The Teres Major is a small, cylindrical muscle located in the upper back, specifically beneath the shoulder blade. It plays a crucial role in the movement of the arm, assisting in actions such as internal rotation, adduction, and extension. This muscle works closely with the larger Latissimus Dorsi to facilitate various upper body movements. Anatomically, the Teres Major originates from the lower part of the scapula and inserts into the upper arm bone, known as the humerus. It is innervated by the lower subscapular nerve, which is essential for its function. Understanding the Teres Major is important for athletes and individuals engaged in physical activities, as it contributes to shoulder stability and mobility.