问题 单项选择题 A2型题

某患儿脱落的乳牙上患有龋病。在龋病的切片上,观察到部分牙本质中出现裂隙及串珠样结构,这些表现应见于牙本质龋的()。

A.坏死崩解层

B.细菌侵入层

C.脱矿层

D.透明层

E.脂肪变性层

答案

参考答案:B

解析:此题为牙本质病理变化的分析题。典型的形成龋洞的牙本质龋有5层结构,其中主要的病理变化出现在细菌侵入层,包括牙本质小管扩展,内含细菌;牙本质因脱矿即有机成分破坏形成裂隙及串珠样结构等。坏死崩解层在制片过程中大部分消失,脱矿层内无细菌存在,因此无串珠样变化和裂隙;透明层为牙本质小管矿化;脂肪变性层为牙本质小管内的成牙本质细胞突起内有脂肪存在。因此正确答案应选B。

问答题 简答题
单项选择题

In 1957 a doctor in Singapore noticed that hospitals were treating an unusual number of influenza-like cases. Influenza is sometimes called “flu” or a “bad cold”. He took samples from the throats of patients in his hospital and was able to find the virus of this influenza.

There are three main types of the influenza virus. The most important of these are types A and B, each of them having several sub-groups. With the instruments at the hospital the doctor recognized that the outbreak was due to a virus group A, but he did not know the sub-group. He reported the outbreak to the World Health Organization in Geneva. W. H.O. published the important news alongside reports of a similar outbreak in Hong Kong, where about 15%—20% of the population had become ill.

As soon as the London doctors received the package of throat samples, they began the standard tests. They found that by reproducing itself at very high speed, the virus had multiplied more than a million times within two days. Continuing their careful tests, the doctors checked the effect of drugs used against all the known sub-groups of virus type A. None of them gave any protection. This then, was something new: a new influenza virus against which the people of the world had no ready help whatsoever. Having isolated the virus they were working with, the two doctors now dropped it into the noses of some specially selected animals, which contact influenza in the same way as human beings do. In a short time the usual signs of the disease appeared. These experiments revealed that the new virus spread easily, but that it was not a killer. Scientists, like the general public, called it simply “Asian” flu.

The first discovery of the virus, however, was made in China before the disease had appeared in other countries. Various reports showed that the influenza outbreak started in China, probably in February of 1957. By the middle of March it had spread all over China. The virus was found by Chinese doctors early in March. But China was not a member of the World Health Organization and therefore did not report outbreaks of disease to it. Not until two months later, when travelers carried the virus into Hong Kong, from where it spread to Singapore, did the news of the outbreak reach the rest of the world. By this time it was started on its way around the world.

Thereafter, WHO’s Weekly Reports described the steady spread of this virus outbreak, which within four months swept through every continent.

The “Asian” flu virus()

A. was very weak

B. was a killer

C. reproduced very quickly

D. spread very slowly