Lungs

Question 1

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.

Answer 1

1 Many alveoli / alveoli walls folded provide a large surface area;2 Many capillaries provide a large surface area;3 (So) fast diffusion;4 Alveoli or capillary walls / epithelium / lining are thin / short distance between alveoli and blood;5 Flattened / squamous epithelium;6 (So) short diffusion distance / pathway;7 (So) fast diffusion;8 Ventilation / circulation;9 Maintains a diffusion / concentration gradient;10 (So) fast diffusion;

Question 2

Describe the path by which oxygen goes from an alveolus to the blood.

Answer 2

First through alveolar epithelium then through capillary epithelium/endothelium;

Question 3

Miner’s lung is a disease caused by breathing in dust in coal mines. The dust causes the alveolar epithelium to become thicker. People with miner’s lung have a lower concentration of oxygen in their blood than healthy people. Explain why people with miner’s lung have a lower concentration of oxygen in their blood.

Answer 3

they have a thicker alveolar wallso have a longer diffusion pathway / slower diffusion;

Question 4

In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries.(b)(b) (i)Describe how ventilation helps to maintain this difference in oxygen concentration.

Answer 4

(In alveolus) Brings in air containing a high(er) oxygen concentrationRemoves air with a low(er) oxygen concentration;

Question 5

Give one way other than ventilation helps to maintain the difference in oxygen concentration.

Answer 5

Circulation of blood / moving blood

Question 6

Pulmonary tuberculosis is a disease of the lungs.Describe the transmission and course of infection of pulmonary tuberculosis

Answer 6

1 (Bacteria transmitted in) droplets / aerosol;2 (Bacteria) engulfed / ingested by phagocytes / macrophages;3 (Bacteria) encased in named structure e.g. wall / tubercle / granuloma / nodule;4 (Bacteria) are dormant / not active / not replicating;5 If immunosuppressed, bacteria activate / replicate / released;6 Bacteria destroy alveoli / capillary / epithelial cells;7 (Leads to) fibrosis / scar tissue / cavities /calcification;8 (Damage) leads to less diffusion /less surface area / increases diffusion distance;9 (Activation / damage allows bacteria) to enter blood / spreads (to other organs);

Question 7

Emphysema is another disease of the lungs. People with emphysema may feel weak and tired. Explain why.

Answer 7

1 Alveoli break down / collapse / rupture / walls thicken;2 Less surface area / increases diffusion distance / less diffusion;3 Loss of elastin / elastic tissue / elastase involved;4 (Alveoli / lungs) cannot recoil / spring back / have reduced elasticity / more difficult to expel air;5 Reduced diffusion gradient / air not replenished / less air leaves lungs;6 Less oxygen enters blood / tissues;7 Less respiration / less energy released / less ATP produced

Question 8

Emphysema reduces the efficiency of gas exchange in the lungs. Explain why.

Answer 8

1. Alveoli break down / collapse / rupture / fewer alveoli / larger alveoli or alveolar wall/epithelium walls thicken2. Reduced surface area / increased diffusion pathway3. (So) less diffusion4. Less elastin / elastic (tissue) / not recoiling / loss of elasticity / elastin permanently stretched5. Reduced flow rate / less air expelled6. So small / reduced diffusion or concentration gradient;

Question 9

Describe what happens to the diaphragm between inspiration to bring about the change in its shape

Answer 9

1. Flatten/moves down2. (Diaphragm muscle) contracts

Question 10

Air moves into the lungs between times during inspiration. Explain how the diaphragm causes this

Answer 10

1. Diaphragm contracts/moves down/ flattens2. Increases volume (of thorax)3. Decrease in pressure4. Air moves from high to lower pressure/down pressure gradient

Question 11

Describe how oxygen in air in the alveoli enters the blood in capillaries

Answer 11

1. Diffusion2. Across (alveoli)epithelium/ (capillary) endothelium

Question 12

Pulmonary ventilation = …………………………………………… × ……………………………………….

Answer 12

Tidal volume and ventilation rate

Question 13

Describe two adaptations of the structure of alveoli for efficient gas exchange. What do we call this type of exchange?

Answer 13

1. Thin walls/cells2. (Total) surface area is large(Simple) diffusion

Question 14

Fire-breathers blow a fine mist of paraffin oil onto a flame. Some of this mist can be inhaled and may eventually lead to fibrosis.People who have been fire-breathers for many years often find they cannot breathe out properly. Explain why.

Answer 14

1. Loss of elasticity/elastic tissue (elastin)2. Scar tissue3. Less recoil