Deck 15: The Digestion and Absorption of Food

Question 1

Andrew has his gall bladder removed after developing several large gall stones.After surgery,he cannot release large batches of bile into the duodenum,instead,bile is added slowly in small amounts.Which of the following might be TRUE?

A)Carbohydrate digestion may be compromised.
B)He may become deficient in water-soluble vitamins such as B₁₂.
C)He may become deficient in fat-soluble vitamins such as vitamin E.
D)He may start to suffer from protein deficiency.
E)None of these would occur.

Answer 1

C

Question 2

Andrew has his gall bladder removed after developing several large gall stones.After surgery,he cannot release large batches of bile into the duodenum,instead,bile is added slowly in small amounts.What nutrient group might Andrew have trouble digesting when consumed in larger quantities?

A)Lipids
B)Proteins
C)Carbohydrates
D)Nucleic acids
E)None of these

Answer 2

A

Question 3

Which occurs mainly in the small intestine?

A)Gastrin is secreted.
B)H⁺ is secreted from epithelial cells into the lumen.
C)Pepsinogen is activated.
D)Acidic chyme is neutralized.
E)Bile salts are manufactured.

Answer 3

D

Question 4

Susan recently had bariatric surgery which removed 85% of her stomach tissue and left her with a much reduced stomach volume.Which of the following is TRUE of Susan post-surgery?

A)She is not able to completely digest proteins and amino acids.
B)Her chyme will tend to become more acidic than before the surgery.
C)She will have a reduced ability to absorb water from her meals.
D)She will have a reduced ability to form her food into a bolus.
E)She will be able to store less ingested foods and will require smaller,more frequent meals.

Question 5

What structure secretes the enzyme that breaks down starch to smaller carbohydrates?

A)The esophagus
B)Pancreatic exocrine cells
C)Pancreatic duct cells
D)The liver
E)The large intestine

Question 6

Which is NOT a function performed by saliva?

A)Moistening and lubricating food for swallowing
B)Starch digestion
C)Enabling the sense of taste
D)Killing bacteria
E)Emulsifying lipids

Question 7

Julia has just been diagnosed with anemia.Oddly,during her appointment her doctor kept talking about her digestive system and some item that was not being produced in adequate amounts.Julia can't remember what digestive secretion is to blame for her anemia.Which of the following is the most likely culprit?

A)HCl
B)Lipase
C)Bile
D)Amylase
E)Intrinsic factor

Question 8

Sarah is taking antacids every day.This habit is raising her stomach and duodenal pH close to neutral.Which of the following enzymes may have decreased activity?

A)Amylase
B)Lipase
C)Trypsin
D)Pepsin
E)Chymotrypsin

Question 9

Which of the following molecules crosses the luminal membrane of intestinal cells by facilitated diffusion?

A)Glucose
B)Lactose
C)Fructose
D)Galactose
E)Maltose

Question 10

Which accurately describes lipase?

A)It is mainly produced in the liver,and secreted into the small intestine.
B)It emulsifies lipids.
C)It is secreted by the endocrine pancreas.
D)It is produced in the exocrine pancreas,and catalyzes the degradation of chylomicrons into proteins and fats. 
E)It catalyzes the breakdown of triglycerides into monoglycerides and free fatty acids.

Question 11

Which of the following statements about the transport of the absorbed products of fat digestion is TRUE?

A)Free fatty acids and monoglycerides are transported to the liver via the hepatic portal vein.
B)Products of fat digestion first go to the lymph system,and then to the veins leading to the heart.
C)Triglycerides are transported to the liver via the hepatic portal vein to be processed.
D)Free fatty acids and monoglycerides are assembled into triglycerides before they are absorbed from the lumen of the gut into epithelial cells lining the tract.
E)Products of fat digestion are absorbed in the distal portion of the ileum,bound to intrinsic factor.

Question 12

You're going hiking and want to pack emergency food in case you get lost or the hike takes longer than you anticipate.Your goal is to pack a food that will have the biggest increase on your blood glucose level to be able to supply your hiking muscles with glucose for cellular respiration.Which of the following foods will lead to the biggest and most immediate increase in blood glucose?

A)A snack rich in lipids,such as slices of cheese
B)A snack rich in protein,such as a dried meat stick
C)A snack rich in digestible polysaccharides such as a cooked potato
D)All of these will have equal impacts on blood glucose level
E)A snack rich in cellulose,such as a bag of celery

Question 13

Iron is stored in the body mainly as a protein-iron storage complex called

A)glycogen.
B)hemochromatosis.
C)myoglobin.
D)transferrin.
E)ferritin.

