Glial Cells

Microglia - book caption

Microglia are phagocytic cells within the CNS.

Satellite Cells - book caption

Neuron cell bodies within ganglia (clusters of cell bodies in the PNS) are surrounded by satellite cells.

Ependymal Cells - book caption

*Ciliated ependymal cells lining the ventricles of the brain and the central canal of the spinal cord help move cerebrospinal fluid. *Ependymal cells of the surface of of the choroid plexus secrete cerebrospinal fluid.

Oligodendrocytes - book caption

*Extensions from oligodendrocytes form part of the myelin sheaths of several axons within the CNS

Astrocytes - Function

*Play a role in regulating the extracellular composition of brain fluid *Release chemicals that promote the formation of tight junctions between the endothelial cells of capillaries -These endothelial cells and tight junctions form the blood-brain barrier *Reactive astrocytosis - Respond to tissue damage in the CNS -In response to injuries of CNS tissue, astrocytes participate in walling off the injury site and limiting the spread of inflammation into healthy tissue -Reactive scar-forming astrocytes also limit the regeneration of the axons of injured neurons *Release chemicals that promote development of synapses *Assistance in the regulation of synaptic activity via the synthesis, absorption and recycling of neurotransmitters

Schwann Cells - book caption

*Schwann cells form the myelin sheath of an axon within the PNS

Ependymal Cells - function

*Specialized ependymal cells and blood vessels form the choroid plexuses -These are located within certain regions of the ventricles -The choroid plexuses secrete cerebrospinal fluid *Use cilia to keep cerebrospinal fluid moving throughout brain cavities

Microglia - appearance and function

*A glial cell of the CNS *Become mobile and phagocytic in response to inflammation -Phagocytize necrotic tissue, microorganisms and foreign substances that invade the CNS *Microglia and Brain Damage: -Numerous microglia migrate to areas damaged by infection, trauma or stroke to perform phagocytosis -A pathologist can identify these damaged areas in the CNS during an autopsy because of the large number of microglia are found in them

Oligodendrocytes - appearance and function

*A glial cell of the CNS *Have cytoplasmic extensions off of the cell body. *These cytoplasmic extensions can surround an axon *If the cytoplasmic extension wraps many times around the axon a myelin sheath forms *A single oligodendrocyte can form myelin sheaths around portions of several axons

Ependymal Cells - appearance

*A glial cell of the CNS *Line the ventricles of the brain and the central canal of the spinal cord *The free surface frequently have patches of cilia that help move cerebrospinal fluid through brain cavities *The basal surface has long processes that extend deep into the brain and spinal cord

Astrocytes - Appearance

*A glial cell of the CNS *Star shaped because of cytoplasmic processes that extend from the cell body *These extensions widen and spread out to form foot processes *Foot processes cover the surfaces of blood vessels, neurons and pia mater (membrane covering the outside of the brain and spinal cord) *Also have an extensive network of cytoskeleton microfilaments to form a supporting framework

Astrocytes - book caption

Astrocyte processes form foot processes, which cover the surface of neurons, blood vessels, and the pia mater. The astrocytes provide structural support and play a role in regulating what substances from the blood reach the neurons.

Satellite Cells - appearance and function

A. Satellite Cells *A glial cell of the PNS *Surround neuron cell bodies in sensory ganglia *Provide support and nutrition to the neuron cell bodies *Protect neurons from heavy metal poisons, such as lead and mercury, by absorbing the metals and reducing their access to the neuron cell bodies.

Schwanns Cells - appearance and function

B. Schwann Cells *A glial cell of the PNS *Glial cells in the PNS that wrap around axons *If it wraps many times around an axon, a myelin sheath is formed *Can only form part of the myelin sheath around one axon (unlike oligodendrocytes that can be around portions of multiple axons)