问题 问答题 简答题

孕妇感染后引起胎儿先天性畸形的微生物及其表现。

答案

参考答案:

孕妇感染了病原微生物可经垂直传播感染胎儿而造成先天性畸形,常见的病原微生物有:

(1)梅毒螺旋体。可通过胎盘进入血流,并扩散至肝、脾、肾上腺等内脏大量繁殖,引起胎儿全身性感染,出生后这样先天性梅毒的婴儿呈现锯齿形牙,间质性角膜炎,先天性耳聋等症状。

(2)风疹病毒。孕妇在孕期4个月内感染风疹病毒可经胎盘引起垂直传播,导致胎儿先天性畸形或先天性风疹综合征,表现为先天性心脏病、耳聋、失明及智力低下等。

(3)单纯疱疹病毒。妊娠妇女因单纯疱疹病毒原发感染或潜伏感染的病毒被激活,病毒可经胎盘感染胎儿影响胚胎细胞的有丝分裂,引起胎儿畸形及智力低下。

(4)巨细胞病毒。病毒通过胎盘感染胎儿,引起造血系统、中枢神经系统损伤,出现小脑畸形,视神经萎缩等。

(5)人类免疫缺陷病毒。妊娠妇女可经胎盘将病毒传给胎儿,引起流产、死胎、胎儿畸形等,亦可经产道将病毒传给新生儿,还可经乳汁将病毒传给婴儿,使其机体CD4细胞受破坏而导致免疫功能低下或缺陷最后易导致机会病原菌感染,甚至发生癌变而死亡。

(6)人 * * 瘤病毒。孕妇感染此病毒时,生殖器部位可出现尖锐湿疣,分娩时可经产道将病毒传给新生儿。其表现主要是受病毒感染部位可呈现 * * 状瘤病变,甚至可发生癌变,常见有宫颈癌、肛门癌、口腔癌等。

完形填空

(E)

A.Importance of Transport in Trade

B.Birth of Transport-related Industries and Trade

C.Role of Transport in Trade Development

D.Another Means to Develop TradeE.Higher Living Standard

F.Modern Life Needs Modern Traffics

80.

Transport is one of the aids to trade.By moving goods from places where they are plentiful to places where they are scarce, transport adds to their value.The more easily goods can be brought over the distance that separates producer and consumer, the better for trade.When there were no railways, no good roads, no canals, and only small sailing ships, trade was on a small scale.

81.

The great advances made in transport during the last two hundred years were accompanied by a big increase in trade.Bigger and faster ships enabled a trade in meat to develop between Britain and New Zealand, for instance.Quicker transport makes possible mass-production and big business, drawing supplies from, and selling goods to, all parts of the globe.Big factories could not exist without transport to carry the large number of workers they need to and from their homes.Big city stores could not have developed unless customers could travel easily from the suburbs and goods delivered to their homes.Big cities could not survive unless food could be brought from a distance.

82.

Transport also prevents waste.Much of the fish landed at the ports would be wasted if it could not be taken quickly to inland towns.Transport has given us a much greater variety of foods and goods since we no longer have to live on what is produced locally.Foods which at one time could be obtained only during a part of the year can now be obtained all through the year.Transport has raised the standard of living.

83.

By moving fuel, raw materials, and even power, for example, through electric cables, transport has led to the establishment of industries and trade in areas where they would have been impossible before.Districts and countries can concentrate on making things which they can do better and more cheaply than others and can then exchange them with one another.The cheaper and quicker transport becomes, the longer the distance over which goods can profitably be carried.Countries with poor transport have a lower standard of living.

84.

Commerce requires not only the moving of goods and people but also the carrying of messages and information.Means of communication, like telephones, cables and radio, send information about prices, supplies, and changing conditions in different parts of the world.In this way, advanced communication system also help to develop trade.

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