Lungs 3.1.2

Question 1

State the pathway of air into the lungs

Answer 1

1. Nose/mouth
2. Trachea
3. Bronchi
4. Bronchioles
5. Alveolus

Question 2

What are the alveoli?

Answer 2

They consist of the surfaces where the exchange of gases takes place.

Question 3

What are the lungs protected by?

Answer 3

The ribs

Question 4

What are the ribs held together with?

Answer 4

The intercostal muscles

Question 5

What is the layer of muscle known as beneath the lungs?

Answer 5

The diaphragm

Question 6

Name the 4 stages involved within gas exchange

Answer 6

• Gases pass by diffusion through the thin walls of the alveoli
• Oxygen from the air in the alveoli to the blood in the capillaries
• Carbon dioxide from the blood to the air in the alveoli
• The lungs maintain a steep concentration gradient

Question 7

How are the lungs adapted for gas exchange? (6 adaptations)

Answer 7

• Alveoli are very small yet numerous, which enables a large surface area for gas exchange
• The alveoli are lined with a thin layer of moisture, which evaporates and is lost as we exhale; this reduces the cohesive forces of water
• The barrier is permeable to oxygen and carbon dioxide, as they’re small and non polar
• Alveoli and capillary walls are one cell thick
• Capillaries are very narrow so RBC’s are squeezed against their wall, making them closer to the air flow in the alveoli
• Good blood supply which helps to maintain a steep concentration gradient, so the gases continue to diffuse

Question 8

Explain the mechanism of ventilation during inspiration.

Answer 8

1. Diaphragm contracts and becomes flatter
2. External intercostal muscles contract to raise the ribs
3. The volume of the thoracic cavity is increased
4. The pressure in the thoracic cavity drops
5. Air is moved into the lungs

Question 9

Explain the mechanism of ventilation during expiration.

Answer 9

1. The diaphragm relaxes and is pushed up by the displaced organs underneath
2. The external intercostals relax and the ribs fall
3. The internal intercostal muscles contract to pull the ribs in (only during exercise/coughing or sneezing)
4. The volume of the thoracic cavity is decreased
5. The pressure in the lungs increases
6. Air is moved out of the lungs