Serratus posterior superior

The serratus posterior superior (Latin: musculus serratus posterior superior) is a broad rectangular-shaped muscle of the back that is located in the upper back between the cervical and thoracic regions. It lies deep to the rhomboid muscles. The serratus posterior superior extends between the vertebrae of the spine and ribs of the thorax. It is smaller than the inferiorly located serratus posterior inferior muscle, and both muscles are separated by a wide distance. Together with the serratus posterior superior, the serratus posterior superior forms the intermediate layer of the back muscles.

Origin

The serratus posterior superior muscle originates from the inferior part of the nuchal ligament and the spinous processes of the cervical and thoracic vertebrae (usually C7 - T3).

Insertion

The muscle fibers go in an inferolateral direction and insert on the superior borders of the 2nd to 5th ribs lateral to their angles.

Action

The serratus posterior superior muscle elevates ribs 2 to 5. It is also one of the accessory respiration muscles and aids in inspiration.

Innervation

The serratus posterior superior is innervated by the 2nd to 5th intercostal nerves.

Blood supply

The serratus posterior superior muscle receives arterial blood supply from the posterior intercostal arteries - branches of the thoracic aorta.