Spinal cord overview and central canal

Summary

The spinal cord is a long, thin, tubular structure of nervous tissue that connects the brain with the peripheral nervous system. It extends from the lower brainstem (medulla oblongata) down to the lumbar region, tapering near the first and second lumbar vertebrae into the cauda equina. In adults, it is shorter than the vertebral column, so it occupies only part of the spinal canal. The spinal cord is covered by the meninges and enclosed by the neural arches of the vertebrae, providing protection while transmitting motor and sensory information and coordinating reflexes. At the center of the spinal cord is the central canal, a hollow space that contains cerebrospinal fluid (CSF). Surrounding this central canal is gray matter (with butterfly-shaped arrangement of cell bodies), while white matter lies more peripherally and contains myelinated ascending and descending axon tracts. The cord is organized into segments, each giving rise to paired dorsal (sensory) and ventral (motor) roots that combine to form spinal nerves. Two major enlargements occur—cervical and lumbar—corresponding to the nerve supply of the upper and lower limbs, respectively.

Key Points

• 1

  The spinal cord is part of the central nervous system, transmitting motor and sensory signals and coordinating reflexes, and it is protected by the meninges and vertebral column.

• 2

  The central canal runs through the middle of the spinal cord and contains cerebrospinal fluid; it is surrounded by gray matter, while white matter forms the outer tracts.

• 3

  The spinal cord is segmented, with dorsal roots carrying sensory (afferent) information and ventral roots carrying motor (efferent) information; cervical and lumbar enlargements correspond to limb innervation.