Question 14

Which is NOT true about receptors that mediate digestive reflexes?

A)They are located in the gastrointestinal tract wall.
B)They include chemoreceptors,osmoreceptors,and mechanoreceptors.
C)They may relay information to integrative centers in the CNS or to the enteric plexuses.
D)They may be endocrine cells.
E)They only activate feedforward pathways.

Question 15

Which of the following processes is NOT associated with gastrointestinal function?

A)Digestion
B)Filtration
C)Secretion
D)Motility
E)Absorption

Question 16

Which of the following statements regarding protein digestion and absorption is TRUE?

A)Only the exocrine pancreas produces enzymes that can digest proteins.
B)After absorption,the products of protein digestion are carried by blood directly to the liver.
C)Pepsin digests protein mainly in the small intestine.
D)The enzymes that digest protein are secreted in active form.
E)Free amino acids are the only product of protein digestion that can be absorbed from the lumen into intestinal epithelial cells.

Question 17

Which of these is a function of intrinsic factor?

A)It is secreted by salivary glands,and is necessary for digestion of vitamin B₁₂.
B)It is secreted by parietal cells in the gastric mucosa,and its main function is causing insulin release.
C)It is secreted in the stomach,and its main function is activating pepsinogen into pepsin.
D)It is secreted by the small intestine mucosa,and its main function is initiating the intrinsic electrical activity of the pacemaker cells in the stomach. 
E)It is secreted in the stomach,and a deficiency of it would cause anemia.

Question 18

The main source of enzymes that cleave disaccharides into monosaccharides is

A)the pancreas.
B)the liver.
C)gastric secretory cells.
D)the luminal membrane of epithelial cells in the small intestine.
E)the salivary glands.

Question 19

Sarah has been diagnosed with pancreatic cancer.The first treatment is to remove 90% of her pancreatic tissue surgically.Due to the loss of exocrine tissue,which of the following foods will Sarah have more difficulty digesting post-surgery?

A)Lipids
B)Proteins and peptides
C)Starches
D)All of these

Question 20

Which of the following statements regarding digestion and absorption of carbohydrates is TRUE?

A)Carbohydrate digestion begins in the stomach.
B)Lactose intolerance results from an insufficiency of the enzyme amylase.
C)Digestible polysaccharides are broken down into the monosaccharides glucose,galactose,and fructose,which can be absorbed.
D)Sucrose is the main form of carbohydrate that can be absorbed by active transport across the intestinal epithelium.
E)Cellulose from plants is a polymer of glucose that can be easily digested and absorbed by the human GI tract.

Question 21

Which of the following statements concerning secretin is correct?

A)The most potent stimulus for secretin secretion is the presence of fat in the duodenum.
B)Secretin is the most potent stimulus for pancreatic digestive enzyme secretion.
C)Secretin is the most potent stimulus for pancreatic HCO₃⁻ secretion.
D)Secretin stimulates secretion by the parietal and chief cells.
E)Secretin stimulates gastrin secretion by parietal cells.

Question 22

Which of the following statements regarding lipid digestion and absorption is TRUE?

A)The presence of fatty acids in the duodenum stimulates the secretion of CCK,which in turn stimulates secretion of pancreatic enzymes.
B)The presence of fatty acids in the duodenum stimulates the secretion of secretin,which in turn stimulates contraction of the gallbladder.
C)The presence of fatty acids in the duodenum stimulates the secretion of gastrin,which in turn stimulates bile synthesis in the gallbladder.
D)The presence of fatty acids in the duodenum stimulates emptying of the stomach.
E)The presence of fatty acids in the stomach stimulates the secretion of secretin,which inhibits motility of the large intestine.

Question 23

Which of the following statements regarding hormonal regulation of gastrointestinal function is TRUE?

A)An increase of H⁺ in the small intestine stimulates secretion of the hormone secretin,which in turn stimulates HCO₃⁻ secretion by the pancreas.
B)The presence of fatty acids in the stomach stimulates secretion of CCK,which in turn stimulates enzyme secretion by cells in the antrum of the stomach.
C)The presence of amino acids in the small intestine stimulates secretion of gastrin,which in turn stimulates HCl secretion by parietal cells.
D)The presence of fatty acids in the small intestine stimulates the secretion of the hormone secretin,which causes contraction of the gallbladder.
E)The hormone somatostatin stimulates the secretion of H⁺ into the lumen of the stomach.

