7.3 Ventilation and measuring

Question 1

What is ventilation?

Answer 1

Air is moved out of the lungs due to pressure changes in the thorax by breathing movements

Question 2

Describe inspiration.

Answer 2

The diaphragm contracts, flattening
The intercostal muscles contract moving the ribs upwards and outwards
Volume of the thorax increases so the pressure is reduced
Air is drawn into the lungs

Question 3

Describe expiration

Answer 3

Diaphragm relaxes moving back up to its original domed shape
Intercostal muscles relax so the ribs move downwards and inwards
The volume in the thorax decreases and the pressure inside the thorax is greater than the atmospheric pressure
Air moves out of the lungs until the pressure is equal.

Question 4

How can the volume of air moving in and out of lungs be measured?

Answer 4

A peak flow meter measures the rate at which air is expelled from the lungs
Spirometer measures aspects of lung volume or investigates breathing patterns