Triceps brachii


A three-headed muscle, each of different origins, joining together at the elbow.

Triceps brachii composed of three different bundles: Long head, Lateral head, and Medial head.

The long head originates at the infraglenoid tubercle of scapula.

The lateral head originates above the radial sulcus.

The medial head originates below the radial sulcus.

The triceps brachii muscle is the large muscle on the back of the upper limb, and is the muscle principally responsible for extension of the elbow joint.

The long head of the triceps muscle arises from the infraglenoid tubercle of the scapula.

The long head of the triceps muscle extends distally anterior to the teres minor and posterior to the teres major.

The medial head arises distally from the groove of the radial nerve; from the dorsal surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum.

The medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.

The lateral head arises from the dorsal surface of the humerus, lateral and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum.

The three fascicles have their own motorneuron subnucleus in the motor column in the spinal cord.

The medial head is formed predominantly by small type I fibers and motor unit.

The lateral head is composed of large type IIb fibers and motor units.

The long head is composed of a mixture of fiber types and motor units.

The fibers of the three fascicles converge to a single tendon that inserts onto the olecranon process of the ulna, and to the posterior wall of the capsule of the elbow joint.

All three heads of the triceps brachii are innervated by the radial nerve, and the long head is innervated by a branch of the axillary nerve.

The triceps is an extensor muscle of the elbow joint.

The triceps is an antagonist of the biceps and brachialis muscles.

The triceps originates with two heads posteriorly on the humerus and with its long head on the scapula just below the shoulder joint. 



It is inserted posteriorly on the olecranon.


Elbow extension brings  the forearm back to anatomical position, performed by triceps brachii.

It fixates the elbow joint when the forearm and hand are used for fine movements.

The long head fascicle is engaged when sustained force is needed, or when synergistic control of the shoulder and elbow or both are required.

The lateral head is used for movements requiring occasional high-intensity force.

The medial fascicle provides more precise, low-force movements.

With its origin on the scapula, the long head also acts on the shoulder joint and is involved in retroversion and adduction of the arm.

The triceps reflex is often used to test the function of the nerves of the arm.

Triceps is maximally efficient with the elbow flexed 20–30°. 



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