Mechanism Of Breathing

Question 1

What is ventilation/breathing?

Answer 1

Air is constantly moved in and out of the lungs to maintain the diffusion of gases across the alveolar epithelium

Question 2

What are inhalation and expiration caused by?

Answer 2

Pressure changes in the lungs that are brought about by the contraction/relaxation of the diaphragm muscle and the internal and external intercostal muscles

Question 3

What is the difference in movement between muscles and elastic tissue?

Answer 3

Muscles contract and relax
Elastic tissue stretches and recoils

Question 4

What happens during inspiration?

Answer 4

• diaphragm contracts and flattens
• external muscles contract and raise ribs up and out
• volume of thoracic cavity increases
• pressure of thoracic cavity drops below atmospheric pressure
• air enters the lungs down a pressure gradient
• alveoli stretch

Question 5

What happens during expiration?

Answer 5

• diaphragm relaxes and curves upwards
• external muscles relax and ribs move down and in
• volume of thoracic cavity decreases
• pressure of thoracic cavity increases above atmospheric pressure
• air moves out lungs down a pressure gradient
• alveoli recoil due to elastic tissue, making volume smaller and expelling air

Question 6

During forced expiration what do the intercostal muscles do?

Answer 6

Internal intercostal muscles contract
External intercostal muscles relax pulling the rib cage down and in

= antagonistic muscle action