triceps brachii muscle

The triceps brachii muscle, often referred to simply as the triceps, is a three-headed muscle in the posterior compartment of the arm.

Summary

• origin
  • long head: infraglenoid tubercle of the scapula
  • medial head: posterior humerus inferior to the radial groove, both intermuscular septa
  • lateral head: posterior and lateral humerus superior and lateral to the radial groove, lateral intermuscular septum
• insertion: proximal olecranon of the ulna and deep fascia of arm
• innervation: radial nerve, branches of ulnar nerve
• actions
  • extensor of the elbow joint
  • assists in extension of the shoulder joint (long head only)

Gross anatomy

Origin

• long head: infraglenoid tubercle of the scapula
• lateral head: posterior and lateral humerus from the surgical neck of humerus to the top of deltoid tuberosity (superior and lateral to radial groove), and lateral intermuscular septum
• medial head: most of lower posterior humerus (inferomedial to radial groove), both intermuscular septa

Insertion  

• long and lateral head converge into the distal triceps tendon that inserts into the proximal olecranon
• medial head partly inserted into proximal olecranon, partly into deep surface of tendon, and also posterior elbow joint capsule

Relations

• radial nerve and profunda brachii vessels run in radial groove in between origins of lateral and medial heads of triceps
• medial head largely deep to lateral head of triceps
  • in between runs posterior antebrachial cutaneous nerve (branch from radial nerve)
• posterior brachial cutaneous nerve (branch from radial nerve) emerges from around the front of the long head of triceps to become posterior near the intersection with teres major
• posterior circumflex humeral artery and axillary nerve through quadrangular space lateral to the long head of triceps
• teres major anterior to the long head of triceps
• teres minor posterior to the long head of triceps near its origin

Action

• extension of the elbow joint
• assists in extension of the shoulder joint (long head only)
• long head of triceps is important for stabilizing the shoulder joint in abduction
• medial head retracts capsule of the elbow joint on extension

Arterial supply

• branches of profunda brachii artery

Innervation

• radial nerve (C6, C7, C8) (from posterior cord of the brachial plexus), four branches 

Variant anatomy

• patella cubiti may be present (very rare)
• 4 head from the medial humerus
• slip termed dorsoepitrochlearis extending between triceps and latissimus dorsi
• long head of the triceps may be supplied by the axillary nerve

Siehe auch:

• Oberarmmuskulatur
• Sehne des Musculus triceps brachii

und weiter:

• Sulcus radialis
• Ellenbogengelenksmuskulatur
• Verletzungen der distalen Trizepssehne
• Musculus triceps brachii, Caput longum
• Musculus triceps