Principles Ofhaemodynamics Flashcards
What is haemodynamics
How your blood flows ,
Relationship bwteen blood flow, blood pressure, resistance to flow
Darcys law
Role of pressure energy in flow
Flow = P1-P2/R
P1-P2 means pressure difference
R is resistance to flow
Bernoullis law
Role of pressure, kinetic and potential energies in flow
Flow = pressure + kinetic + potential
What is perfusion
Blood flow per given mass of tissue
(Ml/min/g)
Velocity of blood flow
Blood flow affected by cross sectional area though which the blood flows so flow may remain the same but velocity changes if there has been a change to the cross sectional area
What are the three patterns of blood flow
Laminar
Turbulent
Bolus
Describe the laminar blood flow
-found in most arteries, arterioles, venules, veins
-concentric shells
-zero velocity at walls
-maximum velocity at centre
- moves rbc towards centre
Speeds blood flow through narrow vessels
describe the turbulent blood flow
-blood does not flow linearly and smoothly in adjacent layers
-high resistance to flow
-occurs in ventricles when it is mixing
-occurs in aorta at peak flow
describe the bolus blood flow pattern
-capillaries are smaller diamater than RBCs so they move in a single file
-uniform velocity
-little internal friction
-very low resistance
what determines the change from laminar to turbulent flow
reynolds number
when does turbulence occur
when reynolds number exceeds 2000
equation for reynolds number
density x velocity x diameter all divided by viscosity
