teres

Teres is a Latin term meaning rounded or cylindrical, and in anatomy it is used as part of the names of two shoulder muscles, teres major and teres minor. The word itself does not denote a single muscle, but describes a rounded, elongated shape characteristic of these structures.

Teres major originates from the posterior surface of the inferior angle of the scapula and inserts onto the medial lip of the intertubercular sulcus of the humerus. It is innervated by the lower subscapular nerve (C5–C7). Its actions include adduction, medial rotation, and extension of the arm, and it helps stabilize the humeral head within the glenoid fossa.

Teres minor originates from the upper two-thirds of the lateral border of the scapula and inserts onto the inferior facet of the greater tubercle of the humerus, with fibers contributing to the joint capsule. It is innervated by the axillary nerve (C5–C6). Its primary actions are external (lateral) rotation of the arm and, together with the rotator cuff, stabilization of the glenohumeral joint.

Clinically, teres major and minor play roles in shoulder movement and stabilization. Teres minor is a component of the rotator cuff, and injury or nerve damage affecting the axillary nerve can lead to weakened external rotation or shoulder instability. Teres major, while less commonly implicated in isolation, contributes to movements required in overhead and pulling activities.