Muscle · Thoracic spine

Serratus posterior superior

Musculus serratus posterior superior

A thin quadrilateral sheet high on the back, hidden beneath the rhomboids and the trapezius. It arises from the ligament running down the back of the neck and the spinous processes at the neck–thorax junction, then fans downward and outward into the upper borders of the second to fifth ribs, just beyond their angles. Because it lies under two much larger muscles it is never the tissue a hand is on first, which is worth knowing when a complaint sits deep between the shoulder blade and the spine. Its usual action is given as elevating those upper ribs in inspiration, though the sheet is thin and its contribution correspondingly small.