Page 90 - Headlines Histology2024_Neat

• Regulate the composition of the intercellular environment of the CNS. It
takes up excess potassium when these escape from neurons during impulse
conduction.

• Mediate the exchanges of nutrients and metabolites between neurons and
the blood.

• Forms diffusion barriers surrounding synapses.
• Phagocytosis.
• Scar tissue formation (gliosis) during the CNS injury.
Microglia

• They are small cells evenly distributed in gray and white matter.
• They have little cytoplasm with fine highly branched processes. The nuclei are

small, elongated and chromatophilic.
• They are derived from the mesoderm. In normal tissue, the cells are sparse and

difficult to found. In response to tissue damage, microglia transfer into large
amoeboid phagocytic cells by which necrotic tissue is cleared away prior to
gliosis.
• In cases of CNS damage, several cell types may become phagocytic such as
microglia, astrocytes, oligodendroglia, pericytes and blood macrophages.
Ependymal cells

• Ependymal cells line the ventricles of the brain and the central canal of the
spinal cord. They have a cuboidal or columnar shape and are tightly bound
together at their luminal surfaces by zonulae adherents.

• Unlike the epithelia, these cells do not rest on a basement membrane.
• The cell bases from fine processes that interdigitate with the underlying layer

formed by the processes of astrocytes.
• Their luminal surfaces have cilia and microvilli.
Function

• Production of cerebrospinal fluid.

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