11/08 Flashcards
Define Filtration
Movement of fluid out of a capillary
Define Reabsorption
movement of fluid into a capillary
As blood moves across or through an area of vascular resistance the pressure ______
decreases
Where do you measure BP?
proximal to resistance
In the large arteries
what is the exception to measuring bp proximal to resistance?
CVP
In the kidney you have to take in account what kind of pressure?
pre-resistance and post resistance pressures
We only have 1 aorta but we have a bunch of large arteries and those split into even more smaller arteries. As blood moves down larger and larger cross sectional areas, what does it do to blood pressure and why?
brings bp down
Mostly d/t the increase in resistance but some of it is d/t there being many pathways for the blood to choose to go down
the vast majority of the drop in bp that happens between large arteries and capillaries is d/t
the high vascular resistance in the small arteries and arterioles
Most of our vascular resistance is in our
arterioles.
Which vessels do most of our relaxing and constricting?
arterioles
Ohm’s law can be used to describe what properties?
-action potentials with membrane resistance
-blood flow
Which formula is very useful in the body?
Ohm’s law
V=IR
Where is the primary place where nutrient and waste exchange happens?
capillaries
blood flow through the capillaries is controlled by the
arterioles
which vessel has a lot of smooth muscle associated with it?
arterioles
what allows us to regulate our blood flow in our arterioles to downstream tissues ?
smooth muscle cells
what is the surface area of capillaries in the body?
500-700 square meters
small arteries are an important place where we regulate our _____
bp
how many layers of smooth muscle is lined on the small arteries and arterioles?
4?
What kinds of nutrients are delivered to the arterioles?
glucose
fats
cholesterol
Gasses: offloading oxygen & picking up CO2
name of the vascular tree?
Mohrman
How many aortas do we have?
What is the cardiac output?
what is the Cross sectional area of the aorta?
what is the total cross sectional area?
what does that tell us about velocity?
We have 1 aorta so 5L/min CO has to get through that. It only has a 2.5cm2 cross sectional area. With such a low cross sectional area through just 1 aorta that gives us a total cross sectional area of 4.5cm2.
So Velocity is high, especially when the heart is in systole
What are the large veins that return blood to the heart?
venae cavae
What is the internal diameter of the venae cavae?
Is this smaller or larger than the aorta?
3cm
larger
How many venae cavae do we have?
what is the Cross sectional area of the venae cavae?
What is the total cross sectional area?
what does that tell us about velocity?
We have 2 venae cavae both with a cross sectional area of 3cm.
This makes the total cross sectional area 18cm2
This would make velocity lower in the venae cavae than in the aorta.
velocity is ______ in the vena cavae than in the aorta?
Why?
lower
Because there is a much higher total cross sectional area when blood is returning to the right atrium. (18cm2 vs 4.5cm2)
what is the internal diameter of an arteriole?
30 micrometers
Why are arteriole walls thick?
Because they have a lot of smooth muscle cells around them which helps us regulate our SVR and regulate blood flow through any tissue bed.
There is a very high wall thickness to internal diameter ratio in
arterioles
Capillaries have very ___ walls
thin
How many cell layers thick is the capillary wall?
What kind of cell is this?
endothelial cells
1 layer thick
Can capillaries contract or relax?
No, they don’t have any smooth muscle
Why doesn’t NE effect capillaries?
There’s no smooth muscle for it to act on. It only effects the arterioles.
Why is it good that capillaries have thin walls?
Increases nutrient absorption and waste removal d/t having a thin barrier
which vessel has the fastest velocity?
aorta
Order of velocity through vessels from fastest to slowest?
aorta
veins
capillaries
cross sectional areas from smallest to largest.
Don’t have to know the numbers.
aorta 2.5cm2
venae cavae 8cm2
small arteries 20cm2
arterioles 40cm2
small veins 80cm2
venules 250cm2
capillaries 2500cm2
What makes up the tendency for fluid to move through the capillary?
Delta P
30mmHg-10mmHg= 20mmHg
What is the average aortic bp?
100mmHg
Why does pressure drop from 100mmHg to 30mmHg from the left atrium to the capillaries?
The bp has gone down in the upstream high resistance blood vessels
Name for beginning end of the capillary? what is the pressure here?
arteriolar end of capillary
arterial end of capillary
30mmHg
Name for end of the capillary? What is the pressure here?
Venous end
10mmHg
Normal Map is
100mmHg
At the venous end of the capillary there are forces that favor ______
reabsorption
At the arteriolar end of the capillary there are forces that favor ______
filtration
In filtration, fluid and nutrients are ____ the capillary
leaving
In reabsorption fluid and waste products are _______ the capillary
going into
Besides delta P, there are certain variables that determine filtration and reabsorption. What are these called?
the 4 capillary starling forces
what are the starling forces?
- PCAP:BP/hydrostatic of capillary
- PISF:BP/hydrostatic pressure in ISF
- πCAPCapillary Colloid Osmotic Pressure; Oncotic pressure
- πISF: ISF colloid osmotic pressure
Filtration coefficient:
Kf:capillary permeability, #’s and surface area
What is another name for BP in the capillary?
hydrostatic pressure
hydraulic pressure
physical fluid pressure
that exists in the fluid in the capillary
What is the hydrostatic pressure in the capillary?
Why are these pressures important?
30mmHg at arterial end
10mmHg at venous end
They’re important in determining how much fluid goes DOWN the capillary as well as how much fluid goes THROUGH the capillary wall
PCAP stands for:
hydrostatic pressure
blood pressure
physical fluid pressure in the capillary
What is the interstitial fluid pressure?
The pressure outside of the capillaries
PISF stands for:
hydrostatic pressure
blood pressure
physical fluid pressure in the interstitial fluid
Having a high or POSITIVE pressure in the ISF around the capillary would effect filtration and reabsorption how?
oppose filtration at the arterial end
or, if it is high enough, it would promote reabsorption at the venous end
In the interstitium, on average when we’re healthy, the PISF is usually
-3mmHg
The lymphatic system acts like a vacuum