Topic 11

Question 1

Features of gas exchange surfaces

Answer 1

Large surface area: faster diffusion of gasses
Thin walls: short diffusion distance
Good ventilation with air: diffusion gradient mantaines
Good blood supply: maintain high concentration gradient

Question 2

The trachea: cartilage

Answer 2

Rings of cartilage around trachea (and bronchi)
- Cartilage: support airways and keep them open during breathing -> without them sides could collapse inwards when air pressure inside tubes drops

Question 3

Cilia

Answer 3

Passage down to lungs lined with ciliated epithelial cells:
- Cilia (cytoplasm extensions) move mucus up passages towards nose and throat -> removing it from body

Question 4

Mucus

Answer 4

Made: goblet cells
Traps: particles, pathogens and dust -> prevents them from entering the lungs

Question 5

Ventilation of the lungs: Inhalation

Answer 5

Thorax volume increases and pressure decreases -> air drawn in
- External intercostal muscles: contract -> ribs move upwards and outwards
- Diaphgram: contracts -> flattens
- Internal intercostal muscles: relax

Question 6

Ventialtion of the lungs: exhalation

Answer 6

Thorax volume decreases and pressure increases -> air forced out
- External intercostal muscles: relax -> ribs move downwards and inwards
- Diaphgram: relaxes -> rises
- Internal intercostal muscles: contract -> if air is being forced out (forced exhalation)

Question 7

Composition of air: oxygen

Answer 7

Inspired air: 21%
Expired air: 16%

Question 8

Composition of air: carbon dioxide

Answer 8

Inspired air: 0.04%
Expired air: 4%

Question 9

Composition of air: nitrogen

Answer 9

Inspired air: % varies
Expired air: saturated

Question 10

Reasons for differences in inhaled and exhaled air: oxygen

Answer 10

Removed from blood by respiring cells -> returns to lungs with lower concentration

Question 11

Reasons for differences in inhaled and exhaled air: carbon dioxide

Answer 11

Produced by respiring cells into blood -> returns to lungs with higher concentration

Question 12

Reasons for differences in inhaled and exhaled air: water vapour

Answer 12

Evaporated from lining of alveoli into air -> warmth of body

Question 13

Test for carbon dioxide

Answer 13

Limewater: clear -> cloudy/milky when carbon dioxide bubbled through

Question 14

Effect of exercise on breathing

Answer 14

Exercise: increases frequency and depth of breathing -> muscles working harder and aerobically respiring more needing more oxygen to keep up with energy demand
- Increased depth of breathing: so more carbon dioxide is removed as brain detects increased concentration of caebon dioxide in blood