425265
| Question | Answer |
| Describe and explain the adaptation of human lungs in relation to Fick's Law 5 MARKS | -Short diffusion pathway (1) -caused by thin squamous epithelial cells (1) - large concentration gradient (1) - caused by the constant removal of oxygen by the blood and constant renewal of oxygen by the alveoli (1) -large surface area (1) -caused by many small alveoli (1) |
| Describe the pathway of oxygen from an alveolus to the blood 3 MARKS | - Diffuses (1) -Through the alveolar epithelium (1) - Into the blood via capillary endothelium (1) |
| Explain how ventilation maintains a concentration gradient 2 MARKS | - Air high in oxygen is constantly entering the alveoli (1) - Air low in oxygen is continuously being removed from the alveoli (1) - Blood high in oxygen is constantly being removed |
| Describe and explain the process of inspiration 5 MARKS | - Intercostal muscles contract (1) - Therefore the ribs move up and out) (1) - Diaphragm muscle contracts and diaphragm flattens - Volume increases (1) - Pressure increases relative to atmospheric pressure so air moves in (1) |
| Describe and explain the process of expiration 5 MARKS | - The intercostal muscles relax (1) - Therefore the ribs move down and in (1) - The diaphragm muscle relaxes and the diaphragm returns to a dome shape (1) - Volume decreases (1) - Pressure increases relative to atmospheric pressure so air moves out (1) |
| Explain how paralysis of the diaphragm leads to breathing difficulties 2 MARKS | Diaphragm will not flatten (1) So lung volume will not increase (1) |
| Describe and explain the effects of pulmonary fibrosis 4 MARKS | - Elastin may be destroyed so lungs no longer able to force air out of alveoli (1) - A lack of ventilation means the concentration gradient cannot be maintained (1) - Scar tissue (1) - Increase length of diffusion pathway (1) |
| Explain why during an asthma attack less oxygen diffuses into the blood 2 MARKS | - Airways restricted (1) - Air in alveoli not replaced, so less oxygen (1) - Concentration gradient not maintained (1) - Rate of diffusion is lower (1) |
| Explanation of symptoms of asthma 4 MARKS | - Difficulty breathing due to constricted bronchioles (1) - Wheezing sound caused by air passing through restricted bronchioles (1) - Tight feeling in chest, not being able to ventilate the chest adequately (1) - Coughing, a reflex response to obstructed bronchioles (1) |
| Explain the effects of allergies on asthma 5 MARKS | - Allergens cause white blood cells lining the bronchioles to release histamine (1) - Lining of bronchioles becomes inflamed (1) - Cells of epithelial lining secrete mucus (1) - fluid leaves capillaries and enters airways (1) - muscles surrounding bronchioles contract and constrict airways (1) - Lack of ventilation means conc. gradient is not maintained (1) |
| Explain the effect of emphysema 4 MARKS | - Elastin in the lung tissue has been permanently stretched (1) - Lungs no longer able to force out air (1) -Lack of ventilation means concentration gradient is not maintained (1) - Surface area of alveoli is reduced and they sometimes burst (1) - Diffusion of gases is less efficient (1) |
| Explain the symptoms of emphysema 3 MARKS | - shortness of breath due to difficulty inhaling, due to loss of elasticity in the lungs (1) - chronic cough due to body's effort to remove damaged tissue (1) - bluish skin colouration due to low level of oxygen in blood as a result of poor gas exchange (1) |
| Describe the course of infection of TB 6 MARKS | - bacteria grow in upper regions of lungs where there is a plentiful supply of oxygen (1) - white blood cells accumulate at site of infection (1) - leads to inflammation and enlargement of the lymph nodes (1) -years later bacteria may re-emerge and cause a second infection (1) - bacteria can destroy lung tissue, can result in cavities and scar tissue (1) - sufferer can cough up damaged tissue with blood (1) |
| Explain the symptoms of pulmonary fibrosis 4 MARKS | - shortness of breath due to a considerable volume of lungs being occupied by fibrous tissue (thickened epithelium - diffusion pathway increased )(1) - chronic dry cough due to fibrous tissue obstructing the airways - pain and discomfort in chest due to pressure and scarring due to coughing (1) - weakness and fatigue due to reduced intake of oxygen in the blood (1) |
| What is Fick's Law? 1 MARK | rate of diffusion = surface area x conc. grad. / length of diffusion pathway (1) |
| Calculate pulmonary ventilation 1 MARK | PV = tidal volume x ventilation rate |
| What is tidal volume ? 1 MARK | The volume of air taken in at each breath when resting in 0.5 dm3 (1) |
| What is ventilation rate? 1 MARK | The number of breaths per minute (Exam tip - usually between 12 - 20) (1) |
| What are the risk factors of lung disease? 5 MARKS | - smoking (1) - air pollution (1) - genetics (1) - infections (1) - occupation (1) |
| Who may be more vulnerable to TB ? 5 MARKS | - Young children (1) - Elderly / patients (1) - Pregnant women (1) - People with HIV/AIDS (1) - People undergoing chemotherapy (1) |
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