Gas exchange

Question 1

How are the airways kept clean?

Answer 1

• Goblet cells produce mucus
• Mucus traps the dirt/bacteria
• Cilia (cells with hairlike structures) waft the ladened mucus up to the mouth where it is swallowed and destroyed by HCl in the stomach

Question 2

What is ventilation?

Answer 2

Movement of air into and out of the lungs

Question 3

Describe the process of breathing in (inhalation)

Answer 3

• External intercostal muscles contract
• Ribs move up and out
• Diaphragm contracts and flattens
• Volume inside thorax increases
• Pressure decreases
• Air is sucked into the lungs

Question 4

Describe the process of breathing out

Answer 4

• Internal intercostal muscles contract
• Ribs move down and in
• Diaphragm relaxes and become dome shaped
• Volume inside thorax decreases
• Pressure increases
• Air is forced out of the lungs

Question 5

Compare inhaled and exhaled air

Answer 5

Inhaled air contains more oxygen and less carbon dioxide than exhaled air

Question 6

How are the alveoli adapted for gas exchange?

Answer 6

• Large surface area
• Good blood supply
• Thin walls - short diffusion pathway
• Moist - dissolve gases

Question 7

Describe the effects of smoking on the body

Answer 7

• Cilia are paralysed - build up of mucus - smoker’s cough - infection - bronchitis
• Smoke damages alveolar walls - walls break down - decreased surface area for gas exchange -
  emphysema
• Carcinogens - tumour growth - lung cancer
• Carbon monoxide combines irreversibly with haemoglobin in red blood cells -
  Carboxyhaemoglobin - less oxygen transported