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15

Instructor’s Manual forThe Digestive System

LEARNING OBJECTIVES WITH RATIONALEAfter completing this chapter the student will be able to:

1. List in sequence each of the component parts or segments of the alimentary canal from the mouth to the anus and identify the accessory organs of digestion.

The component parts of the alimentary canal from mouth to anus are mouth, pharynx (throat), esophagus, stomach, small intestine (duodenum, jejunum, ileum), and large intestine (cecum, colon, rectum, anal canal).

Accessory organs of digestion include teeth and tongue, salivary glands (parotid, submandibular, sublingual), gallbladder, pancreas, and vermiform appendix.

2. List and describe the four layers of the wall of the alimentary canal. Compare the lining layer in the esophagus, stomach, small intestine, and large intestine.

The four layers that make up the wall of the alimentary canal include (from the inside layer moving out) mucosa or mucous membrane, submucosa, muscular coat or muscularis, and adventitia or serosa. Although the same four tissue coats form every organ of the alimentary tract, their structures vary in different organs. The mucosa of the esophagus is composed of tough, stratified, abrasion-resistant epithelium. The mucosa of the remainder of the tract is a delicate layer of simple columnar epithelium designed for absorption. In the stomach region, the mucosa is lined with thousands of microscopic gastric glands that secrete gastric juice and hydrochloric acid. When the stomach is empty, its mucous lining lies in folds called rugae. The mucous lining of the small intestine, like that of the stomach, contains thousands of microscopic glands. These are called intestinal glands, and they secrete intestinal digestive juice. The intestinal lining is made up of multiple circular folds called plicae. These folds are covered with thousands of tiny “fingers” called villi. Inside each villus lies a rich network of blood capillaries that absorb the products of digestion. No villi are present in the mucosa of the large intestine. As a result, less surface area is available for absorption, and the efficiency and speed of movement of substances through the wall of the large intestine are much lower than in the small intestine.

The submucosa is a connective tissue layer just below the mucosa. It contains nerves and blood vessels. The two layers of muscle tissue called the muscularis move food, by means of contraction in a motion called peristalsis, through the digestive tube. Contraction also mixes food with digestive juices and mechanically breaks down food. The serosa is the outermost covering or coat of the digestive tube. In the abdominal cavity it is composed of visceral peritoneum. The intestines are anchored to the posterior wall of the abdominal cavity by a large double fold of peritoneal tissue called the mesentery.

3. Discuss the basics of protein, fat, and carbohydrate digestion and give the end products of each of these processes.

Very little carbohydrate digestion occurs before food reaches the small intestine. Salivary amylase found in saliva begins the chemical breakdown of carbohydrates, but it has little time to work because food is usually swallowed quite fast. Gastric juices contain no carbohydrate-digesting enzymes. Once food reaches the small intestine, pancreatic and intestinal juice enzymes digest starches and sugars. A pancreatic enzyme (amylase) starts the process by changing polysaccharides such as starches into disaccharides (double sugars). Three intestinal enzymes—maltase, sucrase, and lactase—digest disaccharides by changing them into monosaccharides (simple sugars). Maltase digests maltose (malt sugar), sucrase digests sucrose (cane sugar), and lactase digests lactose (milk

Structure & Function of the Body, 14th ed.Copyright © 2012 by Elsevier Inc. All rights reserved. Thibodeau & Patton

634 Chapter 15 The Digestive System ____________________________________________________________

sugar). The end products of carbohydrate digestion are simple sugars (monosaccharides). The most abundant monosaccharide is glucose.

Protein digestion starts in the stomach. Pepsin, an enzyme found in gastric juice, causes the giant protein molecules to break up into simpler compounds. Then in the intestine other enzymes (trypsin in pancreatic juice and peptidase in intestinal juice) complete protein digestion. Every protein molecule is made up of many amino acids joined together. When enzymes have split up the large protein molecule into its separate amino acids, protein digestion is completed. The end products of protein digestion are amino acids.

