3.1.2 mammalian gaseous exchange system

Question 1

alveoli

Answer 1

folds of lung epithelium to increase SA

Question 2

bronchi & bronchioles

Answer 2

smaller airways leading to lungs

Question 3

diaphragm

Answer 3

layer of muscle beneath lungs

Question 4

intercostal muscles

Answer 4

muscles between ribs - contraction of external intercostal muscles raises rib cage

Question 5

trachea

Answer 5

main airway leading from back of mouth to lungs

Question 6

ventilation

Answer 6

refreshing of air in lungs so higher oxygen concentration than in blood & lower carbon dioxide concentration

Question 7

adaptations of alveoli/lungs

Answer 7

• lined by thin layer of moisture which evaporates & lost when exhale
• lungs produce surfactant which coats internal surface of alveoli = reduces cohesive forces between water molecules & stops collapse

Question 8

adaptations to reduce diffusion distance

Answer 8

• alveolus wall 1 cell thick
• capillary wall 1 cell thick
• capillary & alveolus wall consist of squamous cells (flattened & thin)
• capillaries & alveolus in close contact
• capillaries are narrow so RBC squeezed against wall = closer to alveoli

Question 9

adaptations to reduce diffusion distance

Answer 9

• alveolus wall 1 cell thick
• capillary wall 1 cell thick
• capillary & alveolus wall consist of squamous cells (flattened & thin)
• capillaries & alveolus in close contact
• capillaries are narrow so RBC squeezed against wall = closer to alveoli

Question 10

describe the good blood supply

Answer 10

• co2 transported from tissues to lungs = concentration of co2 in blood higher than air of alveoli so it can diffuse
• o2 transported away from lungs = o2 concentration in blood lower than alveoli

Question 11

describe the mechanism of inhalation (ventilation)

Answer 11

1. diaphragm contracts & moves down becoming flatter
2. external intercostal muscles contract raising rib cage
3. volume of chest cavity increases
4. pressure in chest cavity drops below atmospheric pressure
5. air moved into lungs

Question 12

describe the mechanism of exhalation (ventilation)

Answer 12

1. diaphragm relaxes & pushed up by displaced organs
2. external intercostal muscles relax & ribs fall (internal intercostal muscles can contract to push air out forcefully eg. exercise)
3. volume of chest cavity decreased
4. pressure of chest cavity increases above atmospheric pressure
5. air moved out of lungs