[单选题]
Air is carried to the lungs by e
qe7ueh * 3ib/entering through the nostrils into the
g3wxp: 08ptjqow , pftu2(3aunasal cavity, and then as shown in
3ug0pjw waq f82tx(pu 3o:t,p the pathway below.
Which of the following statements are correct descriptions of structures P and Q?
A.
B.
C.
D.
参考答案:
D
本题详细解析:
Air enters the nasal cavity and then passes down the trachea (P). The trachea’s wall consists of C shaped rings of cartilage. Air that passes down the trachea first enters the bronchi, then bronchioles and finally reaches the alveoli (Q). A characteristic of alveoli is the presence of a large number of air sacs and the presence of cells that secrete a surfactant.
Choice A is incorrect because the trachea does not contain a large number of air sacs; these air sacs are known as alveoli.
Choice B is incorrect because the trachea does not secrete a surfactant. However, it does secrete an immunoglobulin rich mucus. Additionally, Muscles that contract and relax to form a dome are that of the diaphragm and not the alveoli.
Choice C is incorrect because the diaphragm, not the trachea, consists of muscles that relax to form a domed shape.
