医学英语(阅读一分册)翻译及答案

Chapter 1

Passage 1 Human Body

In this passage you will learn:

1. Classification of organ systems2. Structure and function of each organ system3. Associated medical terms

To understand the human body it is necessary to understand how its parts are put together and how they function. The study of the body's structure is called anatomy; the study of the body's function is known as physiology. Other studies of human body include biology, cytology, embryology, histology, endocrinology, hematology, immunology, psychology etc.

了解人体各部分的组成及其功能，对于认识人体是必需的。研究人体结构的科学叫解剖学；研究人体功能的科学叫生理学。其他研究人体的科学包括生物学、细胞学、胚胎学、组织学、内分泌学、血液学、遗传学、免疫学、心理学等等。

Anatomists find it useful to divide the human body into ten systems, that is, the skeletal system, the muscular system, the circulatory system, the respiratory system, the digestive system, the urinary system, the endocrine system, the nervous system, the reproductive system and the skin. The principal parts of each of these systems are described in this article.

解剖学家发现把整个人体分成骨骼、肌肉、循环、呼吸、消化、泌尿、内分泌、神经、生殖系统以及感觉器官的做法是很有帮助的。本文描绘并阐述了各系统的主要部分。

The skeletal system is made of bones, joints between bones, and cartilage. Its function is to provide support and protection for the soft tissues and the organs of the body and to provide points of attachment for the muscles that move the body. There are 206 bones in the human skeleton. They have various shapes - long, short, cube - shaped, flat, and irregular. Many of the long bones have an interior space that is filled with bone marrow, where blood cells are made. 骨骼系统由骨、关节以及软骨组成。它对软组织及人体器官起到支持和保护作用，并牵动骨胳肌，引起各种运动。人体有206根骨头。骨形态不一，有长的、短、立方的、扁的及不规则的。许多长骨里有一个内层间隙，里面充填着骨髓，这即是血细胞的制造场所。

A joint is where bones are joined together. The connection can be so close that no movement is possible, as is the case in the skull. Other kinds of joints permit movement: either back and forth in one plane - as with the hinge joint of the elbow - or movement around a single axis - as with the pivot joint that permits the head to rotate. A wide range of movement is possible when the ball - shaped end of one bone fits into a socket at the end of another bone, as they do in the shoulder and hip joints.

关节把骨与骨连接起来。颅骨不能运动，是由于骨与骨之间的连接太紧密。但其它的关节可允许活动，如一个平面上的前后屈伸运动，如肘关节；或是绕轴心旋转运动，如枢轴点允许头部转动。如果一根骨的球形末端插入另一根骨的臼槽里，大辐度的运动（如肩关节、髋关节）即成为可能。

Cartilage is a more flexible material than bone. It serves as a protective, cushioning layer where bones come together. It also connects the ribs to the breastbone and provides a structural base for the nose and the external ear. An infant's skeleton is made of cartilage that is gradually replaced by bone as the infant grows into an adult.

软骨是一种比一般骨更具韧性的物质。它是骨连结的保护、缓冲层。它把肋骨与胸骨连结起来，也是鼻腔与内耳的结构基础。一个婴儿的骨骼就是由软骨组成，然后不断生长、骨化，使婴儿长大成人。

The muscular system allows the body to move, and its contractions produce heat, which helps maintain a constant body temperature. Striated muscles can be consciously controlled. The ends of these muscles are attached to different bones by connective tissue bands so that when the muscle contracts, one bone moves in relation to the other. This makes it possible to move the whole body, as when walking, or to move just one part of the body, as when bending a finger. Contractions of the heart and smooth muscles are not under conscious control. Smooth muscles are found in the walls of organs such as the stomach and the intestines and serve to move the contents of these organs through the body.肌肉系统使躯体运动，肌肉收缩产生的热有助于维持一个恒定的体温。人体能够有意识地控制条纹肌。结缔组织使肌肉末端附着于不同的骨面上，所以当肌肉收缩时，两骨彼此靠近而产生运动。这也就使整个人体可以运动起来，如走路，运动躯体某个部位，如弯曲手指。心脏收缩和平滑肌收缩就不是被意识所控制的。器官壁内层的平滑肌，如胃肠壁的平滑肌把胃肠中的物质运送到全身。

The circulatory system. All parts of the body must have nourishment and oxygen in order to function and grow, and their waste products must be removed before they accumulate and poison the body. The circulatory system distributes needed materials and removes unneeded ones. It is made up of the heart, blood vessels, and blood, which together make up the cardiovascular system. The blood is also part of the body's defense system. It has antibodies and white blood cells that protect the body against foreign invaders. 循环系统：机体的所有部分需要营养物质和氧气来使之发挥功能和生长，也需要在这些器官所产生的废物积聚而危害生命之前将其排除。循环系统运送有用物质，排泄废物。心血管系统是循环系统的组成之一；心血管系统包括心脏、血管及血液。血液也是机体防御系统的一个部分，血液中有抗体及白细胞来防止机体受到外来的侵袭。

The heart is a muscle that is divided into two nearly identical halves: one half receives blood from the lungs and sends it to the rest of the body, the other half sends blood that has traveled through the body back to the lungs. When the heart muscle contracts, the blood is forced out into arteries and enters small capillaries. Blood returns to the heart through veins. 心脏是一块被分为几乎对等两半的肌肉。一半吸收来自肺部的血液，并将血液运送到机体的其余部位，另一半使流经全身的血液回流人肺。心脏收缩时，动脉把全身血液输送到毛细血管。静脉输送血液返回心脏。

Also functioning in circulation is the lymphatic system. Some of the fluid that surrounds cells does not reenter the blood vessels directly. This fluid, called lymph, returns to the heart by way of another system of channels - the lymph vessels. Lymph nodes along these vessels filter the fluid before it reenters the blood. The spleen is a large lymphatic organ that filters the blood. 淋巴系统也是循环系统的一个组成部分。一些细胞周围的体液不是直接回流入血管通道，这种体液叫淋巴液，它是流经另一个管道系统——淋巴管而回流人心脏。沿淋巴管的淋巴结将淋巴液过滤，过滤后再回流人血液。脾是一个过滤血液的大淋巴器官。

The respiratory system takes in oxygen from the air and expels carbon dioxide and water vapor. Air enters the nose and mouth and travels through the larynx, and trachea. The trachea divides to enter each of the two lungs and then divides more than 20 times to form a very large number of small air spaces. Oxygen from the air enters the blood through capillaries in the walls of these air spaces, and the blood release carbon dioxide into the air spaces to be exhaled. 呼吸系统从空气中摄取氧气，并将二氧化碳、水蒸气排出体外。空气经鼻腔、口腔人喉管、气管。气管分成左右支气管，各连结左右肺，左右支气管再分枝20多次，在终端形成大量微小的肺泡。从空气摄取的氧气流经这些肺泡壁内的毛细血管流入血液，血液再经肺泡把释放出的

