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Triceps brachii

The triceps brachii (Latin: musculus triceps brachii) is a sizable three-headed muscle of the upper limb. It is located in the posterior compartment of the upper arm together with the anconeus muscle. The triceps brachii arises from two bones - the scapula and humerus. It extends almost the entire length of the humerus and inserts on the ulna. The triceps brachii is composed of three heads - long, lateral and medial. It is the primary forearm extensor.

Triceps brachii
Origin

Long head - infraglenoid tubercle of scapula

Lateral head - posterior surface of humerus superior to radial groove

Medial head - posterior surface of humerus inferior to radial groove

InsertionOlecranon of ulna
Action

Entire muscle - extension of forearm

Long head - extension and adduction of arm

InnervationRadial nerve (C6 - C8)
Blood supply Deep brachial and superior ulnar collateral arteries
Upper arm muscles, Biceps brachii, Triceps brachii, Brachialis, Anconeus, Upper extremity, Muscles
Muscles of upper arm by Anatomy.app
Triceps brachii, Muscles of upper arm, Arm muscles, Muscles of upper limb, Posterior compartment muscles, Posterior compartment muscles of upper arm, Posterior view of triceps brachii
Triceps brachii by Anatomy.app

 

Origin

All three heads of the muscle have different origin sites:

  • Fibers of the long head of the triceps brachii originate from the infraglenoid tubercle of the scapula.
  • Fibers of the lateral head arise from the posterior surface of the humerus superior to the radial groove.
  • And finally, the fibers of the medial head originate from the posterior surface of the humerus inferior to the radial groove.
Triceps brachii, Origin of triceps brachii, Muscles of upper arm, Arm muscles, Muscles of upper limb, Posterior compartment muscles, Posterior compartment muscles of upper arm, Lateral view of triceps brachii
Origin of triceps brachii by Anatomy.app

 

Insertion

Fibers of all three heads merge and form a single tendon that inserts on the olecranon of the ulna.

Triceps brachii, Insertion of triceps brachii, Muscles of upper arm, Arm muscles, Muscles of upper limb, Posterior compartment muscles, Posterior compartment muscles of upper arm, Medial view of triceps brachii
Insertion of triceps brachii by Anatomy.app

 

Action

The primary function of the triceps brachii muscle is the extension of the forearm at the elbow joint. Also, the long head provides the extension and adduction of the arm at the shoulder joint.

Triceps brachii, Biceps brachii, Action of triceps brachii, Action of biceps brachii, Function of biceps brachii, Function of triceps brachii, Arm muscles, Muscles of upper limb, Muscles of upper arm
Action of triceps and biceps brachii muscles by Anatomy.app

 

Innervation

The triceps brachii is innervated by the radial nerve (C6 - C8) - a branch of the brachial plexus.

 

Blood supply

The triceps brachii muscle receives arterial blood from the deep brachial and superior ulnar collateral arteries. Both are branches of the brachial artery.