本题目来源于试卷: Form and Function B.6 Gas Exchange，类别为 IB生物学
[单选题]
How do different mus;qqq7a74 fe qbcles co /delj9nsbs 50t4alu5ntribute to the decrease in air pressure inside the lungs, causinge5t4dls l/0n9u5 sbja inhalation?
A. Muscles on the abdominal wall contract
B. Diaphragm relaxes
C. External intercostal muscles shorten
D. Internal intercostal muscles shorten
参考答案: C
本题详细解析:
The process of air entering the lungs is known as inhalation. The term “inspiration” is used instead of inhalation sometimes. In order for inhalation to take place, the pressure inside the lungs must be lower compared to atmospheric pressure. To decrease the pressure inside the lungs, the external intercostal muscles must contract and become shorter to pull the ribs up and out, increasing the volume inside the thorax. Choice A is incorrect because abdominal wall muscles relax during inhalation. Lengthening of the abdominal muscles can contribute to inhalation by pushing the abdominal wall out which increases the volume inside the thorax. Choice B is incorrect because when the diaphragm relaxes it forms a dome shape and therefore reduces the volume of the thorax. This occurs during exhalation. Choice D is incorrect because internal intercostal muscles relax and lengthen during inhalation. They contract and shorten during exhalation.
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