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CHAPTER 18
QUICK CHECK
Page 481
1. The alimentary canal is the principal structure of the digestive system. It is an irregular tube that is
open at both ends. The alimentary canal is often referred to as the gastrointestinal tract.
2. Digestion, absorption, and metabolism
3. Mucus produced by the lining of the gastrointestinal tract protects the epithelium from digestive juices
and lubricates food passing through the lumen.
4. Incisors, canines, premolars, and molars
Page 483
1. Crown, neck, and root
2. Snuff dipper’s pouch is a condition that results from leukoplakia developing in the fold between the
“cheek and gum” in users of smokeless tobacco.
3. Dental caries is tooth decay. Gingivitis is an inflammation or infection of the gums. Periodontitis is
the inflammation of the periodontal membrane or periodontal ligament.
4. Cleft lip and cleft palate
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1. The three pairs of salivary glands are the parotids, submandibulars, and sublinguals. Mumps is a
viral infection found in the parotids.
2. The three layers of the stomach are longitudinal, circular, and oblique.
3. GERD (gastroesophageal reflux disease) is a result of a backward flow of stomach acid up into the
esophagus, causing burning and pressure behind the breastbone.
4. Fundus, body, and pylorus
Page 493
1. Helicobacter pylori
2. Duodenum, jejunum, ileum
3. Gastroenteritis is an inflammation of the stomach and small intestine.
4. Bile is formed in the liver. The function of bile is to mechanically break up or emulsify fats.
Page 499
1. Cholelithiasis is a condition that is a result of having bile (gall) stones. Cirrhosis is a degeneration of
the liver.
2. The gallbladder concentrates and stores bile that is produced in the liver.
3. Cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal
4. Appendicitis
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1. Mesentery and greater omentum
2. Mechanical digestion breaks food into tiny particles, mixes them with digestive juices, moves them
along the alimentary canal, and eliminates the digestive wastes from the body. Chemical digestion
breaks down large, nonabsorbable food molecules into smaller, absorbable molecules that can pass
through the intestinal mucosa into the blood and lymph. Chemical digestion consists of numerous
chemical reactions catalyzed by enzymes.
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3. Enzymes selectively speed up the breakdown of specific nutrient molecules.
4. The end products of carbohydrate digestion are simple sugars (glucose); of fat digestion are fatty
acids and glycerol; and of protein digestion are amino acids.
ACTIVE LEARNING
Review Questions
1. The mucosa or mucous membrane of the esophagus is composed of tough, stratified, abrasionresistant epithelium. The mucosa of the remainder of the gastrointestinal tract is a delicate layer of
simple columnar epithelium designed for absorption and secretion. The submucosa is a connective
tissue layer that lies just below the mucosa and contains many blood vessels and nerves. The
muscularis is composed of two layers of muscle tissue. The wave-like contractions of the muscular
tissue, called peristalsis, move food and digestive juices through the digestive tract. Serosa is the
outermost covering of the gastrointestinal tract. In the abdominal cavity, the serosa is composed of
the visceral peritoneum.
2. The uvula and soft palate together prevent food and liquid from entering the nasal cavities.
3. Incisors have a sharp cutting edge; they have a cutting function. Canine teeth, sometimes called
cuspids, pierce or tear food that is being eaten or chewed. Premolars and molars have large, flat
surfaces with two or three grinding or crushing “cusps” on their surface. They provide extensive
breakdown of food in the mouth.
4. The crown is the portion of the tooth that is exposed and visible in the mouth and is covered with
enamel. The neck of the tooth is the narrow portion surrounded by gum tissue and joins the crown to
the root. The root fits into the socket of the upper or lower jaws.
5. Leukoplakia is characterized by white patches in the mouth that smokers often develop and may
develop into malignant tumors.
6. Gingivitis is the general term for an inflammation or infection of the gums. Periodontitis is the
inflammation of the periodontal membrane or ligament that anchors the tooth to the bone of the jaw.
7. Parotid glands, the largest of the salivary glands, lie just below and in front of each ear. The ducts
empty into the mouth opposite the second molar tooth on either side of the upper jaw. The
submandibular glands open into the mouth on either side of the lingual frenulum. The sublingual
glands open into the floor of the mouth.
8. The upper esophageal sphincter (UES) helps prevent air from entering the tube during respiration,
and the lower esophageal sphincter (LES) prevents backflow of acidic stomach contents.
9. Peristalsis is the wave-like muscle contractions of the muscularis layer that move food through the
gastrointestinal tract.
10. Triple therapy for ulcers includes bismuth subsalicylate (Pepto-Bismol), tetracycline, and either
metronidazole or clarithromycin.
