Origin: Iliac crest and ventral surface of the ilium and spinous processes and supraspinous ligament.
Insertion: Ends on accessory processes of the sixth to first lumbar vertebrae.
Action: Extension of the vertebral column. Raising of the cranial portion of the body from the pelvis, sacrum, and loin; in conjunction with the other muscles, fixation of the vertebral column; deflection of the back by fixation of the cervicothoracic junction; sudden raising of the caudal portion of the body; which is initiated by means of the rear extremities.
Nerve: Dorsal branches of the thoracic and lumbar nerves