Hemodynamics & Vasculature Flashcards
What is transmural pressure?
The difference in pressure between the inside and outside of a vessel
The biggest drop in pressure occurs from the __________.
arteries to the arterioles
The systemic pressure is much _______ than the pulmonary pressure.
greater
Why is the pulmonary pressure less than the systemic pressure?
Because the resistance is much less; this is an important concept, because the cardiac output is equal between the left and right sides
Flow is _______ and is determined by ________.
volume/time; cardiac output (because the CV system is a closed loop, the flow at the aorta is equal to the flow throughout all of the capillaries)
Velocity is ________ and is given by ______.
distance/time; Q (flow) / A (cross-sectional area)
What is the equation for flow?
Q = (difference in pressure) / (total resistance)
Flow is ________ the vessel radius.
proportional to the fourth power of (so increasing the radius by double increases the flow by sixteen times)
Flow is inversely proportional to __________.
viscosity (primarily determined by hematocrit) and length
In a system of parallel vessels, the total resistance is equal to _________.
1 / (sum of the reciprocals of the individual resistances)
In a system of parallel vessels, the pressure will be _______ across each, but the flow will _____________.
the same; different due to varying resistances
Resistances in series are _________.
additive
In laminar flow, the velocity is greatest in the _________.
center
What factors induce turbulent flow?
High velocity, low viscosity, damage to endothelium, larger diameters, and abrupt changes in diameter
The pulse pressure is given by ________.
systolic pressure minus diastolic pressure
What is the mean arterial pressure (MAP)?
diastolic pressure + 1/3 pulse pressure; the equation is set up like this because diastole is longer than systole–but at higher HRs the diastole is shorter and MAP approaches the mean of systole and diastole
What is the equation for tension?
T = (transmural pressure x radius) / (wall thickness); this is why an aneurysm can lead to a ruptured vessel–increasing the radius puts more tension (stress) on a vessel.
Bulk transport is __________.
the flow multiplied by the concentration of a substance
Fick’s principle is _________.
flow multiplied by the change in concentration of a substance; this is used to measure how much of something is used
Cardiac output is ___________.
the volume of blood pumped by the heart in a minute
Increasing the number of parallel resistances _______ the total resistance.
decreases
What is the equation for compliance?
C = (change in volume) / (change in pressure); thus, the more compliant a vessel is, the more it will it will change in volume for a given change in pressure
What is fractional oxygen extraction?
E[O2] = (O2a - O2v) / O2a; this gives the percentage of oxygen that was extracted from the artery
Using Poiseuille’s equation, we can see that three things determine vasculature resistance in the body: __________.
radii of vessels, viscosity, and length
Vessels lose compliance with age, a process called __________.
arteriosclerosis