二氧化碳排出体外。

The digestive system consists of a tube extending from the mouth to the anus. In it, food and fluids are taken in, moved through the body, and broken down into small molecules that are absorbed into the circulatory system. This breakdown, known as digestion, is both a mechanical and a chemical process.消化系统是一个从口腔直到肛门的管道。食物和液体在消化道里被吸收，在肠道里移动时，被分解成小分子物质后再进入循环系统。这种分解，即消化，是一个机械过程，也是一个化学过程。

Food enters through the mouth, where chewing and saliva start to break it up and make it easier to swallow. Next, the food travels down through the esophagus to the stomach. Contractions of the stomach's muscular wall continue to break down the food mechanically, and chemical digestion continues when acid and enzymes are secreted into the stomach cavity. 食物进入口腔里，咀嚼和唾液开始将食物粉碎，使之便于吞咽。接着，食物经食管人胃。胃肌壁的收缩继续机械化地分解食物，而当酸和酶分泌入胃腔时，化学性消化开始。

The liquified food gradually passes into the small intestine. In the first part of the small intestine, called the duodenum, enzymes from the pancreas are added. These enzymes complete the chemical breakdown of the food. The digestion of fat is aided by bile, which is made in the liver and stored in the gall bladder. The small intestine of an adult is about 21 feet (6.4 meters) long. Most of its length is devoted to absorbing the nutrients released during these digestive activities. 液体化食物逐渐进入小肠。小肠的起始部分叫十二指肠，胰腺分泌的酶辅助食物消化。这些酶完成食物的化学分解。肝脏分泌的胆汁贮存在胆囊内，胆汁有助于脂肪消化。一个成年人的小肠有21英尺（6.4米）长。小肠的大部分肠段用来吸收消化过程中释放的营养物质。

The liquid remainder of the food enters the large intestine, or colon, which is about 12 feet (3.7 meters) long. It is more than twice as wide as the small intestine. In the large intestine most of the fluid is absorbed, and the relatively dry residues are expelled. 液状的剩余食物进入大肠，或结肠，它大约有12英尺（3.7米）长。大肠是小肠的两倍多宽。大部分液体在大肠内被吸收，相对干化的残余物被排出体外。

The urinary system maintains normal levels of water and of certain small molecules such as sodium and potassium in the body. It does this by passing blood through the kidneys, two efficient filtering organs that get rid of any excess of various molecules and conserve those molecules that are in short supply. 泌尿系统维持水分及体内某些小分子物质，如钠、钾的正常水平。身体是通过让’肾过滤血液来做到这一点的。肾是两个有效的过滤器官，它滤出各种多余的小分子物质，保留那些供应不足的小分子物质。

The fluid that leaves the kidneys, known as urine, travels through a tube called the ureter to the bladder. The bladder holds the urine until it is voided from the body through another tube, the urethra. 从肾流出的液体，即尿，通过输尿管人膀胱。膀胱起贮存尿液的作用，直到尿经膀胱另一端的管道排出。

The endocrine system. The two systems that control body activities are the endocrine system and the nervous system. The former exerts its control by means of chemical messengers called hormones. Hormones are produced by a variety of endocrine glands, which release the hormones directly into the blood stream. 内分泌系统。内分泌和神经是调控机体活动的两个系统，前者依靠其化学信使——激素发挥作用。激素是由各种内分泌腺体制造，并直接被释放入血流

A major gland is the pituitary, which is located under the brain in the middle of the head. It

produces at least eight hormones, which affect growth, kidney function, and development of the sex organs. Because some of the pituitary's hormones stimulate other glands to produce their own hormones, the pituitary called the master gland. 脑垂体是一个主要腺体，它位于头中部脑下方。它至少分泌八种激素，这些激素对人体生长、肝功能及性器官发育有影响。因为脑垂体分泌的一些激素促进其他腺体分泌激素，所以脑垂体是主要腺体。

Another gland, the thyroid, is located between the collar bones. Its hormone controls the rate of the body's metabolism. The sex organs (ovaries end testes) make the sex cells and also make hormones that control certain characteristics of males and females. Located on top of each kidney is the adrenal gland, which produces cortisone and adrenaline. The pancreas produces not only digestive enzymes but also 3 insulin and glucagon, which control the body's use of sugar and starches. 另一个腺体，甲状腺，位于锁骨之间。甲状腺激素调控着机体新陈代谢的速度。性器官（卵巢、睾丸）分泌性细胞和性激素，这些激素控制着男性和女性的某些特征。每边肾上方是肾上腺，它分泌可的松和肾上腺激素。胰腺不仅分泌消化酶，而且分泌胰岛素和高血糖素，这两种激素控制机体的糖分及淀粉的消耗。

The nervous system. The brain, the spinal cord and the nerve - also controls body activities. The lower parts of the brain control basic functions such as breathing and heart rate as well as body temperature, hunger, and thirst. Above these regions are the centers for sight, sound, touch, smell, and taste, and the regions that direct voluntary muscular activities of the arms and legs. Performed here are the higher functions of integrating and processing information. 神经系统——脑、脊髓及神经，也调控机体活动。脑的偏下部位控制着诸如呼吸、心跳、体温、饥渴的基本活动。而脑的偏上部位则是视觉、听觉、触觉、嗅觉及味觉中心，也是指挥臂、腿随意肌肉运动的区域。神经系统更高级的功能是整合、处理信息。

The brain receives and sends information by means of nerves, many of which lie partly in the spinal cord. The spinal cord is protected by the spinal column. Nerves enter and leave the spinal cord at each level of the body, traveling to and from the arms, legs, and trunk. These nerves bring information from the various sense organs. The information is processed by the brain, and then messages are carried back to muscles and glands through out the body. 脑通过神经收集并传送信息，许多神经部分地分布在脊髓里。脊髓由脊柱保护。在机体每一级，神经传人、传出脊髓，往返于臂、腿、躯体。这些神经输送来自各种感觉器官的信息。信息经脑处理后输送回全身及腺体

The reproductive system is constructed differently for males and females. The male reproductive system is responsible for producing, transporting and maintaining viable sperm (the male sex cell). It also produces the male sex hormone, testosterone, which regulates the development of a beard, pubic hair, a deep voice and other bodily characteristics of the adult male. 男、女性的生殖系统不同。男性生殖系统产生、输送、维持能存活的精子（男性性细胞）。它也分泌男性激素、睾酮，以此调节胡须、阴毛、深沉嗓音极其他成年男子身体发育的特征。

