spinalcord

The spinal cord is a cylindrical portion of the central nervous system that extends from the brainstem down through the vertebral column to about the level of the first or second lumbar vertebra in adults. It acts as a major conduit for signals between the brain and the rest of the body and also mediates many reflexes on its own.

The spinal cord consists of gray matter in the center, shaped like a butterfly, surrounded by white matter. The gray matter contains dorsal horns, which process sensory information, ventral horns, which contain motor neurons, and, in the thoracic and upper lumbar regions, lateral horns that are involved in autonomic functions. The white matter comprises ascending sensory tracts and descending motor tracts that compose the major communication pathways.

Spinal nerves arise from the spinal cord at segmental levels via dorsal and ventral roots. The dorsal roots carry sensory information, while the ventral roots transmit motor commands. Below the conus medullaris, the nerve roots form a bundle known as the cauda equina, which travels within the lower part of the vertebral canal.

The spinal cord receives blood supply from the anterior spinal artery and two posterior spinal arteries, with additional reinforcement from segmental medullary arteries. Venous drainage occurs through anterior and posterior spinal veins into the vertebral venous plexus.

Functionally, the spinal cord integrates and transmits neural signals, coordinates reflexes, and serves as a relay for information traveling to and from the brain. Developmentally, it arises from the neural tube, with distinct regions that give rise to motor and sensory neurons.

Injury or disease can disrupt motor and sensory function below the affected level. Common conditions include traumatic spinal cord injury, disc herniation causing compression, spinal stenosis, and inflammatory or demyelinating diseases such as transverse myelitis.