Capillary Exchange 1 Flashcards

1
Q

What is filtration?

A

Hydraulic flow down a pressure gradient

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2
Q

What are the 2 types of transport processes?

A

Endothelial transcytosis via vesicles/caveolae system
Convective transport

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3
Q

What capillaries require facilitated diffusion?

A

Brain capillaries

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4
Q

What is the equation for the Starling Principle?

A

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

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5
Q

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

A

Reduces Pc and therefore favors reabsorption

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6
Q

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

A

Increases Pc and therefore favors filtration

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7
Q

What does vasomotion create?

A

Variable local flow rates

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8
Q

What effect does arteriolar vasodilation have on capillary perfusion?

A

More open capillaries -> more uniform perfusion

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9
Q

How is absorption maintained?

A

Addition of fluid to extravascular space

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10
Q

What does the rate of fluid movement depend on?

A

Pressure gradient
Hydraulic conductance (Lp)

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11
Q

What is Lp determined by?

A

Number, width and length of the channels

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12
Q

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

A

Membrane’s molecular sensitivuty

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13
Q

What is the reflection co-efficient for plasma proteins?

A

0.9

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14
Q

What is the Classic Starling Equation for fluid filtration?

A

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

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15
Q

What are the 3 types of capillaries?

A

Continuous, fenestrated and discontinuous

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16
Q

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

17
Q

What is the glycocalyx?

A

Semi-permeable membrane of the capillaries

18
Q

What is the Michel-Weinbaum Theory of Fluid Exchange?

A

Qf = Lp. S. [(PC – PIF) - σ(πP - πg)]

19
Q

How is filtration across continuous capillaries kept low?

A

Vasomotion and diminished subglycocalyx oncotic pressure

20
Q

How is filtrate returned to the blood?

A

Lymphatic drainage into thoracic veins and absorption into lymph node capillaries

21
Q

What is Fick’s Law?

A

Mass of solute transported per unit time

22
Q

What does the Rate of Diffusion depend on?

A

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

23
Q

Define Fick’s Law.

A

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

24
Q

What does Fick’s Law depend on?

A

Temperature, solvent viscosity and solute size

25
When does free diffusion occur?
Solute diffuses through a large volume of solvent
26
What is the effect of membrane on diffusion?
Available area is reduced Pathlength is longer
27
What is the equation for available area?
Π(r-a)^2
28
What is the fractional available space (ϕ, phi)?
Π(r-a)^2/Πr^2 or (r-a)^2/r^2
29
What is the equation for the pore area available for diffusion?
Ap x ϕ
30
When does hydrodynamic drag increase?
As solute radius approaches pore radius
31
What is D'?
Diffusion coefficient in restricted diffusion
32
What is diffusion process slowed by?
Increased pathlength Limited available area Steric exclusion Increased hydrodynamic drag within pores