The female productive system is responsible for producing and transporting ova (the female sex cells), eliminating ova from the body when they are not fertilized by sperm, nourishing and providing a place for growth of an embryo when an ovum is fertilized by sperm, and nourishing a newborn child. The female reproductive system also produces the female sex hormones, estrogen and progesterone, which regulate the development of breasts and other bodily characteristics of the mature female. 女性生殖系统产生、输送卵子（女性性细胞），将未受精的卵子排出体外，而当精、卵结合时，女性生殖系统培养、提供胚胎生长场所，并孕育新生

儿。女性生殖系统也分泌女性性激素——雌激素和孕酮，以此调节乳房及其他成熟女性身体发育的特征。

The skin is a complete layer that protects the inner structures of the body, and it is the largest of the body's organs. It keeps out foreign substances and prevents excessive water evaporation. The nerves in the skin provide tactile information. The skin also helps keep the body's temperature close to 37 °C, heat is conserved by reducing blood flow through the skin or is expended by increasing blood flow and by evaporation of sweat from the skin. Hair and nails are accessory structures of the skin. 皮肤是保护肌体内层结构的完整层，也是机体的最大器官。皮肤防御外来侵袭，防止过多水分蒸发。皮肤上的神经提供触觉信息。皮肤也能将体温维持到98.6华氏度（约37摄氏度）。通过皮肤的血流量降低时，热量就被储存起来，通过皮肤的血流增加及汗液蒸发时，热量就散发。头发及指甲是皮肤的附属结构。

Cells and Tissues细胞与组织

In this passage, you will learn:1.Human body systems as a whole 2.Vital parts of a cell 3.Four kinds of tissues

Cells are organized into tissues, and tissues are arranged into organs, which in turn are grouped into systems. Each body system serves its specific functions. Bear in mind however that the body functions as a whole----no system is independent of the others. They work together to maintain the body’s state of internal stability, termed homeostasis. Now let’s begin our discussion with cells, the smallest unit of living matter that can exist by itself. 细胞构成组织，组织构成器官，器官又进一步构成系统。人体的每个系统都有其特定功能，但是，请记住这里:机体是作为一个整体来发挥作用的，没有哪个系统能够独立于其他系统而存在，是整体系统共同作用保持了机体内部的稳定状态，即体内平衡。现在，我们先讨论细胞─能独立存在活性物质的最小单位。

The body can be studied from its simplest to its most complex level, beginning with the cell. All body functions result from the activities of billions of the specialized cells. Some plants and animals consist of only a single cell. Others are composed of many billions of cells. 从细胞开始，我们能够从最简单到最复杂的水平来研究机体。所有人体的功能都来自亿万个特定细胞活动，有的动植物仅由一个细胞构成，其他生物则由亿万个细胞构成。

Cells exist in a variety of shapes and sizes. They may, for example, be cube-shaped or flat. Scientists who study cells have determined that a single cell may be as large as a tennis ball or so small that thousands would fit on the point of a needle. The yolk of a hen’s egg is actually a very large cell. By contrast, bacteria----each one of which is a tiny cell----are among the smallest cells. Regardless of its shape or size, every cell contains the “machinery” needed to maintain life. While normally cells function with great efficiency, they are subject to various disorders that result in disease. 细胞有很多种形状和大小。列如：有可能是立方形或扁形的。科学家的研究发现单独一个细胞可以像网球一样的大小，或小到几千个细胞才能刚好填满针头。鸡的蛋黄是一个非常大的单细胞。微小的细菌呢算是最小的细胞。不管是细胞大小或形状的不同，每个细胞都有“需要存活的机制”。对每个正常的细胞，有效力的细胞，都存在许多问题，能导致疾病。

The size of cells is usually measured in microns. A micron is a millionth of a meter, and about 25,000 microns equal one inch. The smallest bacteria are about 0.2 micron in diameter. The average cell in the human body----about ten microns in diameter----is a speck barely visible without the aid of a microscope. 细胞的大小是以“微米”为长度单位。微米是一米的一百万分之一，25000微米等于一寸。最小的细菌的圆径是0.2微米。人体正常细胞的评价圆径约十

微米，肉眼勉强可以看得到，不需要显微镜的帮助。

The study of cells is the branch of biology called cytology. The science that deals with cells on the smallest structural and functional level is called molecular biology. 研究关于“细胞”是生物学的分支，成为细胞生物学。在最微小水平针对细胞的结构及功能的研究成为分子生物学。 All cells consist of protoplasm, the “living jelly.” The protoplasm of a typical cell forms three vital parts----the cell membrane, the cytoplasm, and the nucleus. The membrane encloses the other cell structures. Much of the chemical work of the cell is done in the cytoplasm, which surrounds the nucleus. The nucleus, enclosed by its own membrane, is the control center of the cell. (see Figure 1-1) 所有细胞都是以“原生质”，又称“生命胶质”所形成的。典型细胞的原生质形成了三个重要部分，细胞膜、细胞质和细胞核。细胞膜圈住了细胞的其他结构。大部分的化学反应都在细胞核周围，细胞质完成的。被自己的膜包围的细胞核是细胞的控制中心。 the cells Membrane细胞膜

Cells can survive only in a liquid medium that brings in food and carries away waste. For one-celled organisms this fluid is an external body of water----the ocean, a lake, or a stream. For many-celled plants and animals, however, the medium is part of the organism----in plants, the sap; in animals, the blood. 细胞只能存活在能供养分又能排除废物的液体媒介中。对单细胞生物来说，这就是细胞外的液体，如：大海里、河里或水流中。在对多细胞生物而言，这种媒介就是生物体的一部分，植物以汁液的形式，动物以血液的形式。

The cell membrane is semipermeable, or differentially permeable----some substances can pass through it, but others cannot. This characteristic enables the cell to admit useful substances and to reject harmful substances from the surrounding fluid as well as to force out, or excrete waste products into the fluid. 细胞膜是半渗透性或区别性的渗透膜，即某些物质能渗透。这个特殊性使细胞对细胞周围只吸收了需要的物质而排除掉有害的物质，包括细胞内的废物通过液体化后排出细胞外。

The cell membrane is an extremely thin but tough band of protein and phospholipid molecules. Phospholipids are chemicals similar to stored fat. On the evidence of electron micrographs, biologistsbelieve that it has pores through which certain small molecules pass intact. Substances probably pass through the cell membrane in several ways. Small chambers located on the cell membrane called caveolae gather chemical signals and channel them into the cells. The caveolae may also help distribute proteins throughout the cell. Large molecules enter the cell by a process called diffusion, in which they may be dissolved by substances in the cell membrane. They can then through the membrane without difficulty. Some cells take in large molecules by means of pinocytosis. In this process, the cell membrane forms a pocket around large molecules floating against it. The molecule-and-fluid-filled pocket then breadsloose from the membrane to become a bubblelike vacuole, and the vacuole then drifts into the cytoplasm. Finally, the vacuole wall breaks up and the molecules are released into the cytoplasm. 细胞膜是一种非常薄但确以很坚固的蛋白磷脂膜形成。磷脂是一种类似于储存的脂肪的蛋白物质。通过电子显微镜，生物学家相信细胞膜有孔，使较小的物质完全可以通过。物质可通过多种方式从细胞膜进入。细胞膜上的结构，称“小穴”，可接受化学信号再传到细胞内。小穴还可能参于细胞蛋白的分配。大的分子可通过“渗滤”进入细胞内，或被细胞膜内体分解，使它们更容易的进入细胞内。有些细胞可通过“胞饮”方式吞饮较大的物质。这个过程是通过细胞膜在大物质形成了“带”把它包围着，将它以泡状的“液泡”引入细胞质，最后包围解散，大物质成功的进入细胞内。 The cytoplasm细胞质

