Serratus posterior superior
The serratus posterior superior (Latin: musculus serratus posterior superior) is a thin rectangular muscle that is located in the upper back and back part of the thorax. It lies deep to the rhomboid muscles.
The serratus posterior originates from the inferior part of the nuchal ligament, and the cervical and thoracic parts of the vertebral column (usually C7 - T3).
The muscle fibers pass in an inferolateral direction and insert into ribs 2 to 5 slightly beyond their angles.
The serratus posterior superior acts to elevate ribs 2 to 5, therefore, aiding in deep respiration.
The intercostal nerves (2nd through 5th) innervate the serratus posterior superior.
The serratus posterior superior is supplied by the intercostal arteries.