NCIt definition : A group of three muscles (iliocostalis, longissimus, and spinalis) that originate
at the sacrum, ilium, and lumbar vertebrae spines and insert into the ribs and vertebra
in order to extend the vertebral column.;
Alternative definition : CDISC: A group of three paired epaxial muscle bundles (iliocostalis, longissimus,
and spinalis) extending along and lateral to the spinous processes of the cervical,
thoracic, and lumbar vertebrae; primary function is extension and rotation of the
spine.;