EN | DE | PT Contact How to study Login Register

Triceps brachii muscle - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 852,397 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Triceps brachii muscle

Why do we need such a powerful extensor of the elbow? Is gravity not sufficient? When in daily life do we need to powerfully extend our elbows? The answer is: not very often. The reason we have such a powerful muscle in the extensor compartment of the elbow is due to our evolutionary ancestors who needed powerful extensor to climb trees and hang from branches.

The location of the triceps brachii muscle in the posterior compartment of the arm defines its role. The power of the muscle is presented through its three heads that originate from different places within the scapula and the humerus, but eventually unite to form the unique body of the muscle that inserts at the ulna.

Key Facts
Bundles Long head, lateral head, medial head
Origin Long head - infraglenoid tubercle of the scapula
Lateral head - proximally to the radial sulcus at the dorsal humerus
Medial head - distally from the radial sulcus at the dorsal humerus
Insertion Olecranon process of the ulna
Vascularization Deep brachial artery (branch of the brachial artery), posterior circumflex humeral artery (branch of the axillary artery)
Innervation Radial nerve and axillary nerve (branches of the brachial plexus)
Movements Extension of the forearm, adduction of the forearm, extension of the shoulder
Antagonist muscle Biceps brachii muscle

This article will describe all of the important anatomical facts about the triceps brachii muscle, as well as the movements it provokes.

Anatomy

The triceps brachii (triceps) is a large, three-headed muscle of the upper arm, consisting of the following:

  • long head: originates at the infraglenoid tubercle of the scapula. From there it courses between the teres major and teres minor and divides the axillary space into two halves.
  • medial head: has its' origin at the dorsal humerus distally from the radial sulcus. Its' fibers are connected with the medial intermuscular septum.
  • lateral head: originates at the dorsal humerus proximally from the radial sulcus where it is fixed to the lateral intermuscular septum.

All three heads together form a thick tendon which inserts at the olecranon of the ulna and additionally to the capsule of the elbow joint and antebrachial fascia. Under the triceps tendon lies an important bursa preventing excessive friction of the tendon with the olecranon (subtendinous bursa of triceps brachii).

Innervation

The radial nerve (C6-C8), which supplies the triceps, is in close relationship with the muscle. First it runs within the radial sulcus of the humerus where it is covered by both the medial and lateral heads of the triceps. From there it courses to the crook of the arm along the lateral bicipital groove between the triceps and biceps.

Due to its' superficial course, the triceps determines the contour of the dorsal upper arm. The proximal part of the triceps is partly covered by the deltoid. Both the lateral and long heads can be easily palpated, whereas the medial head lies more deeply, as it is overlaid by the other two.

Function

The triceps is the most important extensor muscle of the elbow. Hereby the medial head is the most active of all three. Its' antagonists (particularly the biceps and brachialis) are physiologically more powerful than the triceps, which is why we have a slight bend at the elbow when our arms are freely hanging during rest.

Recommended video: Triceps brachii muscle
Origin, insertion and innervation of the triceps brachii muscle.

Furthermore, the long triceps head also crosses the shoulder joint making it the only two-jointed triceps part. During contraction it pulls the upper arm towards the trunk (adduction) and behind (retroversion). The distal fibers of the triceps fulfill another task, namely the protection of the capsule of the elbow joint during extreme extending movements.

Clinical Points

Due to the muscle's superficial position, the triceps can be easily damaged in accidents. The most common causes are a forced flexion against the contracted triceps as well as direct blows to the elbow during physical activity. Classic symptoms include pain, swelling and a severe loss of extending power in the elbow. An actual triceps tendon rupture, on the other hand, occurs very rarely and is usually associated with a pre-damaged tendon, e.g. due to chronic bursitis, rheumatoid arthritis or Marfan syndrome, or a complete osseous tear at the olecranon.

During physical examination, the triceps serves as a reference muscle for the nerve roots C7 and C8. Clinically these are tested through the triceps tendon reflex in which a strike to the insertion tendon with a reflex hammer activates a reflexive contraction of the muscle.

Triceps brachii muscle - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 852,397 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.306-307
  • J. E. Muscolino: The muscular system manual – The skeletal muscles of the human body, 2.Auflage, Elsevier Mosby (2005), S.554-557
  • W. Graumann/D.Sasse: CompactLehrbuch der gesamten Anatomie – Band 2 – Bewegungsapparat, Schattauer Verlag (2003), S.301-303 D.
  • W. Stoller: Magnetic resonance imaging in orthopaedics and sports medicine, 3.Auflage, Lippincott Williams and Wilkins (2007), S.1599-1601
  • M. Trojer: Die Trizepssehnenruptur – Operative Versorgung einer seltenen Verletzung mit Ankernahttechnik, Kreiskliniken Altötting- Burghausen (link)
  • I. Reuter: Trizepssehnenreflex, Lexikon Orthopädie und Unfallchirurgie, Springer Medizin (link)

Author:

  • Achudhan Karunaharamoorthy

Illustrators:

  • First Illustration Gallery - Yousun Koh, Paul Kim
  • Second Illustration Gallery - Yousun Koh, Paul Kim
  • Third Illustration Gallery - Begoña Rodriguez
  • Fourth Illustration Gallery - Paul Kim
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Muscles of the arm and the shoulder

Main muscles of the upper extremity

Biceps brachii muscle level

Continue your learning

Article (You are here)
Other articles
Well done!

Register now and grab your free ultimate anatomy study guide!

Create your free account.
Start learning anatomy in less than 60 seconds.