11. The tube leading from the gallbladder is called the cystic duct. The tubes leading from the liver are
called the hepatic ducts. These ducts unite to form the common bile duct that drains bile into the
duodenum of the small intestine. Cholecystokinin is a hormone that stimulates the contraction of the
gallbladder that pushes bile into the duodenum.
12. The formation of gallstones is related to the amount of cholesterol in the blood. Severely obese
individuals produce higher levels of cholesterol and have a greater risk of developing gallstones than
people who are not obese. However, significant and rapid weight loss greatly increases the risk of
developing gallstones.
13. Hepatitis is a general term for the inflammation of the liver. It is characterized by jaundice, liver
enlargement, anorexia, abdominal discomfort, gray-white feces, and dark urine.
14. Pancreatic juice contains enzymes that digest all three major kinds of foods. It contains sodium
bicarbonate to neutralize the hydrochloric acid from the stomach.
15. Bacteria in the intestine can add nutrients from the breakdown of cellulose and other fiber. Bacteria
are responsible for the synthesis of some of the vitamin K needed for blood clot formation and
produce some of the B-complex vitamins.
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16. The seven subdivisions of the large intestine are (1) the cecum, (2) the ascending colon, (3) the
transverse colon, (4) the descending colon, (5) the sigmoid colon, (6) the rectum, and (7) the anal
canal.
17. The mesentery is an extension between the parietal and visceral layers of the peritoneum. It is
shaped like a giant, pleated fan. Its smaller edge attaches to the lumbar region of the posterior
abdominal wall. Its long, loose outer edge encloses most of the small intestine, anchoring it to the
posterior abdominal wall. The greater omentum is a pouch-like extension of the visceral peritoneum
from the lower edge of the stomach, part of the duodenum, and the transverse colon. It is shaped like
an apron and hangs down over the intestines and contains spotty deposits of fat.
18. Peritonitis is the inflammation of the peritoneum resulting from infection or another irritating condition.
Ascites is an abnormal accumulation of fluid in the peritoneal space.
19. Mechanical digestion breaks food into tiny particles, mixes them with digestive juices, moves them
along the alimentary canal, and eliminates digestive waste from the body. Chemical digestion breaks
down large nonabsorbable food molecules into molecules that are able to be absorbed by the
intestinal mucosa and moved into the blood or lymph.
20. Carbohydrate digestion begins in the mouth, where salivary amylase digests starch into maltose.
Because food spends so little time in the mouth, this digestion is usually incomplete. The pancreas
also produces amylase, and the digestion of starch is completed in the small intestine. The small
intestine produces the enzymes that complete the digestion of carbohydrates. These intestinal
enzymes—maltase, sucrase, and lactase—change double sugars into simple sugars, mainly glucose.
The end product of carbohydrate digestion is simple sugars, with the most abundant being glucose.
21. Fat digestion begins in the small intestine where bile, which is made in the liver and stored in the
gallbladder, emulsifies large droplets of fat into smaller droplets of fat. After this occurs, pancreatic
lipase splits the fat molecules into the end products of fat digestion, glycerol and fatty acids.
22. Protein digestion starts in the stomach. Rennin and pepsin are the two enzymes that cause the giant
protein molecules to break up into somewhat simpler compounds. Pepsin is made in an inactive
form, called pepsinogen, which is activated by the hydrochloric acid in the stomach. In the small
intestine, trypsin in pancreatic juice and peptidases in intestinal juice complete protein digestion. The
end products of protein digestion are amino acids.
23. After food is digested, it is absorbed through the mucous membrane lining of the small intestine into
the blood or lymph. Many salts and sodium are actively transported through the intestinal mucosa.
Water follows by osmosis. Other nutrients are also actively transported into the blood. Fats are
unable to enter the blood, so they enter the lymphatic vessels or lacteals found in the intestinal villi.
Critical Thinking
24. The small intestine would have to be unreasonably long to provide the same surface area that is
provided by the plicae, villi, and microvilli. Our abdominal cavity would have to be huge to
accommodate the small intestine. The other alternative (if the small intestine stayed the same length)
would be to pass huge amounts of food through the digestive tract. Because only very small portions
of food could be absorbed at one time, a large quantity of food would be required to provide adequate
nutrition.
25. Bile acts to emulsify fats, taking large droplets of fat and turning them into smaller particles. This
increases the surface area that is exposed so that lipase, the enzyme that digests fats, can make the
digestion process more efficient.
26. Lactase is necessary for the digestion of lactose sugar into simple sugar, so lactase is probably not
functioning properly. Foods that contain lactose, such as milk and milk products, should be avoided.
