消化系统专业英语

1、Chapter 4The Digestive SystemIn this passage you will learn: The digestive system as a whole Anatomy and physiology of the major organs in the digestive system Associated medical termsIntroduction. The digestive system, also called the gastrointestinal or alimentary canal, contains the organs involv

2、ed in the ingestion and processing of food. The primary functions of the digestive system are: ingestionthe entry of food into the body ; digestionthe physical and chemical breakdown of food into nutrients that can be used by the body's cells; absorptionthe passage of these nutrients from the ga

3、strointestinal tract into the bloodstream; and eliminationthe excretion of solid waste materials that cannot be absorbed into the blood. Anatomy and Physiology. Anatomically, the digestive system consists of a 30-foot long, mucous membrane-lined tube beginning with the mouth, where food enters the b

4、ody, and ending with the anus, where solid waste is excreted. The digestive system is composed of 9 main organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. The liver, gallbladder, and pancreas are also called accessory organs of the digesti

5、ve system. Although food does not pass through these organs, they aid in the processing of food and nutrients. The organs of the digestive system are illustrated in Figure 5-1 and described in the paragraphs below.Figure 5-1The oral cavity. The process of digestion begins in the mouth, also called t

6、he buccal cavity, which is the opening through which food enters the body. The mouth has the ability to mechanically reduce the size of the food that is placed in it. The lips form the opening to the mouth, while the cheeks or bucca form the borders of the oral cavity. The structures within the oral

7、 cavity including the teeth, tongue, and palate, are involved in the chewing (mastication) and swallowing (deglutition)of food. They also play a role in speech.The teeth are used to cut, tear, and crush food into smaller pieces. They are classified mainly by their shapes and locations. Incisors and

8、cuspids are in front of the mouth; molars are in the back. Each tooth consists of a mass of nerves and blood vessels, called pulp, surrounded by a hard substance called cementum and a white smooth substance called enamel. The teeth are embedded in fleshy tissue called gums or gingivae. Together, the

9、 gums and other structures that support the teeth are known as the periodontium. Humans have two sets of teeth, the deciduous dentition of child-hood , which fall out and are replaced by the permanent dentition of adulthood.The tongue extends across the floor of the oral cavity and is attached by mu

10、scles to the lower jaw bone. It manipulates food in the mouth during mastication and deglutition. The tongue is covered with a series of cone-shaped small projections called papillae in which there are taste buds that can sense flavors, such as sweet, bitter, salty, and sour.The palate forms the roo

11、f of the mouth. It is divided into two parts; the hard palate and the soft palate. The hard palate forms the anterior portion of the mouth, while the soft palate lies posterior to it. Hanging from the soft palate is a small tissue called the uvula. The word uvula means little grape. Around the oral

12、cavity are three pairs of salivary glands. These exocrine glands produce a fluid called saliva, which is released, from the parotid gland, submandibular gland and sublingual gland on each side of the mouth. During swallowing, the soft palate and uvula move upward to prevent food from entering the na

13、sal cavity, the uvula also helps to guide the food into the pharynx.The pharynx, or throat, is a long muscular tube that serves as a passageway for food from the mouth to the esophagus and as a passageway for air from nose to the windpipe (trachea). When swallowing occurs, a flap of tissue, the epig

14、lottis, covers the trachea so that food can 't enter and becomes lodged there.The esophagus is a long muscular tube extending from the pharynx to the stomach. Food is propelled by rhythmic contractions of muscles in the wall of the esophagus. This process, called peristalsis, is also how food is

15、 moved through the stomach and intestines. It is something like squeezing a marble (bolus of food) through a rubber tube.The stomach, a pouch-like organ located in the upper part of the abdominal cavity, connects the esophagus with the small intestine. It is composed of an upper portion called fundu

16、s, a middle section known as the body, and a lower portion, called the antrum. Entry of food from the esophagus into the stomach is controlled by a ring of muscles known as the cardiac sphincter. The cardiac sphincter relaxes and contracts to move food from the esophagus into the stomach, whereas th

17、e pyloric sphincter allows food to leave the stomach when it has sufficiently digested. When the stomach is empty, the mucous membranes lining its walls are highly folded; buried within these folds, or rugae, are numerous digestive glands. As the stomach fills, the nigae unfolded, exposing the diges

18、tive glands and stimulating them to secrete digestive enzymes and hydrochloric acid. These substances help transform food present in the stomach into a semifluid substance called chyme. The pyloric sphincter allows food to pass into the small intestine only after it has been transformed into chyme.T

19、he small intestine (small bowel) is the region of the gut where nearly all of the chemical digestion of the nutritional components of food takes place. It is a coiled long tube that winds from the pyloric sphincter of the stomach to the beginning of the large intestine, filling much of the abdominal

20、 cavity. By convention, the small intestine is divided into three sections. (l)The duodenum, which is only a 25cm section, receives chyme from the stomach, helps regulate gastric emptying. (2) The jejunum, the central section, is the primary absorptive region. (3) The last section, the ileum is atta

21、ched to the large intestine. In the wall of the entire small intestine are millions of tiny, microscopic projections called villi. It is through the capillaries in the villi that completely digested nutrients pass into the bloodstream and lymph vessels. Materials that cannot be absorbed pass from th

22、e small intestine to the large intestine.The large intestine. Compared with the small intestine, the large intestine is relatively inactive and has much less functions. Extending from the end of the ileum to the anus, It is divided into four parts: cecum, colon, sigmoid colon and rectum.The cecum, a

23、 pouch on the right side, is connected to the small intestine by the ileocecal valve, which controls the passage of fluid waste from the small intestine into the large intestine. Hanging off from the cecum is the appendix, a small organ with no clear function.The colon, which comprised the main leng

