The white matter of the spinal cord consists mainly of myelinated axons (thread-like extensions of neurons) and is located around the gray matter. The white matter is arranged into three paired columns or funiculi:

Ventral (anterior) funiculus - situated between the ventral horns of the gray matter and anterior median fissure;
Lateral funiculus - found on either side of the spinal cord between the anterior horns and posterior horns of the gray matter;
Dorsal (posterior) funiculus - located between the dorsal horns of the gray matter and posterior median fissure.

Ascending and descending tracts

The nerve cell axons within these columns are grouped into separate bundles of nerve fibers called tracts (pathways). The nerve fibers within one tract share the same origin, destination, course and function.

These pathways connect different parts of the brain with the spinal cord and periphery of the body, and they all are classified into two groups:

The ascending tracts transmit sensory (afferent) impulses from the periphery of the body and the spinal cord to the brain;
The descending tracts transmit motor (efferent) information from the brain to the spinal cord and the periphery of the body.

Note: The name of the tract usually indicates the origin and termination sites. For example, the corticospinal tract means that the pathway begins in the cerebral cortex and ends in the spinal cord.

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White matter of spinal cord