Chapter Test
1. digestion, absorption
2. frenulum
3. uvula, soft palate
4. crown, neck, root
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Answer Keys
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
parotid, submandibular, sublingual
submucosa
Mucosa
esophagus
fundus, body, pylorus
hydrochloric acid, pepsin
chyme
pylorospasm
duodenum, jejunum, ileum
villi
lacteals
common hepatic duct, cystic duct
sodium bicarbonate
transverse colon
mesentery, greater omentum
absorption
e. effect bile has on fat droplets
i. enzyme that is made in both the salivary glands and the pancreas and digests starch
j. enzyme that is made in the stomach and digests protein
k. hormone that stimulates the contraction of the gallbladder
b. enzyme that is made in the small intestine and digests protein
l. duct that connects the gallbladder to the common bile duct
f. enzyme that is made in the pancreas and digests protein
g. the final end product of carbohydrate digestion
d. the final end product of protein digestion
c. gland that produces bile
a. enzyme that is made in the pancreas and digests fat
h. one of the final end products of fat digestion
g. a general term for gum inflammation or infection
d. inflammation of the periodontal membrane
a. inflammation of the stomach and intestines
j. open wounds caused by gastric acid, often associated with Helicobacter pylori
i. inflammation of the gallbladder
b. a liver inflammation; B type is more serious than A type
c. inflammation of abnormal outpouchings in the large intestine
f. a general term for the inflammation of the large intestine
h. inflammation of the peritoneum
e. abnormal accumulation of fluid in the peritoneal space
Case Studies
1. Improper care of the teeth and gums may lead to gingivitis (gum inflammation). If untreated, the
gingivitis may progress to periodontitis, which causes loosening of the teeth. Teeth may also be lost
through a failure to treat caries (tooth decay), a condition that also results from poor dental hygiene.
2. Famotidine, like cimetidine, decreases secretion of stomach acid. Because hypersecretion of
stomach acid is the usual cause of progressive ulceration of the gastrointestinal lining, this treatment
should slow or stop the damage and allow healing of the ulcer. Because it is more potent than
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Answer Keys
cimetidine, smaller, less frequent doses are required. Sucralfate helps in the treatment of ulcers by
sticking to and protecting the areas of the gastrointestinal tract that have a damaged mucous coat—
specifically, the areas that already have damage (that is, the ulcer itself). The antipepsin effect
prevents the stomach enzyme, pepsin, from digesting the proteins in exposed tissues lining the
gastrointestinal tract and possibly perforating the gastrointestinal wall.
3. The barium swallow test, also called an upper GI study, stretches (fills) the stomach with barium
contrast material and makes it easily visible in x-ray photography. In a hiatal hernia, the bottom of the
esophagus may be abnormally stretched and the cardiac sphincter dilated. An x-ray photograph
would likely show the barium backing up into the lower esophagus. If stomach acid backed up in that
way, it would produce the heartburn symptom experienced by Fred. Backflow or reflux would more
likely occur when bending or reclining because gravity would pull the stomach contents toward the
esophagus. When an individual is standing up, gravity pulls the stomach contents away from the
esophagus.
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CHAPTER 19
QUICK CHECK
Page 513
1. Carbohydrates, fats, and proteins
2. Metabolism is the use the body makes of foods after they have been digested, absorbed, and
circulated to cells.
3. Answer may include any three of the following functions: The liver plays an important role in
mechanical digestion of lipids (bile), metabolism of all three kinds of foods, helps maintain a normal
blood glucose concentration, synthesizes several kinds of protein compounds, detoxifies the body of
various poisonous substances, and stores several substances, including iron and vitamins A and D.
Page 517
1. The series of chemical reactions that make up the process of glucose catabolism are glycolysis, citric
acid cycle, and electron transport system.
2. Energy is transferred from glucose to ATP in the form of high-energy electrons that enter a chain of
carrier molecules in the mitochondria.
3. Once absorbed into the body, proteins are broken down into amino acids. The body then builds
amino acids into complex protein compounds (enzymes and proteins that form the structure of the
cell).
4. Essential amino acids are those that must be in the diet.
Page 519
1. Most vitamins attach to enzymes or coenzymes and help them work properly.
2. Basal metabolic rate (BMR)
3. When the number of calories in your food intake equals the total metabolic rate (TMR), your weight
remains constant. When your food intake provides more calories than your TMR, you gain weight;
when your food intake provides fewer calories than your TMR, you lose weight.
Page 521
1. Anorexia nervosa is characterized by a chronic refusal to eat. Bulimia is characterized by an
insatiable craving for food alternating with periods of self-deprivation. Anorexia and bulimia are both
behavioral disorders.
