APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -The latissimus dorsi muscle at the level of the shoulder is the most important internal rotator, as it is the most important for the adduction and flexion of the shoulder.

Detailed explanation-2: -The latissimus dorsi works collaboratively with the teres major and pectoralis major to perform actions of the upper extremity. Together, these muscles will work to adduct, medially rotate, and extend the arm at the glenohumeral joint.

Detailed explanation-3: -Muscles that have their origins in the posterior (back of) shoulder joint extend the arm. These muscles include the latissimus dorsi and posterior fibres of the deltoids, with both acting as the prime mover. Teres major also assists this action. Pectoralis major and latissimus dorsi act as antagonists.

Detailed explanation-4: -The latissimus dorsi is responsible for extension, adduction, transverse extension also known as horizontal abduction (or horizontal extension), flexion from an extended position, and (medial) internal rotation of the shoulder joint. It also has a synergistic role in extension and lateral flexion of the lumbar spine.

Detailed explanation-5: -For a shoulder extension, your body uses the latissimus dorsi, teres major and minor and posterior deltoid muscles.