Teres Major Muscle Beneath the Skin

Description

Along the posterior shoulder, the teres major is isolated beneath the reflected skin and superficial fascia, arising from the dorsal surface of the inferior angle and adjacent lateral border of the scapula. Its fibers run superolaterally to the proximal humerus, inserting on the medial lip of the intertubercular sulcus (crest of the lesser tubercle), immediately medial to the bicipital groove. Superiorly it sits inferior to teres minor and the scapular spine region, while inferiorly it blends in proximity with latissimus dorsi; together they form the posterior axillary fold, with the deltoid positioned more laterally over the glenohumeral region. Fibers are clearly oriented. Bone landmarks remain implicit. Teres major matters because it is the muscular bridge between scapular motion and humeral positioning, producing adduction, extension, and medial rotation that clinicians test during resisted shoulder extension from flexion and during pull movements. Its superior border helps define the quadrangular space (teres minor above, long head of triceps medially, humerus laterally), a corridor where the axillary nerve and posterior circumflex humeral artery can be compromised in posterior shoulder trauma or iatrogenic dissection. Surgeons also exploit its tendon in latissimus dorsi and teres major transfers to restore external rotation or elevation in selected massive rotator cuff tears, so a clean appreciation of its insertion relative to the bicipital groove and subscapularis is practical. Use this plate for musculoskeletal anatomy teaching of the posterior shoulder and axilla, for sports medicine texts addressing adduction and internal rotation strength testing, and for operative atlases discussing posterior axillary fold exposure, quadrangular space anatomy, and tendon transfer planning. Anatomical accuracy verified by SciePro's Medical Advisory Board.