schwann cells powerpoint

7/27/2019 Schwann Cells Powerpoint

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By Emily C, Grace G, Abigail M and Liam T


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Oligodendrocyte Development Germinal layer, here all cells can divide

Some cells lose the ability to divide and detach from thegerminal layer

Move outward to form a new layer = Intermediate/mantlelayer

Germinal layer is now the ventricular layer

Cells in the intermediate layer differentiate either to

neurons or glia through local signals (sonic hedgehog) Neurons send projections outwards and some glial cells

will move out and wrap around axons, forming myelination(white matter) This is in the mantle zone.


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Oligodendrocytes


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Schwann Cell Development Derived from neural crest cells which migrate

peripherally.

Neural Crest cells become Schwann cell precursors,

(the mechanism for which is unknown) at aroundembryonic day 14-15

At day 15-17 they become Immature Schwann cells

These steps are reversible

The immature Schwann cells fate is determined by theaxon on which they wrap around only those aroundlarge diameter axons will be myelinating Schwanncells.


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Schwann Cell

http://www.nature.com/nrn/journal/v6/n9/images/nrn1746-f1.jpg


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Differences

http://blustein.tripod.com/Oligodendrocytes/08-zoom.jpghttp://faculty.southwest.tn.edu/rburkett/_derived/A&P1_nervous_system_lab.htm_txt_AP1_N4.gif

Schwann Cells Oligodendrocytes

PNS CNS

Form around one axon Form around multiple axons

SCP Oligodendroblasts


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Function-Myelin Sheath Formation

In PNS Nerve bundle invaded by Schwann cells

Multiply rapidly, segregating individual axons.

Axons with large diameter, undergo myelination.

Plasmalemmma of the Schwann cell forms a doublemembrane structure, by wrapping around axon.

Cytoplasmic surfaces then condense into myelin

sheath.


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In CNS

Cytoplasmic loop on end of mesaxon

Loop` is restricted to small portion of sheath. Beleived that internode, diameter of axon and number

of myelin layers all increase at the same time.

But the process is still understood poorly.


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DiseaseDemyelinating Dysmyelinating

Multiple Sclerosis Progressive multifocal

leukoencephalopathy

(Trauma)

Leukodystrophy Schizophrenia


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Leukodystrophies Genetic disorders that cause damage to white matter.

Autosomal recessive

Resulting from the loss of function of myelin

producing enzymes.


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Metachromatic leukodystrophy Found in 1 in 40,000 people

Deficiency in arylsulfatase-A enzyme

Picture from page 584 of molecular pathology


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Multiple SclerosisVariety of disorders

Remission and relapse orprogressive form of the

disease

Immune damage to myelin

Geographical factors

Causes lesions in whitematter

http://special.lib.gla.ac.uk/exhibns/month/oct2003.htmlhttp://upload.wikimedia.org/wikipedia/commons/6/6c/Monthly_multiple_sclerosis_anim_cropped_no_text.gif


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Autoimmunity hypothesis slide. Picture from page 585 of molecular pathology


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Progressive multifocal leukoencephalopathyAn example of infectious demyelination

Caused by the JC virus

Virus found in 40% of people without symptoms Disease arises in immunocomprimised pateints

http://archneur.jamanetwork.com/article.aspx?articleid=783327


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Referenceshttp://www.nature.com/nrn/journal/v6/n9/box/nrn1746_BX1.html

http://ghr.nlm.nih.gov/condition/metachromatic-leukodystrophy

http://ac.els-cdn.com/S0092867400800938/1-s2.0-S0092867400800938-main.pdf?_tid=8bf26afa-5168-11e3-a58c-00000aacb35e&acdnat=1384899701_d849c55c0ef26b5d323efdd86d4afbc3

http://ghr.nlm.nih.gov/condition/metachromatic-leukodystrophy

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3029296/

http://www.sciencedirect.com/science/article/pii/S0301008202000588

http://www.ncbi.nlm.nih.gov/books/NBK27954/

http://www.nature.com/nrn/journal/v6/n9/full/nrn1746.html

http://www.sciencedirect.com/science/article/pii/S0301008202000588

http://newsatjama.jama.com/2012/01/23/fda-approves-test-to-assess-risk-of-deadly-viral-illness-linked-to-natalizumab/
http://www.nature.com/nrn/journal/v6/n9/box/nrn1746_BX1.html


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