8.6 Ventilation of the lungs in humans

Question 1

What type of breathing allows mammals to bentilate their lungs

Answer 1

• negative pressure breathing
• This occurs when the presure inside the lungs is below the atmospheric pressure outside of the lungs.

Question 2

What type of process is breathing in?

Answer 2

• Breathing is an active process because muscles contract and therefore need energy

Question 3

Describe breathing in

Answer 3

• External intercostal muscles contract
  
  • Internal intercostal muscles are antagonistic to the internal muscles, e.g. whatever the external intercostal muscles do the internal intercostal muscles do the opposite
• Ribs pulled upwards and out
• Diaphrahm muscles contract pulling the diaphragm flat
• Volume in thoracic cavity increases
• Pressure reduces in the lungs
• Atmospheric pressure is now higher than the pressure in the lungs,
• So air is forced into the lungs

Question 4

What is the process of breathing in called

Answer 4

inspiration

Question 5

What is the process of breathing out called

Answer 5

expiration

Question 6

What is the process of breathing out, expiration?

Answer 6

• It is essentially the opposite of inspiration
• Intercostal muscles relax
• The ribs move downwards and in
• The diaphragm muscles relax so the diaphragm domes upwards into the thoracic cavity
• This increases the pressure in the lungs
• Air pressure in the lungs is higher than the atmospheric pressure outside of the lungs so air is forced out.

Question 7

What happens when lungs have taken in oxygen

Answer 7

• The lungs are elastic
• They recoil
• Pushing air out

Question 8

Why does friction not occur when lungs expand and relax

Answer 8

• Lungs are surrounded by a plural membrane
• Which is seperated by a pleural space
• That contains fluid
• Which acts as a lubricant stopping friction

Question 9

Why do the alveoli not collapse when you exhale?

Answer 9

• The inside surfaces of the alveoli are coated with a surfactant
• Which is an anti sticking mixture of phospholipi and protein
• The mixture has a low surface tension
• Which prevents the alveoli collapsing during exhaling
• It also allows gasses to disolve before they diffuse in or out.