The teres major is a thick, somewhat flattened muscle in the upper limb that helps move the arm. It's located on the back of the shoulder and works with other muscles to enable a range of motions.
Anatomy and Location
- The teres major is a rectangular muscle.
- Origin: It originates from the inferior angle and lower part of the lateral border of the scapula (shoulder blade).
- Insertion: It inserts onto the medial lip of the intertubercular groove (bicipital groove) of the humerus (upper arm bone).
Function
The teres major primarily functions to:
- Extend the humerus: It helps bring the arm backward.
- Adduct the humerus: It pulls the arm towards the midline of the body.
- Internally rotate the humerus: It rotates the arm inward.
It often works synergistically with the latissimus dorsi muscle to perform these actions.
Relation to Other Muscles
The teres major is often referred to as the "lat's little helper" because of its similar function to the latissimus dorsi. It's also part of the posterior axillary wall. Furthermore, the teres major helps to form the inferior border of the triangular space, and the inferior border of the quadrangular space of the shoulder.
Clinical Significance
While less commonly injured than other rotator cuff muscles, the teres major can be affected by strains or tears, particularly in athletes involved in overhead activities. Pain, weakness, and limited range of motion are common symptoms of teres major injuries.
In summary, the teres major is an important muscle in the shoulder that contributes to the movement and stability of the arm.
