L8 -rheology Flashcards
what is blood rheology
deals with deformation and flow of matter so it’s about blood flow
function of blood
transport stuff like gases, heat, nutriients, metabolites, signals and immune system
constituents of blood
plasma, buffy coat (white blood cells and platelets) and RBCs
structure and features of RBCs
biconcave disc
- has no nucleus
- has plasma membrane supported by spectrin (a protein network)
- adapted for transport, viscosity and deformability
how does the structure of a small artery affect the flow of blood
the area is greater than the diameter of the RBCs so it can flow freely
how does the structure of an arteriole affect the flow of blood
RBCs flowing in the column like structure
how does the structure of a capillary affect the flow of blood
the cells deform so it can fit through
how does the poiseuille’s law relate to blood flow
the vel of the blood in the centre is the highest but decreases as it get nearer to the edge so this is laminar flow
what is resistance proportional to in terms of blood flow in vessels and poiseulle’s law
viscosity so the more viscous the blood, the higher the resistance
what affects the resistance of the blood in a large vessel
blood viscosity
what affects the resistance of the blood in a small vessel
plasma viscosity and the cellular properties of the RBCs
factors controlling viscosity
haematocrit and plasma viscosity
what is haematocrit
-ratio of RBCs to total vol of blood so around 40-45% of vol of RBCs
how does haematocrit affect viscosity
as the haematocrit increases, the viscosity increases
- oxygen flux increases for a given pressure
- but if the viscosity is too great, the resistance becomes too great and this impedes the flow
what is plasma viscosity
conc of other stuff like proteins, ABs, WBCs
how does plasma viscosity affect the blood viscosity
if the plasma viscosity increases maybe due to an immune response , the blood viscosity increases too
-but If the viscosity is too great, the resistance is too great and this impedes the blood flow
how does the RBC deform and aggregate in high flow condition
- becomes more spindle-shaped to align with the flow
- less aggregation
how does the RBC deform and aggregate in low flow condition
-the cells become more stuck together and they aggregate which is mediated by plasma proteins like fibronogen
what happens to WBC and platelets when there is RBC aggregation in the blood vessel
get pushed towards to the edge of the flow so they can exit to the site of inflammation
what blood vessel is most similar to the size of the RBC
capillary so the cells deform and squeeze through the vessel
when does traffic jam of RBC occur in the vessel
where there is or are WBCs moving in front as it is larger than the RBCs and closer to the size of the capillary or a vessel
what happens to the shape of WBC when they get activated
spherical normally but deforms once activated due to bacterial infection
factors affecting the deformation and circulation of WBC and RBCs
cell geometry, membrane deformability and cytoplasm and viscosity
describe the effect of the cell geometry on the deformation and circulation of WBC and RBCs
- the larger the size, the larger the degree of deformation is needed so for WBCs, it’s larger than RBC
- SA:V - WBC spherical so it’s easier to deform and for RBC, It can shape w/o changing its shape
describe the effect of the membrane deformability on the deformation and circulation of WBC and RBCs
- where it’s resistant to deformation) so RBC can change shape w/o being damaged)
- and disruption (having membrane skeleton provides stability)
what is spectrin
- protein network supporting the RBC membrane so ti can deform
- stretches due to its coil structure then recoil
features of RBC membrane
- can control the cell shape
- flexible
- stable so withstand flow stress
- have pumps and transportes to regulate haemoglobin vol and haemeostasis contents
types of blood cells
RBC, WBC, platelets
what blood cells can adhere and cant adhere to the vessel wall
RBC- doesnt
WBC-adhere for immune response
-platelets - adhere for clotting
steps in WBC adhesion and migration along the wall
- in contact with the vessel wall
- captured and rolls along the wall by help of selectins
- stops due to integrin activation
- spreads along the vessel wall
- migrate over the endothelium
- move into the gap of the wall
- then now in or under the vessel
the blood flow is fast, how is wbc caught when it’s travelling fast too
-adhering causes the cells to slow down
how is adhesion stabilised
with integrin activation
