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05. Year 1: Cardiovascular System COPY > Exchange and the Lymphatic System > Flashcards

Exchange and the Lymphatic System Flashcards

1
Q

What are capillaries specialised for?

A

Exchanging nutrients

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2
Q

Why are capillaries thin walled?

A

Presents a small diffusion barrier

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3
Q

What is the advantage of capillaries having a small diameter?

A

Large surface area:volume ratio

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4
Q

What does the ultrastructure of capillaries relate to?

A

Function

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5
Q

What are the 3 kinds of capillaries?

A

Continuous

Fenestrated

Discontinuous

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6
Q

What are the 2 different kinds of continuous capillaries?

A

No clefts or channels such as in the brain

Only clefts such as in muscle

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7
Q

What is present in fenestrated capillaries?

A

Clefts and channels

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8
Q

Where are fenestrated capillaries found?

A

Intestine

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9
Q

Where are continuous capillaries found?

A

Brain

Muscle

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10
Q

Where are discontinuous capillaries found?

A

Liver

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11
Q

What is present in discontinuous capillaries?

A

Clefts and massive channels

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12
Q

What is the difference between continuous and fenestrated capillaires?

A

Continuous have leaky junctions whereas fenestrated have large pores

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13
Q

What causes more of a nutrient to diffuse across a capillary?

A

If the cell uses more of it, it creates a larger concentration gradient and so more diffuses across

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14
Q

What are the 2 ways that nutrients can cross capillaries?

A

Diffusion

Carrier mediated transport

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15
Q

What is an example of carrier mediated transport?

A

Glucose transporter

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16
Q

How do polar substances diffuse across capillaries?

A

Through clefts/channels

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17
Q

How to non-polar substances diffuse across capillaries?

A

Across the membrane

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18
Q

What does hydrostatic pressure do?

A

Pushes fluid out of capillaries

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19
Q

What pushes fluid out of capillaries?

A

Hydrostatic pressure

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20
Q

What does osmotic (oncotic) pressure do?

A

Draws fluid back into capillaries

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21
Q

What causes osmotic pressure?

A

Hydrostatic pressure pushing fluid out of capillaries builds up an osmotic pressure

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22
Q

What is the balance between hydrostatic and osmotic pressures called?

A

Starling’s forces

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23
Q

What makes up Starling’s forces?

A

Capillary hydrostatic pressure vs interstitial fluid hydrostatic pressure

Plasma osmotic pressure vs interstitial fluid osmotic pressure

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24
Q

What formula describes net filtration pressure?

A

Net filreation pressure = (PC - PIF) - (πP - πIF)

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25
Q

Overall how much fluid is lost and gained from capillaries each day?

A

20L is lost

17L is gained

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26
Q

If 20L of fluid is lost from capillaries and 17L is gained each day, what happens to the remaining 3L?

A

Goes into the lymphatic system

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27
Q

What eventually happens to fluid that is drained into the lymphatic vessels?

A

Returned to venous circulation

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28
Q

What happens when the lymphatic system becomes overwhelmed?

A

Oedema

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29
Q

What is an oedema?

A

Accumulation of excess fluid

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30
Q

What is an accumulation of excess fluid called?

A

Oedema

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31
Q

What can an oedema be caused by?

A

Lymphatic obstruction

Raised hydrostatic pressure

Low osmotic pressure

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32
Q

What can cause a lymphatic obstruction?

A

Filariasis or surgery

33
Q

What can cause a raised hydrostatic pressure?

A

Ventricular failure

34
Q

What can cause low osmotic pressure?

A

Hypoproteinemia

Increased permeability

35
Q

What can increased permeability be caused by?

A

Inflammation such as rheumatism

36
Q

What can hypoproteinemia be caused by?

A

Nephrosis

Liver failure

Nutrition

37
Q

What redirects blood?

A

Arterioles not capillaries

38
Q

Why do capillaries not redirect blood?

A

They do not have any smooth muscle around them

39
Q

What is varying the resistance of arterioles done by?

A

Altering the radius

40
Q

What is Darcy’s Law?

A
41
Q

What is Poiseuille’s Law?

A
42
Q

What equation to you get by substituting Poiseuille’s Law back into Darcy’s Law?

A
43
Q

What equation describes flow?

A
44
Q

Why does varying the resistance of one set of vessels not only affect the flow through that region of the body?

A

Because it changes the total peripheral resistance so affects the mean arterial pressure

45
Q

What formula describes the mean arterial pressure?

A

MAP = CO x TPR

46
Q
A
47
Q

What does MAP stand for?

A

Mean arterial pressure

48
Q

What does TPR stand for?

A

Total peripheral resistance

49
Q

Why is mean artieral pressure very important?

