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Cardiovascular Physiology > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

What blood vessel group is considered the “stopcocks” of circulation?

A

Arterioles

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2
Q

Which vessel group is considered storage vessels?

A

Veins

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3
Q

Which vessel group takes part in exchange of gases, water, and solutes?

A

Capillaries

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4
Q

Which vessels are in between arterioles and capillaries?

A

Metarterioles

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5
Q

What is the role of metarterioles?

A

Sphincters that regulate flow into the capillaries.

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6
Q

Which group of vessels has the greatest cross-sectional area and surface area?

A

Capillaries

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7
Q

How do precapillary sphincters regulate blood flow?

A

If one area within the capillary bed requires blood, the other areas will constrict their sphincters to redirect blood flow.

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8
Q

Is capillary distribution the same from tissue to tissue?

A

No; some areas have more dense capillary beds.

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9
Q

Do true capillaries have smooth muscle?

A

No; they are incapable of active constriction or relaxation.

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10
Q

Why can capillaries withstand high intravascular pressures?

A

The Law of LaPlace. Radius is directly proportional to wall tension

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11
Q

What are the four methods of exchange across the capillary endothelium?

A
  1. Diffusion.
  2. Bulk Flow.
  3. Vesicular transport.
  4. Active transport
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12
Q

What substances are exchanged across the endothelium via diffusion?

A

Oxygen.
Carbon dioxide.
Lipid-soluble substances.

(from high to low concentration)

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13
Q

What substances are exchanged across the endothelium via bulk flow?

A

Water, electrolytes, small molecules.

via intercellular clefts or “pores”

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14
Q

What substances are exchanged across the endothelium via vesicular transport?

A

Proteins

larger molecules

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15
Q

What substances are exchanged across the endothelium via active transport?

A

Ions, glucose, amino acids.

low to high/across chemical gradients, must use ATP

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16
Q

What is the normal distribution of fluid in the body by liter?

A

3L Plasma.
11L Interstitial Fluid.
28L Intracellular Fluid

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17
Q

How many liters of extracellular fluid?

A

14L

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18
Q

What three things does interstitial volume depend on?

A
  1. Rate of filtration.
  2. Rate of reabsorption.
  3. Lymph flow
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19
Q

Which substance is the major determinmant of oncotic pressure?

A

Proteins

20
Q

What is capillary hydrostatic pressure (Pc)?

A

Pressure in the capillary that forces fluid OUTWARD through the capillary membrane

21
Q

What is interstitial fluid hydrostatic pressure (Pif)?

A

Normally a negative pressure which creates an outward force (from capillary to interstitial) for fluid

22
Q

What factor creates a negative interstitial fluid hydrostatic pressure?

A

Lymphatics create negative pressure via pumping action

23
Q

What is the more abundant plasma protein?

A

Albumin

24
Q

How are proteins similar to sodium in the body?

A

Proteins want to pull fluid to themselves. Similar to salt (water follows salt), fluid follow proteins as well

25
Q

What is plasma colloid osmotic pressure (Pie-p)?

A

aka- Plasma oncotic pressure.

Tends to cause inward (into capillary) movement of fluid.

26
Q

What is interstitial fluid osmotic pressure (Pie-if)?

A

aka- Interstitial fluid oncotic pressure.

Tends to cause outward (out of capillary) movement of fluid

27
Q

What is the Gibbs-Donnon effect?

A

Albumin exerts a greater osmotic force than can be accounted for solely on the basis of the number of molecules dissolved in the plasma. (Albumin attracts Na+ which attracts Cl-, which ultimately increases osmotic force and pulls fluid towards them).

28
Q

Which two ions does albumin naturally attract?

A

Sodium (Na+) and Chloride (Cl-)

29
Q

Does the Gibbs-Donnan effect increase or decrease osmotic/oncotic pressure (pulling power)?

A

Increases

30
Q

What is filtration the sum of?

A

The sum of the hydrostatic and osmotic forces favor the net movement of water from the capillary to the interstitial space.

31
Q

Does filtration or reabsorption happen more on the arterial side? Venule side?

A

Filtration- Arterial side

Reabsorption- venule side

32
Q

What is reabsorption the sum of?

A

The sum of the hydrostatic and osmotic forces favors the net movement of water from the interstitial space to the capillary

33
Q

What is the net driving force of filtration?

A

Net driving force >0

34
Q

What is the net driving force of reabsorption?

A

Net driving force<0

35
Q

Over time, is there a net overage or deficit of filtration and how does the body compensate for this?

A

There is an overage over time.

This is all equaled out because of the lymphatic system

36
Q

Describe dehydration in how it correlates to filtration/reabsoprtion?

A

Decrease capillary hydrostatic pressure
Increase oncotic pressure.
More fluid being pulled from interstital

37
Q

What is the Starling Forces equation?

A

Net driving force= (Pc-Pif) - rc(Pie-c-Pie-if)

38
Q

What does the Starling equation conclude?

A

That there is more fluid going out of the capillary than going in

39
Q

What does muscular contraction do to lymphatics?

A

Distortion of and opening of spaces.

40
Q

What is the cause for the negative pressure in the interstitial fluid space?

A

Lymphatics

41
Q

How is plasma filtrate returned via the lymphatic circulation?

A
  1. Tissue pressure.
  2. Intermittent skeletal muscle activity.
  3. Lymphatic vessel contraction.
  4. System of one-way valves
42
Q

What does the lymphatic system return to circulation?

A

Protein.
Bacteria.
Fat.
Excess fluid

43
Q

What four things can cause edema?

A
  1. Increased capillary hydrostatic pressure.
  2. Decrease plasma oncotic pressure.
  3. Increased capillary permeability.
  4. Lymphatic obstruction
44
Q

What is an example of something that increases capillary hydrostatic pressure?

A

Heart failure (High CVP) or venous obstruction

45
Q

What is an example of something that decreases plasma oncotic pressure?

A

Hypoproteinemia from malnutrition.

Or low albumin in elderly

46
Q

What is an example of something that increases capillary permeability?

A

Proinflammatory mediators-

  • Histamine
  • Bradykinin

Damage to structural integrity of kidneys-

  • trauma
  • burns
  • severe inflammation
47
Q

What is an example of lymphatic obstruction?

A

Filariasis

Cardiovascular Physiology (7 decks)

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