Serratus anterior muscle

The serratus anterior, also known as serratus magnus, is a muscle of the chest. It originates at the side of the chest from the upper 9 ribs; it inserts along the entire length of the anterior aspect of the medial border of the scapula. It is innervated by the long thoracic nerve from the brachial plexus. The serratus anterior acts to pull the scapula forward around the thorax. The muscle is named from Latin: serrare = to saw (referring to the shape); and anterior = on the front side of the body. (Wikipedia)