Fat digestion may begin in the stomach when an enzyme called gastric lipase is secreted. However, most fats go undigested, until they are emulsified by bile in the duodenum of the small intestine. After this takes place, the pancreatic enzyme (steapsin or pancreatic lipase) splits fat molecules into their building blocks, fatty acids and glycerol. The end products of fat digestion are fatty acids and glycerol.

4. Define and contrast mechanical and chemical digestion.Mechanical digestion breaks food into tiny particles, mixes these particles with digestive juices,

moves them along the alimentary canal, and finally eliminates the digestive wastes from the body. Chewing (mastication), swallowing (deglutition), peristalsis, and defecation are the main processes of mechanical digestion.

Chemical digestion breaks down large, nonabsorbable food molecules into smaller, absorbable molecules that are able to pass through the intestinal mucosa into blood and lymph. Chemical digestion includes the chemical reactions catalyzed by enzymes in saliva, gastric juice, pancreatic juice, and intestinal juice.

5. Define peristalsis, bolus, chyme, jaundice, ulcer, and diarrhea.Peristalsis—the movement of food through the digestive tube; brought about due to contractions

of the muscularis or muscular coat.Bolus—a small rounded mass created after food has been chewed; allows food to be swallowed.Chyme—a semisolid mixture that is food mixed thoroughly with gastric juice.Jaundice—a yellowish skin discoloration that occurs when excessive amounts of bile are

absorbed into the blood.Ulcer—an open wound or sore in an area of the digestive system that is acted upon by acid

gastric juice. Two common sites for ulcers are the stomach and the duodenum. Left untreated, ulcers cause persistent pain and they may actually perforate the wall of the digestive tube, causing hemorrhage and inflammation of the abdominal cavity.

Diarrhea—a state in which fecal material is liquid.

LECTURE OUTLINE INSTRUCTOR'S NOTES

I. OVERVIEW OF THEDIGESTIVE SYSTEM (Figure 15-1 and Table 15-1)A. Irregular tube called alimentary canal or

gastrointestinal (GI) tract and accessory organs of digestion

B. Food must first be digested, then absorbed, and later metabolized

II. PRIMARY MECHANISMS OF THE DIGESTIVE SYSTEM (Table 15-2)A. Ingestion—complex foods taken into the GI tractB. Digestion—group of processes that break

complex nutrients into simpler ones1. Mechanical digestion- breakup of large

chunks of food into smaller bits2. Chemical digestion- breaks large molecules


____________________________________________________________ Chapter 15 The Digestive System 635

LECTURE OUTLINE INSTRUCTOR'S NOTESinto smaller ones

C. Motility—a number of GI movements resulting from muscular contraction

D. Secretion—release of digestive juices and hormones that facilitate digestion

E. Absorption—movement of digested nutrients into the internal environment of the body

F. Regulation—neural, hormonal and other mechanisms that regulate digestive activity

III. WALL OF THE DIGESTIVE TRACT (Figure 15-2)The wall of the digestive tube is formed by four layers of tissue:A. Mucosa—type varies depending on GI location

(tough and stratified or delicate and simple epithelium); mucus production

B. Submucosa—connective tissue layerC. Muscularis—circular, longitudinal, and oblique (in

stomach) layers of smooth muscle; important in GI motility1. Peristalsis— “wavelike” movement pushes

food down the tract (Figure 15-3)2. Segmentation – “back and forth” movement

(Figure 15-4)D. Serosa—serous membrane that covers the

outside of abdominal organs; it attaches the digestive tract to the wall of the abdominopelvic cavity by forming folds called mesenteries

IV. MOUTHA. Roof—formed by hard palate (parts of maxillary

and palatine bones) and soft palate, an arch-shaped muscle separating mouth from pharynx; uvula, a downward projection of soft palate (Figure 15-5)

B. Floor—formed by tongue (skeletal muscle covered by mucous membrane) and its muscles; papillae, small elevations on mucosa of tongue; taste buds, found in many papillae; lingual frenulum, fold of mucous membrane that helps anchor tongue to floor of mouth (Figure 15-5)

