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  • 原免疫系统

    A castle surrounded by a moat, symbolizing defense and protection against enemies.

    How does your body keep most enemies out?
    ::你的身体怎么把敌人都挡在外头?

    Many would consider the moat around this castle, together with the thick stone castle walls, as the first line of defense. Their role is to keep the enemy out, and protect what's inside.
    ::许多人会认为这座城堡周围的护城河 加上厚厚的石墙 以及厚厚的城堡墙 是第一道防线

    The First Line of Defense
    ::第一防线

    A colored electron microscope image of a 1-cm long parasitic worm.

    Does this organism look like a space alien? A scary creature from a nightmare? In fact, it’s a 1-cm long worm that lives in the and causes serious harm. It enters the body through a hair follicle of the skin when it’s in a much smaller stage of its . Like this worm, many other organisms can make us sick if they manage to enter our body. Fortunately for us, our immune system is able to keep out most such invaders.
    ::这个生物体看起来像外星人吗? 恶梦中的恐怖生物吗?事实上,它是一个1厘米长的长的虫子,它活在恶梦中并造成严重伤害。 当它处于小得多的皮肤阶段时,它会通过皮肤的毛囊进入身体。 像这个虫子一样,许多其他生物体如果能够进入我们的身体,也会让我们生病。幸运的是,我们的免疫系统能够阻止大多数这样的入侵者。

    The immune system protects the body from worms, germs, and other agents of harm. The immune system is like a medieval castle. The outside of the castle was protected by a moat and high stone walls. Inside the castle, soldiers were ready to fight off any invaders that managed to get through the outer defenses. Like a medieval castle, the immune system has a series of defenses. In fact, it has three lines of defense. Only that are able to get through all three lines of defense can harm the body.
    ::免疫系统可以保护身体免受蠕虫、细菌和其他伤害因素的伤害。免疫系统就像中世纪的城堡。城堡外部有护城河和高石墙的保护。在城堡内,士兵们准备与任何能够通过外防御的入侵者作战。像中世纪的城堡一样,免疫系统有一系列防御系统。事实上,它有三条防线。只有能够穿越所有三条防线的防线才能伤害身体。

    The body’s first line of defense consists of different types of barriers that keep most pathogens out of the body. Pathogens are disease-causing agents, such as and . These and other types of pathogens are described in the table . Regardless of the type of pathogen, however, the first line of defense is always the same.
    ::人体的第一道防线是由不同种类的屏障构成的,这些屏障使大多数病原体远离身体。 病原体是疾病致病剂,例如和。 这些病原体和其他病原体在表格中都有描述。 然而,不管病原体的类型如何,第一道防线总是一样。

    Type of Pathogen Description Diseases associated with pathogens of this type

    Bacteria
    ::细菌

     

    Microscopic view of Escherichia coli bacteria, highlighting their single-celled structure.

    Escherichia coli
    ::埃舍里希亚大肠

    		Single-celled organism without a . Strep throat, staph infections, tuberculosis , food poisoning, tetanus, pneumonia , syphilis

    Viruses 
    ::病毒

    Microscopic view of herpes simplex virus particles, illustrating viral structure and replication.

    Herpes simplex
    ::简单疹

    		Non-living particles that reproduce by taking over living . Common cold, flu, herpes, cold sores, measles, AIDS, genital warts , chicken pox, small pox.

    A death-cap mushroom growing among dried leaves on the forest floor.

    Death-cap mushroom
    ::死亡帽子蘑菇

    		Simple organisms, including mushrooms and yeasts, that grow as single cells or thread-like filaments.    Ringworm , athlete's foot, candidiasis , histoplasmosis, mushroom poisoning.

    Micrograph of Giardia lamblia, a single-celled organism causing various diseases.

    Giardia lamblia
    ::贾尔迪亚羊羔

    		Single-celled organism with a nucleus. Malaria , "traveler's diarrhea", giardiasis , trypanosomiasis, sleeping sickness

     

    Mechanical Barriers
    ::机械障碍

    Mechanical barriers physically block pathogens from entering the body. The skin is the most important mechanical barrier. In fact, it is the single most important defense the body has. The outer layer of the skin is tough and very difficult for pathogens to penetrate.
    ::皮肤是最重要的机械屏障。事实上,皮肤是身体最重要的防线。皮肤的外层是坚硬的,病原体很难穿透。

    Mucous membranes provide a mechanical barrier at body openings. They also line the respiratory, GI, urinary, and reproductive tracts. Mucous membranes secrete mucus , a slimy substance that traps pathogens. The membranes also have hair-like cilia . The cilia sweep mucus and pathogens toward body openings where they can be removed from the body. When you sneeze or cough, pathogens are removed from the nose and throat (see Figure ). Tears wash pathogens from the , and urine flushes pathogens out of the urinary tract. 
    ::粘膜膜为身体开口提供了机械屏障,它们还连接呼吸道、GI、尿道和生殖道。 粘粘性物质,即粘粘性物质,诱发病原体。 粘膜也有毛状粘膜。 粘膜和病原体扫向身体开口,可以将其从身体上移走。 当打喷嚏或咳嗽时,病原体从鼻子和喉咙中移走(见图 )。 眼泪洗去病原体,尿液冲出尿道的病原体。

    Person sneezing, demonstrating the body's mechanical barrier against pathogens.
    A sneeze can expel many pathogens from the respiratory tract. That’s why you should always cover your mouth and nose when you sneeze.

    Chemical Barriers
    ::化学壁垒

    Chemical barriers destroy pathogens on the outer body surface, at body openings, and on inner body linings. Sweat, mucus, tears, and saliva all contain that kill pathogens. Urine is too acidic for many pathogens, and semen contains zinc, which most pathogens cannot tolerate. In addition, stomach acid kills pathogens that enter the GI tract in food or .
    ::化学屏障摧毁了外体表面、身体开口和内衬的病原体。 汗水、黏液、眼泪和唾液都含有杀死病原体的病原体。 尿液对许多病原体来说太酸,精液含有锌,大多数病原体都无法忍受。 此外,胃酸还杀死了进入GI草原的病原体。

    Biological Barriers
    ::生物障碍

    Biological barriers are living organisms that help protect the body. Millions of harmless bacteria live on the human skin. Many more live in the GI tract. The harmless bacteria use up food and space so harmful bacteria cannot grow.
    ::生物屏障是有助于保护人体的生物体,数百万无害细菌生活在人类皮肤上,更多的生物生活在GI草原上,无害细菌利用食物和空间,有害细菌无法生长。

      

     

     

     

    Summary
    ::摘要

    • Barriers that keep out pathogens are the body’s first line of defense.
      ::排除病原体的障碍是人体的第一道防线。
    • The first line of defense includes mechanical, chemical, and biological barriers.
      ::第一防线包括机械、化学和生物屏障。

    Review
    ::回顾

    1. What is the role of the body’s first line of defense?
      ::该机构的第一道防线的作用是什么?
    2. Identify three types of barriers in the body’s first line of defense. Give an example of each type of barrier.
      ::找出该机构第一道防线的三种障碍。 请举例说明每一种障碍。
    3. Which type of pathogen causes the common cold? Which type causes athlete’s foot?
      ::哪种病原体导致普通寒冷?哪种病原体导致运动员脚?