1、醫學英語教程-生物醫學Unit 6 Reading A The Kidney and Its Working Unit 腎及其工作單位For many diners, eating tender, pale green shoots of asparagus is a pleasurable springtime event, but the gastronomic experience has a peculiar sequel：The next time they urinate ,even if just 20 minutes after eating, they notice the

2、characteristic scent of asparagus. A chemical in the food crosses the gut ,enters the bloodstream, is filtered out by the kidneys, and appears in the urine with amazing speed. Actually, the chemical is acted on no faster than any other compound. The kidneys are simply marvels at processing body flui

3、ds and filtering out the urea; the sodium ,potassium ,or chloride ions ;and the glucose, water ,and other materials that need to be excreted. The key to a kidney's rapid functioning lies in its complicated internal structure and in the effcient plumbing system of which it is a part. 對許多用餐者來說，吃到淺

4、綠鮮嫩的蘆筍是春季的一大享受，但享用完這種美食后會有一個奇特的后續：即使飯后僅20分鐘,人們便會在上廁所時注意到尿液中有蘆筍特殊的氣味。蘆筍中的某種化學物質以萬分驚人的速度穿過腸子,進入循環的血液,并被腎臟過濾出來,最后出現在尿液中。事實上，這一化學物的作用并不比其他化合物更快些。起到加速體液循循環并過濾出尿素,鈉、鉀、氯離子、葡萄糖、水及一切需排泄的這些驚嘆不已的作用的是腎臟。腎臟能快捷地發揮作用的關鍵就在于其復雜的內部結構，以及它作為其中一部分的高效率管道系統。The Kidneys and Other Organs of the Excretory Systerm腎臟和排泄系統的其他器官

5、It is sometimes stated that urination is our most compelling bodily function. You will probably agree if you have ever been hungry, tired ,cold ,and had a full bladder simultaneously and can recall the order in which you addressed those needs. This urgency has to do with the necessary waste removal

6、role of the excretory system and with the system's particular anatomy. 人們有時說排尿是我們身體最急迫的功能。如果你曾經有過饑餓、疲倦、寒冷及膀胱滿脹等感覺并能回憶起你處理這些身體需要的順序，你就會同意以上那種說法。這種急迫感與排泄系統必要的排廢作用和該系統特別的解剖結構有關。The main organs of the excretory system are the two plump, dark red, crescent- shaped kidneys, each about the size of an a

7、dult's fist and located high in the abdominal cavity behind the stomach and the liver. For each kidney to carry out its vital blood-filtering activities ,it must receive a large, steady flow of blood.排泄系統的主要器官是兩個圓滿的、暗紅色的、月牙狀的腎臟。每個約有成人拳頭大小, 位于腹腔上部胃、肝的后面。因為腎臟擔負過濾血液的重要任務，所以必須接收到強大持續的血流。This it does

8、 through the renal arteries, twin branches directly off the body's main blood vessel, or aorta. Cleansed blood then leaves each kidney in large renal blood vein that drains into the body's largest vein. As the kidneys filter and remove excess water and waste substances from the blood, these

9、materials collect as a concentrated urine in a central cavity in each kidney, then flow down a long tube called a ureter. The two ureters dump urine into a single storage sac, the urinary bladder, which in an adult can hold about 500 ml (a pint) of fluid. The bladder can distend to hold a bit more,

10、but when it is full, it causes considerable pressure on nearby nerves and a feeling of urgency that can temporarily eclipse all other concerns. During urination ,the urine exits the body through the urethra ,the single tube that drains the bladder.它穿過腎動脈，腎動脈即是直接離開人體主要血管或是主動脈的兩條并行的血管。緊接著，干凈的血液離開每一個腎后

11、進入一管腔大的、可以排入靜脈血至人體最大靜脈的腎靜脈。同時，兩個腎過濾與清除血液中多余的水以及代謝廢物，這些物質的收集后就成為在每一個腎的中央管內的濃縮后的尿液，接著這些尿液就沿著一條長長的管腔輸尿管向下流動。這兩條輸尿管把尿液傾倒入一個單個的用于儲藏的囊腔內，這個囊腔便是成年人可以裝得下500ml（一品脫）的液體的泌尿的膀胱。膀胱可以膨脹以至于多裝一些尿液，但是當它飽滿的時候，它可以對附近的神經造成相當大的壓力以及急尿的感覺，這樣可以暫時地使所有其他的問題消失。在排尿期間，尿通過尿道，從膀胱外導尿的一根導管排出體外。The kidney has three distinct visible

12、zones; an outer renal cortex zone: where initial blood filtering takes place; a central zone（renal medulla），divided into a number of fan-shaped pyramid regions that help conserve water and valuable solutes; and a hollow inner compartment（renal pelvis） ，where urine collects before it passes out of th

