Human Gas Exghange

Question 1

What are the different parts of human breathing system?
See p.6

Answer 1

1. Tongue
2. Epiglottis (closed off trachea when food is swallowed to direct through oesophagus)
3. Oesophagus
4. Trachea
5. Cartilage rings
6. Intercostal muscles
7. Ribs

Question 2

Different parts of breathing system (2)
See p.6

Answer 2

8. Bronchi (split from the trachea).
9. Bronchioles
10. Left lung
11. Pleural membranes
12. Diaphragm
13. Pleural cavity

Question 3

What is cartilage present in and what is its function

Answer 3

Trachea in rings and bronchi as plates
Provides strength to trachea + bronchi and holds open airways so little resistance for air

Question 4

What is the ciliated epithelium present in and what is its function?

Answer 4

Trachea, bronchi, bronchiole (alveoli has squamous epithelial)
- on the outer membrane of cells
- wafts mucus up airways to mouth, which is swallows and germs are killed by stomach acid

Question 5

Where are goblet cells present and what is their function?

Answer 5

Trachea, bronchi and bronchioles
Shaped like a goblet,
secrete mucus which traps bacteria, dirt and dust

Question 6

How does gas exchange occur in the alveoli

Answer 6

Deoxygenated blood enter the capillaries surrounding the alveoli. Oxygen diffuses out of the air in the alveoli into the red blood cells in the capillary. Carbon dioxide diffuses out of the plasma in the capillary into the air into the alveoli, where it is exhaled

Question 7

Why are the alveoli very efficient for gas exchange?

Answer 7

1. Provide a large surface area by having multiple alveoli.
2. Maintain the concentration gradient by their extensive network of capillaries carrying O2 and CO2 to and from the alveoli
3. They have a single layer of squamous epithelial cells for a short diffusion pathway
4. There is a layer of fluid on the inside of the alveolus + surfactant lines the alveoli
5. They have a permeable membrane

Question 8

How do lungs inhale?

Answer 8

1. External intercostal muscles contract, pulling the rib cage upwards and outwards.
2. This pulls out the pleural membrane, reduces pressure in the pleural cavity and the inner pleural membrane moves outward. This pulls on the surface of the lungs and causes alveoli to expand.
3. The diaphragm contracts, pulling it from a dome shape to a flattened shape.
4. The combined effect is: volume of thorax and lungs increase, pressure decreases, and air enters travelling down pressure gradient

Question 9

How do lungs exhale (relaxed)

Answer 9

1) external intercostal muscles relax and the ribcage falls under its own weight. The diaphragm then relaxes and gut pressure pushes it back into its domed shape. There is also elastic recoil of lung tissue.
The combined effect is: volume of thorax and lungs decrease, pressure increases, air is forced out

Question 10

How do the lungs exhale (forced)

Answer 10

Internal intercostal muscles contract, pulling the ribcage down and in. Abdominal muscles contract pushing the diaphragm down.
The combined effect is that:
Volume of thorax and lungs decrease, pressure increases and air is forced out.
Forced exhalation takes place during exercise and singing

Question 11

What is smooth muscle present in and what is its function?

Answer 11

Trachea, bronchi and bronchioles
Contracts to narrow airway, reduces water and heat loss

Question 12

What are elastic fibres present in and what is their function?

Answer 12

Trachea, bronchi, bronchioles and alveoli
Stretch when breathing in and recoil when breathing out to help force air out of lungs

Question 13

What is trachea and bronchi structure

Answer 13

P8 SUPPORT BOOKLET
Trachea has incomplete ring of cartilage as at back is oesophagus so it doesn’t obstruct it