ch 21
List the four basic processes of the digestive system, and describe each
1. Digestion is the chemical and mechanical breakdown of foods into smaller units. 2. Absorption is the active or passive transfer of substances from the lumen of the GI tract to the extracellular fluid. 3. Motility is the movement of material in the GI tract as a result of muscle contraction. 4. Secretion refers to both transepithelial transfer of water and ions from the ECF to digestive tract lumen and also the release of substances synthesized by GI epithelial cells.
Bile is A) secreted by hepatocytes only. B) manufactured by the gallbladder only. C) released into the stomach only. D) secreted by hepatocytes and manufactured by the gallbladder. E) secreted by hepatocytes, manufactured by the gallbladder, and released into the stomach.
A
Chief cells secrete A) pepsinogen. B) gastrin. C) mucus. D) hydrochloric acid. E) intrinsic factor.
A
In response to the hormone cholecystokinin, the pancreas secretes a fluid that contains A) enzymes. B) bicarbonate. C) bile. D) only proteinases. E) only amylase.
A
In the digestive system, HCl is released by ________, whereas HCO3- is secreted primarily from the ________. A) parietal cells of the stomach, pancreas B) the pancreas, parietal cells of the stomach C) parietal cells of the stomach, liver D) the liver, parietal cells of the stomach
A
Match each product with the cell or region that secretes or contains it. A. enzymes B. HCl C. HCO3- D. mucus E. more than one of these brush border
A
Match the hormone with the correct statement. A. gastrin B. cholecystokinin C. secretin D. motilin E. gastric inhibitory peptide Secreted by cells in the stomach
A
Match the structure to its function. A. mouth B. stomach C. rectum D. small intestine E. large intestine Carbohydrate digestion begins here.
A
________ are tiny droplets of fatty acids, monoglycerides, and bile salts. A) Micelles B) Enterocyte membranes C) Chylomicrons D) Lacteals
A
________ involve short segments of intestine that alternately contract and relax. They are responsible for ________. A) Segmental contractions, mixing B) Peristaltic contractions, pushing a bolus forward C) Segmental contractions, pushing a bolus forward D) Peristaltic contractions, mixing
A
________ is intestinal gas produced by bacteria in the colon during the metabolism of indigestible carbohydrates. A) Flatus B) Defecation C) Haustra D) Tenia Coli
A
Muna came down with the flu. She experienced severe vomiting, determined to be primarily stomach contents, for three days, and now is having chest pains. She is calling one of her symptoms "heartburn," but reported that it felt as if she had swallowed a small apple whole. Certain that she was having a heart attack, Muna rushed to the doctor. The doctor took her history and symptoms, and reassured her that she only had esophagitis. How did the physician conclude this? Is her blood pH higher or lower than normal?
Acid reflux irritated the esophageal lining, causing it to swell. Her pH is higher than normal due to loss of H+ from her stomach.
What would be the nutritional consequence of excessive antacid use
Antacids make the stomach pH higher than normal, which will interfere with protein digestion because the enzymes would not be as efficient.
A drug that blocks the action of carbonic anhydrase in parietal cells would result in A) a lower pH during gastric digestion. B) a higher pH during gastric digestion. C) decreased production of pepsinogen by chief cells. D) increased protein digestion in the stomach. E) decreased gastrin production
B
A drug that blocks the action of the hormone cholecystokinin would affect A) the amount of bile produced by the liver. B) pancreatic secretions. C) the level of intestinal gastrin. D) secretions of the duodenal glands. E) All of the answers are correct
B
Bile is produced in the ________ and stored in the ________. A) gallbladder, liver B) liver, gallbladder C) pancreas, hepatocytes D) hepatocytes, pancreas
B
Bile salts aid in the digestion of fats by ________ large fat droplets. A) generating B) emulsifying C) absorbing D) digesting fats within
B
Decreased levels of bile salts in the bile would interfere with digestion of A) protein. B) fat. C) carbohydrates. D) nucleic acids. E) vitamins and minerals
B
Diarrhea often accompanies intestinal infections. Why? A) The immune system increases the production of enzymes for added protection. B) Bacterial toxins enhance the secretion of Cl- from the cells, which causes water movement into the intestine. C) Dehydration of the body will kill the bacteria causing the infection. D) Loss of electrolytes will kill bacteria.
B
Digestion is essentially completed in the A) stomach. B) small intestine. C) large intestine. D) anus.
B
In response to the hormone secretin, the pancreas secretes a fluid that contains A) enzymes. B) bicarbonate. C) bile. D) only proteases. E) only amylase.
