Capillary Exchange 1

Question 1

What is filtration?

Answer 1

Hydraulic flow down a pressure gradient

Question 2

What are the 2 types of transport processes?

Answer 2

Endothelial transcytosis via vesicles/caveolae system
Convective transport

Question 3

What capillaries require facilitated diffusion?

Answer 3

Brain capillaries

Question 4

What is the equation for the Starling Principle?

Answer 4

NFP = (Pc + πif) - (Pif + πP)
NFP = (Pc - Pif) - (πP - πif)

Question 5

What is the effect of arteriolar constriction on the Starling Principle?

Answer 5

Reduces Pc and therefore favors reabsorption

Question 6

What is the effect of arteriolar dilation on the Starling Principle?

Answer 6

Increases Pc and therefore favors filtration

Question 7

What does vasomotion create?

Answer 7

Variable local flow rates

Question 8

What effect does arteriolar vasodilation have on capillary perfusion?

Answer 8

More open capillaries -> more uniform perfusion

Question 9

How is absorption maintained?

Answer 9

Addition of fluid to extravascular space

Question 10

What does the rate of fluid movement depend on?

Answer 10

Pressure gradient
Hydraulic conductance (Lp)

Question 11

What is Lp determined by?

Answer 11

Number, width and length of the channels

Question 12

What does the reflection co-efficient (sigma) measure?

Answer 12

Membrane’s molecular sensitivuty

Question 13

What is the reflection co-efficient for plasma proteins?

Answer 13

0.9

Question 14

What is the Classic Starling Equation for fluid filtration?

Answer 14

Qf = Lp. S. [(PC – PIF) - σ(πP - πIF)]

Question 15

What are the 3 types of capillaries?

Answer 15

Continuous, fenestrated and discontinuous

Question 16

What is greater: intracellular cleft osmotic pressure (πg) or interstitial fluid oncotic pressure (πif)

Answer 16

πif

Question 17

What is the glycocalyx?

Answer 17

Semi-permeable membrane of the capillaries

Question 18

What is the Michel-Weinbaum Theory of Fluid Exchange?

Answer 18

Qf = Lp. S. [(PC – PIF) - σ(πP - πg)]

Question 19

How is filtration across continuous capillaries kept low?

Answer 19

Vasomotion and diminished subglycocalyx oncotic pressure

Question 20

How is filtrate returned to the blood?

Answer 20

Lymphatic drainage into thoracic veins and absorption into lymph node capillaries

Question 21

What is Fick’s Law?

Answer 21

Mass of solute transported per unit time

Question 22

What does the Rate of Diffusion depend on?

Answer 22

Depends upon concentration difference, diffusion distance and physical properties of the solvent and solute

Question 23

Define Fick’s Law.

Answer 23

Js = -DS (∆ C/ ∆ x)
Js - mass of solute diffused per unit time
∆C - concentration difference
∆ x - diffusion distance
S - surface area
D - diffusion coefficient

Question 24

What does Fick’s Law depend on?

Answer 24

Temperature, solvent viscosity and solute size

Question 25

When does free diffusion occur?

Answer 25

Solute diffuses through a large volume of solvent

Question 26

What is the effect of membrane on diffusion?

Answer 26

Available area is reduced
Pathlength is longer

Question 27

What is the equation for available area?

Answer 27

Π(r-a)^2

Question 28

What is the fractional available space (ϕ, phi)?

Answer 28

Π(r-a)^2/Πr^2 or (r-a)^2/r^2

Question 29

What is the equation for the pore area available for diffusion?

Answer 29

Ap x ϕ

Question 30

When does hydrodynamic drag increase?

Answer 30

As solute radius approaches pore radius

Question 31

What is D’?

Answer 31

Diffusion coefficient in restricted diffusion

Question 32

What is diffusion process slowed by?

Answer 32

Increased pathlength
Limited available area
Steric exclusion
Increased hydrodynamic drag within pores