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South College Human Physiology > Week 4- Cardiovascular Physiology > Flashcards

Week 4- Cardiovascular Physiology Flashcards

1
Q

What is the microcirculation?

A

Vessels from the first-order arteriole to the first-order venule

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2
Q

What happens in the microcirculation?

A

This is the site of nutritional exchange

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3
Q

What/where can the microcirculation serve non-nutritional functions?

A
  • Glomeruli of the kidneys (filtration)
  • Skin (temperature regulation
  • Signaling and host defense
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4
Q

What do precapillary sphincters do?

A
  • If metabolic demands are greater further down the line, the sphincters contract
  • This creates a high pressure spot, pushing the blood away
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5
Q

What is another name for arteriold?

A

Resistance vessels

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6
Q

How innervated are arterioles?

A

Highly innervated

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7
Q

Structure of the capillary wall

A
  • Endothelial cells (stacks)

- Basement membrane

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8
Q

What holds the endothelial cells together?

A

Tight junctions

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9
Q

What is made possible by the range of permeability in the tight junctions?

A
  • If they are very tight, very impermeable

- If they are more loose, there is room for cells (think inflammatory response, WBC)

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10
Q

Types of capillaries

A
  • Continuous
  • Fenestrated
  • Sinusoidal
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11
Q

Which type of capillary is most predominant?

A

Continuous

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12
Q

Where might continuous capillaries be found?

A
  • Skeletal muscle

- Blood-brain barrier

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13
Q

How permeable are continuous functions?

A

Highly impermeable

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14
Q

Where might fenestrated capillaries be found?

A
  • Small intestine

- Kidney

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15
Q

What are fenestrae?

A

Pores that allow transport of substances from the inside to the outside

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16
Q

Why are the fenestrated capillaries more permeable?

A

They are located in places like the small intestine where absorption of nutrients is very important

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17
Q

Where might sinusoidal capillaries be found?

A

Liver

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18
Q

What is another name for sinusoidal capillaries?

A

Discontinuous capillary

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19
Q

What component of capillary structure is missing from sinusoidal capillaries?

A

The basement membrane

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20
Q

What makes sinusoidal capillaries so leaky?

A

The large fenestrations and gaps between endothelial cells

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21
Q

What kind of substances pass directly through the capillary membrane?

A

Lipid-soluble substances like O2 and CO2

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22
Q

What do lipid-insoluble substances pass through?

A

Intercellular clefts

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23
Q

Ultimately, what determines the permeability of the membrane?

A
  • Diameter of the cleft (larger = easier)

- Size of the molecule (smaller = easier)

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24
Q

In skeletal muscle, what percentage of capillaries are perfused?

A

~20%, more become active during exercise

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25
Q

What are the implications for delivery and diffusion of substances when many capillaries are closed?

A

Less efficient delivery, since a single capillary is responsible for providing nutrients for more tissue

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26
Q

What determines PO2?

A

The amount of O2 in the plasma

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27
Q

What factors impact the PO2 in the capillary?

A
  • [O2]
  • O2 content of blood
  • Capillary blood flow (F)
  • Capillary radius
  • Radius of tissue cylinder
  • O2 consumption of surrounding tissues
  • Axial distance (x) along the capillary
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28
Q

What does PO2 determine?

A

Rate of diffusion

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29
Q

Interstitium

A

Space between cells

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30
Q

Interstitial fluid

A

Fluid filling the interstitum

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31
Q

What major types of solid structures are in the interstitum?

A
  • Collagen fibers

- Proteoglycan filaments

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32
Q

What are proteoglycan filaments?

A

Coiled molecules composed of hyaluronic acid

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33
Q

What makes up most of the fluid in the interstitum?

A
  • Gel, fluid proteoglycan mixtures

- Little free fluid under normal conditions

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34
Q

What are Starling forces?

A

Forces governing the passive exchange of fluids across a semipermeable membrane

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35
Q

Compartments at play with cardiovascular system Starling forces

A
  • Capillary

- Interstitial space

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36
Q

Types of forces with the Starling forces

A
  • Hydrostatic forces

- Colloid osmotic forces

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37
Q

What are hydrostatic forces

A

Pressure of the fluid in either the capillary or the interstitial fluid

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38
Q

What are colloid osmotic forces

A

Osmotic forces produced by molecules such as proteins that generate osmotic pressure

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39
Q

What are the capillary Starling forces?

A
  • Capillary pressure (Pc)

- Plasma colloid osmotic pressure (IIp)

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40
Q

What direction does the capillary pressure go?

A

Out of the capillary against the capillary wall

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41
Q

What direction does the plasma colloid osmotic pressure go?

A

Into the capillary (water flows in)

42
Q

What are the interstitial fluid Starling forces?

A
  • Interstitial fluid pressure (Pif)

- Interstitial fluid colloid osmotic pressure (IIif)

43
Q

What direction does the interstitial fluid pressure go?

A

Into the capillary against the capillary wall

44
Q

What direction does the interstitial fluid colloid osmotic pressure go?

A

Out of the capillary (water flows out)

45
Q

What is the equation for net filtration?

A

NFP = Pc - Pif - IIp + IIif

46
Q

What does a positive NFP indicate?

A

Water out of the capillary into the interstitial space (filtration)

47
Q

What does a negative NFP indicate?

A

Water into the capillary from the interstitial space (reabsorption)

48
Q

Which end of the capillary will have a positive NFP?

A

Arterial

49
Q

Which end of the capillary will have a negative NFP?

A

Venous

50
Q

Between the capillary and interstitial forces, which one will change most from the arterial to the venous end?

A

Capillary forces (Pc and IIp)

51
Q

Classic Starling Model

A

The four forces acting together to filter and absorb fluids

52
Q

How are the predictions different in the revised Starling model?

