Gas exchange (physio)

Question 1

Factors affecting diffusion of gases across alveolar-capillary barrier

Answer 1

Partial pressure of gases

Thickness of barrier

Surface area

Question 2

Factors affecting blood flow factors (which can affect gas exchange)

Answer 2

Perfusion of alveoli

Rate of blood flow through alveoli

Question 3

How does diffusion of gases occur?

Answer 3

Diffuse from areas of high partial pressure -> low until partial pressures are equalised btw compartments

Question 4

Define partial pressure of gas

Answer 4

Pressure that gas exerts in a mixture of gases

Question 5

How does gas diffuse from alveolus to capillary blood?

Answer 5

PO2 higher in alveolus compared to capillary blood -> drive diffusion across alveolar capillary membrane

Question 6

Effects of barriers on gas diffusion across alveolar capillary membrane

Answer 6

Thicker barrier -> less efficient diffusion

Question 7

How does blood flow thru alveoli affect gas exchange?

Answer 7

Gas exchange occurs when blood perfuses capillary
- blood flow ceases -> no gas exchange

Question 8

How does rate of blood flow affect gas exchange?

Answer 8

Alveolar gases take tie to diffuse and equilibrate w/ blood -> diff gas diffuse/equilibrate at diff rate
- faster -> less time for diffusion

Question 9

How does functional surface area of lungs affect gas exchange?

Answer 9

Gas exchange occurs only if alveoli are ventilated and have adequate diffusion and perfusion
- areas of ventilation decrease -> gas exchange decrease

Question 10

Factors needed in order for gas exchange to occur

Answer 10

Ventilation -> fresh air must reach alveoli

Efficient diffusion at alveoli

Perfusion of alveoli by blood

Question 11

What can cause abnormal (decreased) diffusion?

Answer 11

Decreased difference in partial pressure of gas
- eg: decrease PO2 in alveolus at high altitude

Abnormal thickening of alveolar-capillary barrier
- eg: fibrosis, edema

Decreased alveolar vol/ no. of functional alveoli
- eg: pneumonia

Question 12

How does blood flow problems affect gas exchange?

Answer 12

Blood flow reduced -> gas exchange decrease
- eg: blood clot

Blood flow increase -> gas exchange decrease
- less time for gas to equilibrate
- doesn’t usually affect healthy indiv
- affects those w/ diseased alveoli w/ thickened membranes (eg: lung fibrosis)

Question 13

Adverse effects of smoking

Answer 13

Cancer

Gum disease

COPD

Increased risk of infection and asthma

Increased risk of heart failure