V. TEETHA. Structures of a typical tooth

1. Crown, visible portion of the tooth, covered by enamel—the hardest tissue in the body

2. Neck, joins the crown of the tooth to the root, surrounded by pink gingival tissue (gum tissue)

3. Root, fits into the bony socket and anchors the tooth to the bone with a fibrous periodontal membrane (Figure 15-6)

B. Names of teeth—incisors; cuspids, also called canines or “eyeteeth;” bicuspids, also called premolars; tricuspids, also called molars

C. Twenty teeth in temporary set (also called deciduous); average age for cutting first tooth



LECTURE OUTLINE INSTRUCTOR'S NOTESabout 6 months; set complete at about 2 years of age

D. Thirty-two teeth in permanent set; 6 years about average age for starting to cut first permanent tooth; set complete usually between ages of 17 and 24 years (Figure 15-5)

VI. SALIVARY GLANDS (Figure 15-7)A. Saliva- exocrine gland secretion flows into ducts

1. Serous type—watery and contains enzymes (salivary amylase) but no mucusa. produced by serous type secretory cells

(Figure 15-7, B)2. Mucus type—thick, slippery and contains

mucus but no enzymesa. lubricates food during masticationb. produced by mucus type secretory cells

(Figure 15-7, B)B. Parotid glands (Figure 15-7)—largest of the

salivary glands; lie just below and in front of each ear at the angle of the jaw; secrete saliva containing mucus and salivary amylase into ducts to be conveyed to the mouth cavity

C. Submandibular glands—ducts open into the mouth on either side of the lingual frenulum; produces both serous and mucus type saliva (Figure 15-7, B)

D. Sublingual glands—multiple ducts open into the floor of the mouth; produce only mucus type saliva

VII. PHARYNX—tubelike structure of muscle lined with mucous membrane; functions are part of both respiratory and digestive systems (see three divisions as described in Chapter 14)A. Anatomical components: nasopharynx,

oropharynx, laryngopharynx (see anatomical description Chapter 14 and Figure 14-4)

B. Oropharynx most involved segment in digestive process of swallowing or deglutition1. Regulation of deglutition movements via

motor cortex of cerebrum (voluntary) and “deglutition center” of brainstem (involuntary)

VIII. ESOPHAGUS—muscular tube lined with mucous membrane that connects the pharynx with the stomach; food enters stomach by passing through lower esophageal sphincter (LES) or cardiac sphincter

IX. STOMACH (Figure 15-8) Lies in the upper part of the abdominal cavity just under the diaphragm; serves as a pouch to receive chewed food from the esophagusA. Size—expands considerably after large meal;

about size of large sausage when emptyB. Cardiac sphincter—ring of muscle tissue at the

end of esophagus; keeps food mixed with gastric



LECTURE OUTLINE INSTRUCTOR'S NOTESacids from reentering the esophagus

C. Pylorus—lower part of stomach; pyloric sphincter muscle closes opening of pylorus into duodenum

D. Wall—many smooth muscle fibers; contractions produce churning movements (peristalsis)

E. Lining—mucous membrane; many microscopic glands that secrete gastric juice and hydrochloric acid into stomach; mucous membrane lies in folds (rugae) when stomach is empty

X. SMALL INTESTINE (Figure 15-9)A. Size—about 7 meters (20 feet) long but only 2

cm or so in diameterB. Divisions

1. Duodenum2. Jejunum3. Ileum

C. Wall—contains smooth muscle fibers that contract to produce peristalsis and segmentation movements

D. Lining—mucous membrane; many microscopic glands (intestinal glands) secrete intestinal juice; villi (microscopic finger-shaped projections from surface of mucosa into intestinal cavity) contain blood capillaries and lymph lacteals for nutrient absorption; each villus is covered by microvilli that further increase the surface area for absorption of nutrients

XI. LIVER AND GALLBLADDERA. Size and location—liver is largest gland; fills

upper right section of abdominal cavity and extends over into left side

B. Liver secretes bile which contains significant quantities of cholesterol and bile salts that act as detergents to emulsify fat; bile that is eliminated in feces also carries cholesterol from the body

