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Physl > Cardiovascular Physiology 28 > Flashcards

Cardiovascular Physiology 28 Flashcards

1
Q

What are the ways that material are exchanged across the walls of Cappilaries?

A
  • Diffusion
  • Vesicle transport
  • Bulk flow
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2
Q

Why does blood flow very slowly in the capillaries?

A

To maximize the time for the exchange of substances between the plasma and the interstitial fluid

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3
Q

What is Diffusion?

A

The movement of a substance from a region of high concentration to a region of low concentration down its concentration gradient

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4
Q

Why is Diffusion the most important mechanism?

A

Because it is able to exchange nutrients and metabolic end products

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5
Q

How do Lipid soluble substances go through capillary cell walls?

A

Through diffusion

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6
Q

How do Lipid insoluble substances go through capillary cell walls?

A

Water filled channels
•Intercellular cleft
•Fenestrae
•Fused vesicle channels

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7
Q

Which substances are lipid soluble in Capillaries?

A

Oxygen and Carbon Dioxide

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8
Q

Which substances are lipid insoluble in Capillaries?

A

Ions and Glucose

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9
Q

What is Transcytosis?

A

The use of vesicles to cross endothelial cells

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10
Q

What is a fused vesicle channel?

A

When endocytic and exocytic vesicles form a water-filled channel across the cell

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11
Q

How do substances move through a fused vesicle channel?

A

By diffusion

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12
Q

What is Bulk Flow?

A

The movement of protein free plasma across the capillary wall

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13
Q

What are the Capillary walls highly permeable to?

A

Plasma and all plasma solutes, except proteins

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14
Q

What cannot cross a capillary wall?

A

Plasma proteins

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15
Q

What crosses the capillary in Bulk during bulk flow?

A

Various constituents of a fluid such as sodium and potassium are crossing the capillary wall in bulk or as a unit

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16
Q

What is the function of Bulk Flow?

A

The distribution of the extracellular fluid volume

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17
Q

What does the Extracellular fluid include?

A

The plasma and the interstitial fluid

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18
Q

What is Filtration?

A

The movement of protein-free plasma from the capillary to IF

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19
Q

What is Reabsorption?

A

The movement of protein-free plasma from IF to capillary

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20
Q

What is Bulk flow driven by?

A

Different pressures

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21
Q

Why does bulk flow occur?

A

Because of differences in the hydrostatic and colloid osmotic pressures between the capillary plasma and the interstitial fluid

22
Q

What is Hydrostatic pressure?

A

The force of a fluid against a membrane

23
Q

What drives bulk flow?

A

Hydrostatic pressure

24
Q

What is Capillary Hydrostatic Pressure (Pc)?

A

The pressure exerted by the blood on the inside of the capillary walls

25
Q

What does Capillary Hydrostatic Pressure (Pc) tend to do?

A

It tends to force protein free plasma out of the capillaries into the interstitial fluid

26
Q

What is Interstitial Fluid Hydrostatic Pressure (PIF)?

A

The pressure exerted on the outside of the capillary wall by the interstitial fluid

27
Q

What does Interstitial Fluid Hydrostatic Pressure (PIF) tend to do?

A

Tends to force fluid into the capillaries, but is very negligible

28
Q

Which Hydrostatic Pressure is very negligible and does not contribute significantly to bulk flow?

A

Interstitial Fluid Hydrostatic Pressure (PIF)

29
Q

What is the Colloid Osmotic Pressure?

A

The osmotic pressure due to the presence of impermeable proteins

30
Q

Why isn’t the water concentration between the Plasma and the Interstitial Fluid equal?

A

Proteins that are impermeable and thus draw water towards them inside the capillary

31
Q

What is the Blood Colloid Osmotic Pressure (πc)?

A

The Osmotic Pressure due to the presence of a large number of non-permeating plasma proteins such as albumin in the blood

32
Q

Why don’t sodium and potassium influence water concentration in the plasma and the interstitial fluid?

A

Because the are found in equal amounts in the plasma and interstitial fluid

33
Q

What do the Plasma Proteins do in terms of water?

A

The pull water into the capillaries

34
Q

What is the Interstitial Fluid Colloid Osmotic Pressure (πIF) due to?

A

The small amount of plasma proteins that escape the capillaries into the interstitial fluid

35
Q

What does the Interstitial Fluid Colloid Osmotic Pressure (πIF) favor?

A

Movement of fluid out of the capillary, but it is negligible

36
Q

Which Pressures are negligible in bulk flow?

A
  • Interstitial Fluid Colloid Osmotic Pressure (πIF)

* Interstitial fluid Hydrostatic Pressure (PIF)

37
Q

What equation calculates the net exchange pressure at a given point across a capillary wall?

A

Net exchange pressure = Pc + πIF - PIF - πc

38
Q

What are the outward pressures in Bulk flow?

A
  • Capillary Hydrostatic Pressure

* Interstitial fluid osmotic pressure

39
Q

What are the Inward Pressures in Bulk flow?

A
  • The osmotic force due to the plasma protein concentration

* The interstitial fluid hydrostatic pressure

40
Q

Which forces have a positive value?

A

Forces directed out of the capillary

41
Q

Which forces have a negative value?

A

Forces directed into the capillary

42
Q

How is the Hydrostatic pressure affected as blood moves from the arterial end to the venous end?

A

Hydrostatic pressure decreases going from the arterial end to the venous end

43
Q

How is the colloid osmotic pressure (πc) affected as blood moves down a capillary?

A

Colloid Osmotic Pressure (πc) remains the same along the length of the capillary

44
Q

What does it mean if the Net Exchange Pressure is a positive number?

A

It favours filtration from the capillary into the interstitial fluid at the arterial end of the capillary

45
Q

What does it mean if the Net Exchange Pressure is a negative number?

A

It favours absorption from the interstitial fluid into the capillary

46
Q

What are the Starling Forces?

A
  • Blood Hydrostatic Pressure (Pc)
  • Blood Colloid Osmotic Pressure (πc)
  • Interstitial fluid hydrostatic pressure (PIF)
  • Interstitial fluid colloid osmotic pressure (πIF)
47
Q

Where do the Starling forces favor filtration?

A

At the arterial end a of a capillary

48
Q

Where do the Starling forces favor absorption?

A

At the venous end of a capillary

49
Q

Which Starling force changes along the length of a capillary and why?

A

The capillary hydrostatic pressure. It decreases along the length of a capillary due to friction

50
Q

When and where does the transition between filtration and reabsorption occur?

A

It occurs when the sum of the outward pressures is equal to the sum of the inward pressures. Closer to the venous end of the capillary

51
Q

Why does more filtration than absorption occur in capullaries?

A

Because the filtration transition to absorption occurs closer to the venous end

Physl (94 decks)

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