2. Obesity is a risk factor for a variety of life-threatening diseases, including diabetes mellitus, many
forms of cancer, and heart disease.
3. Answer may include any eight of the following causes: Anorexia, dysphagia, gastrointestinal
obstruction, nausea, pain, poverty, social isolation, substance abuse, tooth problems, diarrhea,
glycosuria, hemorrhage, malabsorption, burns, fever, infection, trauma and surgery, and tumors
Page 523
1. Radiation (flow of heat waves away from the body); conduction (transfer of heat energy to the skin
and then the external environment); convection (transfer of heat energy to air that is continually
flowing away from the skin); and evaporation (absorption of heat by water)
2. The high body temperature associated with infectious fever is thought to enhance the body’s immune
system responses, eliminating pathogens.
3. Heat exhaustion results in the loss of water and electrolytes, which can cause weakness, vertigo,
nausea, loss of consciousness, and skeletal muscle cramps. Heatstroke can result in tachycardia,
headache, hot, dry skin, confusion, convulsions, and loss of consciousness.
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ACTIVE LEARNING
Review Questions
1. The chemical reactions that build food molecules into more complex chemical compounds constitute
the process of anabolism. All chemical reactions that release energy from food molecules make up
the process of catabolism.
2. The liver helps maintain normal blood glucose concentration; it carries on the first steps in protein and
fat metabolism. It also synthesizes and releases plasma proteins, detoxifies various poisonous
substances in the blood, and stores several substances, such as iron and vitamins A and D.
3. Glycolysis is the first step in carbohydrate metabolism. It occurs in the cytoplasm of the cell,
converting glucose into pyruvic acid, releasing energy. This process does not require oxygen.
4. The citric acid cycle is the second step in carbohydrate metabolism. It occurs in the mitochondria of
the cell and converts pyruvic acid into carbon dioxide, releasing energy. This process requires
oxygen.
5. Most of the energy released in the processes of glycolysis and the citric acid cycle is in the form of
high-energy electrons. The electron transport system almost immediately transfers the energy of the
electrons to molecules of adenosine triphosphate.
6. The energy transferred to adenosine triphosphate molecules (ATP) differs in two ways from the
energy stored in food molecules. The energy in ATP is stored very briefly, released almost
instantaneously, and can be used directly to do cellular work. The release of energy from food
molecules occurs much more slowly because it accompanies the long series of chemical reactions
that make up catabolism. Energy from food cannot be used directly to do cellular work.
7. Growth hormone, hydrocortisone, epinephrine, and glucagon are the most important hormones that
increase blood glucose.
8. Fats are primarily energy foods. If cells have inadequate amounts of glucose to catabolize, they
immediately shift to the catabolism of fat.
9. In a healthy person, proteins are catabolized to release energy to a very small extent. When fat
reserves are low, the body can start to use its protein molecules as an energy source.
10. Nonessential amino acids are necessary for life, but the body has the ability to make them from other
amino acids.
11. Any three of these water-soluble vitamins: thiamine, riboflavin, niacin, pantothenic acid, pyridoxine,
cyanocobalamin, the B-complex vitamins, biotin, folic acid, and vitamin C. Any three of these fatsoluble vitamins: A, D, E, and K.
12. Avitaminosis is a vitamin deficiency. Scurvy is a disorder caused by the deficiency of vitamin C. (Any
other disorder caused by a vitamin deficiency would also be correct.)
13. Vitamin A hypervitaminosis first manifests itself with dry skin, hair loss, anorexia, and vomiting. It
progresses to severe headaches, mental disturbances, liver enlargement, and occasionally cirrhosis
of the liver. Acute vitamin A hypervitaminosis is characterized by vomiting, abdominal pain, and
headache.
14. Any three of these minerals: calcium, chlorine, cobalt, copper, iodine, iron, magnesium, manganese,
phosphorus, potassium, sodium, or zinc.
15. Vitamins and minerals attach to enzymes and allow them to work properly. Minerals are also
necessary for nerve conduction and muscle contraction.
16. The basal metabolic rate is the rate at which food is catabolized under basal conditions. Basal
conditions occur when an individual is resting, but awake, not digesting food, and not adjusting to a
cold external body temperature. The total metabolic rate is the total amount of energy used by the
body per day. Total metabolic rate is related to the level of activity; the more active a person is, the
higher the total metabolic rate.
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17. Marasmus results from an overall lack of calories and proteins. It is characterized by progressive
wasting of muscle and subcutaneous tissue accompanied by fluid and electrolyte imbalances.
Kwashiorkor results from a protein deficiency in the presence of sufficient calories. It also causes
wasting of tissue, pronounced ascites, and flaking dermatitis.
