Peripheral Vasculature

Question 1

What are the 4 things that transcapillary solute diffusion depends on?

Answer 1

the concentration difference
surface area for exchange
diffusion distance
permeability of capillary wall to the substance

Question 2

Why is the capillary system to efficient at diffusion?

Answer 2

It maximizes area available for exchange while minimizing distance to diffuse.

Question 3

What are the two general ways things can diffuse across a capillary?

Answer 3

1. lipid soluble substances can just diffuse through the membrane
2. Charged substances use pores (is the organ in question allows)

Note that molecules larger than 40 angstroms just can’t cross capillaries because the pores aren’t big enough

Question 4

Net fluid OUT of the capillary is called what>

Net fluid INTO the capillary is what?

Answer 4

out = filtration

in - reabsorption

Question 5

What determines the direction fluid will move - in or out of the capillary?

Answer 5

the balance between hydrostatic pressure and oncotic pressure

Question 6

What is hydrostatic pressure and what is ocncotic pressure?

Answer 6

hydrostatic = the pressure of blood forcing fluid OUT

oncotic - attraction of water into the lumen due to higher protein concentrations in the lumen

Question 7

What is the starling hypothesis for the direction of fluid flow?

Answer 7

net filtration rate is equal to a constant K times (hydrostatic pressure in the cap - hydrostatic pressure in the interstitial fluid) - (oncotic pressure in the capillary - oncotic pressure in the fluid)

Question 8

A positive value from that equation will give you what? filtration or reabsorbtion?

Answer 8

positive value - filtration (moving out of the capillary)

negative value - reabsorption (moving into the capillary)

Question 9

What are the hydrostatic and oncotic pressures of the interstitial fluid?

Answer 9

usually 0

Question 10

Where in the vascular system does filtration occur?

Answer 10

arteriole end of the capillary

Question 11

Where in the vascular system does reabsorption occur?

Answer 11

the venule end of the capillary

Question 12

Why does fluid leak out of the capillaries in injured tissue?

Answer 12

injured tissue releases histamine, which makes capillaries leaky. This means proteins from inside the vessel will leak into the interstitial fluid so you decrease the oncotic pressure pushing fluid in and the hydrostatic pressure stays. this means you get a net movement of fluid out of the capillaries and edema

Question 13

What other body system is responsible for keeping the interstitial protein concentration low and removing excess capillary filtrate?

Answer 13

the lymphatic tissue

Question 14

If vessels are in series, how do we calculated the total resistance across them?

Answer 14

You sum their total resistances.

Question 15

For vessels in series, what vessel will have the highest impact on pressure and flow?

Answer 15

whichever vessel has the highest resistance

Question 16

For vessels in parallel, what is the primary determinant for resistance?

Answer 16

it’s not the diameter of individual capillaries, but rather the TOTAL cross-sectional area of ALL capillaries in the parallel. So the more cpaillaries there are, the higher the cross sectional area, the lower the resistance (think of it as more route options and therefore less resistance)

Question 17

How do we calculate the total resistance in a parallel network then?

Answer 17

we sum the inverse of the resistances, which is equal to the inverse of the total resistance

Question 18

If all the resistances are equal in a series, what can we do to find the total resistance?

Answer 18

just divide that resistance by the number of vessles in parallel

Question 19

Because the total cross-sectional area of vessels changes througout the body, what must also change to maintain flow rate?

Answer 19

flow velocity

Question 20

What are the two types of flow that can occur within a vessel?

Answer 20

laminar (smooth, streamline, low-friction)

turbulent (disorder, mixing, high friction)

Question 21

Where in the vessel is blood flowing the fastest?

Answer 21

in the center - no friction

Question 22

What sort of reservoir does the peripheral venous system serve as?

Answer 22

a volume reservoir

Question 23

What’s the “secondary” volume reservoir?

Answer 23

central venous system of great veins of the thorax and the right atrium

Question 24

What happens to stroke volume when peripheral veins constrict?

Answer 24

peripheral blood is displaced and enters the central venous system, increasing central venous volume, pressure, cardiac filling and augments stroke volume

Question 25

What happens to blood pressure as you go down the ranks of vasculature from arteries to veins?

Answer 25

blood pressure decreases

Question 26

What is central venous pressure?

Answer 26

about 0 mmHg - the filling pressure for return to the right side of the heart

Question 27

What set of vasculature has the highest resistance to flow?

Answer 27

arterioles

Question 28

If individual organs have blood flowin gin series and blood flows between organs in parallel, how do you determine total peripheral resistance?

Answer 28

You add the sum of resistance within individual organs to find that’s organ’s resistance

then you add the inverse of all the organ resistances to find the TPR

Question 29

How is the elastic nature of veins describe?

Answer 29

compliancy - the change in volume over the change in pressure….
even small changes in pressure can cause a large amount of blood to shift into/out of the peripheral venous pool

Question 30

How are the arteries capable to converting the pulsatile flow from the heart into a steady laminar flow through the vascular bed?

Answer 30

THey store pressure energy in the walls during expansion so that they can continue pumping blood continuously via elastic recoil even when the heart isn’t pumping.

Question 31

Describe how you can take a blood pressure in terms of blood flow types?

Answer 31

1. you collapse the artery with a cuff
2. as you let pressure out, you’ll reach a point where blood can just barely start going through - since the radius is too small it will be turbulent flow whch you can hear - this is systole
3. you keep letting air out until the flow can convert back to laminar - this is diastole

Question 32

what is the mean arterial pressure?

Answer 32

the average effective pressure that drives the blood through the systemic organs.

Question 33

What is the equation for meal arterial rpessure - both of them?

Answer 33

Pa = CO a TPR
Pa = Pd + 1/3(Ps - Pd)

Question 34

What factors determina arterial pulse pressure?

Answer 34

it’s equal equal to systolic pressure minus diastolic pressure

so it’s determined by stroke volume and compliance (increases with stroke volume and decreases with compliance)

Question 35

What happens to arterial pulse pressure as one ages?

Answer 35

1. increase arterial volume
2. increased arterial stiffness and decreased compliance
3. thus, increased arterial pulse pressure and increased mean arterial pressure

Question 36

done

Answer 36

done