- a series of pairs of muscles of small muscles extending the full length of the spine just superficial to the rotators and each spanning 2 or 3
intervertebral spaces before inserting;
origin: posterior surface of the sacrum, the dorsal end of the iliac crest, the transverse processes of the lumbar and the thoracic vertebrae
and the articular processes of the 4th to the 7th vertebrae;
insertion: spinous processes of all the vertebrae except the atlas;
action: acting unilaterally, lateral flexion and rotation to the opposite side; acting bilaterally, extension and hyperextension of the spine;
nerve supply: posterior rami of the spinal nerves;
synergists: rotators, Interspinales, Intertransversarii groups