Long Head of Triceps Brachii

Origin

The long head of triceps brachii muscle originates, via a flat tendon, from the infraglenoid tubercle of the scapula.

Insertion

The fibers of the medial, lateral, and long heads of triceps brachii muscle all converge to a single triceps brachii tendon, which inserts onto both the superior end of the olecranon of ulna and the antebrachial fascia.

Key Features & Anatomical Relations

The triceps brachii muscle is found in the posterior compartment of the arm. It is a fusiform type of skeletal muscle and is composed of three heads: medial, lateral, and long, where:

- the medial head is located deep to the lateral and long heads;

- the long head is located medial to the lateral head.

The triceps brachii muscle is located:

- posterior (superficial) to the deep brachial artery and radial nerve;

- lateral to the teres major and teres minor muscles.

Regarding the long head of triceps brachii specifically, its proximal end is located between the teres major and teres minor muscles.

Actions & Testing

The triceps brachii muscle extends the forearm at the elbow joint. This action is not affected by pronation or supination of the forearm. The long head is generally only active in the presence of resistance, and it also assists in extension and stabilization of the glenohumeral (shoulder) joint.

The triceps brachii muscle can be tested by extending the forearm at the elbow joint against resistance, during which it can be palpated (Standring, 2016).

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.