18. Any three of these mechanisms: Heat can be lost from the skin by (1) radiation—the flow of heat
waves away from the body; (2) conduction—the transfer of heat energy to the skin and then to the
external environment; (3) convection—the transfer of heat energy to the air that is continually flowing
away from the body; or (4) evaporation—the absorption of heat by water (sweat) vaporization.
19. Malignant hyperthermia is an inherited condition characterized by abnormally increased body
temperature and muscle rigidity when exposed to certain anesthetics.
20. In heat exhaustion, the body is able to maintain a normal body temperature. In heat stroke, the body
is unable to maintain a normal body temperature and it can become dangerously high.
Critical Thinking
21. Absorption is the movement of food from the digestive system into the circulating fluids of the body,
either blood or lymph. Assimilation occurs when food molecules are moved from the blood and flow
into the cells, undergoing chemical changes there.
22. The hepatic portal system allows the blood that has just absorbed nutrients and other substances to
be processed by the liver before being distributed throughout the body. Thus, excess nutrients and
vitamins can be stored by the liver and toxins can be removed.
23. The diagram should be similar to Figure 19-2 on page 514 of the textbook.
24. The man weighed 180 pounds when he came back from vacation.
3300 x 10 = 33,000
2600 x 10 = 26,000
33,000 − 26,000 = 7000/3500 = 2 + 178 = 180
25. No, because any excess protein can be converted to glucose or fat. Weight gain or loss depends on
the total number of calories consumed minus the total number of calories burned. The source of the
calories could be carbohydrates, proteins, or fat.
Chapter Test
1. assimilation
2. Catabolism
3. prothrombin, fibrinogen
4. A, D
5. insulin
6. hypercholesterolemia
7. water, fat
8. Basal metabolic rate
9. total metabolic rate
10. convection
11. evaporation
12. Fat metabolism
13. protein
14. Nonessential amino acids
15. b. the part of carbohydrate metabolism that does not require oxygen
16. d. the part of carbohydrate metabolism that requires oxygen
17. c. process that converts high-energy molecules from the citric acid cycle into ATP
18. g. the part of the cell in which the citric acid cycle takes place
19. a. part of the cell in which glycolysis occurs
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Answer Keys
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
e. the body’s direct source of energy
h. glucose anabolism
f. molecule that results when adenine triphosphate loses a phosphate group
f. condition that results in the development of scurvy
k. a vitamin excess, usually involving fat-soluble vitamins
a. behavioral disorder characterized by a chronic refusal to eat
g. behavioral disorder characterized by insatiable craving for food alternating with self-deprivation;
many include food binges
c. type of malnutrition that results from an overall lack of calories
j. type of malnutrition that results from a lack of protein with sufficient total calories
b. increased body temperature caused by exposure to anesthetics
d. an overheating problem in which the body is dehydrated, but the body temperature is normal
i. overheating problem in which the body temperature can be as high as 105° F; potentially lifethreatening
h. a body temperature lower than 95° F
e. local tissue damage caused by ice crystals forming in the cell
Case Studies
1. Your friend is probably suffering from heat exhaustion. Because of the loss of fluid and electrolytes
while sweating, her body’s internal environment has become imbalanced, producing the symptoms of
nausea and muscle cramps (called heat cramps in this case). First aid for your friend should include
rest in a cool environment—perhaps in an air-conditioned building or in the shade—and plenty of
isotonic fluids (e.g., Gatorade).
2. Scurvy, an abnormal condition resulting from a deficiency of vitamin C, certainly can cause the loss of
teeth, as well as other forms of degeneration or injury. Without sufficient vitamin C, the body cannot
maintain the collagen fibers that hold together most of the body. The collagen forming the periodontal
ligament (PDL) that holds each tooth in its socket can loosen enough to make tooth loss unavoidable
(see Chapter 18). In the past, sailors were particularly vulnerable to scurvy because they often did
not have sufficient fresh vitamin C–containing foods available to them on long voyages.
3. The body requires an assortment of 20 amino acids to synthesize proteins needed for normal body
function. These proteins include functional proteins, such as enzymes, neurotransmitters, and protein
hormones, as well as structural proteins, such as collagen and keratin that hold the body together.
Some of these 20 amino acids can be manufactured by the body from compounds already present,
so they are considered nonessential in the diet. However, some of them cannot be made by the
body, so they are essential in the diet. Without sufficient essential amino acids in her diet, Andrea
may suffer consequences, such as an inability to produce one or more important proteins. She need
not be overly concerned, however, because the proper combination of vegetables can easily supply
all the essential amino acids Andrea needs.
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