Chapter 4 - Spinal cord

Abstract

This chapter provides an overview of spinal cord. The spinal cord lies within the vertebral canal. The cord has two enlargements associated with the innervation of the limbs. The greatest diameter occurs at the cervical enlargement in cord segments from C4 to Tl and is associated with the brachial plexus. The lumbar enlargement extends from cord segments L1 to S3. The spinal cord is enclosed in three layers or meninges. The innermost pia mater adheres to the surface of the cord. The dura mater is the outermost layer, and it is lined by the arachnoid mater, both these extending to the level of vertebra S2. The subarachnoid space between the pia and arachnoid is filled by cerebrospinal fluid. Each spinal cord segment gives origin to a pair of spinal nerves. There are 31 pairs of spinal nerves—8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. An adult spinal cord is shorter than its vertebral column and spinal cord segments are situated rostral to the numerically corresponding vertebrae.