The Serratus Anterior lies deep to the rhomboids. It arises by digitations from the first eight or nine ribs. These digitations insert on the medial border of the costal surface of the scapula, with the first digitation reaching the superior angle of the scapula, and the lower four digitations reaching the inferior angle of the scapula. The long thoracic nerve innervates the serratus anterior.
Injury to the long thoracic nerve results in paralysis of the serratus anterior muscle. If the upper limb encounteres anterior resistance, the medial border of the scapula protrudes posteriorly. This condition is known as winged scapula.