The cytoplasm is mainly water. Its water content varies from a minimum of about 65 percent to a

maximum of about 95 percent. The solids in the cytoplasm include granular proteins, carbohydrates, droplets of fat, and pigments. The cytoplasm is thus a colloidal system. 细胞质主要成分是“水”。水分含量有百分之65到最高，百分之95。细胞质内的固体包括蛋白颗粒、碳水化合物、脂肪小滴和色素。细胞质是胶体性的。

The cytoplasm may be either watery or syrupy, depending on the concentration of solids dispersed in the fluid. When the solid content decreases, these structures seem to vanish. Changes in concentration also produce an apparent steaming of the cytoplasm from place to place within the cell. This occurs, for example, when food molecules enter the cell. 细胞质可能是水性或糖浆性，根据散在细胞质内固体的浓度。当固体成分浓度增多，膜状和纤维状结果在细胞质显出。而当固体成分浓度减少时，膜状和纤维状的结构就消失。浓度的变化还可以表现细胞质内局部流动的变化。食物分子进入时可见。

Most of the cell’s constant work of keeping alive is performed in the cytoplasm. Here food molecules are changed into the material needed for energy and materials for growth or stiffening of the cell membrane are manufactures needed by the rest of the organism. For example, plant cells containing chlorophyll manufacture glucose----a plant food----from carbon dioxide and water. 大部分为了细胞存活的工作都在此处（细胞质）完成的。在此处，食物物质将被转化成提供细胞能量的材料和提供细胞生长的材料，或细胞膜的增强剂所生产。多细胞植物的细胞质还是生产了对其他生物提供食物的物质。列如：植物叶绿素所产生的葡萄糖，植物的食物，从水和二氧化碳合成。

One of the cytoplasm’s key energy transactions occurs in the sausage-shaped mitochondria. Each mitochondrion has an inner and an outer membrane. Like the cell membrane, the membranes of the mitochondrion are semipermeable. Food molecules that pass into the cytoplasm are taken into the mitochondria and oxidized, or burned, for energy. 细胞质能量转换的要点发生在锥状形的线粒体。每个线粒体都有内膜和外膜。像细胞膜一样，线粒体的膜也是半渗透性。进入线粒体的食物分子被氧化提供出能量。

The endoplasmic reticulum, a network of membranous tubes, runs through the cytoplasm. In the opinion of some biologists, this network is a continuous structure that begins at the cell membrane, twists through the cytoplasm, and ends at the membrane surrounding the nucleus. Located along the endoplasmic reticulum as well as elsewhere in the cytoplasm are numerous ribosomes. These tiny granules consist in part of ribonucleic acid (RNA). Proteins are manufactured at the ribosomes. The Golgi complex, or Golgi apparatus, is a membranous structure composed of stacks of thin sacs. Newly made proteins move from the endoplasmic reticulum to the Golgi complex, where they are stored for later secretion. 胞浆网，在细胞质中由膜所形成管状的网。有些生物学家认为这是一种连续性结构，始点为细胞膜，在细胞膜内扭绞，终点为细胞核的膜。分布于胞浆网包括细胞质中某处的是核糖体。这些小颗粒是核糖核酸所形成的。蛋白质是在核糖体合成的。高尔基体是膜状囊包堆成层形成的。新合成的蛋白从胞浆网移动到高尔基体储存，为了后来分泌所用。

Vacuoles drift through the cytoplasm and usually carry food molecules in solution. Lysosomes are structures somewhat similar in appearance to vacuoles but denser. They appear to have a digestive function. Each lysosome is filled with digestive enzymes and encased in a membrane. Lysosomes are believed to break down food substances brought into the cell by pinocytosis. It has been suggested that the Golgi complex plays a part in the formation of lysosomes. 在细胞质内游动的液泡一般是带着食物分子的溶液。溶酶体是一种有点像液泡的结构，但较稠。它是用来消化的。每个溶酶体的膜内都是添装着消化酶。我们认为它是消化

通过“胞饮”方式的大物质。也认为高尔基体对溶酶体的形成有关系。

The Nucleus细胞核

Near the center of the cell is a roundish or oval-shaped nucleus. The nucleus controls the growth and division of the cell. It also contains the structures that transmit hereditary traits. 细胞的中央，圆形或椭圆形的就是细胞核。细胞核控制细胞的生长和分化。也装着遗传信息。

Enclosed by a two-layered membrane, the nucleus contains a liquid called nucleoplasm as well as strands of deoxyribonucleic acid (DNA) covered with a coating of protein. A strand of DNA consists of a long series of genes, which are the units of heredity of plants and animals. Genes determine the characteristics of a cell. They do this by regulating the production of RNA, which in turn controls the manufacture of specific proteins. 被两层膜圈住着，细胞核内含有称为“核质（浆）”的液体和脱氧核糖核酸的蛋白层。脱氧核糖核酸缕是很长的基因系列所组成的，它是植物和动物的遗传信息。基因决定了细胞的特征。它是通过调节核糖核酸，使核糖核酸产出特异的蛋白。

Human cells, for example, make only proteins unique to human beings DNA strands are usually too thinly strung out to be seen with an optical microscope. Because the strands are readily stained with dyes, they are called chromatin. When a cell begins to divide, however, the chromatin thickens into the form of chromosomes. 列如：人的细胞，只产出人独特拥有的蛋白。脱氧核糖核酸缕一般都很细小过光学显微镜能观察到。因为脱氧核糖核酸缕能够染色后部分被染，称“染色质”。细胞分化过程中，染色体拾起变厚形成了“染色体”。

