Biceps and triceps muscles. Left: biceps contracted. Right: triceps contracted
Any muscle that has three points of origin. Most commonly "triceps" refers to the triceps brachii muscle – a large extensor along the back of the upper arm in humans. It originates just below the socket of the scapula (shoulder-blade) and at two distinct areas of the humerus, the bone of the upper arm. The tricpes extends downward and attaches to the upper part of the ulna, in the forearm.