Page 100 - Headlines Histology2024_Neat

• The gray matter consists mainly of neuron cell bodied while the white
matter consists of bundles of myelinated and non-myelinated axons. Lipid
in the myelin sheaths of the axons gives the white appearance of the white
matter.

Spinal cord

• In cross section, the gray matter is located centrally taking a butterfly or H-
shape. A central canal containing cerebrospinal fluid and lined by
epindymal cells lies in the center of gray matter.

• The H-shaped gray matter has two dorsal horns; two ventral horns and two
lateral horns. The ventral horns are more prominent and contain the cell
bodies of large motor neurons. The dorsal horns are much less prominent
and contain the cell bodies of small sensory neurons. The lateral horns in
the thoracic and lumber regions contain the cell bodies of preganglionic,
sympathetic efferent neurons.

• The cervical and lumber regions of the spinal cord have a much greater
diameter with a much more extensive gray matter volume. These regions
give the extensive sensory and motor innervation of the fore and hind limbs.

• The white matter of the spinal cord is located peripherally around the gray
matter. It consists of ascending (sensory) and descending (motor) tracts.
The volume of the white matter increases from the sacral to cervical region.
Externally, the white matter is divided bilaterally by deep ventral median
fissure and dorsal median septum.

• On each side, a dorso-lateral sulcus marks the line of entry of the dorsal
nerve roots. The site of exit of the ventral nerve roots is also marked by two
ventrolateral sulci.

• The triangular area of the white matter between the dorsal horns represents
the ascending dorsal columns that convey fibers for the senses of vibration,
proprioception and touch to the brain.

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