简述气管管壁的组织结构。
参考答案：
气管管壁分为三层，即粘膜、粘膜下层和外膜，上皮为假复层纤毛柱状上皮，主要含纤毛细胞和杯状细胞，粘膜下层内有较多混合腺，外膜中“C”字形的透明软骨。随着气管分支为主支气管、叶支气管和小支气管，管径变小，管壁变薄，三层分界变得不明显。而上皮仍为假复层纤毛柱状，但逐渐变薄；杯状细胞和腺体都逐渐减少；软骨变为软骨片，而平滑肌纤维相对增多，呈现为不成层的环行平滑肌束。分支内径约lmm时即为细支气管，上皮变成单层纤毛柱状，杯状细胞、腺体和软骨片逐渐减少或消失，环行平滑肌更为明显，粘膜常形成皱襞。内径为0.5mm时称终末细支气管，上皮为单层柱状，主要细胞为无纤毛的克拉拉细胞，杯状细胞、腺体和软骨片全部消失，有完整的环行平滑肌。
| The question of what children learn and how they should learn it is continually being debated and redebated. Nobody dares any longer to defend the old system, the learning of lessons parrot-fashion and the grammar with-a-whip system, which was good enough for our grandparents. The theorists of modem psychology have stepped in to argue that we must understand the needs of children. Children are not just small adults; they are children who must be respected as such. Well, you may say, this is as it should be, and a good idea. But think further. What happens "Education" becomes the responsibility not of teachers, but of psychologists. What happens then Teachers worry too much about the psychological implications of their lessons, and forget about the subjects themselves. If a child dislikes a lesson, the teacher feels that it is his fault, not the child’s. So teachers worry whether history is "relevant" to modem young children. And do they dare to recount stories about violent battles Or will this make the children themselves violent Can they tell their classes about children of different races, or will this encourage racial hatred Why teach children to write grammatical sentences Verbal expression is better. Sums Arithmetic No, no; real-life mathematical situations are more understandable. You see you can go too far. Influenced by educational theorists, who have nothing better to do than write books about their ideas, teachers leave their teacher-training colleges filled with grand, psychological ideas about children and their needs. They make elaborate, sophisticated preparations and try out their "modem methods" on the long-suffering children. Since one "modem method" rapidly replaces another, the poor kids will have had a good bellyful by the time they leave school. Frequently the modem methods are so sophisticated that they fail to be understood by the teachers, let alone the children; even more often, the relaxed discipline, so essential for the "informal" feeling the class must have, prevents all but a handful of children from learning anything. |
What do the modem psychologists maintain
A．Children must be understood and respected.
B．Children are small adults and know what they need.
C．Children are better off without learning lessons.
D．Education of children is the responsibility of psychologists.