A nucleus not undergoing division has at least one nucleolus. The nucleolus contains a concentration of RNA. Biologists think RNA is made initially in the nucleus according to a DNA “blueprint” and stored there until needed for protein manufacture. 细胞核分化核仁不会减少，最少要有一个核仁。核仁含有丰富的核糖核酸。生物学家认为核糖核酸原本在核仁里，根据脱氧核糖核酸的蓝图造出而藏在此处直到有蛋白合成的需要。

the nucleus of animal cells is a spherical structure called the centrosome, from which asters radiate. The centrosome contains a pair of rodded structure called centrioles, which usually lie at right angles to each other. Although centrioles and centrosomes have not been seen in plant cells, biologists believe that plant cells contain similar structures. 靠近动物的细胞核的圆形结构叫“中心体”，可见呈放射状散发的星体。中心体内含有一对棍状结构，称为“中心粒”，一般都形成正确固定的角度。无法在植物细胞发现中心体和中心粒，但生物学家认为植物应该有存在类似功能的其他结构。 Tissues组织

Cells are organized into tissues that perform specific functions. The four basic tissue types are as follows: 多细胞组成了组织，为了特异的功能。四种基本的组织：

Epithelial tissues----covers and protects body structures and lines organs, vessels, and cavities. 上皮组织 : 覆盖及保护着身体结构和分清器官、导管和空腔。

Connective tissues----supports and binds body structures. It contains fibers and other nonliving material between the cells; included are fat tissues, cartilage, bone and blood. 结缔组织: 支柱和联结着身体结构。包括细胞之间的纤维和其它无生物结构。包括脂肪组织、软骨、骨头和血液。

Muscle tissues----contracts to produce movement. The three types are：skeletal or voluntary muscle that moves the skeleton; the cardiac muscle of the heart; and the smooth muscle that forms the walls of the abdominal organs. Cardiac and smooth muscle can function without conscious control and are thus described as involuntary muscle. 肌肉组织: 通过收拾来产生动

作。分为三种：骨骼肌，作用于一般骨骼移动。心机，心脏的肌肉。平滑肌，形成胃肠道壁的肌肉。心机和平滑肌是非意识性，不随意性肌肉。

Nervous tissue——makes up the brain, spinal cord, and nerves. It coordinates and controls body responses by transmitting electrical impulses. 神经组织: 组成大脑、脊椎和神经。它是通过动作电位来超空身体。

The simplest tissues are membranes. Mucous membranes secrete thick fluid called mucus that protects underlying tissues. Serous membranes secrete a thin, watery fluid. They line body cavities and cover organs. 最简单的组织就是膜。粘液膜分泌出粘稠的胶液，起得组织保护作用。粘液组织分泌出较稀的粘液，起得身体导管的分界和覆盖着各个器官。

Human diseases

In this passage you will learn: 1.disease and pathology 2.the classification of diseases 3.germs’ invasion of the human body 4.the body’s defense against invasion 5.the body’s immunity to diseases

The brief survey of the human body in Chapter One has given us a glimpse into two different studies that are considered the fundamentals of medical sciences, namely anatomy and physiology. However, the picture is not complete without considering pathology, the science that deals with the structural and functional changes produced by the disease. In fact, the modern approach to the study of disorder emphasizes the close relationship of the pathological and physiological aspects and the need to understand the fundamentals of each in treating any body diseases. 第一章中，通过对人体的概论，即解剖学与生理学，我们对两种被认为是医学基础的不同学科有了一个大致的印象。然而如果我们不考虑病理学，这门涉及由疾病带来的结构和功能变化的学科，上述的人体概论就不是完整的。实际上，现代对疾病的研究方法强调了病理学与生理学方面的密切关系，强调了我们在治疗任何人体疾病方面需要了解病理学与生理学基础的重要性。

Then what is a disease? It may be defined as a condition that impairs the proper function of the body or of one of its parts. Every living thing, both plants and animals, can succumb to disease. People, for example, are often infected by tiny bacteria, but bacteria, in turn, can be infected by even more minute viruses. 那么什么是疾病呢？它可能被定义为正常的功能或是部分功能遭受损害时的一种状态。每一种生物、植物和动物，都会受制于疾病。例如，人类常常被微小的细菌所感染，但是，反过来说，细菌又能够被甚至更加微小的病毒所感染。

Hundreds of different diseases exist. Each has its own particular set of symptoms and signs, clues that enable a physician to diagnose the problem. A symptom is something a patient can detect, such as fever, bleeding, or pain. A sign is something a doctor can detect, such as a swollen blood vessel or an enlarged internal body organ. 许多种疾病存在于世。每一种都有其特定的症状、征兆和线索，医生能以此诊断疾病之所在。症状是病人自己就能觉察到的，比如，高烧、流血，或是疼痛。而征兆则是医生能够观察到的，比如，血管扩张或是体内器官肿大。

Diseases can be classified differently. For instance, an epidemic disease is one that strikes many persons in a community. When it strikes the same region year after year it is an endemic disease. An acute disease has a quick onset and runs a short course. An acute heart attack, for example, often hits without warning and can be quickly fatal. A chronic disease has a slow onset and runs a sometimes years-long course. The gradual onset and long course of rheumatic fever makes it a chronic ailment. Between the acute and chronic, another type is called subacute. 疾

病可以划分为不同的种类，例如，流行病是一种在某一社区内侵袭许多人的疾病。当它年复一年地袭击同一社区，就成了一种地方病。急性病发作快，但病程短，举个例子来说，急性心脏病发作常常没有前兆，而且会很快致命。慢性病发作则慢，但病程有时会长达几年之久。风湿热正是由于发病慢、病程长而成为一种慢性失调病（慢性病）。而介于急性与慢性之间的另一种类型，就被称为亚急性。

Diseases can also be classified by their causative agents. For instance, an infectious, or communicable, disease is the one that can be passed between persons such as by means of airborne droplets from a cough or sneeze. Tiny organisms such as bacteria and fungi can produce infectious diseases. So can viruses. So can tiny worms. Whatever the causative agent might be, it survives in the person it infects and is passed on to another. Sometimes, a disease-producing organism gets into a person who shows no symptoms of the disease. The asymptomatic carrier can then pass the disease on to someone else without even knowing he has it. 疾病也可以依其病原体来划分，例如，传染病也叫作可传播的疾病，就是一种通过咳嗽和打喷嚏造成的空气小粒来传播的疾病。极小的有机体，如，细菌和真菌可导致传染病。病毒和小虫子也不例外。不论病原体会是什么样，只要它存活于人体内就能够传染给别人。有时，一个致病的有机体侵人人体后，该人却没有显示带病的症状。于是无症状的病原携带者甚至在自己也不知情的情况下就把疾病传染给了他人。

Noninfectious diseases are caused by malfunctions of the body. These include organ or tissue degeneration, erratic cell growth, and faulty blood formation and flow. Also included are disturbances of the stomach and intestine, the endocrine system, and the urinary and reproductive systems. Some diseases can be caused by diet deficiencies, lapses in the body's defense system, or a poorly operating nervous system. 非传染性疾病是由身体功能失调引起的。这包括血管或组织退化、异常细胞生成，以及异常的血液生成和血液循环。当然其中也包括胃、肠、内分泌系统和泌尿生殖系统的紊乱。一些疾病也可能是由饮食不足、身体抵抗力下降、或是神经系统工作不造成的。