Question 24

The type of smooth muscle contraction occurring in the esophagus during swallowing is called

A)peristalsis.
B)mass movement.
C)segmentation.
D)distension.
E)eccentric.

Question 25

During the contractions of gastric emptying

A)the stomach is induced to contract by increased sympathetic activity.
B)the pyloric sphincter opens to allow stomach contents to pass quickly and completely into the duodenum.
C)the pyloric sphincter closes to allow only a small amount of liquefied chyme to pass into the duodenum with each contraction of the stomach.
D)the strength of stomach wall contractions is increased when the duodenum secretes cholecystokinin.
E)the strongest contractions are in the antrum of the stomach because the intrinsic pacemaker frequency is fastest there.

Question 26

Which of the following statements regarding neural regulation of gastrointestinal function is TRUE?

A)Networks of neurons in the wall of the GI tract innervate the wall's smooth muscle.
B)Smooth muscle of the GI tract is innervated by both sympathetic and somatic motor nerves.
C)If the autonomic nerves to the GI tract were cut,digestion and absorption of food could no longer take place.
D)The nerve plexus of the GI tract exists in a single layer,just outside of the serosa.
E)There are no afferent neuronal pathways from the GI tract to the central nervous system.

Question 27

Which of the following plays a central role in stimulating the secretion of the hormone gastrin?

A)The hormone secretin
B)The hormone cholecystokinin (CCK)
C)Distention of the stomach
D)An increase in [H⁺] in the lumen of the stomach
E)Histamine

Question 28

Which of these are secretions of the parietal cells of the gastric mucosa?

A)HCl and pepsinogen
B)pepsinogen and intrinsic factor
C)gastrin and intrinsic factor
D)HCl and gastrin
E)HCl and intrinsic factor

Question 29

Which is TRUE regarding the secretion of HCl in the stomach?

A)H⁺ is actively transported into the gastric lumen by ATPase pumps in the mucosal membrane.
B)H⁺ is actively cotransported into the lumen by secondary active transporters coupled to K⁺.
C)The pH of the blood leaving the area of the parietal cells is lower than the normal ECF value of 7.4.
D)H⁺ diffuses passively from mucosal epithelial cells into the lumen of the stomach,following Cl⁻.
E)Cl⁻ and HCO₃⁻ are exchanged across the luminal membrane of epithelial cells via a passive transport protein.

Question 30

Which is TRUE regarding the three phases of the control of HCl secretion?

A)In the intestinal phase,an increase in osmolarity of the contents of the duodenum decreases HCl secretion.
B)In the gastric phase,distension of the stomach decreases HCl secretion.
C)In the cephalic phase,increased nutrient concentration in the duodenum stimulates HCl secretion.
D)In the intestinal phase,increased peptide concentration in the stomach inhibits HCl secretion.
E)In the gastric phase,decreased H⁺ concentration in the stomach inhibits HCl secretion.

Question 31

Which of the following pathways is activated during the cephalic phase of gastrointestinal control?

A)Sympathetic nerves to enteric nervous system
B)Secretion of cholecystokinin
C)Secretion of secretin
D)Parasympathetic nerves to enteric nervous system
E)Short reflexes between the small intestine and stomach

Question 32

You are a new pediatrician at an office where you've inherited cases from a previous doctor and are sitting down to go through case files.Today you'll be seeing Trevor,a toddler who has been diagnosed with a disease called megacolon.Back in medical school you learned that megacolon can be characterized by partial paralysis of the the nerves found within the wall of the GI system.Which of the following is likely to be among Trevor's symptoms?

A)Incomplete denaturation of ingested proteins
B)Discolored feces due to lack of Bile
C)Diarrhea
D)Constipation and a swollen-looking belly
E)Abnormal blood glucose regulation

Question 33

Which of the following is NOT a part of the swallowing reflex?

A)Respiration is inhibited.
B)The glottis closes.
C)The upper esophageal sphincter relaxes.
D)The lower esophageal sphincter relaxes.
E)The pyloric sphincter relaxes.

Question 34

Which of the following statements about neural control of digestion is FALSE?

A)Parasympathetic stimulation is excitatory to digestion.
B)Sympathetic stimulation is generally inhibitory to digestion.
C)Local neural networks (nerve plexuses)regulate digestive functions.
D)Nerve plexuses receive input from the autonomic nervous system
E)Parasympathetic stimulation inhibits GI exocrine gland secretions.

