Gas exchange Banker

1. (a) Which tissue is present in the wall of the trachea but absent from the wall of a bronchiole?A smooth muscleB cartilageC ciliated epitheliumD elastic fibres [1]

1. (a) What is the function of the elastic fibres in the walls of the airways and alveoli?A to contract and narrow the airwaysB to stretch during inspiration and recoil during expiration, helping to push air outC to trap dust and bacteriaD to keep the trachea open when air pressure inside it falls [1]

1. (a) Describe how the cartilage differs in the trachea, the bronchi and the bronchioles. [3]
2. (b) Explain the function of the cartilage in the trachea. [2]

1. (a) Describe how goblet cells and ciliated cells work together to protect the lungs from infection. [3]
2. (b) Suggest why there are no goblet cells or cilia in the alveoli. [2]

1. (a) Explain why the cartilage in the trachea is C-shaped rather than a complete ring. [2]
2. (b) State the function of the smooth muscle in the walls of the bronchi and bronchioles. [1]
3. (c) Name the structure in the airways where gas exchange takes place. [1]

1. (a) Describe how the cilia in the trachea move mucus. [2]
2. (b) Whooping cough is caused by bacteria that release a toxin which damages ciliated cells. Suggest why people with whooping cough cough violently and often. [2]

1. (a) A photomicrograph shows an airway about 0.8 mm in diameter. Its wall has no cartilage, a thick layer of smooth muscle, elastic fibres and a lining of ciliated cells with very few goblet cells.A tracheaB bronchusC bronchioleD alveolar duct [1]

1. (a) Which structures produce the mucus that lines the trachea?A goblet cells and mucous glandsB ciliated cells and goblet cellsC cartilage and mucous glandsD squamous epithelial cells and goblet cells [1]

1. (a) During an asthma attack the airways narrow and breathing becomes difficult. Which tissue contracts to cause this narrowing?A cartilageB elastic fibresC smooth muscleD squamous epithelium [1]

The wall of the trachea was examined from the lumen outwards. Four structures were described:P: a layer of tall cells with tiny hair-like projections on their free surfaceQ: single cup-shaped cells scattered among the cells of P, filled with pale-staining vesiclesR: clusters of secretory cells in the connective tissue beneath P, with ducts opening onto the surfaceS: a thick C-shaped band of bluish, glassy tissue with cells in small spaces (lacunae)

1. (a) Name the tissues P, Q, R and S. [4]
2. (b) State the function of tissue S and one other tissue named in your answer to (a). [2]

1. (a) In cystic fibrosis the mucus in the airways is much thicker and stickier than normal. Suggest why people with cystic fibrosis suffer from frequent lung infections. [3]
2. (b) Suggest why people with cystic fibrosis may also become breathless. [2]

A student viewed a transverse section of trachea with a light microscope. With the objective used, one eyepiece graticule division equals 4.0 µm. The ciliated epithelium measured 12 divisions thick and the cartilage measured 85 divisions thick.

1. (a) Calculate the actual thickness of the ciliated epithelium and of the cartilage. [2]
2. (b) Calculate how many times thicker the cartilage is than the epithelium. Give your answer to 2 significant figures. [1]
3. (c) On a photomicrograph of a bronchiole, a scale bar 20 mm long represents 100 µm. The diameter of the bronchiole on the photomicrograph is 96 mm. Calculate the actual diameter of the bronchiole in µm. [2]

1. (a) An electron micrograph of the surface of a ciliated cell has a magnification of ×6000. A cilium on the micrograph is 45 mm long. Calculate the actual length of the cilium in µm. [2]
2. (b) Convert your answer to nanometres. [1]
3. (c) Ciliated cells contain many mitochondria close to the bases of the cilia. Explain why. [2]

1. (a) In a rare inherited condition, enzymes released by white blood cells in the lungs break down elastic fibres faster than normal. Suggest and explain how this would affect breathing out. [3]
2. (b) Alveolar walls damaged in this way may break down so that several alveoli merge into one larger air space. Explain why this reduces the rate of gas exchange. [2]

1. (a) Copy and complete the table by writing present or absent in each box.Feature | trachea | bronchiole | alveoluscartilage | ? | ? | ?ciliated epithelium | ? | ? | ?smooth muscle | ? | ? | ?elastic fibres | ? | ? | ? [4]
2. (b) Name the type of epithelium that lines the alveoli and explain how it is adapted for its function. [2]

1. (a) Mucus contains glycoproteins. Name two organelles that you would expect to be abundant in a goblet cell and explain the role of each in producing mucus. [4]
2. (b) Name the process by which mucus is released from the goblet cell. [1]

1. (a) Which statements about the wall of a bronchus are correct?1 It contains irregular plates of cartilage.2 It is lined by ciliated epithelium with goblet cells.3 It contains smooth muscle.A 1, 2 and 3B 1 and 2 onlyC 2 and 3 onlyD 1 only [1]

