[TA] a large caliber spinal or radicular artery that courses centrally along the posterior or anterior root of a spinal nerve, supplying it and the surrounding meninges in the fashion of any spinal/radicular artery, but then continues on to reach and anastomose with the anterior or posterior (longitudinal) spinal artery. Only 4-9 of the spinal or radicular arteries are medullary spinal arteries, found mainly in the lower cervical, lower thoracic, and upper lumbar levels, the largest of which is the segmental medullary artery.great segmental medullary artery, spinal arteries, (anterior and posterior) radicular arteries. SYN: arteriae medullares segmentales [TA], medullary spinal arteries.