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CardioRenal II > Phys - Capillary Dynamics > Flashcards

Phys - Capillary Dynamics Flashcards

1
Q

Primary function of the cardiovascular system

A

1.) Delivery of O2 and metabolic substrates 2.) Removal of waste products

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2
Q

What two steps are involed in vascular transport of substrates and waste products

A

1.) Convective blood flow to the capillaries 2.) Exchange of fluids and solutes between the capillaries and parenchyma (diffusion and osmosis)

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3
Q

Importance of the lymphatic system

A

very important for removing excess fluid and plasma protains that have filtered from the mircocirculation into the interstitial space = MAINTAINING INTERSTITIAL HOMEOSTASIS

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4
Q

What is the Interstitial space

A

Gel matrix composed of large mucopolysaccharides (primarily hyularonic acid) that hold everything together (tightly coiled and packed into a meshwork)

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5
Q

Functions of the interstitial gel matrix

A

1.) Fills the interstitial space around the tissue and parencyma (provides a pathway for diffusion) 2.) Fluid Trapping - prevents free flow of fluid throughout the body) 3.) Immobilization of trapped particulate matter and bacteria (minimizes the stread of infection)

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6
Q

Describe the characteristics of arterioles in microcirculation

A

1.) Greatest Resistance 2.) Greatest change in pressure (biggest drop)

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7
Q

what are exchange vessels

A

capillaries and small venules

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8
Q

Describe the characteristics of exchange vessels in microcirculation

A

1.) Largest cross sectional area 2.) large surface area 3.) Low pressure 4.) Low velocity

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9
Q

What makes microcirculation well suited for exchange of substrates and oxygen

A

Combination of low pressures, low flow velocity and large surface area

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10
Q

Describe the microcirculatory arcade

A

Tree like branching pattern. Terminal arterioles (metarterioles) to capillaries to small venules and ultimately to larger venules and veins.

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11
Q

How does change in arterial size change resistance

A

small changes result in BIG changes in resistance (1/r^4)

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12
Q

Composition of the capillary wall

A

single layer of thin endothelial cells overlying a basement membrane (basal lamina)

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13
Q

Intercellular clefts

A

endothelial cells in the capillary overlap and are attached through junctional complexes to form intercellular clefts - restrict the movement of larger solutes

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14
Q

what lines the capillary endothelium on the luminal side

A

glycolax “fuzzy coat”

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15
Q

List three ways solutes move across the capillary wall

A

1.) Diffusion 2.) Bulk Flow 3.) Vesicular transport

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16
Q

What is the most important means of soulute exchange

A

Diffusion (can occur in both directions)

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17
Q

What dictates capillary diffusion

A

Flicks law of diffusion

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18
Q

Flicks law of diffusion

A

smaller things have a smaller diffusion coefficient - Inversely proportional to the thickness of the barrier

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19
Q

What is bulk flow

A

When water moves out it washes solutes with it (solutes move with water out of the capillaries) through intercellular clefts

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20
Q

Where is bulk flow important

A

glomerular capillaries

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21
Q

What is vesicular transport

A

Movement of large macromolecules through pinocytotic channels. Occurs on both the luminal and abluminal surfaces and occurs in both directions.

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22
Q

How does water move across an exchange vessel

A

1.) Osmosis (both directions) 2.) Bulk flow (OUTWARD ONLY)

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23
Q

How does water move across the capillaries

A

1.) Transcellular route 2.) Paracellular route

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24
Q

Water: Transcellular route

A

through endothelical cells via water channels (eg: aquaporin 1 on the luminal membrae) High surface area

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25
Q

Water: Paracellular route

A

through intercellular clefts between the endothelial cells. LOW surface area

26
Q

What is filtration

A

movement of water OUT of the capillaries

27
Q

What is reabsorption

A

movement of water INTO the capillaries

28
Q

Filtration vs Reabsorbtion… Which exceeds the other

A

Filtration exceeds reabsortion resulting in NET FILTRATION (goes into the lymph)

29
Q

What are the driving forces for fluid movement

A

1.) Hydrostatic Pressures 2.) Oncotic Pressures

30
Q

List the types of hydrostatic pressures

A

1.) Capillary pressure (Pc) 2.) Interstitial hydrostatic pressure (Pi)

