Mechanism of Breathing + Gaseous Exchange (RS)

Question 1

What is inspiration?

Answer 1

Breathing in, letting air enter through your nose or the mouth

Question 2

What is expiration?

Answer 2

Breathing out, letting air leave through the nose or the mouth

Question 3

What happens during inspiration?

Answer 3

• The diaphragm and external intercostal
  muscles contract
• When the diaphragm contacts it flattens
• External intercostal muscles raise the ribs
  upwards and outwards
• This increases the area/size of the thoracic cavity
• This causes air to enter the lungs

Question 4

What happens during expiration?

Answer 4

• The diaphragm and external intercostal
  muscles relax
• Internal intercostals contract
• When the diaphragm relaxes and the internal
  intercostal muscles contacts they lower the
  ribs downwards and inwards
• This decreases the area of the thoracic cavity
• This causes air to leave the lungs

Question 5

Process of Gaseous Exchange

Answer 5

• Gaseous exchange is the process by which gas is exchanged between each other.
• In the lungs, gaseous exchange occurs by diffusion between the air in the
  alveoli and blood in the capillaries surrounding their walls.
• It delivers oxygen from the lungs to the bloodstream and removes carbon
  dioxide from the bloodstream to the lungs.
• The alveolar and capillary walls form a membrane with gas on one side
  and blood flowing on the other.
• Gaseous exchange occurs readily by simple diffusion across the
  respiratory membrane.
• Blood entering the capillaries from the pulmonary arteries has a lower
  oxygen concentration and a higher carbon dioxide concentration than the
  air in the alveoli.
• Oxygen diffuses into the blood via the surface of the alveoli, through the
  thin walls of the capillaries, through the red blood cell membrane and
  finally latches on to haemoglobin.
• Carbon dioxide diffuses in the opposite direction, from the blood plasma
  into the alveoli.