iliocostalis lumborum (muscle)

il·i·o·cos·ta·lis lum·bo·rum (mus·cle)

[TA]
deep back (erector spinae) muscle; origin, posterior aspect of sacrum and thoracolumbar fascia; insertion, the angles of lower six ribs; action, extends, abducts, and rotates lumbar vertebrae; nerve supply, dorsal branches of thoracic and lumbar nerves.