B3 - Gaseous Exchange

Question 1

What is the function of the breathing system?

Answer 1

To allow oxygen to diffuse into the blood stream to provide cells with oxygen for aerobic respiration and to allow waste gases carbon dioxide and water vapour to diffuse out of the bloodstream.

Question 2

Outline the process of inhalation.

Answer 2

1) The rib muscles contract - this pulls the ribcage upwards and outwards.
2) The diaphragm contracts which makes it flatten.
3) There is now a much bigger space inside the thorax.
4) The low pressure in the thorax draws air into the lungs from outside the body to equalise the pressure.
5) This allows air into the air sacs and allows oxygen to diffuse into the bloodstream.

Question 3

Outline the process of exhalation.

Answer 3

1) The rib muscles relax. This drops the ribcage down and in.
2) The diaphragm relaxes which returns it to it’s domed shape.
3) The space inside the thorax is now much smaller.
4) The increased pressure in the thorax forces air out of the lungs.
5) The air leaving the lungs contains carbon dioxide and water vapour which have diffused out of the lungs.

Question 4

Why could people struggle to breathe and get enough oxygen into their lungs?

Answer 4

The tubes leading to the lungs could be narrowed (could be caused by asthma, allergic reactions or bronchitis)

Paralysis from accidents

Damage to the alveoli which decreases the total surface area for gaseous exchange.