Breathing & Gas Exchange

Question 1

What happens when we breathe in?

Answer 1

1) Air passes down the trachea, which splits into 2 tubes called bronchi, one leading to each lung.
2) Each bronchus divides into smaller tubes called bronchioles, eventually leading into microscopic air sacs called alveoli.

Question 2

Whats the pleural cavity?

Answer 2

Between the pleural membranes and the lungs is a space called the pleural cavity, filled with a liquid called pleural fluid. This acts as a lubricant to make sure the surfaces of the lungs don’t stick to the inside of the chest.

Question 3

What are cilia?

Answer 3

Some cells are covered in tiny hair like structures called cilia, which beat backwards and forwards, sweeping trapped particles out of the mouth.

Question 4

Whats the process of gas exchange?

Answer 4

1) Deoxygenated blood is pumped to the lungs and passes through the capilaries surrounding the alveoli.
2) Because the air in the alveolus has a higher concentration of O2 than the blood entering the capillary network.
3) O2 diffuses from the air across the wall of the alveolus and into the blood.
4) At the same time theres a diffusion gradient of CO2 in the other direction into the alveolus. The CO2 is breathed out and oxygenated blood goes back to the heart.

Question 5

Explain ventilation in the lungs

Answer 5

1) When you breathe in , your external intercostal muscles contract pulling the ribs up. At the same time the muscles of the diaphragm contract, pulling the diaphragm down. Both these movements increase the volume of the chest and cause a slight drop in pressure inside the thorax compared with the air outside.
2) When you breathe out, the external intercostals relax, and the internal intercostals contract, pulling the ribs down and in. At the same time the diaphragm relaxes and goes back to its normal shape. The volume of the thorax decreases and the pressure in the thorax is raised. The difference in pressure forces air out of the lungs.

Question 6

Whats emphysema?

Answer 6

Smoking damages the walls of the alveoli, which break down and fuse together forming enlarged, irregular airspaces. This greatly reduces the surface area for gas exchange which becomes very inefficient.

Question 7

Whats carbon monoxide?

Answer 7

When this gas is breathed in, it enters the bloodstream and interferes with the ability of the blood to carry oxygen.
Carbon monoxide combines with hemoglobin much tighter than O2, forming a compound called carboxyhemoglobin.
When this occurs the blood carries much less O2 around the body.