题目

阅读理解 There is an old saying in English,Laughter is the best medicine. Until recently, few people took the saying very seriously. Now however,doctors have begun to study laughter and the effects(作用) it has on the human body. They have found evidence that laughter reallycan improve people's health. Tests were carried out to study the effectsof laughter on the body. People watched funny films while doctors checked theirheart rate, blood pressure, breathing and muscles. It was found that laughterhas similar effects to physical exercise. It increases blood pressure, theheart rate and th根据图心脏结构和人体血液循环示意图，回答下列问题。 (1)图甲是人体心脏结构示意图，心脏结构中，心壁最厚的是__________，保证血液从心房流向心室的结构是________(填字母)。(2)图乙由3到2为________循环。经过此循环后，血液成分的变化是______________________________。(3)小李同学感冒咳嗽，服用感冒药后，药物到达心脏四腔的先后顺序是________________(用图乙中的数字表示)。(4)若从图甲中的a处注水，水将从________(填字母)处流出，原因是______________，这体现了生物体结构和功能相适应的生物学观点，请再举一条该器官的结构和功能相适应的例子。____________________________________。