C. Ducts (Figure 15-10)1. Hepatic—drains bile from liver2. Cystic—duct by which bile enters and leaves

gallbladder3. Common bile—formed by union of hepatic

and cystic ducts; drains bile from hepatic or cystic ducts into duodenum

4. Release of bile—fat in chyme stimulates release of cholecystokinin which contracts the gallbladder to release bile into the duodenum

D. Gallbladder1. Location—undersurface of the liver2. Function—concentrates and stores bile

produced in the liver

XII. PANCREASA. Location—behind stomachB. Functions—exocrine and endocrine gland

1. Pancreatic cells secrete pancreatic juice into



LECTURE OUTLINE INSTRUCTOR'S NOTESpancreatic ducts; main duct empties into duodenum (exocrine function); contains enzymes to digest all three major kinds of food

2. Pancreatic islets (islets of Langerhans)—cells not connected with pancreatic ducts; secretes two hormones: glucagon (alpha cells) and insulin (beta cells) into the blood

XIII. LARGE INTESTINE (Figure 15-12)A. Divisions

1. Cecum: ileocecal valve is connection with the small intestine; consistency of chyme changes with the reabsorption of water and salts; now called feces; presence of bacteria releases additional nutrients from cellulose and other fibers

2. Colon—ascending, transverse, descending, and sigmoid

3. RectumB. Opening to exterior—anusC. Wall—contains smooth muscle fibers that

contract to produce churning, peristalsis, and defecation

D. Lining—mucous membrane; absorption of water, salts, vitamins; no villi so much less surface area

XIV. APPENDIX Blind tube off cecum; no important digestive functions in humans; “vermiform” means shaped like a worm

XV. PERITONEUM (Figure 15-14)A. Definitions—peritoneum, continuous serous

membrane lining abdominal cavity and covering abdominal organs; parietal layer of peritoneum lines abdominal cavity; visceral layer of peritoneum covers abdominal organs; peritoneal space lies between parietal and visceral layers with enough fluid between them to keep them moist and enable them to slide freely against each other during breathing and digestion

B. Extensions—largest ones are the mesentery and greater omentum; mesentery is extension of parietal peritoneum, which attaches most of small intestine to posterior abdominal wall; greater omentum, or “lace apron,” hangs down from lower edge of stomach and transverse colon over intestines

XVI. DIGESTION (Table 15-3) Physical and chemical changes to food to prepare nutrients to be absorbed and used by cellsA. Mechanical digestion—chewing, swallowing, and

peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract

B. Chemical digestion—breaks up large food



LECTURE OUTLINE INSTRUCTOR'S NOTESmolecules into compounds having smaller molecules; brought about by digestive enzymes

C. Carbohydrate digestion—mainly in small intestine1. Pancreatic amylase—changes

polysaccharides (starches) into disaccharides

2. Intestinal juice enzymesa. Maltase—changes maltose (malt sugar)

into glucoseb. Sucrase—changes sucrose (ordinary

cane sugar or table sugar) into glucosec. Lactase—changes lactose (milk sugar)

to glucoseD. Protein digestion—starts in stomach; completed

in small intestine1. Gastric juice enzymes, renin and pepsin,

partially digest proteins by causing the giant protein molecules to break up into somewhat simpler compounds

2. Pancreatic enzyme, trypsin, completes digestion of proteins to amino acids

3. Intestinal enzymes, peptidases, complete digestion of partially digested proteins to amino acids

E. Fat digestion1. Bile contains no enzymes but emulsifies fats

(breaks fat droplets into very small droplets)2. Pancreatic lipase changes emulsified fats to

fatty acids and glycerol in small intestine

XVII. ABSORPTIONA. Meaning—digested food moves from intestine

into blood or lymphB. Where absorption occurs—foods and most water

from small intestine through villi; some water also absorbed from large intestine

C. Surface area—new studies use fractal geometry to demonstrate the seemingly infinite surface area of the small intestine (Figure 15-8); the plicae (folds) have villi, the villi have microvilli, and the microvilli have bumps that further increase the surface area

CLASSROOM APPLICATIONThe following questions can be used as individual assignments or for small-group discussion. Note: to copy the questions, cover the answers with a blank sheet of paper and print, thus leaving space for answers or note-taking.