B
Maltose is broken down by maltase into two molecules of A) galactose. B) glucose. C) starch. D) amylase.
B
Match each product with the cell or region that secretes or contains it. A. enzymes B. HCl C. HCO3- D. mucus E. more than one of these parietal cells
B
Match the hormone with the correct statement. A. gastrin B. cholecystokinin C. secretin D. motilin E. gastric inhibitory peptide inhibits gastric emptying
B
Match the hormone with the correct statement. A. gastrin B. cholecystokinin C. secretin D. motilin E. gastric inhibitory peptide stimulates bile release
B
Match the structure to its function. A. mouth B. stomach C. rectum D. small intestine E. large intestine Fat digestion begins here.
B
Match the structure to its function. A. mouth B. stomach C. rectum D. small intestine E. large intestine Protein digestion begins here.
B
Most absorbed nutrients first enter the blood of the ________ system. A) lymphatic B) hepatic portal C) arterial D) immune
B
The gastric phase of gastric secretion is triggered by the A) sight, thought, or smell of food. B) entry of food into the stomach. C) entry of chyme into the small intestine. D) entry of chyme into the large intestine. E) release of cholecystokinin and secretin by the small intestine.
B
Vitamin ________ must be complexed with a protein called ________ to be absorbed from the small intestine. A) D, somatomedins B) B12, intrinsic factor C) K, hydrogen sulfide D) A, Olestra
B
Vomiting and diarrhea are similar since both A) use normal GI motility to move substances. B) work to rid the body of damaging agents. C) are stimulated by the CNS. D) are used to prepare patients for surgery.
B
Which of the following events does NOT occur when you swallow? A) Respiration is inhibited. B) The upper esophageal sphincter closes. C) The epiglottis closes. D) The lower esophageal sphincter relaxes.
B
Which of the following is an accessory organ of digestion? A) stomach B) pancreas C) spleen D) colon E) esophagus
B
After processing in the stomach, the gastric contents are referred to as A) feces. B) food. C) chyme. D) filtrate.
C
During the cephalic phase of gastric secretion, A) the stomach responds to distention. B) secretin inhibits parietal and chief cells. C) there is an increased flow of action potentials along the vagus nerve to the stomach. D) the intestine reflexively inhibits gastric emptying. E) production of gastric juice slows down.
C
Enzymatic digestion of fats involves ________, which breaks down ________. A) amylase, carbohydrates B) bile, cholesterol C) lipase, triglycerides D) pepsin, proteins
C
Functions of the large intestine include A) chemical digestion of chyme. B) temporary food storage. C) absorption of water and compaction of feces. D) absorption of most products of digestion. E) All of these answers are correct.
C
G cells of the stomach secrete A) cholecystokinin. B) secretin. C) gastrin. D) enterokinase. E) pepsin.
C
Most products of fat digestion are absorbed by A) capillaries. B) veins. C) lymphatic vessels. D) arterioles.
C
Nearly 90% of our dietary calories from fat are in the form of A) steroids. B) phospholipids. C) triglycerides. D) cholesterol. E) fat-soluble vitamins.
C
Nutrient absorption occurs primarily in the A) stomach. B) liver. C) small intestine. D) large intestine. E) stomach and small intestine.
C
Rugae, plicae, and villi are all features that accomplish A) secretion of enzymes. B) secretion of hormones. C) an increase in surface area. D) immune function. E) mechanical digestion
C
Cholesterol is absorbed without being digested into smaller pieces. How does this compare to absorption of carbohydrates and proteins? Which characteristic of cholesterol suggests it would be transported by simple diffusion? What is the evidence that transport proteins are involved in cholesterol absorption? Does this discovery rule out transport by simple diffusion?
Carbohydrates are digested to monosaccharides before they are absorbed. Proteins are absorbed as amino acids, di- or tripeptides, or even oligopeptides. As a lipid, cholesterol can dissolve in the phospholipid bilayer and therefore cross membranes by simple diffusion. The drug ezetimibe inhibits cholesterol absorption, suggesting there must be a membrane transporter. This discovery does not rule out additional transport of cholesterol by simple diffusion, but does suggest there is a significant amount of transport dependent upon a transport molecule.
Essential nutrients are those that our cells require but cannot make, and thus they must be present in the diet. Only some amino acids and some fatty acids are essential. What does that suggest about extreme diets that eliminate fats or proteins? What does that suggest about our carbohydrate intake? Describe the typical American diet, in terms of relative amounts of ingested carbohydrates, fats, proteins, and nucleic acids. Propose some explanations for why one of those is predominant.
