glia

types of vertebrate glial cells

astroglia, microglia, oligodendroglia and schwann cell

astroglia look and function

star-shaped and symmetrical.

Nutritive and support function

microglia appearance and function

small, mesodermally derived

defensive function

oligodendroglia appearance and function

asymmetrical

form myelin around axons in brain and spinal cord CNS

schwann cell appearance and function

asymmetrical

wraps around peripheral nerves to form myelin PNS

radical glia

·Embryonic scaffold throughout CNS

·Guides for radial migration of neurons

·Produce matrix and adhesion proteins

in adults- it persists in cerebellum (bergmann glia) and in retina (muller cells)

ependymal cells

-line central canal and ventricles of the brain

-cuboidal cells but have no basement membrane

-have beating cilia when lining the ventricles

-specialized ependymal cells participate in the secretion of Cerebral Spinal Fluid (CSF)

origin of neurons, astrocytes and oligodendrocytes

from neural tube

origin of schwann cells

neural crest

origin of microglia

derived from macrophages

gliogenesis

no microglia or schwann cells

how does microglia develop

evidence for the monocytic origin of microglia

•Bone marrow chimeras show that the brain becomes populated by donor specific cells of the haemopoietic origin

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•Exogenously labelled monocytes enter the developing CNS and immunocytochemical studies show the changes in morphology as monocytes transform to microglia.

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•Microglia share many cell surface and cytoplasmic antigens exclusively restricted to macrophages

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Immunocytochemical studies of transplanted CNS tissue show that the transplanted CNS tissue becomes populated by microglia bearing host specific makers for myelomonocytic cells

types of microglia

ameboid and ramified

ameboid

•Round cells - clustered, found in development. Develop in cultures of glia derived from neonatal brain. Concentrated in the corpus collosum. Proliferate.

ramified

•Adult form found in the brain - having numerous, fine processes. Found throughout the brain - “resting”. Don’t proliferate when resting

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