Glial Cells and Misc. Nervous Tissue Histology

Type of Cell given below, give embryonic origin: microglia

mesoderm!

Type of Cell given below, give embryonic origin: Schwann cells Dorsal root ganglia Autonomic ganglia

neural CREST

Type of Cell given below, give embryonic origin: Neuroblasts/neurons Glioblast/glia → astrocyte and oligodendroglia Ependymal cells

neural PLATE (neuroepithelium)

With greater _______ and greater ________, there is a greater conduction velocity along that axon

Thickness of myelin sheath AND greater distance between nodes.

What is the glial cell of the retina called?

a Muller cell embryonic origin = neural plate??

Ependymal cells (CNS)

-*filter the blood to form cerebrospinal fluid!!!* -line the lumen of the CNS - e.g. The brain ventricles and the central canal of the spinal cord -*THEY ARE SIMPLE CUBOIDAL OR COLUMNAR CELLS WITH APICAL CILIA* -long processes, intimately associated with astrocytes -these cells are remnants of the peripheral epithelium.

Astrocytes (CNS); 2 types!

-have numerous processes radiating from cell body; LOOK LIKE A STAR -*their role is to create and maintain boundaries and/or compartments in the CNS* -often associated with blood vessels; may regulate passage of materials in blood to the brain ...*help form the BBB* -can detect infection and call over microglia -form processes on edge of CNS at brain and spinal cord = *glia limitans* Types 1. Fibrous astrocytes: many thinner processes, found in WHITE matter 2. Protoplasmic astrocytes: many thicker processes, found in GREY matter

Myelin sheath (both PNS and CNS) components

-multiple layers of membrane wrapped around axon -has tight junctions: between Schwann cell membrane and axonal membrane to prevent unwanted ion flux -Schmidt-lantermann incisures (clefts): little pockets of Schwann cell cytoplasm that nourish and maintain the myelin

Oligodendroglial cell picture 3

-note: cell body is very rounded, processes aren't super thick

Microglia (CNS)

-phagocytes of the CNS -*derived from mesoderm* -part of the mononuclear phagocyte system -move actively about in CNS, searching for diseased or forming cells -have irregular shape reflective of their mobility and their elongated, *heterochromatic nuclei!!!*

Oligodendroglia cells (CNS)

-produce myelin for the CNS -*each oligodendroglia typically myelinates numerous processes - both dendrites and axons, on several different neurons* --> major difference between them and Schwann cells. Each oligodendroglia has multiple arms that reach out to myelinate, Schwann cells only do one at a time.

Schwann cells (PNS)

Myelin producing cells of the PNS; *derived from migratory neural crest cells.* Schwann cells are arranged end to end like sausages on a spit. Schwann cell membrane cover the axon, insulating it from the ECF around the axon --> insulates enough so that depolarization/AP can jump from node to node (on the *nodes of ranvier)* = *saltatory conduction* Are closely associated with bundles of unmyelinated nerve fibers.

Histology of the dorsal horn/spinal cord!!! KNOW

NOTE: the dorsal root ganglion is a neural crest derivative AND IT CONTAINS PSEUDOUNIPOLAR NEURONS!!!

Ependymal cells picture 2

Note: opening is the neural tube!! There are cilia inside there to help move the CSF secreted by the ependymal fluid around! Cell type = either simple cuboidal or simple columnar

Satellite cells (PNS)

Small glia that form halo around various neurons in the PNS; functionally isolate individual neurons; present around dorsal root ganglia, parasympathetic ganglia, and neurons that innervated the gut tube. Functions may also include to nourish the neuron and provide cushioning or protection