Blood supply, gas exchange, ventilation and perfusion 1

Question 1

What gradient does Po2 go down from alveoli to circulation?

Answer 1

100mmHg in alveoli to 40mmHg in circulation.

Question 2

What gradient does Pco2 go down from circulation to alveoli?

Answer 2

46mmHg in circulation to 40mmHg in alveoli.

Question 3

What gradient does Po2 go down from circulation to tissues?

Answer 3

100mmHg in circulation to >_40mmHg

Question 4

What gradient does Pco2 go down from circulation to tissues?

Answer 4

46mmHG in tissues to >_40mmHg in circulation

Question 5

True or false : The rate of diffusion across the membrane is directly proportional to partial pressure gradient.

Answer 5

True

Question 6

True or false: The rate of diffusion is inversely proportional to gas solubility.

Answer 6

False. It is directly proportional.

Question 7

True or false: The rate of diffusion is inversely proportional to thickness of membrane.

Answer 7

True

Question 8

Will air continue to move across the membrane until equilibrium is reached?

Answer 8

Yes

Question 9

There is a larger gradient between Po2 compared to Pco2. so how come pco2 diffuses almost as fast? (200ml/min compared to 250ml/min)

Answer 9

Because co2 is much more soluble than o2, so can travel faster.

Question 10

What is optimal condition for gas exchange?

Answer 10

when ventilation = blood flow. ( the amount of air going into alveoli should match the amount of blood flowing past them in arterioles.)

Question 11

What does distribution of blood flow around the alveoli depend on?

Answer 11

hydrostatic (blood) pressure & alveolar pressure.

Question 12

Describe the blood flow, arteriole pressure, vascular resistance etc. at the top of the lung.

Answer 12

top of lung, low blood flow . alveolar pressure is more than arteriole pressure. vascular resistance is increased.

Question 13

Describe the blood flow, arterial pressure, resistance etc. at the bottom of the lung.

Answer 13

Bottom of the lung has high blood flow. The arterial pressure is more than alveolar pressure, low vascular resistance.

Question 14

What happens when blood flow is higher than ventilation?

Answer 14

Deoxygenated blood just flows past the alveoli without picking up oxygen - SHUNT.

Question 15

What is alveolar dead space?

Answer 15

ventilation is higher than blood flow. The alveoli are ventilated but not perfused.

Question 16

what is physiological dead space?

Answer 16

alveolar dead space + anatomical dead space

Question 17

what is emphysema? (affects gas exchange)

Answer 17

destruction of alveoli reduces surface tension.

Question 18

What is fibrotic? (affects gas exchange)

Answer 18

thickened alveoli membrane slows down gas exchange

Question 19

what is pulmonary edema? (affects gas exchange)

Answer 19

fluid in interstitial space.

Question 20

why does pulmonary edema not affect co2 as much as o2?

Answer 20

Because co2 is much more soluble.

Question 21

what is asthma? (affects gas exchange)

Answer 21

increase airway resistance, decrease airway ventilation. (no barrier to diffusion, but there is less o2 in the actual alveoli.

Question 22

What circulation supplies oxygenated blood to airway smooth muscle, nerves and lung tissue?

Answer 22

Bronchial circulation - via bronchial arteries.

Question 23

Is the pulmonary circulation a high flow and low pressure system?

Answer 23

yes. it is 25mmHg compared to 120mmHg systematic circulation.

Question 24

what does a sample of arteriole blood tell you about and why?

Answer 24

lungs - as they are in equilibrium

Question 25

What does a sample of venous blood tell you and why?

Answer 25

Tissues - as they are in equilibrium

Question 26

What is the difference between arterial partial pressure and gas content?

Answer 26

Arterial partial pressure refers to o2 dissolved in solution, so not on haemoglobin. Gas content includes haemoglobin.

Question 27

what does partial pressure depend on?

Answer 27

o2 solubility

the partial pressure of o2 in the gaseous phase (alveoli) driving it into the solution (blood)

Question 28

What is oxygen tension?

Answer 28

pressure of o2 in alveoli - 100mHg.