Disability and illnesses can also be provoked by psychological and social factors. These ailments include drug addiction, obesity, malnutrition, and pollution-caused health problems. 心理因素和社会因素也会引发残废和疾病，这些病包括吸毒成性、肥胖、营养不良和由污染造成的健康问题。

Furthermore, a thousand or more inheritable birth defects result from alternations in gene patterns. Since tiny genes are responsible for producing the many chemicals needed by the body, missing or improperly operating genes can seriously impair health. Genetic disorders that affect body chemistry are called inborn errors of metabolism. Some forms of mental retardation are hereditary. 而且，有上千种乃至为数更多的遗传性出生缺陷是由于基因变化而造成的。由于小小的基因负责着生产许多身体所需的化学物质，它的遗失或是工作状态不良都会严重损害健康。因基因失调而被影响了的身体化学反应被称之为先天性代谢失调。一些眢力发育迟缓就是因遗传而造成的。

How Germs Invade the Body病菌是怎样侵袭身体

Humans live in a world where many other living things compete for food and places to breed. The pathogenic organisms, or pathogens, often broadly called germs, that cause many diseases are able to invade the human body and use its cells and fluids for their own needs. Ordinarily, the body's defense system can ward off these invaders.人类生活在有一个有许多其它生物竞争食物和求得繁衍的世界里。很多致病的有机体或病原体，通常被我们广义地称为病菌的东西能侵入人体并利用其细胞和组织液来供它们自身的需求。一般来讲，身体防御系统能够阻止这

gradual wasting away of skeletal muscles. 除了上述的疾患外，可能影响骨骼肌的疾病尚有许多，可分为肌萎缩和肌病两个大类。肌萎缩侵犯、损害神经系统，包括那些刺激肌肉的神经，该病直接导致的结果是肌肉持续萎缩和虚弱。肌萎缩性（脊髓）侧索硬化(亦被称为ALS)就是一个典型的例子。肌虚弱也常见于肌病，在这类疾病中，肌肉本身没有正常发挥作用导致了肌肉的软弱。某些肌肉病变，如各类肌营养不良，其特点就是骨骼肌逐渐地消退萎缩下去。

Muscle Atrophy. At the outset we should distinguish between muscle atrophy and dystrophy, both of which may be associated with regressive changes in muscles. Muscle atrophy, is an acquired lesion secondary to some well-defined predisposing cause; muscular dystrophy, on the other hand, refers to a variety of genetically determined primary disorders of muscles to be discussed later.

肌萎缩首先我们应该区分肌萎缩和肌营养不良。两者都与肌肉的消退性病变有关，但肌萎缩是继发于某些明确素因性原因的获得性病变，而肌营养不良则指多种原发的遗传性肌肉病变，下面将对此另有讨论

Atrophic shrinkage, death and disappearance of muscle cells occur under a variety of circumstances, some generalized and some local. Among the systemic disorders are chronic malnutrition, panhypopituitarism, SLE, dermatomyositis and advanced age, which presumably lead to muscle atrophy on the basis of diffuse ischemia. In these disorders, entire muscles are affected uniformly.

全身或局部的肌细胞萎缩，死亡甚至消失在多种情况下都可出现。全身性疾患包括慢性营养不良，全垂体机能减退，全身性红斑狼疮，皮肤肌炎和衰老（衰老被认为是导致肌萎缩的原因之一，其机理是扩散性缺血）。在这些情况下，全身肌肉将不同程度的受累。

Localized muscle atrophy results from interference with the innervation and may be caused by traumatic denervation or neuromuscular disorders, such as polio, the peripheral neuritis and a variety of fortunately rare degenerative neuropathies. Obviously, the distribution of the muscle atrophy depends upon the pattern of involvement of the nerves. Whole muscles, bundles of cells or only a single neuromuscular unit may be affected.局部性肌萎缩是由神经支配障碍所致，也可能因创伤而失去神经支配或神经肌肉疾病引起（如脊髓灰质炎，外周神经炎和各种幸好较少见的退行性神经病变）o很明显，肌萎缩的程度取决于神经受累的情况，整块肌肉、某个肌束、单个神经肌肉单位都可能受累。

Muscle dystrophy. This term refers to a group of genetically determined myopathies characterized by progressive atrophy or degeneration of increasing numbers of individual muscle cells. The histologic changes in the various types of muscular dystrophies are basically the same. However, the distribution of the affected muscles is quite distinctive. This, along with the mode of inheritance, forms the basic of the classification discussed below. Muscular dystrophies must be distinguished from congenital myopathies, which are characterized by fairly specific distinctive morphologic changes. The pathogenesis of muscular dystrophies remains unknown. There is no lack of theories, but supporting evidence is scanty. Recent evidence suggests the existence of a generalized membrane defect, which also involves cells other than myofibers. 肌营养不良本术语指以逐渐加重的肌萎缩或单个肌细胞增速退变为特点的一组遗传性肌肉病变。各种类型的肌营养不良的组织学改变基本相同，但受累肌肉的分布却完全不同。这些不同的分布和遗传模式是我们将要讨论的该病分类之基础。肌营养不良必须与先天性肌病相区别，后者呈鲜明的形态学改变。肌营养不良的发病机理尚不清楚。尽管有不少学说，但证据不足，最新的证据提示全身性的膜缺陷存在，但这种缺陷不仅波及肌纤维，也涉及了细胞。

肌营养不良传统上依据其初始受累的肌肉情况再分为几个亚型，这样做与基因传递

的类型相当吻合。但必须牢记，尽管存在类别差异，但所有类型的组织学改变都是相同的。以下是三种主要形式：

杜兴氏（假性肌肥大）肌营养不良：X染色体连锁隐性；四肢带肌营养不良：常染色体隐性；面肩胛臂肌营养不良：常染色体显性。

杜兴氏肌营养不良是最常见，也是肌营养不良最重要的类型。因其具有x染色体相连的隐性遗传特性，受累者几乎均为男性。出生时症状即可显现。首先受累的是骨盆带肌，然后扩展到肩带肌。其特征性症状是腓肠肌增大或“假性肥大”。在生命的头二十年即可发生完全瘫疾或死亡。

一种良性杜兴氏型可迟至40岁以后发病，这种类型对正常寿命影响较小。

四肢带肌型进行性肌营养不良通常在儿童期发病，由于是常染色体隐性遗传，男、女性受累机会均等。与杜兴氏肌营养不良相比，其假性肌肥大并不明显，预后也不尽相同，大部分病人可带病存活20 - 30年。

面肩胛臂肌营养不良型，顾名思义，开始受累的肌肉是面肌及肩带肌，通常从青少年期开始发病。由于其常染色体显性遗传，故男、女发病机会相等。假性肌肥大亦非常见。很少完全失去功能，寿命正常。

