Teres Muscles

There are two teres muscles. One is the "teres minor," which rotates the arm laterally and assists in bringing it toward the body. As it draws the upper arm bone (humerus) up, it strengthens the shoulder joint. The "teres major" is a thick, flattened muscle that brings the arm toward the body and assists in extending it when the arm is in a flexed position. It is also an aid in rotating, but its function is just the opposite of the teres minor and other muscles in the rotator cuff.