Topic 2 The Respiratory System: Detailed Sequence of Gas Exchange

Question 1

• Gas exchange occurs across moist, sac membranes of alveoli via simple diffusion
• O2 diffuses through alveolar wall, through pulmonary wall, into blood and into red blood cells
• CO2 following same sequence, except in reverse
• The grater the distance O2 needs to travel, the lower the efficacy of gas exchange

Answer 1

1. Diffusion between alveolar chambers and blood

Question 2

• O2 transported through body within hemoglobin in red blood cells

Answer 2

2. Bulk Flow of O2

Question 3

• O2 diffuses out of red blood cells, across capillary walls, into interstitial fluids and across cell membranes
• CO2 completes these steps in reverse

Answer 3

3. Diffusion between blood and cells

Question 4

• CO2 mainly transported as HCO3- ions in plasma, which are produced by carbonic anhydrase in red blood cells
• CO2 can directly mix with plasma as CO2 gas or bind hemoglobin inside red blood cells

Answer 4

4. Bulk Flow of CO2

Question 5

a. Inhalation: diaphragm (muscular structure under lungs) and intercostal muscles (between ribs) contract and flatten
- Lungs increase in volume and decrease in pressure leading to bulk flow of air into lungs
b. Exhalation: passive process; decrease in lung volume/increase in pressure leads to air rushing out, and diaphragm relaxing and expanding

Answer 5

5. Bulk flow of air into and out of lungs