Final answer:
The teres major is a shoulder muscle located inferior to the teres minor and is involved in extending, adducting, and medially rotating the arm. It works with other muscles around the shoulder joint to enable movement and provide joint stability.
Step-by-step explanation:
The teres major is a muscle located in the shoulder area, specifically inferior to the teres minor. Its primary functions include extending the arm, assisting in the adduction (movement toward the body's midline), and medial rotation (turning inward) of the arm.
This muscle, along with others such as the deltoid, subscapularis, supraspinatus, and infraspinatus, contributes to the complex movements and stability of the shoulder joint. For example, while the deltoid is the major abductor of the arm, the teres major helps to balance these movements by providing the opposite action of adduction.
Within the anatomical and ligamental structure of the shoulder joint, the teres major, along with the aforementioned muscles, plays a crucial role in allowing diverse arm movements. These muscles originate from the scapula and are attached to various parts of the humerus, working in coordination to provide a full range of motion and support to the shoulder.
The importance of the teres major and surrounding muscles is underscored by their ability to act as "dynamic ligaments," constantly adjusting their contractile force to provide primary support for the shoulder joint. This intricate mechanism enables the upper limb to perform tasks requiring a significant range of movement and control.