Answer: The spinal cord is a long, thin, cylindrical structure that runs from the base of the brain down through the center of the vertebral column. It is protected by the vertebral column and is surrounded by three layers of protective membranes called meninges. The outermost layer is the dura mater, the middle layer is the arachnoid mater, and the innermost layer is the pia mater. The spinal cord consists of gray matter and white matter. The gray matter is located in the center of the cord and has a butterfly shape. It contains cell bodies, dendrites, and axons of neurons that receive and process sensory information, and send motor signals to muscles and glands. The white matter is located on the outer part of the cord and contains bundles of axons, which form the ascending and descending tracts that carry sensory and motor signals to and from the brain. The spinal cord is segmented, with each segment corresponding to a pair of spinal nerves that exit the cord through spaces between the vertebrae. Overall, the gross and microscopic structure of the spinal cord is designed to receive and process information from the peripheral nervous system, and to send motor signals back out to control movement and other bodily functions.