1. Mr. Harrison, your neighbor, has complained of heartburn and indigestion for over 6 months. He recently went to his physician and was told he has a hiatal hernia. He asks you the following questions.(a) “What is a hiatal hernia and what has taken place physically?”



(b) “My doctor told me I have gastroesophageal reflux disease. Can you explain this disease to me?” What symptoms are usually present?

(c) He shows you a prescription for Prilosec. Mr. Harrison tells you he is unfamiliar with the prescribed drug. You offer to stop by the pharmacy and obtain a printout of information concerning the medication prescribed by his doctor.Write your responses to the above questions. Also obtain a pharmacy printout of information on

the following medications: Tagamet, Zantac, Pepcid, and Prilosec.Answers: (a) A hiatal hernia is a condition in which the diaphragm, through which the esophagus

passes, is enlarged or stretched enabling a portion of the stomach or lower end of the esophagus to extend upward into the chest cavity. Individuals suffering from a hiatal hernia complain most often of heartburn and indigestion. (b) Gastroesophageal reflux disease (GERD) occurs when there is a backflow of stomach contents into the esophagus, which is often the result of a hiatal hernia. Gastric juices that are highly acidic produce burning in the esophagus, and pain may be experienced in the chest area as well. Antacids are often prescribed. (c) Share with the class the information you have obtained from a pharmacy concerning antacids often prescribed for GERD.

2. Design a poster depicting the alimentary canal. Label all of the areas and describe how food passes through each area.

Answer: The alimentary canal or digestive tract extends from the mouth to the anus and is lined with mucous membrane. It is composed of the mouth, pharynx, esophagus, stomach, small intestines (duodenum, jejunum, ileum), large intestines (cecum, colon), the colon (ascending colon, transverse colon, descending colon, sigmoid colon), rectum, and anal canal.

LAB ACTIVITIES1. Have students dissect a rat to locate the esophagus, stomach, intestines, liver, and pancreas.

2. Have students examine prepared slides of the stomach and intestine to identify the mucosa of each.

3. Display for the students gallstones obtained from a local hospital as well as information concerning the chemical makeup of the stones. Have the students research the physiological process by which stones develop.

4. Have students use a mirror and tongue depressor to locate the incisors, cuspids, bicuspids, and molars in their mouths.

5. Have students identify the peritoneum and its folds (omentum, mesentery) in a dissected rat or cat.

6. Have students test the chemical makeup of various food types by using:a. Benedict’s solution to identify sugarsb. Lugol’s solution to identify starches

PRACTICAL/CREATIVE LEARNING ACTIVITIES1. Statistics have shown that about 1 in 10 individuals in the United States suffers from ulcers. One of

the discoveries concerning gastric and duodenal ulcers is that they result from an infection caused by Helicobacter pylori (H. pylori).

Investigate the mode of treatment currently used in the management of bacteria-caused ulcers.Design a poster with the following information: name and define disease, describe common

symptoms. Look up and explain triple therapy, and the current results of this therapy.

2. With a lab partner, have students listen with a stethoscope as their partner swallows a mouthful or two of water. Instruct them to place the stethoscope below the xiphoid process, approximately 1 inch below and slightly to the left. Explain there should be two distinct sounds, one when the water



reaches the cardioesophageal sphincter and one when the peristaltic waves begin and the sphincter opens.

Ask students, “How long does it take for the water to reach the sphincter and for the sphincter to open?” (It should be a matter of seconds.) Have students record their answers and compare the timing with other class members.

3. On a model of the human skull, have students identify the four types of teeth: the incisors, canines, premolars, and molars.

4. Have students make a chart listing the pancreatic enzymes and explaining how they aid in the digestion of fats, proteins, and carbohydrates.

ANSWERS TO CHAPTER 15 TEXTBOOK QUESTIONS

Review Questions1. Name and describe the four layers of the wall of the gastrointestinal tract.

