Pectoralis minor

Like pectoralis major this is a muscle derived from the outermost of the three sheets of the primitive body wall. In contradistinction to pectoralis major, whose costal fibers arise from cartilage, this muscle arises from bone, usually from the third, fourth and fifth ribs, by fleshy slips beneath pectoralis major. The muscle converges in triangular fashion towards the coracoid process. It is inserted by a short thick tendon into the medial border and upper surface of the coracoid process of the scapula. Variations in its costal origin are common, the muscle being often prefixed and occasionally postfixed.

Nerve supply of pectoralis minor:

By both pectoral nerves (C6, 7 and 8).

Action of pectoralis minor:

The function of the muscle is to assist serratus anterior in protraction of the scapula, keeping the anterior (glenoid) angle in apposition with the chest wall as the vertebral border is drawn forwards by serratus anterior. The muscle is elongated when the scapula rotates in full abduction of the arm; its subsequent contraction assists gravity in restoring the scapula to the rest position. Of no great functional significance, it is an important anatomical and surgical landmark, being the guide to the underlying axillary artery and the cords of the brachial plexus.