The teres major muscle is a long, slender muscle located in the posterior compartment of the shoulder. It is situated between the infraspinatus muscle and the latissimus dorsi muscle, and is responsible for several important functions in the shoulder joint.
Location
The teres major muscle is located in the posterior compartment of the shoulder, which is the back portion of the shoulder blade (scapula). It originates from the posterior border of the scapula, specifically from a small bump called the inferior angle of the scapula. From here, it travels downward and medially, inserting into the humerus (upper arm bone) at a point just below the greater tubercle.
The teres major muscle is positioned between the infraspinatus muscle and the latissimus dorsi muscle, and is covered by the posterior deltoid muscle. It is located in close proximity to several other shoulder muscles, including the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) and the triceps brachii muscle.
Structure
The Teres major muscle is composed of muscle fibers arranged in parallel and is innervated by the lower subscapular nerve (C5-C6).
The teres major muscle is covered by a thin layer of fascia, which is a type of connective tissue that surrounds and separates muscles. It is also surrounded by a number of other shoulder muscles, including the infraspinatus muscle and the latissimus dorsi muscle.
The blood supply to the teres major muscle is provided by the posterior circumflex humeral artery, which is a branch of the axillary artery. This artery supplies oxygen and nutrients to the muscle, helping to support its function and health.
Function
The main function of the teres major muscle is to extend, adduct, and medially rotate the arm at the shoulder joint. This means that it helps to move the arm backward, toward the body, and inward, toward the midline of the body.
In addition to these primary functions, the teres major muscle also plays a role in stabilizing the shoulder joint and assisting in other shoulder movements, such as flexion and abduction. It works in conjunction with other shoulder muscles to provide a wide range of shoulder motion, including reaching, lifting, and rotating the arm.
The teres major muscle is particularly important for activities that involve reaching overhead or behind the back, such as throwing a ball or reaching for an object on a high shelf. It is also involved in many exercises that target the upper back and shoulder muscles, such as rows, pull-ups, and lat pull-downs.
Overall, the teres major muscle is an important contributor to shoulder function and stability, and is essential for a wide range of movements and activities.
Clinical significance
The teres major muscle is an important muscle in the shoulder joint, and it can be affected by various injuries and disorders. Here are some clinical considerations related to the teres major muscle:
Tears and strains
One common injury that can affect the teres major muscle is a tear or strain. This can occur due to overuse, sudden impact, or improper technique during physical activity. Symptoms of a tear or strain in the teres major muscle may include pain, weakness, and difficulty moving the arm. Treatment may involve rest, physical therapy, and in some cases, surgery.
Tendinitis
Tendinitis is a condition characterized by inflammation of a tendon, which is the tissue that connects muscle to bone. The teres major muscle has a tendon that attaches it to the humerus, and this tendon can become inflamed due to overuse or repetitive strain. Symptoms of teres major tendinitis may include pain, swelling, and tenderness in the shoulder. Treatment may involve rest, ice, physical therapy, and in some cases, medications or injections.
Frozen shoulder
Frozen shoulder, also known as adhesive capsulitis, is a condition that causes stiffness and limited range of motion in the shoulder joint. It can be caused by a variety of factors, including injury, surgery, or prolonged inactivity. The teres major muscle can be affected by frozen shoulder, as it may become stiff and unable to move properly. Treatment may involve physical therapy, medications, and in some cases, surgery to loosen the shoulder joint.
Rotator cuff injuries
The rotator cuff is a group of muscles and tendons that surround the shoulder joint and help to stabilize and move the arm. The teres major muscle is one of the muscles that makes up the rotator cuff. Rotator cuff injuries can occur due to overuse, trauma, or degeneration, and can cause pain, weakness, and difficulty moving the arm. Treatment may involve physical therapy, medications, and in some cases, surgery.