Answer: a. The mucosa or mucous membrane of the esophagus is composed of tough stratified epithelium. The mucosa of the lower part of the tract is made of simple columnar epithelium that is designed for absorption and secretion. b. Submucosa is connective tissue that lies just below the mucosa. It contains blood vessels and nerves. c. Muscularis is composed of two layers of muscle tissue. This muscle tissue plays an important part in the digestive process. Wavelike contractions of the muscular tissue called peristalsis move food and digestive juices through the digestive tract. d. Serosa is the outer covering of the digestive tube. In the abdominal cavity it is composed of parietal peritoneum.

2. What is the function of the uvula and soft palate?Answer: The soft palate is situated above the posterior portion of the mouth. It consists of soft

muscular tissue that hangs down from the center of the soft palate, appearing somewhat cone-shaped. The soft palate and the uvula together prevent liquid and food from entering the nasal cavities.

3. Explain the function of the different types of teeth.Answer: a. Incisors have a sharp cutting function; found in the four front teeth in each jaw of an

adult. b. Canine teeth, sometimes called cuspids, tear food as it is being eaten or chewed. c. Premolars or bicuspids, as well as molars or tricuspids, have large flat surfaces designed to grind or crush food as it is broken down in the mouth.

4. Describe the three main parts of a tooth.Answer: a. The crown of the tooth is the area exposed and visible in the mouth; it is covered by

enamel. b. The neck of the tooth is the narrow area surrounded by the gum tissue. c. The root fits into the socket of the upper and lower jaws.

5. Name the three pairs of salivary glands and describe where the duct from each enters the mouth.Answer: a. Parotid glands are the largest of the salivary glands; they lie just below and in front of

each ear. The opening of the parotid ducts can be seen inside the cheek area opposite the second molar tooth on each side of the upper jaw. b. The submandibular glands open into the mouth on either side of the frenulum, which is a thin membrane that attaches the tongue to the floor of the mouth. c. The sublingual glands open into the floor of the mouth.

6. What are the functions of the cardiac and pyloric sphincter muscles?Answer: Food enters the stomach through the cardiac sphincter located at the end of the

esophagus. The cardiac sphincter prevents food from reentering the esophagus as the stomach contracts. The pyloric sphincter prevents food from leaving the stomach and entering the duodenum. The smooth muscle fibers of the sphincter stay closed most of the time, thereby holding partially digested food in the stomach, keeping the pylorus closed.



7. Define peristalsis.Answer: Wavelike, rhythmic contractions of the stomach and intestines that move food material

along the digestive tract.

8. Explain how bile from the liver and gallbladder reaches the small intestine. What is the function of cholecystokinin?

Answer: The cystic duct drains bile from the gallbladder, whereas the common hepatic duct drains bile from the liver. The cystic duct and the common hepatic duct join and form the common bile duct, which drain into the small intestines. Cholecystokinin is a hormone secreted by the intestinal mucosa of the duodenum, which then stimulates the gallbladder to release bile into the duodenum.

9. What is contained in pancreatic juice?Answer: Pancreatic juice contains enzymes that digest all three kinds of food, sodium

bicarbonate, and an alkaline substance that neutralizes hydrochloric acid.

10. What do the bacteria in the large intestine contribute to the body?Answer: Material that is not digested in the small intestines is acted upon by the bacteria in the

large intestines. The result being that additional nutrients may be released from cellulose and other fibers and then absorbed. Bacteria in the large intestines also are responsible for the synthesis of vitamin K and for the production of some B-complex vitamins that can then be absorbed into the blood.

11. List the seven subdivisions of the large intestine.Answer: Cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum,

anal canal

12. Describe the mesentery and the greater omentum.Answer: Mesentery is the large double fold of peritoneal tissue that holds the loops of the

digestive tract to the posterior wall of the abdominal cavity. The greater omentum is the pouchlike extension of the visceral peritoneum from the lower edge of the stomach, part of the duodenum, and the transverse colon.

13. Differentiate between mechanical digestion and chemical digestion.Answer: The main processes involved in mechanical digestion are chewing, swallowing,

peristalsis, and defecation. Chemical digestion consists of numerous chemical reactions catalyzed by enzymes in saliva, gastric juices, pancreatic juice, and intestinal juices, which then break down food molecules that pass through the intestinal mucosa into the blood and lymph systems.

