Gas Exchange At The Respiratory Membrane

Question 1

What is Dalton’s law of partial pressures?

Answer 1

The law states that the total pressure in a gaseous mixture is the result of the sum of all partial pressures.

The partial pressure (P) is the pressure exerted by one gas

Question 2

What is Henry’s law of gas in solutions?

Answer 2

Th law states that gas dissolve in proportion to partial pressure and solubility in liquids

Question 3

What is the composition of air and water vapour in the alveolar?

Answer 3

Alveolar air has more carbon dioxide and water but much less oxygen

Question 4

What are the 4 factors affecting diffusion of gases across the alveolar-capillary membrane?

Answer 4

1. Partial pressure differences
2. Solubility (S) and molecular weight of gas
3. Thickness (T) of membrane
4. Cross-sectional are (A) of fluid

Question 5

Along the length of the pulmonary capillaries pO2 quickly achieves equilibrium/saturation where capillary pO2=alveolar; except in what circumstances?

Answer 5

Except in diseases such as long oedema/fibrosis which can increase the distance between alveolar gas and blood.

(emphysema and COPD can’t)

Question 6

Despite the small pressure gradient in pulmonary capillaries, why does Carbon Dioxide diffuse easily? What is its purpose in regulating the amount of Carbon Dioxide?

Answer 6

It diffuses easily due to the high solubility of carbon dioxide as a gas. The purpose of regulation is to ensure that the pH of the body is maintained.

Question 7

Va/Q is a representation of the ratio of alveolar air and cardiac output. What is the ratio when there is a shunt effect and a dead space effect?

Answer 7

A shunt effect is when Va/Q1 where the work of breathing is wasted.