6.7 The mechanism of breathing

Question 1

What is breathing/ventilation? And what does it do?

Answer 1

The movement of air into and out of the lungs to:

• maintain diffusion of gases across the alveolar epithelium
• facilitate gas exchange

Question 2

What is the process of inhalation/inspiration?

Answer 2

• diaphragm contracts and flattens
• external intercostals contract and internal intercostals relax
• causes the ribs to move outwards and upwards
• volume of thorax increases
• pressure in lungs decreases
• atmospheric pressure is greater than pulmonary pressure
• air moves into lungs

Question 3

What is the process of exhalation/expiration?

Answer 3

• diaphragm relaxes and forms a dome shape
• internal intercostals contract and external intercostals relax
• causing ribs to move inwards and downwards
• volume of thorax decreases
• pressure in lungs increases
• pulmonary pressure is greater than atmospheric pressure
• air moves out of lungs