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The cable of nerve tissue running through the spine that relays signals between the brain and body and drives reflexes.
Medically reviewed & updated
The spinal cord is a long, cylindrical bundle of nerve tissue that extends the central nervous system from the brain down through the spine. It serves as the main highway for signals traveling between the brain and the rest of the body and also coordinates many reflexes on its own.
The spinal cord begins at the foramen magnum as a continuation of the medulla oblongata and runs inside the protective bony vertebral (spinal) canal. It is roughly 42 cm long in adult males and 39 cm in adult females. In adults it tapers and ends around the first lumbar vertebra (L1) as a cone called the conus medullaris; below this, a fan of nerve roots called the cauda equina continues. It is wrapped in three protective membranes (meninges) and bathed in cerebrospinal fluid. In cross-section, central H-shaped (butterfly-shaped) gray matter—containing neuron cell bodies and organized into dorsal, ventral, and lateral horns—is surrounded by white matter made of myelinated fiber tracts.
The spinal cord carries information in two directions. Ascending tracts (such as the spinothalamic and spinocerebellar tracts) relay sensory information—pain, temperature, touch, and body position—up to the brain. Descending tracts (such as the corticospinal tract) carry motor commands down to muscles. The cord also gives rise to 31 pairs of spinal nerves—8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal—that connect to the body. In addition, the cord mediates reflex arcs, allowing rapid protective responses (like withdrawing from a hot surface) without waiting for the brain.
Spinal cord injury interrupts these pathways, causing loss of movement and sensation below the level of damage; higher (cervical) injuries affect more of the body and can impair breathing. Compression from herniated discs, tumors, or trauma, and diseases such as multiple sclerosis, can disrupt specific tracts and produce characteristic patterns of weakness or numbness.
This information is educational and is not medical advice.