14. Briefly describe the process of carbohydrate digestion.Answer: Little digestion of carbohydrates occurs prior to reaching the small intestines. Once in

the small intestines, the pancreatic enzyme amylase changes starches into double sugar, mainly maltose. Intestinal enzymes—maltase, sucrase, and lactase—change double sugars into simple sugars, mainly glucose. The end product of carbohydrate digestion is simple sugars, primarily glucose.

15. Briefly describe the process of fat digestion.Answer: Most fats are undigested until emulsification by bile in the duodenum, after which

pancreatic lipase splits fat molecules into fatty acids and glycerol. The end product of fat digestion is fatty acids and glycerol.

16. Briefly describe the process of protein digestion.Answer: Protein digestion starts in the stomach. Two enzymes, renin and pepsin, are in the

gastric juices of the stomach; these cause large protein molecules to break into smaller compounds. Pepsinogen, also in gastric juice, is converted into active “pepsin enzyme” by hydrochloric acid. In the intestines, trypsin in pancreatic juice and peptidases in intestinal juice complete protein digestion. The end product of protein digestion is amino acids.

17. Explain the process of absorption. What function do the lacteals have in absorption?



Answer: After digestion, absorption of food takes place. Absorption is a process by which molecules of amino acids, glucose, fatty acids, and glycerol go from inside the intestines into the circulation body fluids.

Lacteals are lymph vessels located in each villi of the intestines; they serve to absorb fat from the chyme, which passes through the small intestines.

Critical Thinking Questions18. What structures in the small intestine increase the internal surface area? What advantage is gained to

this increase in surface area?Answer: The structures within the lining of the small intestine are called plicae, which are

arranged into multiple circular folds covered with thousands of villi. Inside each villus are blood capillaries that absorb the products of carbohydrate and protein digestion.

19. Bile does not cause a chemical change. What is the effect of bile on fat and why does this make fat digestion more efficient?

Answer: Bile mechanically breaks up or emulsifies large globules of fat into smaller particles. This emulsification function of bile increases the surface area for digestion, making the process more efficient.

20. Some people are lactose intolerant. This means they are unable to digest lactose sugar. What enzyme is probably not functioning properly and what types of food should these people try to avoid?

Answer: A deficiency of the enzyme lactase is necessary for the absorption of lactose from the intestinal tract. These individuals should avoid foods that contain lactose such as milk and milk products.



15

Instructor’s Manual forThe Digestive System

STUDENT ASSIGNMENT

Multiple Choice

Christie is 2 months old. She is unable to keep her formula down. Her mother notices that not only does she spit up after feeding, but that the milk is curdled and undigested.

1. What diagnosis is the doctor likely to make?A. Christie dislikes the milk she is being fed.B. She probably has pylorospasm.C. The mother is advised to hold Christie in a more upright position when feeding her.D. Tonsillitis prevents Christie from swallowing properly.

2. The doctor has ordered oral rehydration for Christie because she is dehydrated. He has prescribed a prepared solution that contains which of the following ingredients?A. water and sugarB. protein and fatC. sugar and saltD. none of the above

3. Janice Kafer is a 36-year-old professional nurse in charge of a very busy pediatric unit. She works long hours under demanding and stressful circumstances. She reveals to her physician that she suffers frequent episodes of stomach pain. After an extensive exam and x-rays he tells her that the first part of the small intestine is inflamed causing her stomach pain. What is this part of the small intestine called?A. duodenumB. jejunumC. esophagusD. pylori orifice

4. The doctor also felt Ms. Kafer had an over production of acid. What is this acid called?A. submucosaB. cecumC. ileocecalD. hydrochloric

5. Mr. Bell, age 51, has noticed blood in his feces. After testing, the doctor informed him of a tumor in the last part of the colon. What is this S-shaped part of the colon called?A. sigmoidB. small intestineC. duodenumD. rugae

6. Duodenal ulcers appear in which of the following?A. stomachB. small intestineC. large intestineD. esophagus



7. What is the portion of the peritoneum that holds the intestinal loops in place called?A. omentumB. mesenteryC. peritoneal cavityD. ligament

