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2.1 Control and Integrative Physiology > Mairead - Capillary Exchange > Flashcards

Mairead - Capillary Exchange Flashcards

1
Q

Write about the structure of capillaries

A

One tunica of simple squamous epithelia (endothelium)

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2
Q

Classify capillaries

A

Continuous

Fenestrated

Sinusoids

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3
Q

What is endotehlium

A

Simple squamous epithelia

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4
Q

Write a note on capillary exchange
(4)

A

In peripheral tissue water and solutes and pushed out of the plasma

This movement mixes the EC fluid and delivers nutrients

Most fluid is returned to the venules, the rest is returned to the circulation via the lymphatic system

With this lymphatic shunt there is accelerated delivery of nutrients and flushing out of bacteria, toxins and debris

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5
Q

What are the three stages to capillary exchange?

A

Diffusion

Filtration

Reabsorption

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6
Q

What is diffusion

A

The net movement of ions or molecules, from a high concentration to a low concentration

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7
Q

When is diffusion rapid?

A

Distances are small

Pressure gradient is large

Molecules are small

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8
Q

What are the five principal diffusion routes?

A

Between endothelial cells

Through protein channels

Across the lipid

Through fenestrations

Through sinusoid gaps

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9
Q

What molecules diffuse between endothelial cells?
(3)

A

Water glucose

Amino acids

Glucose

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10
Q

What diffuses through protein channels?

A

Ions

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11
Q

What diffuses through fenestrations?

A

Water

Large solutes

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12
Q

What diffuses through sinusoid gaps?

A

Water

Large solutes

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13
Q

Where can diffusion of water and soluble compounds occur?

A

Pores allow the movement of water and soluble compounds ONLY in the fenestrated capillaries of the kidney, hypothalamus and glands

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14
Q

What does diffusion through the cell membrane allow?

A

Allow passage of lipids, steroids, gases

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15
Q

What type of diffusion do the sinusoids allow?

A

The movement of plasma proteins and hormones into the bloodstream at the liver

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16
Q

What is filtration?

A

The movement of water out of and into the capillary

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17
Q

What is the driving force of filtration?

A

Hydrostatic pressure

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18
Q

What is CHP

A

Capillary hydrostatic pressure

Blood pressure in a capillary

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19
Q

How does hydrostatic pressure drive filtration?

A

This pressure drives water across the capillary membrane and solutes travel within the water

Only small molecules will be able to pass the rest are filtered (stay in the blood -> formed elements and plasma proteins)

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20
Q

What is capillary hydrostatic pressure?

A

The difference in blood pressure between the 2 ends of the capillary bed
35 - 18 mmHg

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21
Q

In relation to pressure, where does most filtration occur?

A

Where hydrostatic pressure is highest -> the arterial end

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22
Q

How does reabsorption occur?

A

Due to osmosis

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23
Q

What is osmosis

A

The movement of water across a selectively permeable membrane

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24
Q

What is osmotic pressure?

A

The force on the water to move

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25
Q

How are plasma proteins present in blood?

A

As colloids

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26
Q

What does blood colloid osmotic pressure do?
(2)

A

It pulls water (i.e. reabsorbs it) from the interstitial space into the blood

This movement draws fluid from the capillary bed at the venous end

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27
Q

Write a note on the interplay between filtration and reabsorption

A

Hydrostatic pressure forces water out of the blood i.e. out of solution

Osmotic pressure pulls water back into the vessels i.e. into solution

Rates of filtration and absorption vary along the capillary

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28
Q

What is IHP

A

Interstitial hydrostatic pressure

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29
Q

Give a value for capillary hydrostatic pressue

A

35mmHg - 18mmHg

30
Q

Give a value for Interstitial hydrostatic pressure

A

0

31
Q

Give a value for osmotic forces

A

BCOP

32
Q

Give a value for interstitial colloid osmotic pressure

A

0

33
Q

What is the equation for net filtration pressure

A

Net hydrostatic pressure - net osmotic pressure

34
Q

Comment on filtration vs reabsorption

A

Filtration occurs for most of the length as the net filtration pressure > net reabsorption pressure

35
Q

How much fluid is filtered each day

A

24.6L

36
Q

How much of the 24.6L fluid filtered by blood is reabsorbed by veins?

A

85%

37
Q

How much fluid flows through lymphatic vessels each day?

