The triceps brachii, commonly known as the triceps, is a large muscle located on the back of the upper arm. It is responsible for extending the elbow, making it crucial for pushing movements. The triceps is composed of three distinct heads: the long head, the lateral head, and the medial head. The long head originates from the scapula (shoulder blade), while the lateral and medial heads originate from the humerus (upper arm bone). These three heads converge into a single tendon that attaches to the olecranon process of the ulna, which is the bony prominence of the elbow.

Each head of the triceps has specific roles and contributions to arm movements. The long head assists in shoulder extension and adduction in addition to elbow extension, providing stability to the shoulder joint. The lateral head is primarily involved in pushing and pressing actions, contributing significantly to the overall size and definition of the triceps. The medial head, though often less visible, plays a vital role in providing strength and endurance for sustained arm movements. Together, these three heads ensure a balanced and powerful extension of the elbow, making the triceps essential for various activities, from daily tasks to athletic performances.