Teres Major Muscle

Description

Posterior shoulder and proximal arm anatomy centers on the teres major (musculus teres major, rotundus major) as it arises from the dorsal surface of the inferior angle and adjacent lateral border of the scapula, then courses superolaterally to insert on the medial lip of the intertubercular sulcus (crest of the lesser tubercle) of the humerus. Along its lateral border, the muscle lies adjacent to the tendon of latissimus dorsi, and together they form the posterior axillary fold inferior to teres minor and the scapular spine. Medially, the belly relates to the long head of triceps as it descends from the infraglenoid tubercle, with the quadrangular and triangular spaces located superior to its proximal portion. Thick and rounded. Functionally, teres major drives shoulder adduction, internal rotation, and extension, and its morphology matters when you teach how the posterior axillary fold is built and how force couples around the glenohumeral joint change with arm position. Surgeons and anatomists use its borders as surface and deep landmarks when discussing posterior approaches and when orienting to the quadrangular space (axillary nerve and posterior circumflex humeral artery) versus the triangular interval (radial nerve and profunda brachii artery), where misidentification can shift a dissection plane. The tendon’s insertion near the bicipital groove also frames discussions of pain generators around the proximal humerus, including referred discomfort during resisted internal rotation and adduction testing. Works well for gross anatomy labs, functional anatomy modules on the shoulder girdle, and orthopedic or sports medicine teaching materials explaining posterior axillary fold contours and surgical landmarks around the scapula and proximal humerus. Suitable for medical textbooks, patient education handouts focused on posterior shoulder strain patterns, and procedural guides that need clean orientation to teres major versus teres minor and latissimus dorsi. Anatomical accuracy verified by SciePro's Medical Advisory Board.