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RBC Senescence


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How is the Red Cell Membrane composed?

what is the most important protein, why?
it is a lipid sandwich with a matrix of proteins, of which SPECTRIN is most important - it provides flexibility.
what is the RBC lifespan?
120 days
why does the RBC require flexibility?
passes through spaces less than 3 micra in circulation, less than 0.5 micra in the spleen!
What four factors play a role in RBC membrane deformability?
-Membrane deformability
-Cell SA:Vol ratio
-Cytoplasmic viscosity
-Age-dependent changes
how does cytoplasmic viscosity affect deformability?
the more viscous, the harder the cell is.
sickled cells are crystallized cytoplasm and jam in the spleen
What are 7 decreases, 6 Increases with age that cause flexibility to decrease in RBCs?
Decreased: enzyme, K, Phospholipid, water, ATP cholesterol, MCV.

Increased: Na, cell viscosity, met-HgB, MCHC, O2 affinity, memb. bound IgG
What is RBC catabolism?
the breakdown of hemoglobin into its cellular elements
what are the 2 types of RBC catabolism?
Which is more, extra or intravascular catabolism? How much?
Where is extra?
Where is intra?
Extra - 90%. takes place in SPLEEN

Intracellular - 10%, takes place in liver after RBC ruptures in circulation
what are the 5 organs of the RES?
lymph nodes
b marrow
what are the 5 types of cells that constitue the RES?
fixed macroph
free macroph
endothelial cells lining sinusoids
circulating monocytes in blood
what are the 5 components of the spleen that make it great for RBC catabolism?
1. lymphatics - allow for self/nonself recognition.
2. Old folks home - slow/stagnate allows cells to stay a while and get fixed
3. Beauty salon - Ig get picked off, fix damaged membrane, remove inclusions
4. Nursery - retics/polychr. large cells get stuck and mature for a while.
5. Storage site - 20-30% RBCs, platelets

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