问题 问答题 简答题

为什么寄生在终宿主门静脉及肠系膜静脉内的日本血吸虫产出的虫卵会随粪便排出体外?

答案

参考答案:

日本血吸虫成虫寄生在终宿主门静脉、肠系膜静脉,所产的虫卵部分沉积于肠壁小血管中,约经11天卵内的细胞发育成毛蚴。由于毛蚴分泌可溶性虫卵抗原(SEA.可透过卵壳,破坏血管壁,并使周围组织出现炎症、坏死,形成小的脓肿。由于肠蠕动、腹内压增加,以及血管内压的波动,致使脓肿向肠腔破溃,虫卵随溃破的坏死组织落入肠腔,随粪便排出体外。

完形填空

填空(共10小题,每小题1分,共10分):

阅读下面的短文,在标有序号的空白处填入一个适当的词,或填入括号中单词的正确形式,并将序号及相应答案写在答题纸上。

Around the world young people are spending unbelievable sums of money to listen to rock music. Forbes Magazine claims that at least fifty rock stars have an __1__ of between two million and six million dollars per year.

Some observers think the customers are buying more than music. According to one theory, rock music has a special appeal because no real training is needed to produce it. There is __2__ gap between the audience and the performers. Every boy and girl in the audience thinks,” I could sing __3__ that.” So rock has become a new kind of religion, a new form of worship. Young people are glad to worship a rock star because it is a way of worshipping __4__.

Luck is a key word for explaining the success of many. In 1972 one of the luckiest was Don McLean, who wrote and sang “American Pie”. Like most performers, McLean __5__ his own music, so he earns additional money. Records provide only part of a star’s income. Around the world young listeners soon want to see the star in movies, on television, and __6__ person.

__7__ do the rock stars use their money? What do they do when the money starts pouring in like water? Most of the young stars just throw the money around. England’s Elton John bought himself a $5,000 pair of eyeglasses that light up and spell E-L-T-O-N. He also bought himself __8__ cars, “one for each foot”.

In the end the rock star’s life is unrewarding. After two or three years fame and fortune are gone. __9__(leave) with his memories and his tax problems, the lonely ex-performer spends his __10__ (remain) years trying to impress strangers. New stars have arrived to take his place.

单项选择题