Triceps

From Ganfyd

This page refers to triceps brachii in the upper arm. For the muscle in the leg, see triceps surae.

Triceps brachii (commonly 'triceps') is a large muscle of the posterior upper arm and the main extensor of the elbow.

Triceps
System:	Muscle
Function:	Extension of the elbow
Origin:	Long head - infraglenoid tuberosity of scapula Lateral head - posterior surface humerus (between Teres minor and radial groove) Medial head - posterior surface of humerus below radial groove
Branches:
Insertion:	Olecranon process of ulna
Arterial supply:
Venous drainage:
Lymphatic drainage:
Innervation:	Radial nerve (C7, C8)
Vertebral levels:
Search for Triceps in Gray's.

Surface Anatomy

Triceps is palpable posteriorly in the upper arm, providing the majority of the muscle bulk there.

Shape

Triceps arises from three heads - long, lateral and medial. The fibres of the three heads converge at its tendon, which begins midway along the muscle's length. It consists of two aponeuroses, one which is subcutaneous posteriorly in the lower half of triceps, the other central within the muscle. When all three heads have been received, the two aponeuroses unite into a single tendon, just above the elbow. The majority of fibres insert into the olecranon of the ulna, although a few continue laterally over anconeus to blend with the deep fascia of the forearm.

Long head

The long head of triceps arises via a tendon from the infraglenoid tuberosity of the scapula, blending with the capsule of the shoulder joint in its upper part. The muscular fibres continue distally between the other two heads, to join them at the tendon.

Lateral head

The lateral head of triceps arises from the posterior surface of the shaft of humerus, between the insertion of teres minor and the upper part of the radial groove, continuing along the lateral border of humerus and lateral intermuscular septum. The muscle fibres converge towards the tendon.

Medial head

The medial head of triceps arises from the posterior surface of the shaft of humerus, inferior to the radial groove. It extends from the insertion of teres major to a short distance above the trochlea. It also arises from the medial border of humerus and the posterior surface of the medial intermuscular septum. Some fibres are directed distally to the olecranon of the ulna, whilst most converge to the tendon.

Subanconeus

The subanconeus is the name for the few fibres of triceps which insert into the posterior ligament and synovial membrane of the elbow.

Actions

• Extension of the elbow
• Aids in adduction of the humerus at the shoulder in extension
• Supports the inferior shoulder joint (long head)
• Helps to keep the elbow joint synovium tight in elbow movements (subanconeus)

Joints Affected

• Elbow
• Shoulder

Origin

Long head:

• Infraglenoid tubercle of the scapula

Lateral head:

• Upper half of the posterior surface of the humerus

Medial head:

• Lower half of the posterior surface of the humerus inferomedial to the radial groove, and medial intermuscular septum

Insertion

• Olecranon process of the ulna
• Deep fascia of the forearm
• Synovium of the elbow joint (subanconeus)

Nerve Supply

• Radial nerve (C7, C8)

Clinical Relevance

• The long head forms a border of the triangular space
• The long head forms a border of the quadrangular space
• Important in the triceps reflex which indicates function of the spinal cord at C7, C8 level.

Variations

• A fourth head from the medial aspect of the humerus may occur
• A slip between triceps and latissimus dorsi may occur