Which muscle is NOT one of the primary muscles that insert into the intertubercular groove of the humerus?

The deltoid muscle is not one of the primary muscles that insert into the intertubercular groove of the humerus. The intertubercular groove, also known as the bicipital groove, is a significant anatomical landmark where several important muscles attach, specifically those involved in shoulder movement.

The pectoralis major, teres major, and latissimus dorsi are the primary muscles that insert into this groove. The pectoralis major contributes to adduction, internal rotation, and flexion of the shoulder. The latissimus dorsi is involved in extension, adduction, and internal rotation. The teres major assists in similar actions as the latissimus dorsi. In contrast, the deltoid primarily originates from the acromion, clavicle, and scapula, and it is responsible for shoulder abduction, flexion, and extension. Its insertion is located on the deltoid tuberosity of the humerus, which is different from the intertubercular groove.

Understanding the anatomical insertions and functions of these muscles is essential in sports medicine, as it helps in diagnosing and treating shoulder injuries and developing targeted rehabilitation programs.