Teres Major

Introduction

Introduction to Teres Major

The teres major is a thick, rounded muscle located in the posterior shoulder region. It forms part of the scapular-deltoid region of the upper limb and acts as an important stabilizer and mover of the humerus. Although it is situated close to the rotator cuff muscles, it is not considered a member of the rotator cuff because it does not blend with the capsule of the glenohumeral joint.

The muscle extends from the inferior angle of the scapula to the medial lip of the intertubercular sulcus of the humerus. Together with the latissimus dorsi, it contributes to adduction, extension, and medial rotation of the arm.

Study

Location and Relations

Teres major lies inferior to teres minor and superior to latissimus dorsi. It forms part of the posterior axillary fold and contributes to the boundaries of the quadrangular and triangular spaces of the scapular region.

Origin

The teres major originates from the posterior surface of the inferior angle and adjacent lower part of the lateral border of the scapula.

Insertion

Its tendon inserts into the medial lip of the intertubercular sulcus (bicipital groove) of the humerus. The insertion is closely related to that of latissimus dorsi.

Nerve Supply

Teres major is supplied by the lower subscapular nerve (C5–C6), a branch of the posterior cord of the brachial plexus.

Blood Supply

The muscle receives blood mainly from branches of the subscapular and circumflex scapular arteries.

Actions

Teres major adducts, medially rotates, and extends the arm at the shoulder joint. These actions are particularly important during climbing, pulling, rowing, and swimming movements.

Posterior Axillary Fold

The posterior axillary fold is formed primarily by the teres major and latissimus dorsi muscles. This fold can be palpated when the arm is abducted.

Relationship to Anatomical Spaces

Teres major forms the inferior boundary of the quadrangular space and the superior boundary of the triangular interval. These spaces transmit important neurovascular structures in the scapular region.

Clinical Importance

Injuries of teres major are uncommon but may occur in athletes involved in throwing, rowing, or climbing. Damage can lead to weakness of adduction, extension, and medial rotation of the arm.

Summary

Summary

Teres major is a powerful muscle of the scapular-deltoid region. It originates from the inferior angle of the scapula and inserts into the medial lip of the intertubercular sulcus of the humerus. It is supplied by the lower subscapular nerve (C5–C6) and acts to adduct, extend, and medially rotate the arm. The muscle contributes to the posterior axillary fold and serves as an important landmark in the scapular region.