial groove. The medial head of the triceps is mostly covered by the lateral and long heads. The fibres of the three heads then converge to a single tendon which then inserts onto the olecranon process of the ulna (a bony prominence of the elbow which is located on the upper portion of the ulna) ^{[3] [4] [5]}.

Actions

All the heads of the triceps brachii can assist in extension of elbow. However, because the long head crosses the shoulder joint; the long head can also assist in adduction and extension of the arm at the shoulder joint ^{[6] [7]}.

Innervation

The heads of the triceps brachii muscle are innervated by the radial nerve (C6, C7, C8) ^{[8] [9]}.

Blood Supply

Blood is supplied by the deep brachial artery and the long head also gets a blood supply from the posterior circumflex humeral artery ^{[10] [11]}.