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PHYSIOLOGY Exam 3 (Lauren) > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

What are metaarterioles?

A

They are thoroughfare vessels that go stratight from the arterioles to the venule, bypassing the capillary bed altogether

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2
Q

What regulates flow through capillaries?

A

Neural and metabolic mechanisms that can control the precapillary sphincters

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3
Q

Do capillaries have muscles?

A

No, but there are precapillary sphincters where the capillary comes off the arteriole that can close off the capillary

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4
Q

If blood flows through a metarteriole and bypasses a capillary bed, is there exchange of gas/waste products?

A

No

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5
Q

What is the difference between the arteriolar radius and the precapillary sphincters when it comes to regulating blood flow?

A

The arteriolar radius determines the overall blood flow to a particular capillary bed

The capillary sphincters determine which capillaries are perfsued

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6
Q

What are the 3 types of capillaries?

A

Continuous

Fenestrated

Discontinuous

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7
Q

What are continuous capillaries?

A

Capillaries that have tiny clefts between each endothelial cell to allow hydrophilic molecules to pass through

(Found in muscle, skin, lung, and brain)

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8
Q

What are fenestrated capillaries?

A

Capillaries that have fenestrae which are like “windows” in the cell membranes of each cell to allow water and small hydrophilic molecules to pass

(Found in kidneys, intestine, endocrine glands)

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9
Q

What are discontinuous capillaries?

A

Capillaries that have wide gaps between adjacent endothelial cells to allow large molecules and water to pass through

(Found in liver, bone marrow, spleen)

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10
Q

How do lipophilic molecules get through the capillary cells?

A

They diffuse right through the plasma membranes

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11
Q

Does albumin easily leak out the capillaries?

A

No, proteins are usually too large to diffuse through

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12
Q

What is filtration?

A

Movement of fluid OUT of the capillary and into the intersitium

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13
Q

What is absorption?

A

Movement of fluid INTO the capillary from the interstitial space

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14
Q

What are the 4 starling forces that affect capillary fluid movement?

A
  1. Capillary hydrostatic pressure
  2. Interstitial fluid hydrostatic pressure
  3. Plasma oncotic pressure
  4. Interstitial oncotic pressure
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15
Q

Does capillary hydroststic pressure favor filtration or absorption

A

Filtration

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16
Q

What is the capillary hydrostatic pressure dependednt on?

A

Pre- and post- capillary resistances and pressures

17
Q

If you increase resistance in the arterioles, what will happen to the pressure inside the capillary?

A

Decrease

18
Q

If you increase the amount of venular resistance, what happens to the pressure in the capillary?

A

Increase

19
Q

What happens to the capillary pressure if you increase venous pressure?

A

Increases

20
Q

What is the reason for the plasma oncotic pressure?

A

The plasma proteins which can not leave the capillary lumen

21
Q

What is the approximate pressure measurement that is contributed by plasma oncotic pressure?

A

25-40 mmHg

22
Q

Does plasma oncotic pressure favor absorption or filtration

A

Absorption

23
Q

What produces the interstitial hydrostatic pressure?

A

The fluid located in the intermolecular spaces of the interstitial matrix

(Very small pressure)

24
Q

What produces the interstitial oncotic pressure?

A

Proteins in the oncotic pressure

Very small

25
Q

How do you calculate net filtration pressure?

A

NFP= Pc+ πi - Pi - πc

NFP= (capillary hydrostatic pressure) + (interstitial Oncotic pressure) - (hydrotstatic interstitial pressure) - (capillary osmotic pressure)

26
Q

If the net filtration pressure is positive , what direction is the fluid moving

A

Filtration (moving out of capillary lumen)

27
Q

If the net filtration pressure is negative, which direction is fluid moving

A

Absorption (fluid moving into capillary from interstitial space)

28
Q

How do you calcaule the rate of fluid movement (F)?

A

F= Kf x NFP

Kf is the filtration coefficient which reflects the capillary permeability

(NFP=Pc+ πi-Pi-πc)

29
Q

What does Kf represent

A

Kf is the filtration coefficient and it reflects the capillary permeability

30
Q

When you calculate the NFP, you use 4 values. 3 of them stay pretty constant, but one of them is variable. Which is which?

A

Pc (capillary hydrostatic pressure) varies as you move from the arteriole end to the venule end

πi, Pi, and πc tend to stay pretty constant

SO what does that mean? It means that as you move from the beginning to the end of the capillary, you actually move from a positive NFP (filtration) to a negative NFP (absorption)

31
Q

If you increase capillary pressure, do you get more filtration or absorption

A

Filtration

32
Q

If you decrease capillary pressure, do you favor filtration or absorption?

A

Absorption

33
Q

If you decrease the plasma protein level, do you favor absorption or filtration?

A

Filtration

34
Q

If you were hypovolemic and needed to get more fluid back into the bloodstream, what could your body do at the capillary level to accomplish that

A

If you increase the vasoconstriction at the arteriole, it will decrease capillary hydrostatic pressure, which will favor absorption, and your capillaries will absorb fluid from the interstitial space

35
Q

Why doesn’t fluid accumulate in the interstitial spaces? I thought that the overall balance was towards filtration!

A

Becasue the lymph vessels collect interstitial fluid and return it to the bloodstream

36
Q

What kinds of things can increase capillary hydrostatic pressure and favor filtration, possibly causing edema?

A

Arteriolar dilation

Venous constriction

Increased venous pressure

Heart failure

Extra cellular fluid volume expansion

37
Q

What kinds of things would decrease capillary oncotic pressure and favor filtration, and possible cause edema?

A

Decreased plasma protein concentration

Severe liver failure (failure to make protein)

Protein malnutrition

Nephrotic syndrome (losing protein in urine)

PHYSIOLOGY Exam 3 (Lauren) (10 decks)

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