1. (a) Describe four differences between the wall of the trachea and the wall of a bronchiole. [4]
2. (b) Explain why bronchioles can change their diameter but the trachea cannot do so to the same extent. [2]

1. (a) State three rules a student should follow when making a plan diagram of a transverse section of a bronchus. [3]
2. (b) In the bronchus section the total wall thickness was 60 eyepiece divisions, of which 38 divisions were cartilage. Calculate the percentage of the wall thickness made up of cartilage. Give your answer to the nearest whole number. [1]
3. (c) A second section was of a bronchiole. Suggest two features that the student would see in the bronchiole that would allow her to distinguish it from the bronchus. [2]

A woman in Karachi with asthma measured her peak flow (the fastest rate at which she could breathe out) before and 15 minutes after using an inhaler.Before: 220 dm³ min⁻¹After: 380 dm³ min⁻¹

1. (a) Calculate the percentage increase in peak flow after using the inhaler. Give your answer to 3 significant figures. [2]
2. (b) The inhaler contains a drug that causes smooth muscle to relax. Explain how this increases peak flow. [2]
3. (c) Her reading before using the inhaler was 55 % of the expected peak flow for a healthy woman of her age and height. Calculate her expected peak flow. [2]

The table shows the percentage of inhaled particles of different diameters that are trapped in the trachea and bronchi.Particle diameter / µm: 0.5, 2.5, 5, 10Trapped in trachea and bronchi / %: 5, 40, 70, 90

1. (a) Describe and explain the pattern shown by the data. [3]
2. (b) Smog in Lahore contains many particles smaller than 2.5 µm. Suggest why these particles are more harmful to the lungs than larger particles. [2]

Samples of bronchus lining were taken during routine medical procedures from adults living in a large industrial city and from adults in rural villages. The number of goblet cells per mm of epithelium was counted.City group: mean 41 goblet cells per mmVillage group: mean 25 goblet cells per mm

1. (a) Calculate the percentage by which the mean number of goblet cells in the city group is greater than in the village group. [2]
2. (b) Suggest an explanation for the difference between the two groups. [2]
3. (c) Suggest one disadvantage to the city group of having more goblet cells. [1]

1. (a) State three features of alveoli and explain how each increases the rate of gas exchange. [3]
2. (b) Name the process by which oxygen moves from the alveolar air into the blood. [1]

1. (a) Describe the route taken by a molecule of carbon dioxide as it leaves the blood and passes out of the body. [3]
2. (b) Alveolar walls contain macrophages. Suggest the role of these cells. [1]

1. (a) Explain how breathing (ventilation) and blood flow both help to maintain a steep concentration gradient of oxygen between alveolar air and blood. [4]
2. (b) Suggest why the capillaries around the alveoli are so narrow that red blood cells pass through them in single file, pressed against the capillary wall. [2]

1. (a) In pulmonary fibrosis, scar tissue forms in the walls of the alveoli. In one patient the distance between alveolar air and blood increased from 0.5 µm to 3.0 µm. Assuming the rate of diffusion is inversely proportional to the diffusion distance, calculate how many times slower diffusion became. [1]
2. (b) Suggest why patients with pulmonary fibrosis become breathless, especially during exercise. [3]

Climbers on their way to K2 spend time at a base camp at about 5000 m above sea level. The partial pressure of oxygen in the air is 21.2 kPa at sea level and 11.2 kPa at 5000 m.

1. (a) Calculate the percentage decrease in the partial pressure of oxygen between sea level and the base camp. Give your answer to 3 significant figures. [2]
2. (b) Explain why climbers at the base camp become breathless even when resting. [3]

1. (a) How many cell surface membranes does an oxygen molecule cross as it diffuses from the air in an alveolus to a haemoglobin molecule inside a red blood cell?A 2B 3C 4D 5 [1]

A pair of adult human lungs contains about 480 million alveoli. Assume that each alveolus has a diameter of 0.2 mm.

1. (a) Calculate the surface area of one alveolus, treating it as a sphere (surface area = πd²). Give your answer in mm² to 3 significant figures. [1]
2. (b) Calculate the total surface area of the alveoli in m², to 2 significant figures. (1 m² = 10⁶ mm²) [2]
3. (c) State one assumption in this calculation that may make the answer inaccurate, and explain why. [1]

The table shows partial pressures of gases (kPa).Gas: inspired air | alveolar air | deoxygenated blood arriving at lungsOxygen: 21.0 | 13.3 | 5.3Carbon dioxide: 0.04 | 5.3 | 6.1

1. (a) Explain why the partial pressure of oxygen in alveolar air is lower than in inspired air. [2]
2. (b) Calculate the difference in partial pressure (the diffusion gradient) between alveolar air and deoxygenated blood for oxygen and for carbon dioxide. [2]
3. (c) Carbon dioxide still diffuses out of the blood as quickly as oxygen diffuses in, even though its gradient is much smaller. Suggest why. [1]