It is situated at the medial side of the longissimus dorsi, and is intimately blended with it; it arises by three or four tendons from the spinous processes of the first two lumbar and the last two thoracic vertebrae: these, uniting, form a small muscle which is inserted by separate tendons into the spinous processes of the upper thoracic vertebrae, the number varying from four to eight.
This muscle is located on the medial aspect of the longissimus dorsi and is intimately connected with it. It arises from three or four tendons that attach to the spinous processes of the first two lumbar and last two thoracic vertebrae, which then merge to form a small muscle that inserts into the upper thoracic vertebrae via separate tendons.