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Origins, insertions, innervation and functions of the serratus anterior muscle.
Hey, everyone. It’s Matt from Kenhub! And in this tutorial, we will discuss the serratus anterior muscle.
The serratus anterior muscle is a fan-shaped muscle at the lateral wall of the thorax. Its main part lies deep under the scapula and the pectoral muscles. It is easy to palpate between the pectoralis major and latissimus dorsi muscles.
In athletic bodies, the muscle may even be visible to the naked eye along the ribs, underneath the axilla.
The serratus anterior muscle originates at the first to ninth rib and inserts at the ventral surface of the medial border of the scapula.
Because of its course, it has a saw-tooth or serrated appearance, hence the name “serratus anterior.”
The muscle is further divided into three parts. The superior part consists of the part from the first to second rib, extending to the superior angle of the scapula.
The intermediate part is from the second to third rib to the medial border of the scapula. And the inferior part is the section from the fourth to ninth rib to the medial border and inferior angle of the scapula.
This part is the most prominent and powerful one.
The innervation is supplied by the long thoracic nerve, a branch of the brachial plexus.
The contraction of the entire serratus anterior leads to a ventrolateral movement of the scapula along the ribs.
Another function of the serratus anterior is the act of stabilization of the scapula within the shoulder.
Finally, in a fixed scapula, the muscle lifts the ribs and acts as an accessory inspiratory muscle.
Due to the pull of the inferior part at the lower scapula, the shoulder joint is shifted superiorly. This shifting, then, enables the arm to lift above ninety degrees.
In contrast, the superior part depresses the scapula and thus acts antagonistically.