3.2 - Gas Exchange Exam pack mistakes

Question 1

For forced exhalation, describe what happens to the different muscles associated with gas exchange and why this happens

Answer 1

1. Diaphragm relaxes and returns back to its dome shape.
2. Only internal muscles contract
3. External muscles also relax.

The point of this is to decrease the volume in the thoracic cavity and so increase the pressure ( higher than atm ) .So air will move along the pressure gradient out of the lungs into the atmosphere

Question 2

Describe and explain the adaptations of a mammalian breathing system

Points I always miss out
Always refer to ficks law

Answer 2

1. Walls of capillary are thin and closely associated with the alveoli - this provides a short diffusion pathway.
2. They have intercostal and diaphragm muscles that contract and relax - to ventilate lungs and maintain an concentration gradient
3. Have cartilage rings, that keep airways open.

Question 3

When a person starts to breathe out, the % of O2 in the air first exhaled is the same as the % of O2 in the atmospheric air. Why

Answer 3

• this air does not reach the alveoli for oxygen to diffuse into the blood.
• and gas exchange of oxygen can only happen in the alveoli.