flow and pressure Flashcards
describe difference in pulmonary and systemic circulation
pulm: low resistance and pressure - 16mmHg. in series with systemic
systemic: high resistance and pressure - 92mmHg. in parallel with each other
amount of venous return into hear
5L/minequal to CO
what is the flow out of heart (per beat and per min) and a corresponding eqn
per beat = stroke volume = 50mls
per min = CO = 5L/min
CO=SV x HR
what determines filling of heart
central venous pressure.
filling pressure aka preload
what is resistance to flow and what does this affect
TPR
determines pressure load on left of heart - afterload
what are the ways of movement of substances in blood and to cells
1) bulk flow: transport within blood or air due to pressure differnces
2) passe diffusion - doen conc gradient
what is Fick’s law of diffusion and what does it depend on
rate of diffusion in solution.
A=area where diffusion occurs
C=diffusion in concn. of diffusing substance
x=distance over which it has to travel
what is ease of diffusion of substance affected by
temp
solubility of substance
the square root of molecular weight of the substance
why is fick’s law important
diffusion proportional to C and permeability.
diffusion too slow over large distance => flow required transport substances around body
what is the law of flow / Darcy’s law
flow proportional to pressure difference and inversely proportional to resistance to flow
principle for flow in tubes
change in diameter causes large change in resistance and therefore flow (4th power)
flow is inversely proportionate to r^4
what is poiseuille’s law
R = (8VL)/(pi.r4)
r=radius of tube
V=viscosity of fluid
L=length of tube
describe the type of flow in tubes
laminar flow.
vicious drag at the sides slows, fastest in the middle.
cells align in middle - Axial streaming.
what is the Fåhraeus-Lindqvist effect
axial streaming in small vessels reduces viscosity
diameter of capillaries and a rBC
RBC- 7um
capillaries 6um