A

It provides the driving force that pushes blood through useful places like the brain, so a system must monitor and regulate in by controlling the state of construction in arterioles

50
Q

What are the 2 levels of control over smooth muscle surrounding the arterioles?

A

Intrinsic mechanisms

Extrinsic mechanisms

51
Q

What are intrinsic mechanisms concerned with?

A

Meeting the needs of each individual tissue

52
Q

What are extrinsic mechanisms concerned with?

A

Ensuring that the total peripheral resistance (and so mean arterial pressure) of the whole body stays at the right levels

53
Q

What is extrinsic control achieved by?

A

Neural

Hormonal

Angiotensin II

Vasopressin

Atrial natriuretic factor

54
Q

How is the autonomic system used for extrinsic control?

A

Sympathetic nerves release noradrenaline which binds to A1 receptors causing arteriolar constriction and decreases flow through that tissue, increase total peripheral resistance

Parasympathetic system has no effect

55
Q

What receptors does the sympathetic nervous system act on arterioles?

A

A1

56
Q

What effect does parasympathetic nerves have on arterioles?

A

Usually no effect

57
Q

What is a hormone that achieves extrinsic control?

A

Adrenaline

58
Q

Where is adrenaline released from?

A

Adrenal medulla

59
Q

What receptor on arterioles does adrenaline act on?

A

A1

60
Q

How do hormones achieve extrinsic control?

A

Adrenaline causes arteriolar constriction so decrease flow through that tissue and increase total peripheral resistance

61
Q

What is a complication with using adrenaline to achieve extrinsic control?

A

In some tissues (such as skeletal and cardiac muscle) as well as A1 it also binds to B2 receptors which cause arteriolar dilation, increasing flow and decreasing total peripheral resistance

62
Q

What is angiotensis II produced in response to?

A

Low blood pressure

63
Q

What effect does angiotensin II have?

A

Causes arteriolar constriction so increases total peripheral resistance

64
Q

What is vasopressin released in response to?

A

Low blood volume

65
Q

What effect does vasopressin have?

A

Causes arteriolar constriction so increases total peripheral resistance

66
Q

What is atrial natriuretic factor released in response to?

A

High blood volume

67
Q

What impact does atrial natriuretic factor have?

A

Causes arteriolar dilation so decreases total peripheral resistance

68
Q

What is the important effect of B2 receptors in blood vessels?

A

Only in some places of the body so redirects blood to heart and skeletal muscles during fight or flight reaction

69
Q

What is local (intrinsic) control achieved by?

A

Active (metabolic) hyperaemia

Pressure (flow) autoregulation

Reactive hyperaemia

The injury response

70
Q

How does active (metabolic) hyperaemia achieve intrinsic control?

A

1) Increased metabolic activity causes increase in the concentration of metabolites
2) Triggers release of EDRF/NO (paracrines)
3) Causes arteriolar dilation
4) Increased flow to wash out metabolites
5) An adaptation to match blood supply to the metabolic needs of that tissue

71
Q

How is pressure (flow) autoregulation used to achieve intrinsic control?

A

1) Decreased mean arteriolar pressure causes decrease in flow
2) Metabolites accumulate
3) Arterioles dilate and flow is restored to normal
4) An adaptation to ensure that a tissue maintains its blood supply despite changes to mean arterial pressure

72
Q

How is reactive hyperaemia used to achieve intrinsic control?

A

Occlusion (the blockage or closing of a blood vessel) of blood supply causes a subsequent increase in blood flow

An extreme version of pressure autoregulation

73
Q

How is the injury response used to achieve intrinsic control?

A

1) Substance P acts on mast cells which release histamine
2) Histamine causes arteriolar dilation which increases blood flow and permeability
3) Aids delivery of blood born leukocytes to injured area

74
Q

What are areas that are ‘special’ (in terms of pressure)?

A

Coronary circulation

Cerebral circulation

Pulmonary circulation

Renal circulation

75
Q

How is coronary circulation special?

A

Blood flow is interupted by systole

But still has to cope with increased demand during exercise

Does so by showing excellent active hyperaemia

Expressed many B2 receptors

These swamp any sympathetic arteriolar constriction

76
Q

How is cerebral circulation special?

A

Needs to be kept stable whatever the circumstances

Shows excellent pressure autoregulation

77
Q

How is pulmonary circulation special?

A

Decrease in O2 causes arteriolar constriction

The opposite reaction to most tissues

Ensures that blood is directed to the best ventilated parts of the lungs

78
Q

How is renal circulation special?

A

Main function is filtration which depends on pressure

Changes in mean arteriolar pressure would have a big effect on blood volume

Shows excellent pressure autoregulation

05. Year 1: Cardiovascular System COPY (41 decks)

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