Triceps Anatomy: Muscles and Function

The back of the upper arm

In an earlier piece on arm anatomy, we covered the muscles on the front of the upper arm. To round things out, let's look at the back of the upper arm today — the triceps.

This one is a good deal simpler than the biceps. The muscle group on the back of the upper arm consists of just a single muscle, commonly known as the triceps, or in full, the triceps brachii ("three-headed muscle of the arm").

The triceps muscle

The triceps is an extensor of the elbow joint — it straightens the arm. Its long head also assists in moving the arm backward behind the body.

As the name suggests, the triceps is made up of three heads:

• long head (caput longum)
• lateral head (caput laterale)
• medial head (caput mediale)

The long head originates on the shoulder blade; the medial and lateral heads originate on the back of the humerus. All three heads join into a single muscle belly and attach via a shared tendon to the olecranon (the bony point of the elbow).