Triceps
| Triceps | |
|---|---|
 Right-sided triceps brachii seen from behind. (After Testut's Anatomy.) | |
 Triceps brachii seen from behind. | |
| Details | |
| Origin | Long head: infraglenoid tubercle of scapula Lateral head: above the radial groove Medial head: below the radial groove |
| Insertion | Olecranon process of ulna |
| Artery | Deep brachial artery, posterior circumflex humeral artery (long head only) |
| Nerve | Radial nerve |
| Actions | Extends forearm, long head extends, adducts arm, extends shoulder |
| Antagonist | Biceps brachii muscle |
| Identifiers | |
| Latin | musculus triceps brachii |
| TA98 | A04.6.02.019 |
| TA2 | 2471 |
| FMA | 37688 |
| Anatomical terms of muscle | |
The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of three parts: the medial, lateral, and long head. All three heads cross the elbow joint. However, the long head also crosses the shoulder joint. The triceps muscle contracts when the elbow is straightened and expands when the elbow is bent. The long head gets a further contraction when the arm is behind the torso due to how it crosses the shoulder joint. It is the muscle principally responsible for extension of the elbow joint (straightening of the arm).