Triceps brachii muscle

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The triceps brachii muscle is a large three-headed skeletal muscle found in humans. It runs along the back of the upper arm.

The triceps brachii muscle is often simply called the triceps. However, the term triceps (Latin for "three heads") can mean any skeletal muscle having three origins.

The three heads are called:

The Long Head
The Lateral Head
The Medial Head

The long head is attached to the infraglenoid tubercle of the scapula. The lateral and medial heads are attached to the posterior shaft of the humerous, attached to the lateral and medial sides of the spiral groove of the humerous respectively. The lateral head is also superior to the medial head. The fibres converge to a single tendon to insert onto the olecranon process of the ulna.

The triceps account for 60 percent of the arm's mass, but people who exercise the arms with weights often neglect this group of muscles in favour of the biceps brachii.

Action

The Triceps brachii serves to extend the elbow, therefore it is an extensor muscle. The biarticulate long head of the triceps brachii enters passive insufficiency through the completion of elbow flexion when the shoulders are more flexed and abducted or through the completion of shoulder flexion and abduction when the elbows are more flexed. It enters active insufficiency through the completion of elbow extension when the shoulders are more extended and adducted, (other heads of the triceps become more active) or through the completion of shoulder extension and adduction when the elbows are more extended.

When the shoulder is internally rotated, the ability of the long head of the triceps brachii to extend and adduct the shoulder is diminished. The shoulder must be externally rotated in order for the long head of the triceps brachii to assist shoulder adduction.

Difference in size compared to the Although the Triceps brachii is the antagonist of the Biceps brachii, it is relatively smaller than the Biceps. This can be explained when we compare the direction of work of both muscles. The Biceps will work upwards, in against the influence of gravity, whilst the Triceps works downwards, in the same direction as gravity. The Triceps needs thus not be as powerful as the Biceps in order to achieve the same result.

External links

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