A

3.4L

38
Q

Write a note on lymphatic drainage
(3)

A

Important to prevent fluid accumulation in the interstitial space

Returns fluid and proteins to the circulation

Moves fluid into the lymphatic vessels and hence through the lymph nodes

39
Q

What is oedema
(2)

A

Disturbance in net filtration pressure

The abnormal accumulation of interstitial fluid, is not usually detected until the volume has increased by 30%

40
Q

What factors will affect Oedema

A

Any factors that affects HP or COP will shift the balance between filtration and reabsorption

41
Q

Give three examples of things that disturb NFP

A

Haemorrhage (decrease CHP)

No Protein synthesis (COP)

Dehydration

42
Q

List some of the causes of oedema
(5)

A

Damage causes proteins to cross the capillary wall -> increases ICOP and results in swelling in bruised areas

Starvation and lock of protein synthesis -> decreases BCOP

Circulatory obstruction -> CHP increases -> clot, high pressure or coronary problems

Blockage of the lymphatics

Fluid retention -> CHP increases

43
Q

Write a note on renal filtration

A

In kidney blood is filtered to form filtrate

Forces within renal corpuscle force fluid out from the glomerular blood capillaries across the filtration membrane and into Bowman’s capsule

44
Q

What cannot happen without renal filtration?

A

Urine cannot be formed and water soluble waste will not be removed

45
Q

What is GFT

A

Glomerular Filtration Rate

46
Q

What is glomerular filtration rate

A

The amount of filtrate that flows out of all the renal corpuscles every minute (and into the nephron)

47
Q

What percentage of plasma entering the nephrons becomes glomerular filtrate

A

!6-20%

48
Q

How are renal corpuscles particularly suited to filtration
(4)

A

The surface area for filtration (6m2)

The histology of the endothelial-capsular membrane

The efferent arteriole is smaller in diameter than the afferent arteriole, giving a blood hydrostatic pressure of 50mmHg

The endothelial-capsular membrane is very thin

49
Q

Describe the histology of the endothelial-capsular membrane
(3)

A

Endothelial pores

Basement membrane

Filtration slits

50
Q

What does filtration of blood depend on?
(4)

A

Glomerular hydrostatic blood pressure (50 mmHg)

Capsular hydrostatic pressure (15mmHg)

Colloid Osmotic pressure (25mmHg)

Capsular colloid osmotic pressure (0mmHg -> no protein present)

51
Q

What is effective filtration pressure also called?

A

Peff

52
Q

What is the equation for peff?

A

Net hydrostatic pressure - net colloid osmotic pressure

usually 10 mmHg

53
Q

Name two abnormalities in filtration
(2)

A

A decrease in arterial blood pressure -> reduces the glomerular hydrostatic pressure below 40 mmHg -> no filtration will occur

Glomular capillaries become too permeable, as in glomerulonephritis, proteins pass into the filtrate -> increases the Peff

54
Q

What is the term for a renal output of less than 50ml/day

A

Anuria

55
Q

What is anuria

A

A renal output of less than 50ml/day

56
Q

What happens if there is no glomerular filtration?

A

Waste products are not eliminated

pH control is reduced and blood volume control is lost

57
Q

How is GFR controlled
(3)

A

Controlled by local autoregulation

Controlled by hormonal regulation

Controlled by neural ANS regulation

58
Q

Write a note on local autoregulation of GFR

A

Regulation of GFR despite changes in local
blood pressure and blood flow.

Achieved by altering the diameter of the
efferent and afferent arteriole

59
Q

If blood pressure drops, GFR is sustained by what?

A

dilation of afferent arteriole

dilation of capillaries and

constriction of the efferent arteriole

60
Q

If blood pressure rises, GFR is sustained by what?

A

Constriction of the afferent arteriole

61
Q

What hormones are responsible for controlling filtration

A

Renin and atrial natiuretic peptide (ANP)

62
Q

Where is renin released from?

A

The JGA

63
Q

When is renin released from the JGA?

A

The renal blood flow declines

The osmotic pressure of the filtrate in the DCT declines

64
Q

Why would renal blood flow decline
(3)

A

Reduced blood volume

Reduced blood pressure

Vascular blockage

65
Q

What does angiotensin do?

A

Has widespread effects to restore blood pressure

66
Q

What does angiotensin do in the capillary beds

A

Causes general vasoconstriction of all arterioles and precapillary sphincters

67
Q

What does angiotensin do in the nephron

A

It causes constriction of efferent arteriole (including GFR)

68
Q

What does angiotensin do in the adrenal gland

A

It causes release of aldosterone (including Na+ reabsorption in DCT)

69
Q

What does angiotensin do in the CNS

A

It causes the sensation of thirst increased vasomotor tone and the release of ADH (including body water)

70
Q

ANP and BNP

A

joweeb

71
Q

ANS regulation of GFR

A

vnwob

2.1 Control and Integrative Physiology (21 decks)

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