Spinal cord gray matter: structure, horns, and nuclei

Q: In which segments of the spinal cord are lateral horns present?

Lateral horns (cornu laterale) are not present throughout the entire length of the spinal cord, but only at the level of all thoracic and upper lumbar segments (from T₁ to L₃). Anatomically, they appear as small paired protrusions localized in the intermediate zone between the anterior and posterior horns. The functional significance of these structures lies in the fact that they contain the central part of the sympathetic nervous system.

Q: Which Rexed laminae correspond to the nuclei of the spinal cord grey matter?

The nuclei of the spinal cord gray matter correspond to ten vertically arranged Rexed laminae, which represent columns of neurons. Topographically, they are distributed as follows: - Laminae I–V — posterior horns - Laminae VI–VII — intermediate zone - Laminae VIII–IX — anterior horns - Lamina X — area surrounding the central canal

General structure and central canal

Unlike the white matter, which is located peripherally and consists of conduction pathways, the grey matter lies strictly in the center of the spinal cord. Its tissue basis is formed by neuronal cell bodies, nerve cell processes (lacking a myelin sheath), neuroglial elements, and blood vessels.

In the very center of the grey matter lies the central intermediate (grey) substance (substantia (grisea) intermedia centralis). Passing through its thickness is the central canal (canalis centralis). This canal runs along the entire length of the spinal cord:

In its upper part, it opens into the cavity of the fourth ventricle of the brain.
In the lower part (in the region of the medullary conus), the canal widens.
Throughout its entire length, the canal is surrounded by a specialized central gelatinous substance (substantia gelatinosa centralis).

Spatial organization: grey columns and horns

Projections of grey matter running along the spinal cord form volumetric structures — grey columns. On a transverse section, these columns form the so-called horns.

Three main divisions are distinguished:

Anterior column (columna ventralis / anterior). On cross-section, it forms the anterior horn (cornu ventrale / anterius). This is a broad structure that does not reach the outer surface of the spinal cord.
Posterior column (columna dorsalis / posterior). On cross-section, it forms the posterior horn (cornu dorsale / posterius). Unlike the anterior one, it is narrow, long, and reaches the outer surface. The structure of the posterior horn distinguishes three parts: the apex, neck, and base.
Lateral column (columna lateralis). It forms the lateral horn (cornu laterale), which is predominantly expressed in the thoracic segments.

A special zone is located between the lateral horn and the lateral margin of the posterior horn. Here, the grey matter penetrates into the thickness of the white matter, forming the reticular formation of the spinal cord (formatio reticularis).

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Nuclei of the spinal cord grey matter

Neurons of the grey matter are not scattered haphazardly, but are grouped into nuclei with a strict and constant topography. Depending on their localization in a specific column, these nuclei perform various functions: motor, sensory, or autonomic.

Nuclei of the anterior column (motor)

Nucleus name	Latin term	Localization (segments)
Anterolateral	nucleus ventrolateralis	CIV–CVIII and LII–SI
Anteriomedial	nucleus ventromedialis	CII–LIV
Posterolateral	nucleus dorsolateralis	CV–CVIII and LIII–SII
Posteromedial	nucleus dorsomedialis	CI–SII
Central	nucleus centralis	ThI–LIII (sometimes SI–SV)
Accessory nerve nucleus	nucleus nervi accessorii	CI–CVI
Phrenic nerve nucleus	nucleus nervi phrenici	CIV–CVII
Lumbar dorsal	nucleus lumbodorsalis	LIII–SI

Sensory and autonomic nuclei

In the posterior and lateral columns are centers responsible for the perception of sensation and autonomic regulation of body functions.

Nuclei of the posterior column (sensory)

Three key structures are distinguished here:

Substantia gelatinosa (substantia gelatinosa);
Proper nucleus of the posterior horn (nucleus proprius cornus posterioris);
Secondary visceral substance (substantia visceralis secundaria).

Nuclei of the lateral column (autonomic)

These nuclei are localized predominantly in the thoracic and sacral regions:

Thoracic nucleus (nucleus thoracicus) — lies in segments ThI–LII.
Central intermediate substance (substantia intermedia centralis).
Lateral intermediate substance (substantia intermedia lateralis).
Sacral parasympathetic nuclei (nuclei parasympathici sacrales) — located in segments SII–SIV.

Briefly: answers to topical questions

In which segments of the spinal cord are lateral horns present?

Lateral horns (cornu laterale) are not present throughout the entire length of the spinal cord, but only at the level of all thoracic and upper lumbar segments (from T₁ to L₃). Anatomically, they represent small paired projections localized in the intermediate zone between the anterior and posterior horns. The functional significance of these structures lies in the fact that they contain the central part of the sympathetic nervous system.

Which Rexed laminae correspond to the nuclei of the spinal cord grey matter?

The nuclei of the spinal cord grey matter correspond to ten vertically arranged Rexed laminae, which represent columns of neurons. Topographically, they are distributed as follows:

Laminae I–V — posterior horns
Laminae VI–VII — intermediate zone
Laminae VIII–IX — anterior horns
Lamina X — area around the central canal

How to memorize

Remembering the functional distribution of nuclei by columns is simple: Anterior — Motor, Posterior — Sensory, Lateral — Autonomic.

Class and exam questions

What is the main difference between the anterior and posterior horns on a transverse section?

The anterior horn is wide and massive; it does not reach the surface of the spinal cord. The posterior horn is narrow, long, and reaches the outer surface.

Where is the central canal located and where does it open into?

The central canal runs within the thickness of the central intermediate grey substance along the entire length of the spinal cord. Above, it opens into the cavity of the fourth ventricle.

What is the spinal cord reticular formation?

This is a structure formed where the gray matter extends into the white matter, intertwining in a net-like fashion. It is located between the lateral horn and the lateral margin of the posterior horn.

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What else to study on this topic

Topography and functions of the motor nuclei of the anterior horns
Structure of the posterior horn: apex, neck, and base
Autonomic nuclei of the lateral funiculi and the parasympathetic nervous system
Neuronal composition and neuroglia of the gray matter

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Spinal cord gray matter