Glial Cells Diagram – Astrocyte, Oligodendrocyte, Microglia

All 8 parts on the diagram

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Start here: the 4 glial cells and myelin 5

Astrocyte An astrocyte: a star-shaped glial cell whose processes touch neurons and capillaries. It supports neurons, keeps the fluid around them balanced and helps form the blood-brain barrier.
Oligodendrocyte A glial cell whose processes wrap segments of axons in myelin. One oligodendrocyte can myelinate several axon segments.
Myelin sheath Layers of glial cell membrane wrapped round an axon segment. They insulate it so signals travel faster.
Microglia Small glial cells that act as the nervous system’s resident immune cells. They clear debris and germs.
Ependymal cells Glial cells lining the ventricles, with cilia. In the choroid plexus they filter blood to make cerebrospinal fluid.

Other 3

Neuron The neuron, the nerve cell that the glial cells support.
Capillary The astrocytes’ end feet on it are part of the blood-brain barrier. The barrier controls what passes from the blood into the brain.
Ventricle One of the fluid-filled spaces in the brain. It is full of cerebrospinal fluid.

How this list was compiled: Read 2026-09-27. OpenStax, Anatomy and Physiology 2e, section 12.2 Nervous Tissue, https://openstax.org/books/anatomy-and-physiology-2e/pages/12-2-nervous-tissue : the CNS glia are astrocytes, oligodendrocytes, microglia and ependymal cells (the PNS has satellite cells and Schwann cells); astrocytes are star-shaped with many processes, support neurons, maintain the chemistry of the extracellular space and contribute to the blood-brain barrier; an oligodendrocyte insulates axons with myelin and one can myelinate several axon segments; myelin is a lipid-rich sheath of wrapped glial membrane; microglia are smaller, the CNS-resident macrophages; ependymal cells line each ventricle and, at the choroid plexus, filter blood to make cerebrospinal fluid. Licence: own work

The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

How it works

Asked to label the glial cells in the CNS? This diagram shows all four kinds in one patch of brain tissue, round a neuron, a capillary and a ventricle. Start with the 5 main parts.

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Support and insulation

Star-shaped astrocytes support neurons and reach out to capillaries, helping form the blood-brain barrier. Oligodendrocytes wrap segments of axons in a myelin sheath, and one oligodendrocyte can wrap several segments.

Defence and fluid

Microglia are small cells that act as the brain's own immune cells. Ependymal cells line the ventricles, the fluid-filled spaces, and help make the cerebrospinal fluid in them.

Outside the brain and spinal cord the jobs are shared differently: Schwann cells make the myelin and satellite cells give support.

Questions and answers

What are the four glial cells of the CNS?

Astrocytes, oligodendrocytes, microglia and ependymal cells. The peripheral nervous system has two others, Schwann cells and satellite cells.

What is the difference between an oligodendrocyte and a Schwann cell?

Both make myelin. An oligodendrocyte, in the brain and spinal cord, reaches out to several axon segments; a Schwann cell, in the rest of the body, wraps just one.

What do astrocytes do?

They support neurons, keep the chemistry of the fluid around them balanced, clear away excess signalling molecules, react to damage and help form the blood-brain barrier.