Hemodynamics Flashcards
flow of blood through arterial system
arteries -> arterioles -> capillaries
flow of blood through venous system
capillaries -> venules -> veins
function of pulmonary and aortic valves (semilunar)
prevent backflow of blood into ventricles

function of tricuspid and mitral valves
prevent backflow of blood into atria

distinguishing fibers between arteries and veins
- arteries: contain more smooth muscle and elastic fibers
- veins: contain more collagen fibers
what is compliance
the ability of a cardiac chamber (or vessel) to change its volume (V) in response to changes in pressure (P)
C=change in volume / change in pressure
which vessel has the higher compliance: arteries vs veins
- C of veins is highest: can store large amount of volume of blood in veins with relatively low pressure
*steeper the slope, the higher the compliance of the vessel

define zero compliance
no change in volume in the presence of infinite changes in pressure
define infinite compliance
even at zero pressure, the volume of a vessel is infinite
define finite compliance
“real life”
- for a given change in pressure, there will be a change in volume
describe the change in compliance that occurs with growing pressure and volume of vessels
- at low pressures and volumes, compliance is much greater than at high pressures and volumes
- the change in volume for a given change in pressure is greater at higher compliance

what is the pressure gradient of the cardiovascular system
- difference in pressure at two or more points along the systemic circuit
- main driving force
- ventricular ejection provides the continuous pressure gradient, allowing blood to flow
give the equation that gives the velocity of blood flow
v = Q/A
- v = velocity of blood flow (cm/sec)
- Q= flow (ml/sec)
- A= cross sectional area (cm2)
- A = πr2
describe why velocity of blood flow through the capillaries is slow even though v=Q/A
- blood flow is identical throughout the vascular tree
- need to take into consideration the surface area of ALL of the capillaries (which is much larger than the aorta)
- velocity of flow is inversely proportional to the TOTAL cross sectional area

what is the relationship between blood flow, pressure, and resistance
Flow (Q) = change in pressure / resistance
* change in pressure is the driving force and resistance is the impediment to flow
what is vascular resistance
measure of hindrance to blood flow caused by friction between moving blood and the vessel wall
what is Poiseuille’s equation: determines resistance
R = 8 n l / πr4
- R = resistance
- n = viscosity of blood
- L= length of blood vessel
- r= radius
* most important factor is radius
what is the major determinant of flow rate
radius: R = 1/r4
* small radius confers more resistance because blood “rubs” against a larger surface area
how do you determine resistance in a series
R total = R1 + R2 + R3 …

how do you calculate resistance in parallel
1/R total = 1/R1 + 1/R2 + 1/R3

with a series arrangement, total flow through each level equals what? What happens to the pressure as blood flows through each component?
- it is the same; output from the aorta = venous return
- pressure decreased as blood flows through each component
Rtotal = R artery + R arteriole + Rcapillary + Rvenule + Rvein
the cardiac output is distributed in % among the organs. what equations show that
Qi = Q1 + Q2 + Q3
Qi / (Pi-Po) = Q1/ (Pi-Po) + Q2/ (Pi-Po) + Q3/ (Pi-Po)
