Teres minor muscle

The teres minor is a narrow, elongated muscle that forms part of the rotator cuff group, aiding in shoulder stabilization and movement.

Origin

It arises from the dorsal surface of the axillary border of the scapula along the upper two-thirds of its extent. It is also supported by two aponeurotic laminae, one separating it from the infraspinatus and the other from the teres major.

Insertion

Its fibers run obliquely upward and laterally. The upper fibers insert into the lowest of the three impressions on the greater tubercle of the humerus via a tendon. The lower fibers insert directly into the humerus immediately below this impression. The tendon of this muscle passes across and blends with the posterior portion of the shoulder joint capsule.

Function

The teres minor contributes to lateral (external) rotation of the humerus and assists in the stabilization of the humeral head within the glenoid cavity.

Innervation

The muscle is innervated by the axillary nerve, which is derived from the ventral rami of C5 and C6 spinal nerves. The axillary nerve originates from the posterior cord of the brachial plexus and travels posteriorly through the quadrangular space, a region bordered by the teres minor, teres major, long head of the triceps brachii, and surgical neck of the humerus. After passing through this space, the axillary nerve divides into anterior and posterior branches. The posterior branch specifically innervates the deltoid muscle and the teres minor muscle, playing a critical role in shoulder movement and stability.

Blood supply

The teres minor muscle receives its blood supply primarily from the subscapular artery, including one of its branches, the circumflex scapular artery, as well as from the posterior circumflex humeral artery.