A

Absorption is much less

53
Q

Osmotic asymmetry

A

The amount of fluid filtered does not equal the amount of fluid absorbed

54
Q

What is the normal capillary hydrostatic pressure?

A

17 mmHg

55
Q

What is the interstitial fluid pressure in most tissues?

A
  • 3 mmHg (mostly loose subcutaneous tissue)
56
Q

What interstitial fluid pressures do encapsulated have?

A

5-10 mmHg

57
Q

What kind of pressure do natural cavities of the body have?

A

Negative

58
Q

What cavities have this negative pressure?

A
  • Intrapleural space
  • Joint synovial space
  • Epidural space
59
Q

Pressure of intrapleural space

A

-8 mmHg

60
Q

Pressure of joint synovial space

A

-4 to -6 mmHg

61
Q

Pressure of epidural space

A

-4 to -6 mmHg

62
Q

What purpose does the negative interstitial fluid pressure serve?

A
  • Caused by pumping of lymphatic system

- Sucks excess fluid into the lymphatic system

63
Q

What causes the colloid osmotic pressure?

A

Presence of large proteins

64
Q

What proteins cause colloid osmotic pressure?

A
  • Albumin

- Globulins

65
Q

What percentage of total colloid pressure comes from albumin?

A

80%

66
Q

What percentage of total colloid pressure comes from globulin?

A

20%

67
Q

What is the average protein concentration and colloid pressure?

A
  • 3g/dl

- 8 mmHg

68
Q

Edema

A

Excess fluid accumulation

69
Q

Why does edema occur?

A

Abnormal Starling forces

70
Q

What kind of edema could abnormal hydrostatic forces cause?

A
  • Pulmonary edema

- Generalized peripheral edema

71
Q

What will cause pulmonary edema?

A

Left-sided heart failure

72
Q

How is pulmonary edema caused?

A
  • Left-sided HF may cause increased Pc in pulmonary capillaries
  • Arises from left atrium and ventricle not pumping blood into systemic circuit well enough
73
Q

What will cause generalized peripheral edema?

A

Right-sided heart failure

74
Q

How is generalized peripheral edema caused?

A
  • Right-side HF may cause increased Pc in systemic veins

- Arises from right atrium and ventricle not pumping blood into the pulmonary circuit well enough

75
Q

What happens with nephrotic syndrome?

A

Proteins are lost in the urine

76
Q

What kind of edema can nephrotic syndrome cause?

A

Generalized peripheral edema

77
Q

How does nephrotic syndrome cause edema?

A

Decreased IIp causes decreased ability to retain fluids in the capillaries

78
Q

What happens during pregnancy to cause edema?

A
  • Synthesis of plasma proteins does not keep up with increase in plasma volume
  • Results in decreased IIp and generalized peripheral edema
79
Q

How can inflammation in capillary walls cause edema?

A
  • Release vasodilators and cytokines which cause interendothelial clefts to widen
  • Results inn tissue swelling
80
Q

How do head injuries result in edema?

A
  • Cause cerebral edema

- Breakdown tight junctions in cerebral vessels

81
Q

What about impaired lymphatics causes edema?

A
  • Damaged lymph nodes may reduce lymphatic drainage

- Lead to local edema upstream from the affected nodes

82
Q

What is the lymphatic system?

A
  • An accessory route where fluids and protein can flow from interstitial spaces to the blood
  • Important for immunity
83
Q

What does the lymphatic system prevent?

A

Edema

84
Q

What is lymph is derived from?

A

Interstitial fluid that flows into the lymphatics

85
Q

What is the connection between the lymphatic system and the GI tract?

A

Absorption of nutrients from GI tract

86
Q

What happens to fluid that does not re-enter the capillary at the venous end?

A
  • Brought back into circulation via lymphatic vessels

- ~1/10 of fluid

87
Q

How much lymph circulates daily?

A

2-3 L

88
Q

What is the structure of initial lymphatics?

A

Endothelial cells anchored to surrounding connective tissue with anchoring filaments

89
Q

What do overlapping endothelial cells form?

A

Valves preventing backflow

90
Q

What is the effect of pressure from the interstitial fluid (Pif)?

A

As P(if) increases, lymph flow also increases to a certain point

91
Q

At what point does increases in P(if) fail to drive greater lymph flow?

A

~2 mmHg

92
Q

Why does the increase in pressure fail to create more lymph flow?

A

Excessive pressure actually compresses the lymph vessels

93
Q

Phases of lymph flow

A
  • Expansion phase

- Compression phase

94
Q

What happens during the expansion phase?

A
  • Hydrostatic pressure in the interstitial fluid exceeds what’s in the initial lymphatic
  • Microvalves open and fluid enters
95
Q

What happens during the compression phase?

A
  • Hydrostatic pressure inside the initial lymphatic increases, which closes the microvalves
  • Increasing pressure opens the secondary lymph valves, fluid flows downstream
96
Q

In lymphatic vessels, where is smooth muscle present?

A

After the secondary lymph valves

97
Q

What causes lymph to flow?

A
  • Lymphatic pump

- External pumps

98
Q

How does the lymphatic pump function?

A

Lymph vessels stretch –> smooth muscle contracts

99
Q

How much pressure can the lymphatic pump inn large lymph vessels?

A

50-100 mmHg

100
Q

What are the external pumps for the lymphatic system?

A
  • Muscles
  • Movement
  • Adjacent arterial pulsations
  • Compression of tissues by external objects
101
Q

How much does lymph flow increase during exercise?

A

10-30x

102
Q

Key roles of lymphatic system

A
  • Controls concentrations of proteins in the ISF (increased IIif can cause edema)
  • Controls volume of ISF
  • Controls ISF pressure (Pif)

South College Human Physiology (4 decks)

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