Question 35

Which of the following would lead to an increase in the secretion of gastrin?

A)Adding chyme to the duodenum
B)An increase in the presence of starch in the lumen of the stomach
C)An increase in the presence of lipids in the duodenum
D)An increase in the presence of peptides in the duodenum
E)An increase in the presence of peptides in the stomach

Question 36

Which is caused by increased levels of the hormone cholecystokinin?

A)Contraction of the sphincter of Oddi
B)Inhibition of pancreatic enzyme secretion
C)Contraction of the gallbladder
D)Secretion of HCO₃⁻ from the pancreatic duct cells
E)Secretion of gastric H⁺

Question 37

Anders is born with a mutation in the gene for CCK and he produces and secretes an inactive form of this hormone.Which of the following would be TRUE of Anders' digestion?

A)A reduction in the release of pancreatic enzymes
B)A reduction in the release of HCl
C)An increase in the release of bile
D)An increase in the amount of bile salts present in the bile
E)None of these would occur

Question 38

Which occurs during the secretion of hydrochloric acid by gastric epithelial cells?

A)There is a decrease in the pH of blood in the hepatic portal circulation.
B)Bicarbonate ions are secreted into the hepatic portal circulation.
C)Chloride ions are pumped from the cytosol of the gastric epithelial cells into the hepatic portal circulation blood.
D)Both H⁺ and K⁺ are actively pumped from the epithelial cell cytosol into the lumen of the stomach.
E)Vesicles containing H⁺/K⁺ -ATP-ase proteins are endocytosed into vesicles within the gastric epithelial cells.

Question 39

Which of the following is secreted by the chief cells of the gastric mucosa?

A)Pepsinogen
B)HCl
C)Intrinsic factor
D)Gastrin
E)Pepsin

Question 40

During the cephalic phase of gastric stimulation,which of the following does NOT occur?

A)Seeing,smelling,and/or tasting food reflexively increase(s)gastric acid secretion.
B)Parasympathetic stimulation of secretory cells in the gastric mucosa occurs.
C)Gastrin is secreted into the gastric lumen.
D)HCl is secreted into the gastric lumen.
E)Pepsinogen is secreted into the gastric lumen.

Question 41

Elizabeth suffers from a gastric ulcer.She experiences pain during the times when acid is released into the stomach.Which of the following times is Elizabeth likely to experience the most pain?

A)Elizabeth is likely to be in the same amount of pain all the time.
B)During the digestion of a high-fat meal,such as greasy French fries.
C)During the digestion of a high-protein meal,such as a steak.
D)During periods of hunger.
E)During digestion of a high-carbohydrate meal,such as a bagel.

Question 42

Elizabeth has been diagnosed with a gastric ulcer.Carl has been diagnosed with a duodenal ulcer.Both of them are

A)treated by interventions that inhibit digestive enzymes.
B)caused by hypersecretion of gastric acid.
C)treated by interventions that inhibit acid secretion.
D)caused by removal of the gallbladder.
E)found in the large intestine.

Question 43

Bicarbonate is

A)secreted into the lumen by gastric epithelial cells and into the interstitial fluid by pancreatic duct cells.
B)secreted into the lumen by pancreatic acinar (exocrine)cells,and into the interstitial fluid by pancreatic duct cells.
C)secreted into the lumen by pancreatic duct cells,and into the interstitial fluid by pancreatic acinar (exocrine)cells.
D)secreted into the interstitial fluid by gastric epithelial cells,and into the lumen by pancreatic duct cells.
E)secreted into the lumen by both gastric epithelial cells and pancreatic duct cells.

Question 44

In which region(s)of the GI tract do peristaltic contractions occur?

A)The small intestine
B)The large intestine
C)The stomach
D)The esophagus
E)All of these options are correct.

Question 45

Which of the following breakfasts would likely remain in the stomach longest?

A)Toast,orange juice,and coffee
B)Fried eggs,bacon,and hash browns
C)A bowl of cereal with skim milk
D)A boiled egg,toast,and juice
E)The type of meal has no effect on the rate of gastric emptying.

Question 46

Which of the following would be most likely to cause metabolic alkalosis?

A)Severe vomiting
B)Severe diarrhea
C)Hyperventilation
D)Strenuous exercise
E)Hypoventilation

Question 47

A person without a gallbladder

A)cannot secrete bile.
B)cannot store bile.
C)will have no difficulty digesting a large,fat-rich meal.
D)cannot digest fats.
E)cannot store lipase.

