Neuroglia

Neuroglia: Non-Neuronal Cells of the Nervous System

Plan Overview of Neuroglia

In detail

Big picture

Glial Cells & Neuronal Activity Glial cells are 10 times more abundant in the mammalian brain than

neurons.

In the CNS glial cells surround most of the neurons

Glial cells furnish a microenvironment ideal for neuronal activity.

They are six and will be discussed in the following slides.

Overview

1) Oligodendrocytes

Oligodendrocytes (Gr. oligos, small, few + dendron, tree + kytos, cell)

Produce myelin sheath through their extensive processes

Predominately existent in white matter.

Their processes is not visible by light staining microscope.

2) AstrocytesAstrocytes (Gr. astron, star, + kytos)

fibrous astrocytes relatively few long processes are located in the white matter.protoplasmic astrocytes, with many short, branched processes, are found in the gray matter.

1) Support neurons2) Very important in early development 3) They form perivascular feet4) They form Glial limiting membrane5) Glial fibrillary acid protein (GFAP) is an important marker

In detail

(a): X500. Gold chloride. Cytoplasmic processes (P) cell body or soma (S).

Morphological y:fibrous (relatively few and straight processes) protoplasmic (numerous branching processes

(b): X500. Anti-GFAP immunoperoxidase and hematoxylin counterstain.

fibrous astrocyte (A) and its processes. perivascular feet (PF) at the ends of numerous astrocytic processes.

3) Ependymal Cells

low columnar or cuboidal cells.

1. Lining ventricles and spinal cord

2. Cillia for (CSF).

3. Other times microvilli for absorption

4. Joined apically by junctional complexes like epithelia

5. No basal lamina but extend to neuropil

4) Microgliaare small cells with short irregular processes

1. Migrate to neuropil to analyse and the area

2. Major mechanism of defence for CNS.

3. Their origin is not neural tube, but from circulating monocytes in blood.

epithelial-like cells that form a single layer lining the fluid-filled ventricles of (a) the cerebrum (b) the central canal of the spinal cord.

Ependymal cells

5) Schwann cells

also called neurolemmocytes,

Have trophic interactions with neurons.

One neurolemmocyte forms myelin around a segment of one axon

6) Satellite Cells of Ganglia

Form a covering layer over the large neuronal cell bodies in PNS ganglia.

trophic or supportive role, but the molecular basis of their support is poorly understood.

Glial Cell Type Origin Location Main Functions

Oligodendrocyte Neural tube Central nervous system Myelin production, electric insulation

Neurolemmocyte Neural crest Peripheral nerves Myelin production, electric insulation

Astrocyte Neural tube Central nervous system Structural support, repair processes

      Blood-brain barrier, metabolic exchanges

Ependymal cell Neural tube Central nervous system Lining cavities of central nervous system

Microglia Bone marrow Central nervous system Immune-related activity

Big Picture

Glial cell in the CNS:(a): Oligodendrocytes myelinate parts of several axons.

(b): Astrocytes have multiple processes and form perivascular feet that completely enclose all capillaries (only a few such feet are shown here to allow their morphology to be seen).

(c): Ependymal cells are epithelial-like cells that line the ventricles and central canal.

(d): Microglial cells have a protective, phagocytic, immune-related function. Glial cells in the PNS.

Glial cells in the PNS:

(e): Neurolemmocytes: commonly called Schwann cells, form a series enclosing axons.

(f): Satellite cells are restricted to ganglia where they cover and support the large neuronal cell bodies.

References Fundemental Neuroscience for Basic and Clinical Applications, 3rd Ed

Color Textbook of Histology

Janguira’s Basic Histology, 12th Ed

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(a): . X200. H&E.

(b): X200. Gold & hematoxylin.

Glia Limitans

Neuropil

Red arrow = pia mater cell; GL = glia limitans

Quiescent Microglia: Stained with silver