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作者 : Peony Lau (---.hkcable.com.hk)
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日期 : 2007-04-08 01:49 |
HKCEE Biology 1997 I Q2c.
- Some patients may suffer from a kind of heart defect in which valve A(bicuspid valve) cannot close completely. Explain the probable effect of this defect on the function of the heart. (2 marks)
- State the heart chamber which first receives the following substances after their entry into our body:
i carbon monoxide in exhaust fumes (1 mark)
ii vitamin C in food (1 mark)
Are the answers to (i) and (ii) right auricle? |
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作者 : Ho Sir (203.223.---.---)
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日期 : 2007-04-09 09:30 |
1997/Q2c The bicuspid valve makes sure the blood in the left ventricle does not flow back to the left auricle when the left ventricle contracts. If this valve cannot close completely, considerable quantity of the oxygenated blood in the left ventricle will go back to the left auricle but cannot be pumped by the left ventricle to all parts of the body. As a result, most body cells cannot receive enough oxygen and nutrient supply. The heart must work much harder all the time so that the heart muscle would gradually lose its capability to contract.
(i) Carbon monoxide enters the body through the lungs. It is then carried by the pulmonary veins to the LEFT AURICLE.
(ii) Vitamin C enters the body through the gut. It is then carried by the hepatic portal vein to the liver, and then from the liver to the RIGHT AURICLE by the hepatic vein, then inferior vena cava. Your answer (i) is not correct. |
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