重症肌无力是一种反复发作的神经肌肉疾患，其特征是骨骼肌无力与明显的易疲倦性。此病可发生于任何年龄，但发病高峰人群为20岁左右，其次为成年后期，此时受累者多为男性。而年轻人中，女性患者数是男性的3倍，这种年龄的差异与胸腺病损伤有显著相关关系，年长男性更易患胸腺肿瘤而青年女性易患胸腺增生。

重症肌无力主要表现为横纹肌迅速而明显的疲劳。受累较严重的多为较活跃的肌肉，例如：眼外肌，面肌、舌肌和四肢肌。这类病人首要的危险是呼吸肌受累，这可导致窒息，病程发展缓慢，间或以自发的缓解期。不同病人的预后决然不同，很难做出准确的预测。用肾上腺皮质激素治疗非常有效，大概是自身免疫抑制作用的缘故，对大多数病人来说，胸腺切除非常有效，尽管其中有些人并没有胸腺瘤。血浆除去法通常被用来清除循环系统中的胆碱受体抗体。

Passage one The Skeletal System骨骼系统

In this passage you will learn:1.Functions of the skeletal system 2.Types of bones 3.Replacement of bones

Without the skeletal system we would be unable to perform movements, such as walking or grasping. The slightest jar to the head or chest could damage the brain or heart. It would even be impossible to chew food. The framework of bones and cartilage that protects our organs and allows us to move is called the skeletal system.没有骨骼系统我们不会完成运动,如行走或抓握。轻微的撞击头部或胸部就会损伤头部或心脏。它会甚至不能咀嚼食物。骨和软骨的框架下保护我们的器官中,让我们可以继续被称为的骨骼系统。 Functions. The skeletal system performs several basic functions.功能。骨骼系统执行几个基本功能。

◆ Support: the skeletal system provides a framework for the body and, as such, it supports soft tissues and provides a point of attachment for many muscles.支持:骨骼系统,提供了一个框架,用于身体的,同样,它支持软组织的位置时,为客户提供许多的肌肉。

◆ Protection: many internal organs are protected from injury by the skeleton. For example, the brain is protected by the cranial bones, the spinal cord by the vertebrae, the heart and lungs by the rib cage, and internal reproductive organs by the pelvic bones.保护:许多内脏免受伤害骨架。例如,大脑是颅保护骨头、脊髓的脊椎,心脏和肺的肋骨,和内部的生殖器官骨盆骨的。

◆ Movement: bones serve as levers to which muscles are attached. When the muscles

contract, the bones acting as levers produce movement.骨头运动:◆作为杠杆来肌肉附呈。当肌肉收缩,骨骼作为杠杆生产运动。

◆ Mineral storage: bones store several minerals that can be distributed to other parts of the body on demand. The principal stored minerals are calcium and phosphorus.矿产贮存:◆骨头商店可以多种矿物质分发给身体的其他部分有求必应。校长储存矿物质是钙和磷的含量。

◆ Blood cell production: red marrow in certain bones is capable of producing blood cells, a process called hematopoiesis or hemopoiesis. Red marrow consists of blood cells in immature stages, fat cells, and macrophages. Red marrow produces red blood cells, some white blood cells and platelets.◆血细胞生产:红色的骨髓在某些骨头能产下血细胞,这个过程称为造血或hemopoiesis。红色的骨髓由血细胞在不成熟的阶段,脂肪细胞和巨噬细胞。红色的骨髓产生红血球,有些白血球和血小板。

Types of bones. Almost all of the bones of the body may be classified into four principal types on the basis of shape: long, short, flat and irregular. Long bones have greater length than width and consist of a diaphysis and a variable number of epiphyses. For example, metacarpals, metatarsals, and phalanges have only one epiphysis. The femur actually has four. Other long bones have two.类型的骨头。几乎所有的身体的骨头可分为四个主要类型的基础上,形状:长的、短的、公寓、不规则的。长骨有更大的漫长而不是宽度和包括骨干和一个可变数目的epiphyses。例如,metacarpals、跖骨,和趾骨只有一个epiphysis。股骨却有四个。其他长骨生两个

Long bones are slightly curved for strength. A curved bone is structurally designed to absorb the stress of the body weight at several different points so the stress is evenly distributed. If such bones were straight, the weight of the body would be unevenly distributed and the bone would easily fracture. Examples of long bones include bones of the thigh, legs, toes, arms, forearms, and fingers.长骨头稍弯曲以增加强度。弯曲的骨结构的应力专用于吸收体重不同的点的应力是均匀分布。如果这样的骨头就直,机身重量,将分配不均和骨很容易骨折。长骨干的例子包括大腿的骸骨、腿,脚趾、手臂、前臂和手指。

Short bones are somewhat cube-shaped and nearly equal in length and width. Their texture is spongy except at the surface, where there is a thin layer of compact bone. Examples of short bones are the wrist and ankle bones.有些短骨方形和近有着同样的长度和宽度。他们的质地松软的除了在表面,哪里有一层薄薄的紧凑的骨头。短的例子骨头手腕和脚踝的骨头。

Flat bones are generally thin and composed of two more or less parallel plates of compact bone enclosing a layer of spongy bone. Flat bones afford considerable protection and provide extensive areas for muscle attachment. Examples of flat bones include the cranial bones(which protect the brain), the sternum and ribs(which protect organs in the thorax), and the scapulae.扁骨一般瘦,由两个或多或少的小骨附上平行板一层发泡骨。扁骨负担得起相当大的保护和提供广阔的地域肌肉附件。扁骨的例子包括颅骨头(保护大脑),胸片和肋骨保护器官(开始),scapulae。

Irregular bones have complex shapes and cannot be grouped into any of the three categories just described. They also vary in the amount of spongy and compact bone present. Such bones include the vertebrae and certain facial bones.不规则骨有较复杂的外形和不能被分成三大类的了。他们也不同数量的发泡而简洁的骨礼物。这些骨头包括椎骨和一定的面部的骨头。

There are two additional types of bones that are not included in this classification by shape. Sutural or wormian bones are small bones between the joints of certain cranial bones. Their

number varies greatly from person to person. Sesamoid bones are small bones in tendons where considerable pressure develops, for instance, in the wrist. These, like sutural bones, are also variable in number. Two sesamoid bones, the patellas (kneecaps), are present in all individuals.有两个额外的类型的骨头,不包括在这分级的形状。wormian针脚或骨头小骨头关节之间的某些颅的骨头。他们的数目人来说是不相同的。Sesamoid的骨头小骨肌腱相当大的压力在发展,例如,在手腕。这些如同针脚骨头,也变多。两sesamoid超负荷的骨头,patellas(),存在于所有的个体。

