Serratus Posterior Inferior
Serratus posterior inferior originates on T11-L2 and inserts on ribs 9-12, trapping the 9th and 10th thoracic vertebrae. There is a thin sheet of connective tissue that continues from the short bellies of the muscle on the rib to the supraspinous ligament over the spinous process. The width of this aponeurosis varies significantly among dissections. This muscle is the most superficial of the intrinsic back muscles and straps across the erectors, levator costae, and intrinsic spine muscles.
Origin – The spinous processes of T11-L2
Insertion – the inferior border of the last four ribs, just lateral to the angle of the rib
Function – it’s position indicates that it should extend and rotate the trunk, as well as assist in breathing, especially when breathing is forceful, or the trunk is contorted. It is, however, hard to find electromyographical studies that have determined when this muscle contracts.
Tony Preston has a practice in Atlanta, Georgia where he sees clients.
He has written and taught about anatomy, trigger points and cranial therapies since the mid-90s.