Mechanics of Breathing 1

Question 1

What happens during the first stage of inspiration?

Answer 1

• the external intercostal muscles contract to lift the ribs outwards and upwards
• the diaphragm is forced downwards

Question 2

How does this affect the thoracic cavity during inspiration?

Answer 2

the size of the thoracic cavity increases allowing more air to be drawn into the lungs

Question 3

What happens to the partial pressure of the gases in the lungs during inspiration?

Answer 3

• this causes a drop of pressure within the lungs to below atmospheric pressure

Question 4

What happens as a result of the decrease in partial pressure in the lungs during inspiration?

Answer 4

encourages air to be drawn into the lungs

Question 5

What happens during the first stage of expiration at rest?

Answer 5

• external intercostal muscles relax
• the diaphragm relaxes, moving upwards, and the ribs move downwards and inwards

Question 6

How does this affect the thoracic cavity during expiration at rest?

Answer 6

the size of the thoracic cavity decreases pushing the air out of the lungs

Question 7

What happens to the partial pressure of the gases in the lungs during expiration at rest?

Answer 7

the pressure increases so that the air is pushed out of the lungs

Question 8

What happens as a result of the decrease in partial pressure in the lungs during expiration at rest?

Answer 8

the air is pushed out of the lungs

Question 9

what muscles are additionally involved during the expiration during exercise?

Answer 9

pectorals and sternocleidomastoid internal intercostal muscles

Question 10

what happens due to the additional muscles used during expiration during exercise?

Answer 10

actively pull the rib cage down
allows for air to be pushed out more forcefully