本题目来源于试卷: Form and Function B.5 Cell Specialization，类别为 IB生物学
[单选题]
Which of the following characteristics of type-z7zih2x jd+(s4nkud I pneusi :/ 9ajkrvk7mocytes contribute to incre 9i jrkva:7sk/asing the rate of gas exchange?
I.
Cells are flattened
II.
Secretion of a surfactant
III.
Cover less than 10% of the alveolar surface
A. I only
B. II only
C. II and III only
D. I, II and III
参考答案: A
本题详细解析:
Type I pneumocytes are flattened cells found in the alveoli (Statement I). The cells are very thin which means gases have a shorter distance to diffuse. This results in an increased rate of gas exchange. The wall of an alveolus is covered mostly (>90%) by type I pneumocytes (Statement III). Type II pneumocytes cover less than 10% of an alveolus. Type II pneumocytes secrete a surfactant which aids gas exchange because oxygen first dissolves in the surfactant before diffusing across type I pneumocytes (Statement II).
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