13、e kidney and down the ureter. The functional units of the kidney,twisted tubules called nephrons, reach from the outer cortex down into the central zone and drain into the hollow center. 腎臟有三個明顯的可見的區域；一個是外層的腎皮質區域：最初血液過濾發生的位置；中心區（腎髓質），分成若干個扇形的金字塔區域，有助于保存水分和有價值的溶液；還有一個中空的內區域（腎盂），是尿液流出腎臟進入輸尿管之前聚集的地方，在它

14、從腎臟出來和沿著輸尿管向下之前。腎臟的功能單位，扭曲的小管，稱為腎單位，到達淺皮質區向下進入中央區并排入內部中空區。Have you ever cleaned out a desk drawer - sorting,saving certain items for future use,discarding others,and then rechecking the drawer one

15、0;last time ?If so, you have approximated the kidney's general sorting and cleansing action and its three basic processes - filtration,reabsorption,and secretion - all of which involve the nephron. 你有沒有清理過抽屜將物品分類、排序保存供以后使用,丟棄不需要的,最后復查抽屜里的物品?  如果是這樣,你有近似腎的一般分類和清理行動的基本過程 , 過濾、重吸收和分泌所有這些涉

16、及腎元。 A human kidney contains roughly 1 million nephrons,each one a long, twisted,looping tubule. The tubule has one end that is enlarged and cup-shaped like a punched

17、0;basketball and that lies in close contact with blood capillaries;the other end drains away urine. If all the nephrons in an adult's kidney were straightened out and

18、 placed end to end, they would from a microscopically slender tube about 80km（50miles） long.  人類腎臟包含大約100萬腎元,每一個小管長期扭曲,構成環形。小管一端,開杯形放大,像打籃球,位于密切接觸血液毛細血管的地方;另一端排出尿液。如果所有的腎元在一個成年人的腎臟被拉直,從頭拉到尾,它們在顯微鏡下顯示長約80公里(50英里).Nephrons 

19、;are amazingly efficient at selectively removing wastes from the blood circulation while simultaneously conserving water,mineral ions, glucose,and other needed materials.In an adult human,&#

20、160;180 liters or more of blood - enough to fill a bathtub - pass through the 2 million nephrons in the two kidneys each day, we do not, of course,urinate&

21、#160;180liters a day or even the 6 or 7liters of fluid our bodieds contain,but instead the much more reasonable amount of about 1.5 liters per day.  Clearly,the nephrons

22、must accomplish a great deal of water recycling and conservation before they produce that smaller quantity of urine. Let us now take a close look at how a nephron works. 腎單位可以非常有效地選擇性地把廢物從血液循環,同時節約水,礦物離子、葡萄糖和其他必要的材料。成年人體內的180公升的血液足以填滿浴缸,每天通過這200萬個腎元到兩個腎，當然我們沒有每天排180L的尿液，甚至是包含在我們體內6或7升的液體,而是更為合理的每天大約

23、1.5升尿液.很明顯,腎元必須完成大量的水回收和保存之前生產小數量的尿液。現在讓我們來仔細看看腎元是如何工作的。 The nephron's specialized shape enables it to carry out three basic processes - filtration of small molecules from the blood, reabsorption of useful molecules from the urine back into the blood, and secretion of ions and some drugs from th

24、e blood into the urine.腎單位的特殊形狀使其執行三個基本過程過濾血液中的小分子,再吸收有用的分子從回血液、尿液和離子的分泌和一些藥物從血液進入尿液.Filtration過濾 The portion of the nephron that filters water and solutes from the blood is the enlarged, cuplike BowmanS capsule in the kidneys outer cortex. Each BowmanS capsule surrounds a tight bundle of capillarie

25、s called a glomerulus, much the way the fingers of your right hand can wrap around your left fist. This enclosing capsule of kidney tissue surrounding a tuft of blood capillaries forms the closest contact between the excretory and circulatory systems. A finely meshed filter lies between the blood an

26、d the cavity of the Bowmans capsule like a submicroscopic colander. As blood moves along through the capillaries, blood pressure forces the yellowish fluid portion of blood out of the capillaries, through the pores of this delicate filter, and into the BowmanS capsule, just as water pressure forces

27、coffee through a coffee filter. The fineness of the pores is ultimately responsible for the nephrons blood filtration activities:The BowmanS capsule filter allows wastes, water and other small molecules to seep through its minute openings, while the crucial components of bloodred cell, antibodies, a

28、nd other large proteinsremain behind in the capillaries. The passage of water, of sodium, potassium, and chloride ions, and of sugars, amino acids, nd urea out of the capillaries and into the lumen of the BowmanS capsule passive and does not require any special output of energy other than blood pres

