Teres Major Muscle, Lateral View

Description

Positioned on the posterior axillary fold, the teres major runs from the inferior angle and adjacent lateral border of the scapula to the medial lip of the intertubercular sulcus of the humerus. From a lateral shoulder view, its thick, cylindrical belly lies inferior to the teres minor and posterior to the tendon of pectoralis major, approaching the proximal humerus deep to the deltoid. The scapular spine, lateral acromial region with the clavicle superiorly, and the proximal humeral head and shaft frame the muscle’s course. Tendinous fibers converge near the humerus. Clear. Functionally, this orientation clarifies why teres major is grouped with latissimus dorsi as an adductor and medial rotator of the humerus, yet remains distinct from the rotator cuff because it does not insert on the greater or lesser tubercle to stabilize the glenohumeral joint. The lateral perspective helps distinguish teres major from teres minor during posterior shoulder exposure and explains how fibrosis or overuse in throwing, climbing, or swimming can contribute to posterior axillary tightness and altered scapulohumeral rhythm. Its relationship to the quadrangular space and triangular interval also matters when teaching the course of the axillary nerve and posterior circumflex humeral artery versus the radial nerve and profunda brachii. Educators will find this plate well-suited for gross anatomy labs, kinesiology modules on shoulder adduction and extension, and surgical anatomy figures accompanying discussions of posterior axillary fold dissection or tendon transfer planning. Clinicians can also reference it when explaining palpation landmarks and differentiating teres major strain from rotator cuff pathology during physical exam documentation. Anatomical accuracy verified by SciePro's Medical Advisory Board.