24、th of the large intestine, has three divisions. The ascending colon, extending from the cecum to the upper abdominal area. The transverse colon passes horizontally to the left toward the spleen and turns downward (splenic flexure) to the descending colon. The sigmoid colon, shaped like an S, is at t

25、he distal end of the descending colon and leads into the rectum. As fluid waste from the small intestine passes through the various sections of the colon, water is reabsorbed into body. As a result, the fluid waste turns into a solid material known as stool or feces.The rectum serves as a reservoir

26、for feces. It terminates in the lower opening of the gastrointestinal tract, the anus, which is the external opening through which feces are released from the body.Accessory digestive organs. Three important accessory organs of the digestive system are the liver, gallbladder, and pancreas. Although

27、food does not pass through these organs, each plays an indispensable role in the proper digestion and absorption of nutrients.The liver, a large glandular organ located in the upper right quadrant of abdomen, produces agreenish fluid called bile. Bile contains cholesterol, bile acids and bile pigmen

28、ts. It has a deter-gent-like effect on fats. It breaks apart large fat globules so that enzymes from the pancreas can digest the fats. This action is called emulsification. Bile produced in the liver passes through the hepatic duct to the cystic duct and into the gallbladder. Besides producing bile,

29、 the liver has several other vital functions. It manufactures blood proteins, destroys old erythrocytes and releases bilirubin, removes poisons ( detoxification) from the blood, stores and releases glycogen needed by the body.The gallbladder, a pear-shaped sac behind the lower portion of the liver,

30、stores bile, which is continuously secreted by the hepatic cells between meals. When the stomach and duodenum are full, the gallbladder contracts, forcing bile to pass through the cystic duct to the common bile duct and into the duodenum where it helps in digestion.The pancreas, an elongated organ j

31、ust behind the stomach, manufactures digestive juice containing enzymes (amylase and lipase)that aid in the digestion of proteins, starches and fats. These digestive juices pass into the duodenum via the pancreatic duct. The pancreas also secretes insulin and glucagon. Those hormones are needed to h

32、elp release sugar from the blood to be used for energy by the cells of the body.Conclusion. Our digestive system kicks in the minute food enters our mouths. Moving through the digestive tractdown the esophagus, into the stomach, ending up in the small intestinefood is chemically broken down into sma

33、ller molecules, and nutrients are absorbed into the body. From here, solid wastes move into the colon, where they remain for a day or two until they are passed out of the body.New Words and Phrases ExercisesA. Discuss the following topics:1. What are the primary functions of the digestive system?2.

34、Imagine you were lecturing in front of rural health workers on the topic of digestive system, draw a picture to illustrate the whole system.3. Give brief accounts of the structures and functions of each organ?B. Rewrite the following sentences in your own way and use phrases and expressions you are

35、familiar with.For example:By mechanical movement, themouth is able to break down thefood inside into smaller pieces.The mouth has the ability tomechanically reduce the size ofthe food that is placed in it. > >1. Although food does not pass through these organs, they aid in the processing of fo

36、od and nutrients.2. The pharynx, or throat, is a long muscular tube that serves as a passageway for food from the mouth to the esophagus and as a passageway for air from nose to the windpipe.3. The tongue extends across the floor of the oral cavity and is attached by muscles to the lower jaw bone.4.

37、 The teeth are embedded in fleshy tissue called gums or gingivae.5. When the stomach is empty, the mucous membranes lining its walls are highly folded; buried within these folds, or rugae, are numerous digestive glands.6. The esophagus is a long muscular tube extending from the pharynx to the stomac

38、h.7. Food is propelled by rhythmic contractions of muscles in the wall of the esophagus.8. The small intestine is a long coiled tube that winds from the pyloric sphincter of the stomach to the beginning of the large intestine.9. The sigmoid colon, shaped like an S, is at the distal end of the descen

39、ding colon and leads into the rectum.10. Bile has a detergent-like effect on fats. It breaks apart large fat globules so that enzymes from the pancreas can digest the fats.C. Put the following words or phrases into the following sentences and change the form if necessary.incisors and cuspidsperistal

40、sisglucagondeciduousemulsificationpyloric sphincterantnimrectumaccessorysmall intestine1. The teeth are classified mainly by their shapes and locations: _ are in front of the mouth; molars are in the back.2. Human beings have two sets of teeth, the _dentition of childhood and the permanent dentition

41、 of adulthood.3. Food is propelled by rhythmic contractions of muscles in the wall of the peptic tract. This process is called _ .4. The stomach is composed of three portions: fundus, the body, and the _.5. The cardiac sphincter relaxes and contracts to move food from the esophagus into the stomach,

42、 whereas the _allows food to leave the stomach and pass into the small intestine6. Nearly all of the chemical digestion of the nutritional components of food takes place in the _7. The liver, gallbladder, and pancreas are important _organs of the digestive system.8. Bile breaks apart large fat globu

43、les to help digest the fats. This action is called _.9. The pancreas secretes insulin and _. Those hormones are used for energy by the cells of the body.10. The _ serves as a reservoir for feces. It terminates in the lower opening of the gastrointestinal tract, the anus.D. Match Column I with Column

44、 II .Column IColumn IIbileduodenumfecesileumbolusdeglutitiongallbladdermasticationrugaeuvula1 The waste material eliminated from the intestine; stool2 A mass, such as the rounded mass of food that is swallowed3 The fluid secreted by the liver that aids in the digestion and absorption of fats4 The large folds in the lining of the stomach seen when the stomach is empty5 The first portion of the small intestine6 Chewing7 A hanging fleshy mass. Usually means the mass that hangs from the soft palate8 Swallo