Spinal Cord Anatomy: Structure and Pathways

Overview

The spinal cord is a cylinder of nerve tissue running from the brainstem down through the vertebral canal. It is the main highway carrying signals between the brain and the body, and it also controls many reflexes on its own.

Gross Structure

The cord is protected by the vertebral column and the three meninges. It gives off 31 pairs of spinal nerves and shows two enlargements — cervical and lumbar — where the nerves to the limbs arise. In adults the cord ends around the first or second lumbar vertebra, below which the nerve roots form the cauda equina.

Gray and White Matter

A cross-section reveals a butterfly-shaped core of gray matter surrounded by white matter:

• Gray matter contains neuron cell bodies. Its dorsal horns process sensory input, while its ventral horns send out motor commands.
• White matter consists of myelinated tracts that carry information up and down the cord.

Ascending and Descending Tracts

• Ascending tracts carry sensory information (touch, pain, temperature, position) up to the brain.
• Descending tracts carry motor commands from the brain down to the muscles.

Clinical Significance

Because tracts occupy specific positions, the pattern of weakness or sensory loss after an injury reveals where the cord is damaged. Reflexes such as the knee-jerk are processed entirely within the cord, which is why they can persist even when communication with the brain is interrupted.

Summary

The spinal cord combines local reflex circuits with long ascending and descending tracts, making it both a processing center and the body's main communication cable.

For educational purposes only; not a substitute for medical advice.