Mechanics of breathing

Question 1

Pulmonary ventilation

Answer 1

> The process by which we move air into and out of the lungs

Question 2

Inspiration: (rest)

Answer 2

1) External intercostal muscles and diaphragm contract
2) Ribs and sternum move upwards and outwards
3) Diaphragm flattens
4) Thoracic cavity increases in volume and lung volume increases
5) Pulmonary air pressure falls below atmospheric air pressure
6) Causing atmospheric air to be forced into the lungs
7) Until lung pressure equals atmospheric pressure pressure again

Question 3

Inspiration: (during exercise)

Answer 3

> Additional muscles in the chest also contract. The chest cavity volume further increases and more air is forced into the lungs.

Question 4

Expiration: (at rest)

Answer 4

1) External intercostal muscles and diaphragm relax
2) Ribs and sternum move inwards and downwards
3) Diaphragm moves upwards and into a dome shape
4) Thoracic cavity decreases in volume and lung volume decreases
5) Pulmonary air pressure is higher than atmospheric air pressure
6) Causing more atmospheric air to be forced out of the lungs via respiratory passages
7) Until lung pressure equals atmospheric pressure again

Question 5

Expiration: (during exercise)

Answer 5

> Internal intercostal muscles and abdominal muscles contract powerfully, acting on the ribs
Chest cavity volume is further reduced and more air is forced out of the lungs