Synonyms: three-headed upper arm muscle, arm extensor, triceps
German: Musculus triceps brachii
The triceps brachii muscle is a three-headed muscle that belongs to the muscles of the upper arm. The three heads of the muscle are called "Caput longum", "Caput laterale" and "Caput mediale".
Two heads of the triceps brachii muscle have their origin at the humerus (upper arm bone), the third head at the scapula (shoulder blade):
Most parts of the medial triceps head are covered by the lateral and long heads. You can just see its distal part from the outside.
The tendineous insertion of the triceps brachii muscle is formed by the olecranon of the ulna. The insertion tendon already starts in the middle of the muscle. It consists of two combined aponeuroses, of which one covers the lower part of the muscle to the outside, while the other one is passing deep into the muscle mass.
Thus, some parts of the triceps brachii muscle pass over 2 joints, the shoulder and the elbow joint.
The innervation of the triceps brachii muscle is provided by the radial nerve from the brachial plexus (segments: C6 to C8). More recent findings show that the long triceps head frequently is also innervated by a branch of the axillary nerve. [1]
Together with the anconeus muscle, the triceps brachii muscle is responsible for the extension of the forearm in the elbow joint. Thus, it works as direct antagonist of the biceps brachii muscle and of the brachialis muscle. Another task is the fixation of the elbow joint during the precision movements of the hand, eg. when writing.
The Caput longum drawing to the scapula effects a retroversion and a slight adduction of the upper arm.
This page was last edited on 12 October 2016, at 14:09.
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