Triceps Brachii Muscle | Overview and Origin | Actions | Nerve supply | clinical testing

Triceps brachii is a three-headed (tri - three, cep - head) muscle of the arm. It represents the only constituent of the posterior muscle group of the arm, spanning almost the entire length of the humerus. The triceps brachii muscle consists of a long, medial and lateral head, that originate from their respective attachments on the humerus and scapula, and insert via a common tendon on the ulna.
The main function of triceps brachii is extension of the forearm at the elbow joint. In addition, its long head contributes to the extension and adduction of the arm at the shoulder joint. Besides movement, the triceps brachii also plays a role in creating anatomical spaces which are traversed by neurovascular structures. This makes the triceps brachii muscle an important surgical landmark.
Origin and insertion
Long head of triceps brachii muscle (Caput longum musculi tricipitis brachii); Image: Yousun Koh
Long head of triceps brachii muscle (Caput longum musculi tricipitis brachii)
The triceps brachii muscle has three heads, each of which have their own origin:
The long head arises from the infraglenoid tubercle of scapula, which is a rough area at the inferior margin of the glenoid fossa. Its attachment extends slightly above to the adjacent glenoid labrum and blends with the glenohumeral capsule of the shoulder joint, contributing to its stability.
The lateral head originates from a narrow, linear ridge on the posterior surface of the humerus, just superior to the radial groove. A portion of the muscle fibers also arise from the lateral intermuscular septum. Its attachment ascends obliquely beginning from the lateral border of the humerus behind the deltoid tubercle. From here, it extends to the surgical neck of humerus, medial to the insertion of teres minor and above the attachment for the medial head of triceps.
The medial head is overlapped by the long and lateral head of the triceps. It has a broad origin along the entire posterior surface of the humerus inferior to the radial groove. More specifically, its attachment extends over an elongated triangular area on the humerus. The apex of the triangle is located on the medial border of the humerus above the insertion of teres major, while the base is the line that connects the medial and lateral epicondyles of the humerus. The medial head has an additional attachment to the posterior aspect of the medial and lateral intermuscular septum.
Olecranon of ulna (Olecranon ulnae); Image: Yousun Koh
Olecranon of ulna (Olecranon ulnae)
All three muscle bellies converge onto a common tendon, which inserts to the posterior aspect of the proximal surface of the olecranon of the ulna. Laterally, a band of fibres continues inferiorly over the anconeus muscle to blend with antebrachial fascia of the forearm.
Relations
Triceps brachii is the only muscle in the posterior compartment of the arm. The superior portion of the long head of triceps is covered by the posterior border of the deltoid muscle. The long head of triceps can be palpated as an elevation parallel and medial to the posterior border of the deltoid muscle when the elbow is extended.
On its course, the long head of the triceps descends through the wedge-shaped interval between the teres major and minor and the humerus, thereby creating three distinct anatomical spaces.
nnervation
The triceps brachii is innervated by the radial nerve, which gives off a separate branch for each head. The C6 root value of the radial nerve innervates the lateral head, root value C7 innervates the long head, and root value C8 supplies the medial head.
Blood supply
The triceps brachii muscle is mainly supplied by the deep brachial artery and the superior ulnar collateral artery, which arises from the brachial artery. Additional supply to the lateral head of the triceps brachii is provided by the posterior circumflex humeral artery.
Function
The triceps and biceps brachii are the main muscles controlling the movements of the elbow. The main function of triceps brachii is extension of the forearm at the elbow joint.
Clinical notes
It is important to test the integrity of the radial nerve when injuries occur on/or around the arm. A proximal arm injury may completely paralyze all three heads of the triceps muscle and severely limit extension of the forearm, especially against resistance. An injury to the midshaft of the humerus, for example a fracture, can damage the radial nerve as it runs in the radial groove. This injury placement may spare much of the functioning of the triceps muscle and forearm extension may only be weakened, but the patient may present with “wrist drop” due to the paralysis of muscles that extend the wrist.
Any tendon is susceptible to injury; the triceps tendon attachment to the olecranon is no exception. Any activity that overuses the triceps muscle can cause the tendon to become inflamed and damaged, resulting in pain and swelling near the muscle’s attachment to the olecranon

[@vineshbihari2939]

Ma,am Aapka padaya hua ek hi baar me samj agaya 🤗

[@Dr.KareemaTabassum]

Thank you 😊

[@44sunandasoni33]

Thanku so much mam. It's really helpful... 😊

[@bathulajeswanth7283]

Super mam

[@smritiverma7996]

Thank you so much 🙏

[@Dr.KareemaTabassum]

You're welcome 😊

[@vahedunnisabegum9028]

Thank you ma'am 👌

[@Dr.KareemaTabassum]

You're welcome 😊

[@hariskr4u]

Hi mam, will extension of elbow completely goes if radial nerve got injured at radial groove. As the long head get innervation before radial groove will there be partial extension

[@aswinichalamalapalli2588]

As the supply to long head occurs by radial nerve in axilla itself

[@StarlightJosh]

articularis cubitus

[@nilimapatil335]

🙏❤️🥰😊

[@muhammadwaqasdvm139]

what is means by muscle head

[@juliabraulick4428]

it means one section of the muscle