问题 单项选择题 B型题

应激性急性胃炎主要发病机制()

A.胃黏膜微循环障碍

B.抑制前列腺素合成

C.亲脂性,破坏黏膜屏障

D.黏液屏障分泌减少

E.胆盐、磷脂酶A和其他胰酶破坏

答案

参考答案:A

解析:严重创伤、大手术、烧伤、颅内病变、败血症及其他严重脏器病变或MODS等均可引起胃黏膜糜烂出血,严重者发生急性溃疡并大量出血,如烧伤所致称为Curl-ing溃疡,中枢神经系统称为Cushing溃疡。一般认为应激状态下,胃黏膜循环不能正常运行而造成黏膜缺血、缺氧是发病的重要环节,由此可以导致胃黏膜黏液碳酸氢盐分泌不足、局部前列腺素合成不足,上皮再生能力减弱等改变,胃黏膜屏障因而受损。NSAID通过削弱黏膜的防御和修复功能导致消化性溃疡的发病,损害作用包括局部和系统作用两方面。前者指药物直接损伤胃黏膜上皮层;后者主要是通过抑制环氧合酶COX起作用。COX是花生四烯酸合成前列腺素的关键限速酶,分为两种异构体--COX-1和COX-2。COX-1在组织细胞中恒量表达,催化生理性前列腺素合成而参与机体生理功能调节;COX-2主要在病理情况下由炎症刺激诱导产生,促进炎症部位前列腺素合成。传统的NSAID如阿司匹林、吲哚美辛等旨在抑制COX-2而减轻炎症反应,但特异性差,同时抑制了COX-1,导致胃肠黏膜生理前列腺素E合成不足。后者通过增加黏液和碳酸氢盐分泌、促进黏膜血流增加、细胞保护等作用在维持黏膜防御和修复功能中起重要作用。

阅读理解

Ironing a shirt is easy to learn. Just follow the steps in this short guide (指南), and you’ll learn how to iron your shirt properly with the help of the video. The most important thing is this: don’t try to iron a dry shirt.

● Get ready

You will need an iron, an ironing board and a bottle of water. Place the shirt on the ironing board. You can iron in whatever order you like, but most people like to start at the top — the collar. Have a bottle of water ready. Spray (喷) it onto the shirt to make it easier to iron.

● Do the ironing

First, iron the inside of the collar. Second, turn the collar over and iron the other side. Third, iron the back shoulders of the shirt. Fourth, iron the cuffs. Iron the inside, then the outside of the cuffs. Fifth, iron the sleeves. Sixth, iron the back of the shirt. Finally, iron the front of the shirt. Do one side, and then do the other side.

● Dry the shirt

Check your shirt and iron it again if you need to. Now put your shirt on a hanger and let it dry.

小题1: What’s the most important thing if you want to iron a shirt?

A.Have a bottle of water ready.

B.Don’t try to iron a dry shirt.

C.Wash your shirt carefully.

D.Place the shirt on the ironing board.小题2:You will need all of the following things EXCEPT ________ before you iron a shirt.

A.a ruler

B.an iron

C.an ironing board

D.a bottle of water小题3:Most people like to start with ironing ________ of a shirt.

A.the sleeves

B.the back shoulders

C.the cuffs

D.the collar小题4:How many steps are there to do the ironing, according to this guide?

A.Five.

B.Six.

C.Seven.

D.Eight.小题5:The writer tells us it’s easy to learn how to iron a shirt by ________.

A.reading a book

B.watching a video

C.listening to the radio

D.reading the newspaper

填空题