11.1 对病原体的障碍
章节大纲
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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 也是第一道防线The First Line of Defense
::第一防线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 bodies. Fortunately for us, our immune systems are 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厘米长的长虫,活在恶梦中,造成严重伤害。 它通过皮肤的毛囊进入身体,而皮肤的毛囊处于小得多的阶段。 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 "germs" and other harmful substances. The immune system is like a medieval castle. The outside of a medieval castle was protected by a moat and high stone walls. Inside the castle, soldiers were ready to defend the castle against any invaders that got through the outer defenses. Like a medieval castle, the immune system has a series of defenses. Only that are able to get through all the defenses can cause harm to the body.
::免疫系统保护身体不受“ 发热” 和其他有害物质的伤害。 免疫系统就像中世纪的城堡。 中世纪的城堡外面有一条护城河和高石墙的保护。 在城堡内, 士兵们准备保卫城堡, 防止任何入侵者通过外防御。 像中世纪的城堡一样, 免疫系统有一系列防御系统。 只有能够穿过所有防御系统,才能对身体造成伤害。The immune system has three lines of defense. The first line of defense includes a variety of barriers that keep most pathogens out of the body. Pathogens are disease-causing agents such as and . Defenses in the first line are the same regardless of the type of pathogen. This is why they are called nonspecific defenses. Several types of pathogens that are common causes of human disease can be seen in Figure .
::免疫系统有三条防线。第一防线包括各种屏障,使大多数病原体远离身体。病原体是疾病致病剂,例如和。第一防线的防线是相同的,不管病原体的类型如何。这就是为什么它们被称为非特定防线。图中可以看到人类疾病常见的几种病原体。Common Human Pathogens.
::人类共同病原体。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 that the body has against pathogens. It forms a physical barrier between the body and the outside world. The outer layer of the skin is a tough, nearly water-proof coating that is very difficult for pathogens to penetrate.
::机械屏障阻止病原体进入人体。皮肤是最重要的机械屏障。事实上,这是身体抵抗病原体的最重要屏障。它构成了身体与外部世界之间的物理屏障。皮肤外层是坚硬的、几乎防水的涂层,病原体很难穿透。At body openings, such as the mouth and nose, the body has a different mechanical barrier. Instead of skin, mucous membranes line these and other organs that are exposed to the outside environment. They include the organs of the respiratory, gastrointestinal, and urinary tracts. Mucous membranes secrete mucus , a slimy substance that coats the membranes and traps pathogens. Mucous membranes also have cilia , which are tiny projections that have wavelike motions. The movements of cilia sweep mucus and trapped pathogens toward body openings to be removed from the body.
::在口和鼻等身体开口处,身体有不同的机械屏障。 不像皮肤, 粘膜线将这些器官和其他接触外部环境的器官排在一起, 包括呼吸器官、 胃肠器官和尿道。 粘膜分泌粘液, 一种粘粘性物质, 覆盖膜, 并捕捉病原体。 粘膜也有粘膜, 微小的投影, 有波状的运动。 粘膜的移动将粘膜和被困的病原体从身体上移走。Pathogens are removed from the respiratory tract when you sneeze or cough. In addition, tears wash pathogens from the , and urine flushes pathogens out of the urinary tract.
::在打喷嚏或咳嗽时,将病原体从呼吸道中除去;此外,眼泪将病原体从尿道中除去,尿流将病原体从尿道中除去。A sneeze or cough can expel many pathogens from the respiratory tract. That’s why you should always cover your mouth and nose and when you sneeze.
::喷嚏或咳嗽可以将许多病原体从呼吸道中排出。 这就是为什么你应该总是遮住嘴和鼻子以及打喷嚏的时候。Chemical Barriers
::化学壁垒Chemical barriers are that destroy pathogens at the body’s surface. The skin and mucous membranes secrete proteins that kill many of the pathogens that they come into contact with. For example, called lysozymes—which are found in sweat, mucus, tears, and saliva—kill pathogens by breaking open their cell walls . Urine and vaginal secretions are too acidic for many pathogens, and semen contains zinc, which most pathogens cannot tolerate. Hydrochloric acid secreted by mucous membranes lining the stomach kills pathogens that enter the stomach in food or .
::化学屏障是摧毁人体表面病原体的化学屏障。 皮肤和粘膜的隐性蛋白会杀死许多接触过的病原体。 比如,通过破开细胞墙而发现的淋巴素 — — 存在于汗水、黏液、眼泪和唾液中 — — 致命病原体。 尿道和阴道的分泌对许多病原体来说太酸了,而精液含有锌,而大部分病原体都无法忍受。 胃部的粘膜被粘住的盐酸会杀死进入胃中的病原体或食物中的病原体。Biological Barriers
::生物障碍Biological barriers involve living organisms that compete with pathogens. Human skin is covered by millions of bacteria. Millions more colonize the gastrointestinal, urinary, and genital tracts. Most of these bacteria are helpful or at least not harmful. They are important in defense because they help prevent harmful bacteria from becoming established in or on the body. They do this by competing with harmful bacteria for food and space. Helpful bacteria may also change pH or other factors that make conditions less suitable for harmful bacteria.
::生物屏障涉及与病原体竞争的生物体; 人类皮肤被数百万细菌覆盖; 数以百万计的细菌覆盖; 数以百万计的人将肠胃、尿道和生殖道殖民化。 这些细菌大多有用或至少无害。 这些细菌在防御方面很重要,因为它们有助于防止有害细菌在身体内或身体上扎根。 它们这样做的方法是与有害细菌竞争食物和空间。 有用的细菌也可能改变pH值,或使条件不适合有害细菌的其他因素。Summary
::摘要-
Your body's defenses in the first line are the same regardless of the type of pathogen. They are called nonspecific defenses.
::无论病原体的类型如何,你身体在第一线的防御都是一样的。它们被称为非特定防御。 -
The outer layer of the skin is a tough, nearly water-proof coating that is very difficult for pathogens to penetrate.
::皮肤外层是一种坚硬、几乎防水的涂层,病原体很难穿透。 -
Mucous membranes have cilia, which are tiny projections that have wavelike motions. The movements of cilia sweep mucus and trapped pathogens toward body openings to be removed from the body.
::细胞膜有硅亚,这是微小的预测,有波状的动作。 硅亚的粘结和病原体向身体开口的移动,从身体上移走。 -
Helpful bacteria compete with harmful bacteria for food and space. Helpful bacteria may also change pH or other factors that make conditions less suitable for harmful bacteria.
::有益细菌与有害细菌争夺食物和空间。 有益细菌也可能改变pH值或其他使条件不适合有害细菌的因素。
Review
::回顾-
What are nonspecific defenses?
::什么是非特定防御? -
What organs are covered by mucous membranes? What is the function of mucous membranes?
::粘膜覆盖的器官是什么?粘膜的功能是什么? -
Give an example of a chemical barrier found in sweat.
::举例来说,在汗水中发现了一个化学屏障。 -
How do helpful bacteria act as a biological barrier against pathogens?
::有用的细菌如何作为防止病原体的生物屏障?
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Your body's defenses in the first line are the same regardless of the type of pathogen. They are called nonspecific defenses.
