Gas Exchange

Question 1

Adaptions of lungs for gas exchange

Answer 1

A large surface area to volume ratio.
A short diffusion path by capillaries with thin walls.
They are partially permeable.
Good supply of blood.
The lungs have a concentration gradient through circulation.

Question 2

Inspiration

Answer 2

External intercostal muscles contract. The ribs move up and out.
The volume of the thorax increases. The diaphragm contracts. Lung volume increases when breathing in. Atmospheric pressure is bigger than pulmonary pressure.

Question 3

Expiration

Answer 3

Internal intercostal muscles contract. Ribs move down and in.
Volume of the thorax decreases. Diaphragm muscle relaxes. Diaphragm moves up. Lung volume decreases.
Pulmonary pressure is bigger than atmospheric pressure.

Question 4

Pulmonary ventilation

Answer 4

Total volume of air moved into the lungs in one minute.

Pulmonary ventilation = tidal volume x ventilation rate

Question 5

Gas exchange in alveoli

Answer 5

Oxygen goes into the alveoli and dissolves in the moist lining of the alveolus. It then diffuses across the alveolus epithelium and blood capillary. It is then picked up by the red blood cells.