properties of the vascular system Flashcards
two main functions of capillaries
solute exchange and fluid exchange
mechanism by which solutes are exchanged
diffusion due to concentration gradients across wall
diffusion obeys which law
Fick’s law
mechanism by which fluid is exchanged
bulk flow due to pressure gradients across the wall
bulk flow obeys which law
starling’s principle
explain starling’s principle
flow is affected by plasma protein osmotic pressure as well as hydraulic pressure
why does starling’s law apply to capillaries ?
they are permeable to water and small solutes
relatively impermeable to plasma proteins
what are the four starling forces?
hydrostatic pressure in capillary and interstitial
oncotic pressure in capillary and interstitial
flow at rest
5000ml/min
distribution of cardiac output at rest
brain- 650ml, 13%
heart- 215ml, 4%
skeletal muscle- 1030, 20%
skin- 430ml, 9%
kidneys- 950ml- 20%
abdominal organs- 1200ml, 24%
other- 525ml, 10%
cardiac output distribution exercise
brain- 750ml, 4%
heart- 750ml, 4%
muscle- 12,500ml 73%
skin- 1900, 11%
kidneys- 600ml, 3%
abdominal organs- 600, 3%
other- 400ml, 2%
cardiac output during exercise
17,500 ml/min
blood flow definition
refers to the movement of blood through vessels
pressure definition
a measure of the force that the blood exerts against the vessel walls
which direction does blood flow in?
Along a decreasing pressure gradient, from arteries to capillaries to veins
link between velocity of blood flow and cross sectional area
velocity of blood flow varies inversely with the total cross sectional area of blood vessels
as the total cross sectional area of vessels increases, the velocity of flow decreases
where is blood flow slowest? + benefit
slowest in capillaries, allows time for exchange
resistance definition
force that opposes the flow of a fluid
in blood vessels, what causes most of the resistance?
vessel diamater
link between blood flow, diameter and resistance
as the diameter decreases, the resistance increases and the blood flow decreases
difference between flow rate and velocity
velocity is the speed
flow rate is the volume of fluid passing through an area
how else can flow rate be increased?
increasing the diameter
viscosity definition
the thickness of fluids that affects their ability to flow
viscosity relationship with resistance and flow
directly proportional to resistance
inversely proportional to flow
the thicker the blood, the slower the flow, the greater the resistance
anomalous viscosity of blood explained
red blood cells can deform and aggregate, thus viscosity of blood can vary with sheer rate
blood becomes less viscous at high rates, as the blood cells aggregate
