Hemodynamics & Vasculature Flashcards
Arterioles are known as ______ because they are responsible for a big dropoff in ______ as blood comes from the aorta.
- resistance vessels
- pressure
Veinsare known as ________. why?
capacitance vessels
they carry the majority of the blood
What are the main two variables in blood flow?
Where in the body are they highest and lowest?
pressure- highest in aorta lowest in veins and capillaries
volume- largest in veins, much lower most everywhere else
define the blood flow equation and variables.
Q=deltaP/R
flow= change in pressure/resistance
similar to Ohms law (I=V/R)
whats the relationship between flow in and flow out in a given part of the CV system?
flow in MUST equal flow out
Go ahead and make sure you memorize this. She said it will be on the test in multiple forms.
The Total flow through the entire CV system must be ______.
CONSTANT.
this is also something she said was important to know
compare flow vs. velocity
flow- volume per unit time (same constant flow through aorta and ALL the capillaries together).
velocity- distance per unit time (use V=Q/A where A is cross sectional area. velocity is highest in the Aorta because a small cross sectional area compared to the cross-sectional area of ALL the capillaries combined.
Total flow in the CV system is known as ______
Cardiac Output.
rework the flow equation (remember it?) to explain Cardiac Output (CO).
Q=deltaP/R
total flow=CO and delta P can be expressed as mean arterial blood pressure (Pa) minus venous blood pressure (Pv). Resistance can be explained by total peripheral resistance (TPR). Thus:
CO= (Pa-Pv)/TPR
simplify Poiseuilles equation.
Q=deltaP*(pi(R^4)/8nl)
this is just a more accurate manipulation of the blood flow equation (Q=deltaP/R). drop the constants and you get:
Q=deltaP*((r^4)/nl
r=radius
n=viscosity
l=length
you don’t have to memorize this but be able to answer the questions on the next card (you will pretty much have to memorize it).
according to pouseuilles equation, increasing radius will _____ resistance and ______ flow.
decrease
increase
according to pouseuilles equation, increasing viscosity will ______ resistance and ______ flow.
increase
decrease
Flow is proportional to the ____ power of radius.
4th
it is the biggest determinant of flow. This was in red. Remember this guy.
Resistances in parallel _____ total resistance. what is an example
decrease. Total resistance of a parallel network is smaller than the resistance of a single vessel. Changing the resistance of a single vessel (such as a capillary) has little effect on the system.
resistances in series are _____. What is an example?
additive. Rartery + Rarteriole + Rcapillaries= Rtotal
Flow equation assumes what kind of flow? What do we see in the body?
laminar flow
turbulent flow
How is pulsatile pressure in the heart converted to continuous pressure in the capillaries.
arteries are slightly elastic and dampen the pulse by the time it gets to the caps.
FLOW IS CONTINUOUS IN THE CAPILLARIES.
what three things decrease as we travel through the vasculature (from aorta)?
pulse pressure, mean pressure, velocity
What is vascular compliance (use equation)?
the change in vascular blood volume (deltaV) due to a change in blood pressure (deltaV). It represents elastic properties of vessels or chambers (heart).
C=deltaV/deltaP
what is arteriosclerosis (not atherosclerosis)?
loss in compliance of vessels with age.
how do you get pulse pressure?
systolic-diastolic
define law of laplace and explain it.
T=(deltaPtm*r)/u
T=tension
deltaPtm= transmural wall pressure
r=radius
u=wall thickness
Thus, decreased wall thickness leads to increased tension.
And increased radius leads to increased tension.
Think about the heart chambers.
difference between bulk transport and transcapillary transport.
bulk- movement of a substance from the CV from point A to B
transcapillary- movement of a substance between caps and tissues.
What is Ficks principle?
Simply says that the amount of a substance used is the amount put in minus the amount that comes out.
x=Q*([x]i-[x]o)
applying the principle of bulk transport and taking into account tissue or organ consumption.
What can Ficks principle be used to determine?
CO, myocardial O2 consumption, and fractional oxygen extraction (comparing how much oxygen used in body to how much started with).
Thus Ficks can be used to determine transcapillary efflux (or transport).
what is the difference between filtration and reabsorption?
What is this called?
filtration- hydrostatic pressure (forcing fluid out of the vessel) more pressure in vessels than in tissues
reabsorption- oncotic pressure (sucking fluid back into the vessel) more protein in the blood.
Net flux is the total movement taking both of these things into account.
starlings law of the capillaries.
Where is there more filtration vs. reabsoption:
kidney
GI tract
kidney-more filtration
GI tract- more reabsorption
How do small lipid-insoluble molecules make it out of the capillaries?
travel between endothelial cells at inter-endothelial junctions. Big molecules can’t make it through here.
