Exchange and Lymphatic System Flashcards

1
Q

What is the space called between two cells?

A

Cleft - varies in size depending on how close cells are together

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2
Q

Describe the pore size in fenestrated capillaries

A

Large (fenestrations or pores)

Allows direct travel through the cell

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3
Q

Where do you find continuous capillaries?

A

In the brain where there is no clefts or channels in the capillaries

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4
Q

Give an example of what the blood brain barrier might halt the diffusion of?

A

Potassium

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5
Q

Where might you find fenestrated capillaries?

A

In the intestine - contains clefts and channels

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6
Q

Where might you find discontinuous capillaries?

A

Liver - Lots of proteins are made and need to enter the plasma - leav via sinusoids. Contains clefts and massive channels

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7
Q

What part of a blood vessel is very involved in the formation of blood clots?

A

Endothelium

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8
Q

What are the two stages clot formation?

A

Formation of a platelet plug

Formatin of a fibrin clot

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9
Q

When will platelets start releasing clotting factor?

A

When the integrity of the endothelium is compromised and the platelets have access to the collagen of the basement membrane.

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10
Q

What is the function of thrombin?

A
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11
Q

How does the epithelium prevent clot formation?

A

Stops blood contacting collagen

Produces prostacyclin and NO

Produces tissue factor pathway inhibitor (TFPI)

Expresses thrombomodulin

Expresses heparin

Secretes tissue plasminogen activator

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12
Q

What is the effect of stopping blood contacting collagen?

A

No platelet aggregation

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13
Q

What is the effect of prostacyclin and NO?

A

Both inhibit platelet aggregation

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14
Q

What is the effect of tissue factor pathway inhibitor?

A

Stops thrombin production

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15
Q

What is the effect of thrombomodulin?

A

Binds thrombin and inactivates it

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16
Q

What is the effect of heparin?

A

Also inactivates thrombin

17
Q

What is the effect of tissue plasminogen activator?

A

Turns plasminogen into plasmin which digests clot

18
Q

Why is diffusion described as self-regulating?

A

More O2 needed means more O2 enters the cell by means of diffusion

19
Q

Why is diffusion of O2 described as unsaturable?

A

Since there is no use of protein pumps (there is no chance of all pumps being used at once)

20
Q

Why type of substances can cross membranes?

A

Non-polar substances

21
Q

What type of substances travel through clefts and channels?

A

(potassium ions and glucose)

22
Q

What type of molecules are carrier mediated transport?

A

Glucose transporter

23
Q

What are the pressures responsible for the green and black arrows?

A

Green - hydrostatic pressure

Black - oncotic pressure

24
Q

Why does water get drawn back into the capillary?

A

Concentration of proteins increases from left to right (creates osmotic pressure) draws water back in

25
Q

What is the average volumes of water which are lost and regained each day?

A

Lost - 20L

Regained - 17L

26
Q

What causes Kwashiorkor?

A

Hypoproteinaemia no production of osmotic pressure and little water renters the capillary.

27
Q

What is oedema defined as?

A

Accumulation of excess fluid

28
Q

What are the causes of oedema?

A

Lymphatic obstruction (eg to filariasis surgery)

Raised central venous pressure - due to ventricular failure - increase in hydrostatic pressure

Hypoproteinaemia - water leaves the the capillaries y hydrostatic pressure, re-enters via oncotic pressure - absent in this case. Causes - nephrosis, liver failure and nutrition

Increased capillary permeability - inflammation eg. rheumatism

29
Q

Why does heart failure result in oedema?

A

Backward failure of the right ventricle leads to congestion of systemic capillaries, This generates excess fluid accumulation in the body. The increased pressure forces additional fluid out of the blood into the tissue, this results in oedema in the tissue. In right sided heart failure this commonly starts in the ankles where venous pressure is high due to the effects of gravity. It may also occur in the abdominal cavity where the fluid build-up is called ascites.