Complete elimination of proteins or fats would eventually be fatal. Carbohydrates need not be consumed at all, from the standpoint of essential nutrients. In reality, however, a carbohydrate-free diet would cause metabolic problems because of consequences of manufacturing glucose from lipids and proteins, as described in Chapter 22 in the text. About half of the typical dietary intake is carbohydrate, with most of the remainder in the form of fats and proteins. Carbohydrates are the primary molecule in plant products, which makes up most of what we eat because of abundance and price.
Identify the answer choice that lists the GI functions that are most closely regulated by the body. A) absorption and motility B) digestion and motility C) secretion and digestion D) motility and secretion E) motility, secretion, and digestion
D
Match each product with the cell or region that secretes or contains it. A. enzymes B. HCl C. HCO3- D. mucus E. more than one of these goblet cells
D
Match the following structures with their functions. A. pancreas B. pylorus C. rectum D. small intestine E. stomach organ where most digestion occurs
D
Match the structure to its function. A. mouth B. stomach C. rectum D. small intestine E. large intestine Carbohydrate digestion is completed here.
D
Match the structure to its function. A. mouth B. stomach C. rectum D. small intestine E. large intestine Fat digestion is completed here.
D
Match the structure to its function. A. mouth B. stomach C. rectum D. small intestine E. large intestine Protein digestion is completed here.
D
Mucus functions in A) protection only. B) lubrication only. C) enzyme activation only. D) protection and lubrication. E) protection, lubrication, and enzyme activation.
D
The ________ is a significant site of absorption of water and electrolytes, but NOT of nutrients. A) mouth B) stomach C) small intestine D) large intestine E) None of the answers are correct.
D
The enzyme that digests starch into disaccharides is A) lactase. B) maltase. C) sucrose. D) amylase.
D
The exocrine portion of the pancreas consists of lobules called ________, which secrete ________. A) acini, hormones B) islets, digestive enzymes C) islets, hormones D) acini, digestive enzymes
D
The primary products of protein digestion are ________, ________, and ________. A) polysaccharides, disaccharides, monosaccharides B) triglycerides, fatty acids, glycerol C) nucleic acid polymers, DNA, RNA D) free amino acids, dipeptides, tripeptides
D
The release of many GI tract hormones is stimulated by a particular food or substance. Which hormone is INCORRECTLY paired with its stimulus? A) CCK — fatty foods B) secretin — acid in the small intestine C) GIP — glucose in the small intestine D) motilin — acid in the stomach E) gastrin — peptides and amino acids
D
Amylases, the enzymes used to digest carbohydrates, are secreted by A) salivary glands into the mouth only. B) gastric glands into the stomach only. C) the pancreas into the intestine only. D) salivary glands into the mouth and gastric glands into the stomach. E) salivary glands into the mouth and the pancreas into the intestine.
E
An enzyme that will digest proteins into amino acids is A) lipase. B) amylase. C) nuclease. D) maltase. E) carboxypeptidase.
E
Bicarbonate secretion A) neutralizes acid entering from the stomach into the duodenum. B) is secreted by apical Cl--HCO3- exchanger. C) is not dependent on high levels of carbonic anhydrase to maintain bicarbonate production. D) is secreted by the acinar cells. E) neutralizes acid entering from the stomach into the duodenum and is secreted by apical Cl--HCO3- exchanger.
E
Match each product with the cell or region that secretes or contains it. A. enzymes B. HCl C. HCO3- D. mucus E. more than one of these pancreatic cells
E
Match the following structures with their functions. A. pancreas B. pylorus C. rectum D. small intestine E. stomach Chyme is released from here.
E
Powerful contractions that occur a few times each day in the colon are called A) segmentation. B) tonic contractions. C) phasic contractions. D) peristalsis. E) mass movements.
E
Saliva secretion is primarily a result of A) increased sympathetic stimulation. B) decreased parasympathetic stimulation. C) increased somatic motor stimulation. D) decreased somatic motor stimulation. E) increased parasympathetic stimulation.
E
The primary complex carbohydrate ingested and digested by people is A) fiber. B) glycogen. C) glucagon. D) cellulose. E) starch.
E
Name two functions of cholecystokinin
Enhances satiety, stimulates gallbladder contraction and pancreatic enzyme secretion, and inhibits gastric emptying and acid secretion. See Table 21.1 in the chapter
Proteins must first be enzymatically degraded to single amino acids before entering the capillaries of the hepatic portal system. Is this true or false? What is the significance of this? Is absorption of carbohydrates and lipids restricted to monomers? Explain.