29、sure. The fluid, or filtrate, in the capsule in still very much like blood plasma, except that it conrtains no large proteins or cell. 腎過濾水的部分和從血液中分離的溶質是擴大的，杯狀鮑曼氏囊在腎皮質的外面，每個鮑曼氏囊包裹的毛細血管成為腎小球，就像你右手的手指包繞你左手的拳頭。這個封閉的膠囊腎組織周圍的一簇毛細血管形成的排泄和循環系統之間親密接觸，處于血液和腎小囊腔之間的細網狀過濾器就像一個亞濾器。隨著血液移動通過毛細血管，血壓促使一部分血液通過這個精細過濾器

30、的微孔出毛細血管，并且進入鮑曼氏囊，就像水壓促使咖啡通過咖啡過濾器。毛孔的細度基本上是負責腎單位血液的過濾活動：鮑曼氏囊過濾器允許廢物，水和其他小分子通過它的小口處滲出，然而血液的關鍵成分紅細胞，抗體和其它的大分子蛋白質遺留在毛細血管的后面。水，鈉，鉀和氯離子，和糖類，氨基酸，尿素從毛細血管進入腎小囊腔的通道是被動的，除了血壓不需要其他能量的輸出。除了沒有包含大分子蛋白質和細胞，在毛細血管中的流體或者濾出液仍然非常像血漿。As if leaves the Bowmans capsule, the filtrate enters the part of the nephrons twisted

31、tubule nearest the capsule,known as proximal (near) tubule.There,reabsorption begins and returns to the circulation most of the water ,the sodium and chloride ions ,the sugars,and the amino acids that were just filtered out of the blood in the Bowmans capsule.當濾出物離開腎小囊，進入腎單位中最接近腎小囊部分的彎曲小管,被稱為近曲小管。在這

32、里，重吸收啟動，并將從鮑曼氏囊濾出的血液里的大部分水，鈉，氯 離子，糖和氨基酸送回循環系統。These materials move out through the walls of the proximal tubule and pass back into the blood via the surrounding capillaries.Instead of being driven passively by blood pressure,reabsorption of solutes in the proximal tubule depends on energy-costly act

33、ive transport across cell membranes.As the ions are being reabsorbed in this way, 80 to 85 percent of the water in the original filtrate follows them passively back into the capillaries via the process of osmosis.這些物質通過毛細血管壁搬運出去，并且經由周圍的毛細血管回到血液中去。近曲小管的溶質重吸收不是 通過血壓來被動運輸，而是依靠消耗能量的主動運輸來穿透細胞膜。在離子以這種方式被重

34、新吸收時，原濾出液中80%-85%的水通過滲透過程又隨之被動地返回毛細血管。Next,the filtrate passes down the descending arm of the nephrons U-shaped loop of Henles,which is bathed by an increasingly salty fluid. Water leaves the loop of Henles by osmosis and reenters the blood of the capillaries surrounding the tubule.The filtrate then

35、 rounds the bend in the loop of Henles and moves up the ascending arm and through the distal tubule ( far from the Bowmans capsule) toward the collecting duct.然后，濾出物通過腎單位里的U型 亨利袢降支，這個部位不斷受到 鹽分越來越多的液體的沖洗。水通過滲透作用離開亨利袢支，再輸入小管周圍的毛細血管中的血液。濾液繞行亨利袢支的彎曲部分，沿著升支向上移動，并通過遠端小管（遠離腎小囊 ），接近集合管。The walls of the dist

36、al tubule are not permeable to water ,but those of the collecting duct are;and even though the filtrate passing through the duct is already quite concentrated, the surrounding tissues are even saltier.Thus, more water diffuses out of the collecting duct by osmosis and enters the blood of the surroun

37、ding capillaries.水不能通過遠曲小管的 管壁，但收集管的管壁允許水通過；雖然通過收集管的濾過液濃度已經很高，但周圍組織含鹽量更大。因此，更多的水通過滲透作用在集合管中擴散開，并且進入周圍毛細血管中的血液。By the time the filtrate now called urine has reached the part of the collecting tubule in the innermost (and saltiest) region of the kidneys medulla,99 percent of the water originally filte

38、red from the blood in the Bowmans capsule has been reabsorbed and returned to the bodys circulation.等到過濾物（現在稱為尿）到達腎臟髓質最深處（含鹽）區域的收集小管部分時，99%從腎小囊的血液中最先濾過的水被重吸收回到身體循環。Tubular Secretion腎小管分泌While the filtration and reabsorption activities of the kidneys2million nephrons are removing salt and urea from the biood and forming urine, another process-tubular secretion-goes on simultaneously in both the proximal and di