Capillaries Flashcards

1
Q

What is the function of the capillaries?

A

Exchange fluid, nutrients, hormones etc

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2
Q

What is the rate of exchange of nutrients in capillaries related to?

A

Bulk flow

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3
Q

What features of the capillaries contribute to its function?

A

Thin walls with pores

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4
Q

What modifies what goes through capillaries?

A

Size of the pores

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5
Q

Can lipid soluble substances get through capillaries via diffusion? Can proteins? Water soluble ions?

A

Yes for lipid

No for proteins or water solubles

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6
Q

What are the spaces between the capillaries?

A

Intracellular clefts and caveolae

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7
Q

What covers the tissue side of the capillaries?

A

BM

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8
Q

What is vasomotion?

A

intermittent blood flow through capillaries d/t contraction of metarterioles and precapillary sphincters

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9
Q

What structures regulate blood flow through capillaries? What are those regulated by?

A

Through precapillary sphincters

Regulated by tissue oxygen usage

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10
Q

Is there smooth muscle in capillaries? What is the consequence of this?

A

No, means that can close capillaries completely

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11
Q

If you increase surface area (as in the increase CSA for capillaries) what happens to velocity?

A

Decreases velocity

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12
Q

Why can’t capillaries contract or relax?

A

No smooth muscle

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13
Q

Blood flow through capillaries depends on what?

A

What can get through upstream via sphincters, arterioles etc

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14
Q

What is the main metabolic regulator of skeletal muscle? Lesser regulators?

A

pO2

pCO2, pH, flow

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15
Q

What is the main metabolic regulator of the brain? Lesser regulators?

A

pCO2

pO2, adenosine

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16
Q

What is the main metabolic regulator of the heart? Lesser regulators?

A

[adenosine]

pO2, pCO2, pH

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17
Q

How does epinephrine control blood flow through capillaries?

A

Constricts and dilates

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18
Q

How does Norepinephrine control blood flow through capillaries?

A

Constricts

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19
Q

How does dopamine control blood flow through capillaries?

A

Constricts and dilates

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20
Q

How does histamine control blood flow through capillaries?

A

dilates

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21
Q

How does acetylcholine control blood flow through capillaries?

A

Dilates

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22
Q

How does angiotensin II control blood flow through capillaries?

A

Dilates

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23
Q

How do Kinins control blood flow through capillaries?

A

Dilates

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24
Q

How does ADH/vasopressin control blood flow through capillaries?

A

Constricts

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25
Q

How does VIP control blood flow through capillaries?

A

Dilates

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26
Q

How do hormones have opposite effects on the same capillary bed?

A

Different receptors

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27
Q

How does adenosine control blood flow through capillaries?

A

Constricts, dilates

28
Q

How does hypoxemia control blood flow through capillaries?

A

Dilates

29
Q

How does [H+] and [K+] control blood flow through capillaries?

A

Dilates

30
Q

How does hypercapnia control blood flow through capillaries?

A

Dilates

31
Q

How do Kreb cycle intermediaes control blood flow through capillaries?

A

Dilates

32
Q

How does endothelin control blood flow through capillaries?

A

Constricts

33
Q

How does EDRF (NO) control blood flow through capillaries?

A

dilates

34
Q

What determines that rate of exchange of a chemical through a capillary bed?

A

Solubility in lipids or water

Molecular size

35
Q

If a chemical is lipid soluble, how does it pass through capillaries?

A

Direct diffusion

36
Q

If a chemical is water soluble, how does is pass through the capillary bed?

A

Through pore/clefts

37
Q

How does molecular size relate to the rate of passage through capillaries?

A

Inversely related

38
Q

What is colloid osmotic pressure?

A

The force exerted by molecules inside a fluid on the wall that contain it

39
Q

What is capillary hydrostatic pressure (Pc)? How does it relate to flow?

A

Fluid pressure within capillaries that tends to move fluid out

Directly related to flow

40
Q

The hydrostatic pressure of tissues is (high/low) compared to capillaires? How does this affect permeability?

A

Low

Increases permeability

41
Q

A tightly encapsulated tissue (like the kidney) causes what?

A

Increases Pif, to move fluid back into tissue

42
Q

Oncotic pressure within capillaries tend to move fluid (in/out).

A

In

43
Q

Proteins in the interstitium will move fluid (in/out) of the capillaries?

A

Out

44
Q

What is the equation for net pressure?

A

Pc - Pif -(pi)c + (pi)if

45
Q

If net fluid pressure is greater than 0, where will fluid move?

A

out of the capillary

46
Q

If net fluid pressure is less than 0, where will fluid move?

A

Into the capillary

47
Q

How do water soluble substances get through the capillaries?

A

Through the pores in the capillaries

48
Q

How do we describe flow through capillaries (individually or as a sum/product of many?)

A

Sum of many capillaries

49
Q

Where in the body is the only place dopamine will cause capillary constriction?

A

Kidneys

50
Q

What is the effect of adenosine in the kidneys?

A

Constriction of capillary beds

51
Q

What does reabsorption mean in terms of capillary exchange?

A

Reuptake into the capillary

52
Q

What does filtration mean in terms of capillary exchange?

A

Removal from the blood

53
Q

How permeable it the liver to molecules? The brain?

A
Liver = highly permeable
Brain = Not so much
54
Q

What maintains the low hydrostatic pressure in the interstitium?

A

Lymphatic system

55
Q

What is the effect on interstitial hydrostatic pressure if the tissue is surrounded by a tight capsule? What is the effect that this produces on the flow of interstitial fluid (does it go back in, or does it come out faster)?

A

Increases it, causing fluid to move back into the capillary

56
Q

What is oncotic pressure? What is the effect on movement of fluid into/out of capillaries?

A

The pressure exerted by a [C] of some molecule. This causes movement in the direction of higher [C]

57
Q

What is the equation for the net pressure exerted on capillary fluid? What happens if this sum is greater than 0?

A

Pc - Pif - (pi)c + (pi)if

If this sum is >0, then net fluid movement will be out of the capillary

58
Q

In the equation of net pressure in a capillary (Pc - Pif - (pi)c + (pi)if), which component is variable with the location in the capillary?

A

Pc

59
Q

What happens if there is in an increase of Pc?

A

A shift of the curve, meaning that at every point in the capillary, there is a higher rate of filtration

60
Q

What happens if there is decrease in oncotic pressure within the capillary?

A

Shift of the horizontal line downward, meaning that at every point in the capillary, there is a higher rate of filtration

61
Q

What happens to Pc if we decrease resistance within the capillary (say, by opening a sphincter at the venule end of the capillary)?

A

Pc curve shifts down, meaning that at every point along the capillary, there is less filtration occurring

62
Q

Which variables does the lymphatic system change, so that there is a net efflux of fluid out of the capillaries?

A

(pi)if and Pif (both are decreased)

63
Q

What are the three factors mentioned in class, that can serve to increase the Pc? What will this cause?

A

Standing, Heart failure, venous thrombus

These all cause edema

64
Q

What are the three factors mentioned in class, that can serve to decreased the (pi)c? What will this cause?

A

Nephrotic syndrome, starvation, pregnancy

Edema

65
Q

What does inflammation of the capillary wall cause?

A

Edema (I think d/t increase in surface area)