Pressure/ Blood Flow/ ISCH disease Flashcards
what is the function of arteries
they are low resistances vessels conducting blood to the various organs with little loss in pressure.
they act as pressure reserviurs for maintaining blood flow between ventricular contraction
name the 3 features of arteriorlies
major site of blood flow resistance
responsible for the pattern of blood flow distribution
particiapte in the regulation of arterial blood pressure
What is the fuction of capillaries
site of exchange between the blood and tissue
what is the function of the veins
low resistance vessels for blood flow back to the heart
capaity for blood is adjusted to facilitate flow
lable the diagram:
elastic fibers,endothelium,
tunica externa, tunica media/ tunica intima
smooth muscles, internal elastic membrane, external elastic membrane
Give the features of the following
Arteries/
Arterioles
Capillaries
Veins
1) thick, elastic, large lumen radius
2) hihgly muscular, well innervated walls, small lum radius
3) thin walled, large total cross sectional area
4) thin walled, hihgly distensible, large lumen radius
what 3 things does haemodynamics arise from
Pressure , Flow & resistance
define hydrostatic pressure
the pressure exerted by a fluid
what are the units of flow and pressure differnce
1) liters/min or ml/min
2) mmHg- millimeter of mercury
what is the equation for flow rate
Flow rate (l/min)= change in pressure (mmHg)/ resistance of blood vessels (mmHg’min/l)
what is the relationship between flow and Change in pressure
it is directly proportianal to one another
Flow rate depends on
Flow rate depends on the pressure difference NOT the absolute pressure
resistance is the measure of
friction impedeing flow
what is the shape that the distribution of the speeds of flow across a circular tube
it is parabolic
name the 3 factors that resistance depends on
- viscosity of the blood
- vessel lenght
- vessel radius- slight change can cause a notable change in flow
is the radius is increased by 2 times how much is the resistance increased by
16 times as much
link radius with resistance and flow
Resistance= 1/r^4 Therefore
Flow= r^4
what is Poiseuilles equation
Flow rate=
(πΔPr^4)/8ηL
π= Pie
ΔP= change in pressure
r^4= radius to the power of 4
η= viscosity
L= leght of the vessel
what does arterial pressure fluctuate bc of
ventricular systole and diastole
Mean arterial pressure is worked out how
Mean arterial pressure = diastolic pressure + 1/3 pulse pressure
what are arteries known as
pressure reservoir
what happens to the velocitry of flow and total cross sectional area
velocity of flow decreases as it goes from aorta to capillarires and from venules/ veins to vena cava it increases
the total cross sectional area increases from arteries to capillaries then decreases therefore the relationship is linked.
why are arterioles major resistance vessles ?
small radius offers a lot of resistance and therefore reduce blood flow by alot. this drives the blood from the heart to the capillary beds.
what is speical about arteriolar walls
thick layer of smooth muscle richly innverated by nerves of the sympathetic nervous system- sensitve to chemcail changes and certain cirulating hormones.