False. Absorption of small peptides allows peptides to provoke food allergies. The transporters for peptides are also responsible for absorption of some drugs. Carbohydrates are digested to monosaccharides because there are no transporters for larger carbohydrates. Lipids are absorbed as cholesterol, fatty acids, and monoglycerides, primarily by simple diffusion because they are lipophilic.
A condition known as lactose intolerance is characterized by painful abdominal cramping, gas, and diarrhea. The cause of the problem is an inability to digest the milk sugar, lactose. How would this cause the observed symptoms? Why is yogurt less likely to trigger the symptoms
If an individual cannot digest lactose, then the sugar will pass through to the large intestine in an undigested form. The presence of the extra sugar in the chyme increases the osmolarity of the chyme, resulting in less water being reabsorbed by the intestinal mucosa. The bacteria that inhabit the large intestine can metabolize the lactose, and in the process they produce large amounts of carbon dioxide. The gas overstretches the intestine, which stimulates local reflexes that increase peristalsis. The combination of more fluid contents and increased peristalsis produces the symptom of diarrhea. The overexpansion of the intestine by gas causes the severe pain and abdominal cramping, and of course, the increase in intestinal gas release is directly related to increased gas production by the bacteria. Yogurt contains bacteria that digest the lactose prior to the consumption of the yogurt.
List the six types of epithelial cells associated with gastric glands. Briefly describe each one's role in the stomach.
Parietal cells secrete HCl and intrinsic factor; chief cells secrete pepsinogen and gastric lipase; D cells secrete somatostatin; ECL cells secrete histamine; G cells secrete gastrin; mucous cells secrete mucus and bicarbonate
Name the proenzymes secreted by the pancreas. Which one is involved in the activation of the other proenzymes? What are their active forms?
Proenzymes include: trypsinogen, chymotrypsinogen, procarboxypeptidase, procolipase, and prophospholipase. When it comes into contact with enteropeptidase in the brush border of the intestine, trypsinogen is converted to trypsin, which then activates the other proenzymes. The pathway can be found in Figure 21.14 in the chapter.
Where does carbohydrate digestion begin? Which enzyme is involved, and which reaction does it catalyze?
Salivary amylase is secreted into the mouth and digests large glucose polymers, like starch, into smaller glucose chains and the disaccharide maltose
Cody has always carefully controlled her caloric intake, and is lean. During her unplanned pregnancy, she continued to eat the same, hoping that taking prenatal vitamins and minerals would ensure that her fetus would grow normally. Her only complication during pregnancy was persistent constipation and consequent hemorrhoids. She gained only the minimum weight suggested by her doctor, and delivered a healthy, full-term infant; her pre-pregnancy weight was rapidly reestablished. Propose an explanation for how she managed to gain enough weight, did not violate the law of conservation of mass, and for her only complication. What does this suggest about "eating for two" that some pregnant women do?
She must have inefficiently absorbed calories prior to her pregnancy, losing many potential calories in her feces. When she became pregnant, one of her physiological changes included an increase in nutrient (and thus calorie) absorption. This would also contribute to her constipation, as her feces retained less water than normal and thus were more difficult to eliminate. It is not possible for her to have gained more weight than she ate; no one can violate the law of conservation of mass. Most obstetricians recommend only a slight increase in calories during pregnancy for this reason, and women who indulge in overeating too often are likely to gain unnecessary body fat and may produce a fetus that is larger than it should be.
In some severe cases, a person suffering from stomach ulcers may have surgery to cut the branches of the vagus nerve that innervates the stomach. How would this help the problem
The vagus nerve carries neurons of the parasympathetic nervous system. These neurons control gastric secretions, notably the secretion of acid and enzymes. Severing these branches would eliminate neural stimulation from the central nervous system, thus eliminating the release of gastric fluids in response to anxiety and other higher-order stimuli when there is no food in the stomach. Normal digestive function would still occur, governed by various hormones and intramural neural reflexes.
Eric has had trouble sleeping the last two nights and is currently experiencing heart burn which he attributes to the stress of being in finals week and eating too much pizza. His lab partner in Physiology class tells him he should take some diphenhydramine (Benadryl) before he goes to bed because that will help him sleep and his upset stomach. Is this a good suggestion or not?
While longstanding heartburn or insomnia may both be symptoms of more severe underlying conditions that require a visit to a health professional, his lab partner is correct. Diphenhydramine is an antihistamine that is found in many over-the-counter sleep medications. It has anticholinergic properties that could block vagus nerve stimulation preventing acid production.