31
Q

List the types of oncotoc pressures

A

1.) Plasma oncotic pressure 2.) Interstitial fluid oncotic pressure

32
Q

What determines the direction of fluid movement

A

the BALANCE between Hydrostatic and oncotic pressures

33
Q

Capillary hydrostatic pressure (Pc) moves water in what direction

A

pushes water OUT of the capillary

34
Q

Interstitial Hydrostatic pressure (Pi) moves water in what direction

A

Pulls water OUT of the capillary

35
Q

Plama oncotic pressure moves water in what direction

A

pulls water INTO the cappillary

36
Q

Interstitial fluid oncotic pressure moves water in what direction

A

pulls water OUT of the capillary

37
Q

direction of water movement when hydrostatic pressure is greater than oncotic pressure

A

water moves out

38
Q

direction of water movement when hydrostatic pressure is less than oncotic pressure

A

water moves in

39
Q

Describe the change in pressure across the capillary tube

A

Pressure falls along the tube - 25-35 mmHg at the arteriolar end and 7-10 mmHg at the venular end

40
Q

Changes in capillary hydrostatic pressure with increases in arterial pressure and increases in venous pressure

A

increas in arterial pressure with cause an increase in capillary pressure but not directly/by as much because it is blunted (multiplied by 0.3) however, changes in venous pressure directly increase the capillary pressure (85% of venous pressure reaches the capillaries)

41
Q

Determinants of Pc

A

1.) Ratio of postcapillary and precapillary vascular resistance (~0.3) 2.) Arterial pressure (small effect due to 0.3) 3.) Venous pressure (greater effect)

42
Q

How are capillaries protected from sudden changes in arterial pressure

A

myogenic vasoconstriction

43
Q

What is Pc the measure of

A

the fluid pressure in the capillaries

44
Q

what is Pi a measure of

A

the fluid pressure in the interstitial space

45
Q

Interstitial hydrostatic pressure

A

Slightly atmospheric (averages between 0 and -6 mmHg) Due to normally “dry” interstitail space (maintained by lymphatics)

46
Q

Capillary Filtration Coefficient

A

Kf : Describes the conductance (1/resistance) of the vessel wall to water

47
Q

Capillary flow equation

A

Flow = (Pc-Pi)xKf

48
Q

In terms of pressures when does water move out of the capillary

A

when capillary pressure is greater than interstitial pressure

49
Q

Define osmotic pressure

A

Hydrostatoc pressure required to oppose the movement of water acorss a semipermeable membrane in response to a differnece in solute concentrations

50
Q

What is the most important determinant of osmotic force

A

the number of osmotically active molecules in the solution

51
Q

osmotic forces in the vascular bed are due to the presence of what

A

plasma proteins - large molecular size greater than that of the intercellular clefts. Capillaries are relatively impermeable to plasma proteins

52
Q

what is oncotoc pressure

A

the osmotic pressure exerted by the plasma proteins

53
Q

Majority of oncotic pressure is due to the presence of what

A

albumin (78%)

54
Q

Donnan Effect

A

Since plasma proteins are negatively charged they attract cations (particularly Na) to balance the negative charge. The presence of Na increases the number of particles in solution contributing to the effective osmotic pressure

55
Q

Reflection Coefficient

A

descrives the relative permeability of the exchange vessels to the plasma proteins 0-1 (1 is impermeable)

56
Q

Net direction of oncotic forces (movement of water)

A

pulls water in

57
Q

Conditions that increase capillary permeability (ex: allergic reactions or burns) will

A

disrupt the balance of forces across the capillary wall and will increase both the loss of plasma porteins and fluid filtration

58
Q

Net Oncotic forces (movement of water)

A

pulls water in

59
Q

Starling Landis Equation

A

Jv >0 there is net fluid FILTRATION Jv <0 there is net fluid REABSORPTION

60
Q

average net fluid filtration in a 70 kg person? What is the fate of this fluid?

A

3 L/day or 2 ml/min - becomes lymph and is returned to central circulation

CardioRenal II (12 decks)

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