Teres Major Muscle, Gross Anatomy

Description

Posterior shoulder anatomy is centered on the teres major highlighted in red, arising from the inferior angle and adjacent lateral border of the scapula and coursing superolaterally to insert on the medial lip of the intertubercular sulcus of the humerus. Just superior to it, teres minor runs along the lateral border toward the greater tubercle, while latissimus dorsi approaches from an inferior and medial position to converge near the humeral insertion, together shaping the posterior axillary fold. Trapezius spans the upper back superficially, and the posterior deltoid caps the glenohumeral region laterally; deep to these layers, the long head of triceps lies inferior and lateral to the scapular attachment. Fiber direction is clear. Because teres major functions as a powerful humeral adductor and internal rotator, its relationship to latissimus dorsi and the humeral bicipital groove matters when teaching shoulder mechanics and when planning tendon work around the proximal humerus. The inferior border of teres major forms an anatomic gateway into the axilla, a practical landmark during axillary lymph node dissection and when orienting to the quadrangular space region, where misdirected retraction can threaten the axillary nerve and posterior circumflex humeral vessels. Its tendon also enters surgical conversation in latissimus dorsi and teres major transfers for irreparable posterosuperior rotator cuff tears, where line of pull and spacing from the long head of triceps influence routing and fixation. Use this asset in gross anatomy and kinesiology teaching modules to differentiate teres major from teres minor and to explain posterior axillary fold anatomy during shoulder adduction. It also supports operative atlas pages on posterior shoulder exposure, tendon transfer planning, and physical therapy education on internal rotation strength testing. Anatomical accuracy verified by SciePro's Medical Advisory Board.