<P> The cauda equina ( Latin for `` horse 's tail '' ) is a bundle of spinal nerves and spinal nerve rootlets , consisting of the second through fifth lumbar nerve pairs , the first through fifth sacral nerve pairs , and the coccygeal nerve , all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord . The cauda equina occupies the lumbar cistern , a subarachnoid space inferior to the conus medullaris . The nerves that compose the cauda equina innervate the pelvic organs and lower limbs to include motor innervation of the hips , knees , ankles , feet , internal anal sphincter and external anal sphincter . In addition , the cauda equina extends to sensory innervation of the perineum and , partially , parasympathetic innervation of the bladder . </P>
where does the spinal cord become cauda equina
the conus medullaris