Mechanics of breathing

Question 1

What is breathing and what is its purpose

Answer 1

• process of moving air into and out of the lungs
• purpose: exchange O2 and CO2 between lungs and air

Question 2

How does air flow (which way)?

Answer 2

• flows from high pressure to low pressure
• therefore, it flows in and out because of pressure differences
• greater volume in the lungs = lower pressure

Question 3

What do the diaphragm and intercostal muscles do?

Answer 3

• they change volume and pressure of the lungs and thoracic cavity
• during inspiration: they contract
• during expiration: they relax

Question 4

What does the pleural cavity and fluid do?

Answer 4

• When the rib cage expands, they pleura pulls the lungs with it
• increases lung volume

Question 5

What happens during inspiration?

Answer 5

• air flows into the lungs
• this means pressure on the inside must be less than outside
• intercostal muscle: contract and extend ribcage upwards and outwards
• diaphragm: contracts and extends chest cavity downwards
• lungs: volume increases and pressure decreases

Question 6

What happens during expiration?

Answer 6

• air flows out of the lungs
• this means pressure on the inside must be more than the outside
• intercostal muscle: relaxes and moves the ribcage down and in
• disphragm: relaxes and pushes up into the chest cavity
  lungs: volume decreases and pressure increases