Vertebral column and spinal nerves (English)

Spinal nerves C1-C7 exit the vertebral canal through the intervertebral foramina above their respective vertebrae. Spinal nerve C8 does not have an associated vertebra and therefore exits the vertebral canal through the intervertebral foramen below the vertebra C7. As a result, all remaining spinal nerves, beginning at vertebra T1 exit the vertebral canal below their associated vertebrae. Spinal nerves of the sacral region exit the vertebral canal through the sacral foramina while the single coccygeal nerve leaves the vertebral canal over the anterior aspect of the coccyx. Along the length of the spinal cord are two regions of enlargement: the cervical enlargement (spinal segments C5-T1) and the lumbosacral enlargement (spinal segments L2-S3). These enlargements provide innervation to the upper and lower limbs, respectively. The spinal cord is shorter than the vertebral column and terminates at the medullary cone at the level of vertebrae L1/L2. The posterior and anterior roots which extend below the level of the spinal cord (the lumbar, sacral and coccygeal spinal nerves) form a nerve bundle which takes on the appearance of a horse's tail and is thus known as the cauda equina.