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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
How are plasma proteins present in blood?
As colloids
26
What does blood colloid osmotic pressure do? (2)
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
27
Write a note on the interplay between filtration and reabsorption
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
28
What is IHP
Interstitial hydrostatic pressure
29
Give a value for capillary hydrostatic pressue
35mmHg - 18mmHg
30
Give a value for Interstitial hydrostatic pressure
0
31
Give a value for osmotic forces
BCOP
32
Give a value for interstitial colloid osmotic pressure
0
33
What is the equation for net filtration pressure
Net hydrostatic pressure - net osmotic pressure
34
Comment on filtration vs reabsorption
Filtration occurs for most of the length as the net filtration pressure > net reabsorption pressure
35
How much fluid is filtered each day
24.6L
36
How much of the 24.6L fluid filtered by blood is reabsorbed by veins?
85%
37
How much fluid flows through lymphatic vessels each day?
3.4L
38
Write a note on lymphatic drainage (3)
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
What is oedema (2)
Disturbance in net filtration pressure The abnormal accumulation of interstitial fluid, is not usually detected until the volume has increased by 30%
40
What factors will affect Oedema
Any factors that affects HP or COP will shift the balance between filtration and reabsorption
41
Give three examples of things that disturb NFP
Haemorrhage (decrease CHP) No Protein synthesis (COP) Dehydration
42
List some of the causes of oedema (5)
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
Write a note on renal filtration
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
What cannot happen without renal filtration?
Urine cannot be formed and water soluble waste will not be removed
45
What is GFT
Glomerular Filtration Rate
46
What is glomerular filtration rate
The amount of filtrate that flows out of all the renal corpuscles every minute (and into the nephron)
47
What percentage of plasma entering the nephrons becomes glomerular filtrate
!6-20%
48
How are renal corpuscles particularly suited to filtration (4)
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
Describe the histology of the endothelial-capsular membrane (3)
Endothelial pores Basement membrane Filtration slits
50
What does filtration of blood depend on? (4)
Glomerular hydrostatic blood pressure (50 mmHg) Capsular hydrostatic pressure (15mmHg) Colloid Osmotic pressure (25mmHg) Capsular colloid osmotic pressure (0mmHg -> no protein present)
51
What is effective filtration pressure also called?
Peff
52
What is the equation for peff?
Net hydrostatic pressure - net colloid osmotic pressure usually 10 mmHg
53
Name two abnormalities in filtration (2)
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
What is the term for a renal output of less than 50ml/day
Anuria
55
What is anuria
A renal output of less than 50ml/day
56
What happens if there is no glomerular filtration?
Waste products are not eliminated pH control is reduced and blood volume control is lost
57
How is GFR controlled (3)
Controlled by local autoregulation Controlled by hormonal regulation Controlled by neural ANS regulation
58
Write a note on local autoregulation of GFR
Regulation of GFR despite changes in local blood pressure and blood flow. Achieved by altering the diameter of the efferent and afferent arteriole
59
If blood pressure drops, GFR is sustained by what?
dilation of afferent arteriole dilation of capillaries and constriction of the efferent arteriole
60
If blood pressure rises, GFR is sustained by what?
Constriction of the afferent arteriole
61
What hormones are responsible for controlling filtration
Renin and atrial natiuretic peptide (ANP)
62
Where is renin released from?
The JGA
63
When is renin released from the JGA?
The renal blood flow declines The osmotic pressure of the filtrate in the DCT declines
64
Why would renal blood flow decline (3)
Reduced blood volume Reduced blood pressure Vascular blockage
65
What does angiotensin do?
Has widespread effects to restore blood pressure
66
What does angiotensin do in the capillary beds
Causes general vasoconstriction of all arterioles and precapillary sphincters
67
What does angiotensin do in the nephron
It causes constriction of efferent arteriole (including GFR)
68
What does angiotensin do in the adrenal gland
It causes release of aldosterone (including Na+ reabsorption in DCT)
69
What does angiotensin do in the CNS
It causes the sensation of thirst increased vasomotor tone and the release of ADH (including body water)
70
ANP and BNP
joweeb
71
ANS regulation of GFR
vnwob

2.1 Control and Integrative Physiology (21 decks)

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