8. A product of digestion called chyme is formed in which of the following?A. esophagusB. small intestineC. stomachD. large intestine

9. The enzyme pepsin is concerned primarily with the digestion of which of the following?A. sugarsB. starchesC. proteinsD. fats

10. The enzyme amylase converts which of the following?A. starches to sugarsB. sugars to starchesC. proteins to amino acidsD. fatty acids and glycerols to fats

CompletionComplete the following statements using the terms listed below.A. Ileum M. Pyloric sphincterB. Amylase N. Sigmoid colonC. Muscular coat O. CaninesD. Metabolism P. Amino acidsE. Cholecystokinin Q. DuodenumF. Molars R. JejunumG. Cardiac sphincter S. PremolarsH. Digestion T. MucosaI. Incisors U. SubmucosaJ. Greater omentum V. CecumK. Absorption W. BileL. Adventitia X. Serosa

11. The S-shaped portion of the colon is called _____.

12. The portion of the peritoneum that descends from the stomach and the transverse colon to form a lacy apron of fat over the intestines is called the _____.

13. The “building blocks” of protein molecules are _____.

14. The small intestine is made up of three sections called _____, _____, and _____.

15. Fats that enter into the digestive tract are emulsified when they are acted upon by a substance called _____.

16. Foods undergo three kinds of processing in the body: _____, _____, and _____.

17. Fats in the chyme stimulate the secretion of _____, which stimulates contraction of the gallbladder to release bile.



18. The four tissue layers that make up the wall of the digestive tract are _____, _____, _____, and _____.

19. Food enters the stomach by passing through a muscular structure at the end of the esophagus. This structure is called the _____.

20. The four major types of teeth found in the human mouth are _____, _____, _____, and _____.

MatchingSelect the most correct answer from Column B for each item in Column A. (Only one answer is correct for each.)

Column A Column B

_____ 21. Salivary gland A. Frenulum_____ 22. Lining the small intestine B. Large intestine_____ 23. Muscularis C. Throat_____ 24. Tongue D. Mesentery_____ 25. Large intestine E. Appendix_____ 26. Vitamin K F. Esophagus_____ 27. Foodpipe G. Villi_____ 28. Pharynx H. Peristalsis_____ 29. Small structure attached to cecum I. Colon_____ 30. Peritoneum J. Parotid



IdentificationIdentify the numbered structures and write your answers in the corresponding blanks.

31. Gallbladder and Bile Ducts(1) ______________________________________(2) ______________________________________(3) ______________________________________(4) ______________________________________(5) ______________________________________(6) ______________________________________

(7) ______________________________________(8) ______________________________________(9) ______________________________________(10)______________________________________(11)______________________________________(12)______________________________________



32. Stomach(1) ______________________________________(2) ______________________________________(3) ______________________________________(4) ______________________________________(5) ______________________________________(6) ______________________________________(7) ______________________________________

(8) ______________________________________(9) ______________________________________(10)______________________________________(11)______________________________________(12)______________________________________(13)______________________________________



ANSWERS TO CHAPTER 15 STUDENT ASSIGNMENT

Multiple Choice1. B2. C3. A4. D5. A6. B7. B8. C9. C10. A

Completion11. N12. J13. P14. Q, R, A15. W16. H, K, D17. E18. T, U, C, X19. G20. I, O, S, F

Matching21. J22. G23. H24. A25. I26. B27. F28. C29. E30. D

Identification31. Gallbladder and bile ducts: (1) right and left

hepatic ducts; (2) common hepatic duct; (3) common bile duct; (4) accessory duct; (5) pancreas; (6) pancreatic duct; (7) duodenum; (8) major duodenal papilla; (9) sphincter muscles; (10) minor duodenal papilla; (11) gallbladder; (12) cystic duct

32. Stomach: (1) fundus; (2) body; (3) greater curvature; (4) rugae; (5) pylorus; (6) pyloric sphincter; (7) duodenum; (8) lesser curvature; (9) oblique muscle layer; (10) circular muscle layer; (11) longitudinal muscle; (12) cardiac sphincter; (13) esophagus


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