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2. Cardiovascular System > 10. Exchange and the Lymphatic System > Flashcards

10. Exchange and the Lymphatic System Flashcards

1
Q

What allows arterioles to constrict and dilate for good blood regulation and control?

A
  • smooth muscle around it (layers of endothelial cells)
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2
Q

What allows capillaries to have an effective gas exchange mechanism? (2)

A
  • short distance for diffusion due to one cell thick wall

- high SA:volume ratio

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3
Q

Do capillaries have smooth muscle around them?

A

No, just one cell-thick walls

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4
Q

What gross structure features of capillaries makes them ideal for exchange?

A
  1. lots in numbers
  2. thin walled (small diffusion barrier)
  3. small diameter ( big SA; volume)
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5
Q

What are 3 main types of capillaries?

A
  1. fenestrated
  2. continous
  3. discontinous
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6
Q

What determines capillary permeability?

A

Junctions between cells and the holes between them (either cells closely stuck together or slightly separated)

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7
Q

What is the structure of continous capillaries?

A
  • no clefts or channels
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8
Q

Where do continous capillaries exist in the body?

A

in the brain (blood-brain barrier prevents K leaking out acrs)

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9
Q

What is an exception of continous capillaries where clefts exist? (in which body region?)

A

in muscles

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10
Q

What is the structure of fenestrated capillaries?

A

clefts and channels

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11
Q

Where do fenestrated capillaries exist in the body?

A

in the intestine

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12
Q

What is the structure of discontinous capillaries?

A

clefts and massive channels

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13
Q

Where do discontinous capillaries exist in the body?

A

in the liver

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14
Q

Do majority of capillaries have clefts?

A

Yes

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15
Q

What 2 things does clotting involve?

A
  1. formation of a platelet plug

2. formation of a fibrin clot

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16
Q

What enzyme converts fibrinogen to fibrin for forming clots?

A

thrombin

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17
Q

Describe the mechanism for forming clots.

A
  • platelets react with collagen and clump together
  • this forms a platelet plug
  • fibrin clot (made from fibrinogen) then attaches to the platelet plug forming the clot.
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18
Q

What are anti-clotting mechanisms of the endothelium?

A
  1. stops blood contacting collagen
  2. produces prostacyclin and NO (
  3. produces tissue factor pathway inhibitor (TFPI)
  4. expresses thrombomodulin
  5. expresses heparin
  6. secretes tissue plasminogen activator (t-PA)
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19
Q

How does stopping blood contacting collagen prevent clotting?

A

endothelium forms a physical barrier between platelets interacting collagen and no platelet aggregation happens

20
Q

How does production of prostacyclin and NO prevent clots?

A

both inhibit platelet aggregation

21
Q

How does production of tissue factor pathway inhibitor (TFPU) prevent clots?

A

it stops thrombin production

22
Q

How does expression of thrombomodulin prevent clots?

A

it binds thrombin and inactivates it

23
Q

How does expression of hepatin prevent clots?

A

inactivates thrombin

24
Q

How does secretion of tissue plasminogen activator (t-PA) prevent clots?

A

Does the opposite of thrombin (which forms clots), instead it BREAKS down and digests clots forming plasmin and digested clot

25
Q

What are 2 main features of diffusion?

A
  1. self-regulating

2. non-saturable (the more O2 available, the more O2 will travel across, it’s not limited)

26
Q

How do non-polar and polar substances travel across membranes?

A
  • non-polar substances diffuse straight across membrane

- polar substances diffuse through clefts and channels

27
Q

In what 2 ways does exchange in capillaries happen?

A
  1. diffusion

2. carrier-mediated transport/facilitated diffusion (e.g. glucose transporter) which doesn’t use energy

28
Q

Which blood vessels have the highest and lowest pressures?

A
  • arterioles have highest hydrostatic pressure

- venules have lowest hydrostatic pressure

29
Q

What pressure pushes fluid and solute OUT of the capillaries?

A

Hydrostatic pressure (increases filtration

30
Q

What pressure pulls fluid into the capillaries and/ or prevents fluid from leaving?

A

Osmotic (oncotic) pressure

31
Q

Roughly how much fluid in litres is lost each day?

A

~20L

32
Q

Roughly how much fluid in litres is regained each day?

A

~17L

33
Q

Why does concentration of proteins go up as you move along a capillary?

A

Because water continually leaks out of capillary (like a hose) whereas proteins are too big to get through and leak out so conc. increases as you move along the capillary tube

34
Q

What happens to remaining 3L of fluid in capillaries?

A

gets “recycled” and re-used in the lymphatic system

35
Q

What are 2 parts of Starling’s forces?

A
  1. capillary hydrostatic pressure via ISF hydrostatic pressure (first part in equation)
  2. plasma osmotic pressure vs ISF osmotic pressure (second part in equation)
36
Q

What is the general equation for net filtration pressure?

A

(Hydrostatic forces of capillary-ISF) - (plasma osmotic pressure -ISF osmotic pressure)

37
Q

How does lymphatic system regulate body fluids?

A
  • fluid is pushed into intracellular space by hydrostatic pressures
  • this interstitial fluid is reabsorbed into lymph capillaries and becomes lymph
  • lymph squeezed fluid into lymph nodes are return it into venous system eventually
38
Q

What can occur if too much interstitial fluid leaks out of capillaries?

A

oedema

39
Q

Do lymphatic vessels have valves?

A

Yes

40
Q

What is the definition of oedema?

A

accumulation of excess fluid

41
Q

What are the 4 causes of oedema?

A
  1. lympathic obstruction
  2. raised ventral venous pressure (CVP)
  3. hypoproteinemia
  4. increased capillary permeability
42
Q

What can cause a lymphatic obstruction? (2)

A
  • surgery

- filariasis

43
Q

What can cause raised central venous pressure?

A

ventricular failure (blood is pumped out and more is accumulating from the venous side on the right side, which means hydrostatic pressures are not in balance)

44
Q

What can cause hypoproteinemia? (3)

A
  1. nephrosis (losing protein in kidney due to abnormal function)
  2. liver failure
  3. nutrition
45
Q

What can cause increased capillary permeability?

A
  • inflammation (e.g. rheumatism)
46
Q

Which organ is the only place where specific carriers are needed for diffusion purposes?

A

the brain

2. Cardiovascular System (42 decks)

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