3. Physiology
        3.2. Cardiovascular
            3.2.3. Peripheral circulation
3.2.3.1. Haemodynamics

Hemodynamics

See Flow for more details on Hagen-Poiseuille's law and laminar vs turbulent flow.

Laminar flow

Flow = pressure / resistance

Resistance = 8nl/r4pi

Resistance is proportional to viscosity, not density.

 

Turbulent flow

Resistance is proportional to flow.

Resistance is proportional to density, not viscosity

 

Haematocrit

Apparent viscosity varies with haematocrit ratio.

Haematocrit decreases progressively as vessel diameters reduces below 300 micrometer.
--> RBCs tend to accumulate in the faster axial stream of blood
--> RBCs moves at greater speed in axial stream
--> Relative haematocrit ratio decreased
--> Apparent viscosity decreased
* [BL8:p129]

Also, when flow decreases, cells tend to aggregate and increase viscosity.

When flow increases, viscosity decreases
--> "shear thinning"

Note:

A few points to note

Functional cardiac murmur in anaema is due to:

 

 

 

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