CoursesAnatomyNeuroanatomySpinal cordInternal morphology of the spinal cord

CoursesAnatomyNeuroanatomySpinal cordInternal morphology of the spinal cord

Internal morphology of the spinal cord

Learning objectives

On completion of this study unit, you will be able to:

Identify the divisions of the white and gray matter of the spinal cord.
Describe the ascending and descending tracts of the white matter.
Name and locate the nuclei of the anterior, posterior and intermediate horns of the gray matter.
Identify the laminae of the gray matter.

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The spinal cord is composed of a gray matter core which is surrounded by an outer mantle of white matter. Like in the brain, gray matter in the spinal cord is made up of neuronal cell bodies, glial cells and neuropil (unmyelinated axons, dendrites and glial cell processes), while white matter is composed of predominantly myelinated axons which form the ascending and descending tracts of the spinal cord.

The gray matter of the spinal cord can be divided functionally into three main regions: the anterior, posterior and lateral (intermediate) horns (the latter of which is only present in the thoracic and upper lumbar regions). The anterior horn is largely responsible for motor function, the posterior horn for sensory function and the intermediate horn for autonomic (sympathetic) functions.

The gray matter of the spinal cord can also be divided into ten layers or laminae (of Rexed) on the basis of its cytoarchitecture rather than location and function of the cells. The Rexed laminae are numbered sequentially (I-X) from posterior to anterior .

White matter marks the outer portion of the spinal cord, and is divided into three paired columns: the posterior, lateral, and anterior funiculi. The funiculi of the spinal cord are composed of longitudinally arranged nerve fibers which are bundled together into tracts (fasciculi). There are three main types of tracts, divided by their direction and function: ascending, which transmit sensory information, descending, which transmit motor information and intersegmental/propriospinal, which transmit information between spinal cord segments.

Find out more about the structures of the white and gray matter of the spinal cord with the videos below.

Explore structures of the white matter next!

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Take a closer look at the structures of the gray and white matter in the galleries below.

Summary

Key points about the gray matter of the spinal cord
Divisions	Anterior, posterior and intermediate (lateral) horns
Posterior horn	Marginal nucleus (Rexed lamina I) Gelatinous substance (Rexed lamina II) Nucleus proprius (Rexed laminae III, IV, V) Posterior thoracic nucleus (Rexed lamina VII) Function: Sensory innervation
Lateral horn	Intermediolateral nuclei (Rexed lamina VII) Function: Sympathetic innervation
Anterior horn	Medial group (Rexed lamina IX) Central group (Rexed lamina IX) Lateral group (Rexed lamina IX) Function: Motor innervation
Pericentral canal	Gray commissure (Rexed lamina X) Function: Connects anterior and posterior horns of gray matter

Key points about the white matter of the spinal cord
Divisions	Anterior, posterior and lateral funiculi
Tracts	Ascending, descending and intersegmental tracts (fasciculi)
Ascending tracts	Anterolateral system: Spinothalamic, spinoreticular, and spinoolivary tract Posterior column-medial lemniscus pathway: Cuneate and gracile fasciculus Somatosensory pathways to the cerebellum: Anterior and posterior spinocerebellar tract Functions: Transmit conscious and unconscious sensory information specific to pain, temperature, touch, pressure, vibration and proprioception
Descending tracts	Pyramidal tracts: Anterior and lateral corticospinal tract Extrapyramidal tracts: Tectospinal, medial reticulospinal, vestibulospinal, lateral reticulospinal and rubrospinal tract Functions: Transmit voluntary and involuntary motor information
Intersegmental tracts	Posterolateral tract (ascending and descending), medial longitudinal fasciculus (ascending and descending), septomarginal fasciculus (descending), interfascicular fasciculus (descending) Functions: Interconnect neurons at different spinal segments, transmit autonomic functions

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