What pathways run in the anterior funiculus of the spinal cord?

The anterior funiculus contains descending motor pathways. These include the tectospinal, anterior corticospinal, olivospinal, vestibulospinal, and reticulospinal tracts. These pathways primarily carry descending motor impulses from supraspinal centers to the spinal cord.

What ascending tracts run in the lateral funiculus of the spinal cord?

The lateral funiculus contains ascending sensory pathways: the anterior and lateral spinothalamic tracts, the anterior and posterior spinocerebellar tracts, and the spinotectal tract (tractus spinotectalis), which runs alongside the spinothalamic tract. The posterior spinocerebellar tract ascends along the lateral funiculus, while the anterior spinocerebellar tract ascends in the ventrolateral portion of the lateral funiculus.

What descending tracts are localized in the lateral funiculus of the spinal cord?

The lateral funiculus contains descending motor pathways, notably the lateral corticospinal tract and the rubrospinal tract (tractus rubrospinalis), located in the central region of the lateral funiculus. These tracts transmit motor commands from higher centers of the central nervous system.

What is the function of the propriospinal fibers (fasciculi proprii) of the spinal cord?

The fasciculi proprii consist of association fibers surrounding the gray matter. They link adjacent spinal cord segments with motor neurons in the anterior horns, primarily mediating intersegmental reflexes.

What components are found in white matter besides nerve fibers?

In addition to myelinated and unmyelinated nerve fibers, the white matter contains neuroglia, blood vessels, and a small amount of connective tissue.

How do the right and left halves of the white matter connect?

They are connected by the anterior white commissure (commissura alba), which is located anterior to the central canal of the spinal cord.

In which regions does the posterior funiculus divide into two bundles?

In the cervical and upper thoracic regions, where the posterior intermediate sulcus divides it into the medial fasciculus gracilis and lateral fasciculus cuneatus.

Where is the interfascicular (semilunar) fasciculus located?

It is formed by descending fibers and is located in the medial part of the fasciculus cuneatus, primarily identifiable in cervical and upper thoracic segments.

Home › Human Anatomy › White Matter of the Spinal Cord

White Matter of the Spinal Cord

Substantia alba medullae spinalis

For medical students2 min readUpdated 2026-10-10

White matter of the spinal cord (substantia alba) is the outer layer of neural tissue surrounding the gray matter. It acts as a major pathway of nerve fibers, providing bidirectional communication between different levels of the central nervous system.

CompositionMyelinated and unmyelinated fibers

CommunicationAnterior white commissure anterior to the central canal

StructureFibers organized into bundles (fasciculi)

FuniculiAnterior, lateral, and posterior funiculi

Tissue Composition and General Organization

Anatomically, white matter (substantia alba) consists of more than just neural elements. Its components include:

A system of myelinated and unmyelinated nerve fibers
Neuroglial cells
Blood vessels
A small amount of connective tissue

Nerve fibers form compact groups called fasciculi. The left and right halves of the spinal cord are not isolated from each other: their white matter is connected by a transverse structure, the anterior white commissure (commissura alba). Topographically, this commissure is located strictly anterior to the central canal of the spinal cord.

Funiculi of the Spinal Cord

Longitudinal sulci on the surface of the spinal cord (except for the posterior intermediate sulcus) act as natural boundaries, dividing the white matter of each half into exactly three funiculi (funiculi medullae spinalis):

Anterior funiculus (funiculus ventralis / anterior) — located between the anterior median fissure and the anterolateral sulcus.
Lateral funiculus (funiculus lateralis) — occupies the space between the anterolateral and posterolateral sulci.
Posterior funiculus (funiculus dorsalis / posterior) — lies between the posterolateral and posterior median sulci.

An important anatomical variation is observed in the cervical and upper thoracic segments, where the posterior funiculus is further subdivided by the posterior intermediate sulcus into two bundles: the medial fasciculus gracilis and the lateral fasciculus cuneatus.

Tracts and Propriospinal Fibers

Two main types of fibers run through the white matter:

Projection fibers (afferent and efferent) — connect the spinal cord to the brain.
Association fibers — connect segments of the spinal cord to one another.

Association fibers form the fasciculi proprii (propriospinal tracts). These are categorized into anterior, lateral, and posterior propriospinal bundles, and their defining feature is that they closely surround the gray matter on all sides.

Specific structures among the propriospinal fibers include:

Dorsolateral tract (tractus dorsolateralis / Lissauer's tract) — a small bundle lying between the apex of the posterior horn and the outer surface of the spinal cord, close to the posterior root.
Fasciculus septomarginalis — a thin bundle of descending fibers adjacent to the posterior median fissure, best developed in the lower thoracic and lumbar segments.
Fasciculus interfascicularis (semilunar fasciculus) — also composed of descending fibers, hidden in the medial part of the fasciculus cuneatus and well-identifiable in cervical and upper thoracic segments.

Mnemonic

To remember the posterior funiculus subdivision: "Gracilis is medial, cuneatus is lateral." The medial fasciculus gracilis runs closer to the midline, while the lateral fasciculus cuneatus lies lateral to it.

Frequently asked questions

What pathways run in the anterior funiculus of the spinal cord?: The anterior funiculus contains descending motor pathways. These include the tectospinal, anterior corticospinal, olivospinal, vestibulospinal, and reticulospinal tracts. These pathways primarily carry descending motor impulses from supraspinal centers to the spinal cord.
What ascending tracts run in the lateral funiculus of the spinal cord?: The lateral funiculus contains ascending sensory pathways: the anterior and lateral spinothalamic tracts, the anterior and posterior spinocerebellar tracts, and the spinotectal tract (tractus spinotectalis), which runs alongside the spinothalamic tract. The posterior spinocerebellar tract ascends along the lateral funiculus, while the anterior spinocerebellar tract ascends in the ventrolateral portion of the lateral funiculus.
What descending tracts are localized in the lateral funiculus of the spinal cord?: The lateral funiculus contains descending motor pathways, notably the lateral corticospinal tract and the rubrospinal tract (tractus rubrospinalis), located in the central region of the lateral funiculus. These tracts transmit motor commands from higher centers of the central nervous system.
What is the function of the propriospinal fibers (fasciculi proprii) of the spinal cord?: The fasciculi proprii consist of association fibers surrounding the gray matter. They link adjacent spinal cord segments with motor neurons in the anterior horns, primarily mediating intersegmental reflexes.
What components are found in white matter besides nerve fibers?: In addition to myelinated and unmyelinated nerve fibers, the white matter contains neuroglia, blood vessels, and a small amount of connective tissue.
How do the right and left halves of the white matter connect?: They are connected by the anterior white commissure (commissura alba), which is located anterior to the central canal of the spinal cord.
In which regions does the posterior funiculus divide into two bundles?: In the cervical and upper thoracic regions, where the posterior intermediate sulcus divides it into the medial fasciculus gracilis and lateral fasciculus cuneatus.
Where is the interfascicular (semilunar) fasciculus located?: It is formed by descending fibers and is located in the medial part of the fasciculus cuneatus, primarily identifiable in cervical and upper thoracic segments.

Go deeper

Topography of ascending projection fibers of the spinal cord
Topography of descending projection fibers of the spinal cord
Detailed structure of the anterior and lateral fasciculi proprii
Relationship between association fibers and the functional anatomy of gray matter