The arterial supply to the spinal cord comes from two sources (Fig. 2.55). It consists of: longitudinally oriented vessels, arising superior to the cervical portion of the cord, which descend on the surface of the cord; and feeder arteries that enter the vertebral canal through the intervertebral foramina at every level; these feeder vessels, or segmental spinal arteries, arise predominantly from the vertebral and deep cervical arteries in the neck, the posterior intercostal arteries in the thorax, and the lumbar arteries in the abdomen.