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Histology > Alveolar exchange > Flashcards

Alveolar exchange Flashcards

1
Q

What is the partial pressure of atmospheric O2?

A

160 mm hg

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2
Q

What percentage of atmospheric air is oxygen?

A

21%

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3
Q

What state does gas diffuse into at the alveoli?

A

a liquid

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4
Q

What is added to the normal composition of air as it is brought into the lungs?

A

water

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5
Q

What is the composition of air in the lungs by percentages?

A

14% oxygen
75% Nitrogen
5% CO2
6% water

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6
Q

What 5 things affect the rate of diffusion of a gas?

A
  1. solubility of the gas in a liquid
  2. surface area of the barrier across which diffusion occurs
  3. distance of diffusion (membrane thickness)
  4. molecular weight of the gas
  5. Temperature
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7
Q

Why is aqueous diffusion the limiting factor?

A

respiratory gases are highly soluble in lipids (cells and tissue)

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8
Q

What are the partial pressures of O2 across the alveolar membranee on inspiration?

A

inside the alveoli: O2 is 104mm hg

outside the alveoli: O2 is 40 mm hg

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9
Q

What are the partial pressures of CO2 across the alveolar membrane on inspiration?

A

Inside the membrane: CO2 is 40 mm hg

Outside the membrane: CO2 is 46 mm hg

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10
Q

Can distance of diffusion be pathologically increased?

A

Yes

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11
Q

What is the functional residual capacity?

A

The amount of air that remains in the lungs after normal expiration.

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12
Q

What volume of air remains in the lungs after expiration?

A

2300 mL

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13
Q

How much air is being exchanged with each breath?

A

350 mL

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14
Q

What is the function of the functional residual capacity?

A

It acts as a buffer that prevents sudden changes in alveolar gas mix. This keeps blood gas levels relatively constant.

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15
Q

What is the partial pressure of O2 in the blood after it leaves the lungs and mixes with the shunted blood?

A

95 mm hg

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16
Q

What is the partial pressure of oxygen of individual cells in the periphery?

A

23 mm hg

17
Q

Is oxygen more soluble as free O2 or when bound to Hb?

A

When bound to Hb

18
Q

How many oxygen atoms do you get for each binding site on Hb?

A

2 atoms because it is elemental oxygen.

19
Q

What does cooperative binding mean?

A

As each oxygen is bound, the affinity for the next one gets higher.

20
Q

What is the most effective way to increase oxygen delivery to tissues?

A

Increase the concentration of Hb rather than partial pressure of O2.

21
Q

How many subunits are on one Hb? How many Hb are on one RBC?

A

4, many

22
Q

If cooperative binding keeps the O2 on a Hb very tightly, how do they dissociate?

A

When there is a low partial pressure of O2 in periphery, the opposite of cooperative binding occurs where with each O2 that dissociates, the easier it is for the next to dissociate.

23
Q

What is the utilization coefficient? What is this number at rest and at exercise?

A

the percentage of blood that gives up its O2. At rest, it is 25% and during exercise it is 85%

24
Q

Why is the disassociation curve of O2 sigmoidal?

A

The steep part of the curve represents cooperative binding, but as you aadd more you end up with diminishing returns, which is why it levels off at the top.

25
Q

A shift to the right represents what in a dissociation curve? What about a left hand shift?

A

right hand shift means decreased affinity, left hand means increased infinity.

26
Q

What does increased diphosphoglycerate (2,3 DPG) do to a dissociation curve?

A

right shift, or decreased affinity.

27
Q

What is the haldane effect?

A

it states that deoxygenated blood has an increased ability to carry carbon dioxide. It is similar to the bohr effect.

28
Q

How does the haldane effect differ from the bohr effect?

A

haldane effect has to do with the oxygenation of the blood, the bohr effect has to do with pH and CO2.

Histology (5 decks)

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