Bone replacement. Bones undergoing either intramembranous or endochondral ossification are continually remodeled from the time that initial calcification occurs until the final structure appears. Remodeling is the replacement of old bone tissue by new bone tissue. Compact bone is formed by the transformation of spongy bone. The diameter of a long bone is increased by the destruction of the bone closest to the marrow cavity and the construction of new bone around the outside of the diaphysis. However, even after bones have reached their adult shapes and sizes, old bone is perpetually destroyed and new bone tissue is formed in its place. Bone is never metabolically at rest; it constantly remodels and reappropriates its matrix and minerals along lines of mechanical stress.骨更换。intramembranous或endochondral接受或骨骨化常帮自从初始钙化直到最后结构出现。重建旧的是将由新骨组织骨组织。紧凑的骨形成的转型发泡骨。直径长骨被破坏了我的骨头骨髓腔最近,为建设新骨外线超越了骨干。然而,即使是在成人已经达到他们的骨头形状和大小,老骨头被毁,永远是新生骨形成组织是在自己的地方。骨从不新陈代谢的作用,在休息,本公司不断重新改型和reappropriates它的矩阵里沿着线和矿物质机械应力。

Bones shares with skin the feature of replacing itself throughout adult life. Remodeling takes place at different rates in various body regions. The distal portion of the femur (thighbone) is replaced about every 4 months. By contrast, bone in certain areas of the shaft will not be completely replaced during the individual’s life. Remodeling allows worn or injured bone to be removed and replaced with new tissue. It also allows bone to serve as the body’s storage area for calcium. Many other tissues in the body need calcium in order to perform their functions. For example, a nerve cell needs calcium for nerve impulse conduction, muscle needs calcium to contract, and blood needs calcium to clot. The blood continually trades off calcium with the bones, removing calcium when it and other tissues are not receiving enough of this element and resupplying the bones with dietary calcium to keep them from losing too much bone mass.骨头的特点与肌肤股票取代本身在适应成年人的生活作好准备。重构以不同的比率发生在不同的身体地区。远端部分股骨(病症)代替大约每4个月。相比之下,骨头的某些区域轴就不可能完全取代了经个人的生命。重塑允许穿或受伤的骨头被拆卸和更换新组织。它也允许骨作为人体的区域存放的钙。许多其他组织的身体需要钙为了完成他们的功能。例如,一个神经细胞需要钙质,使肌肉神经冲动传导需要钙合同,和血液需要钙质血块。不断地交易的血钙与骨了的时候,消除钙和其他组织都没有得到足够的这个元素和补给作战骨钙与饮食,使他们免遭失去太多的骨骼。

The cells believed to be responsible for the resorption (loss of a substance through a physiological or pathological process) of bone tissue are osteoclasts. In the healthy adult, a delicate homeostasis is maintained between the action of the osteoclasts in removing calcium and the action of bone-making osteblasts in depositing calcium. Should too much new tissue be formed, the bones become abnormally thick and heavy. If too much calcium is deposited in the bone, the surplus may form thick bumps, or spurs, on the bone that interferes with movement at

joints. A loss of too much tissue or calcium weakens the bones and allows them to break easily or to become very flexible. A greatly accelerated remodeling process results in a condition called Paget’s disease. 这些细胞被认为是负责吸收(亏损的物质通过的生理或病理过程中骨组织是破骨细胞。在健康的成年人,一个精致的稳态关键之间保持破骨细胞的作用除钙和作用的存款osteblasts bone-making钙。应该太多形成新组织,骨头变得异常很厚实。如果太过于钙沉积在骨的贸易顺差可能形成厚撞击,与马刺,骨头上的运动,它会妨碍到关节。失去太多的组织或钙削弱的骨头,并允许他们易碎,或是想成为高度的灵活性。一个极大地加速过程重构的结果名为帕哲病的症状,条件。

In the process of resorption, it is believed that osteoclasts send out projections that secrete protein-digesting enzymes released from lysosomes and several acids (lactic and citric). The enzymes may function by digesting the collagen and other organic substances, while the acids may cause the bone salts (minerals) to dissolve. It is also presumed that the osteoclastic projections may phagocytose whole fragments of collagen and bone salts. Magnesium deficiency inhibits the activity of osteoclasts. 吸收的过程中,据说破骨细胞发出后,protein-digesting释放分泌酶溶酶体和几个酸(乳酸和柠檬)。消化的酶可能功能的胶原质及其他有机物质,而酸可以使骨盐(矿物质溶解。它也是假定那骨质预测可能phagocytose整个碎片的胶原蛋白和骨盐。缺乏镁抑制破的活动。

Normal bone growth in the young and bone replacement in the adult depend on several factors. First, sufficient quantities of calcium and phosphorus, components of the primary salt that makes bone hard, must be included in the diet. Manganese may also be important in bone growth. It has been shown that manganese deficiency significantly inhibits laying down new bone tissue. Second, the individual must obtain sufficient amounts of vitamins, particularly vitamin D, which participates in the absorption of calcium from the gastrointestinal tract into the blood, calcium removal from bone, and kidney reabsorption of calcium that might be otherwise be lost in urine.正常骨生长在年轻的和骨置换在成人取决于几个因素。首先,足够数量的钙、磷、部件的主要盐使骨硬,必须包含在饮食。锰可能也有重要的骨骼生长。有证据表明,锰缺陷显著抑制躺新骨组织。其次,每个人都必须获得足够的大量的维生素,尤其是维他命D,它参与吸收钙从胃肠道进入血液、钙的清除、肾重吸收变化骨钙,可能是其他迷失在尿液。

Third, the body must manufacture the proper amounts of the hormones responsible for bone tissue activity. Growth hormone (GH) secreted by the pituitary gland, is responsible for the general growth of bones. Too much or too little of this hormone during childhood makes the adult abnormally tall or short. Other hormones specialize in regulating the osteoclasts. Calcitonin (CT), produced by the thyroid gland, inhibits ostoclastic activity and accelerates calcium absorption by bones, while parathormone (PTH ), synthesized by the parathyroid glands, increases the number and activity of osteoclasts. PTH also releases calcium and phosphate from bones into blood, transports phosphate from blood into urine. And still others, especially the sex hormone, aid osteoblastic activity and thus promote the growth of new bone. The sex hormones act as a double-edged sword. They aid in the growth of new bone, but they also bring about the degeneration of all the cartilage cells in epiphyseal plates. Because of the sex hormones, the typical adolescent experiences a spurt of growth during puberty, when sex hormone levels start to increase. The individual then quickly completes the growth process as the epiphyseal cartilage disappears. Premature puberty can actually prevent one from reaching an average adult height because of the simultaneous premature degeneration of the plates. 第三,身体必须制造适当的大量的荷尔蒙负责骨骼组织的活动。生长激素(GH)由脑垂体分泌,负责一般生长骸骨。过多

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