Question 48

There is an E.coli outbreak in the town of Springfield when almost all the Springfield residents contracted food poisoning at a town hall meeting.E.coli causes severe diarrhea.The local Springfield pharmacy is ordering supplies to stock its shelves as its customers work their way through the outbreak.Which of the following would be helpful for the pharmacy to stock?

A)Antacids to help the residents recover from acidosis
B)Acidic foods such lemonade to help the residents recover from alkalosis
C)Diuretic drugs to help the residents recover from high blood pressure
D)Vitamin B₁₂ supplements to help the residents recover from this specific deficiency
E)All of these would be helpful

Question 49

The primary kind of motility in the stomach during digestion of a meal is

A)peristalsis.
B)segmentation.
C)relaxation of the pyloric sphincter.
D)mass movement.
E)regurgitation.

Question 50

Which is TRUE about gastric motility?

A)The basic electrical rhythm of the gastric smooth muscle (three depolarizations per minute)is the same regardless of whether or not food is present.
B)Gastric contractions are strongest in the fundus of the stomach.
C)The force of contraction is decreased by gastrin and increased by enterogastrones.
D)When a wave of excitation reaches the pyloric sphincter,action potentials become inhibitory and the sphincter opens wide to allow chyme to exit.
E)The term "slow waves" refer to gastric contractions,while "pacemaker" refers to gastric action potentials.

Question 51

Kim had her gallbladder removed last month and has been experiencing some changes to her digestion.One thing that is particularly noticeable is that she has noticed

A)she has trouble digesting high-protein foods such as egg whites.
B)she has trouble digesting high-carbohydrate foods such as rice and pasta.
C)her feces have a different color.
D)she feels more energetic and healthy.
E)an increase in her appetite.

Question 52

The primary kind of motility in the small intestine during digestion of a meal is

A)peristalsis.
B)segmentation.
C)receptive relaxation.
D)migrating motility complex.
E)mass movement.

Question 53

Following diagnosis with pancreatic cancer,Neil had a large portion of his pancreas removed.All of the following will now be found in lower amounts in Neil's GI tract,except one.Which of the following will NOT be affected?

A)Bicarbonate ions
B)Amylase
C)Bile salts
D)Trypsinogen
E)Lipase

Question 54

Julia comes to see her doctor with a variety of symptoms.Her doctor eventually diagnoses her with gallstones.Which of the following was NOT one of Julia's symptoms?

A)Lactose intolerance
B)Abdominal pain
C)Difficulty digesting high-fat meals
D)Nutritional deficiencies
E)Jaundice

Question 55

Which of the following statements about pancreatic enzymes is FALSE?

A)Trypsinogen is secreted in an inactive form.
B)Pancreatic amylase digests carbohydrates.
C)Pancreatic lipase digests fats.
D)Except for trypsinogen,other proteolytic enzymes are secreted in active form.
E)Trypsinogen is activated by enterokinase.

Question 56

Segmentation of the small intestine

A)occurs only between meals,and functions to stimulate the secretion of gastrin and the resulting mass movements that empty the large intestine.
B)occurs at a rate of 3 contractions per minute throughout the small intestine,although the strength of contractions is much greater in the ileum,which has a much thicker layer of smooth muscle in its walls.
C)functions mainly to prevent any forward movement of chyme,so that all digestion and absorption is complete before undigestible materials move into the jejunum.
D)are peristaltic movements that sweep undigestible materials out of the small intestine between meals.
E)mixes chyme with digestive enzymes,brings food molecules near the wall for absorption,and slowly moves small intestine contents toward the cecum.

Question 57

Which of the following is the most potent inhibitor (directly or indirectly)of gastric motility and emptying?

A)Fat in the duodenum
B)Acid in the stomach
C)Carbohydrate in the stomach
D)Gastrin
E)Distension of the stomach

Question 58

Bile is synthesized and secreted by the

A)gallbladder.
B)gastric mucosa.
C)pancreas.
D)duodenum.
E)liver.

Question 59

You are working for an educational video company and you've been asked to go to the hospital imaging center to obtain video of segmentation.The imaging center technician asks you where in the GI tract she should image and when during digestion? You tell her that to obtain the best video of segmentation she should record

A)the esophagus during swallowing.
B)the stomach during digestion of a meal.
C)the small intestine as chyme moves past the pyloric sphincter.
D)the large intestine during fecal compaction.

Question 60

Following diagnosis with pancreatic cancer,Neil had a large portion of his pancreas removed.Which of the following hormones will now be found in lower amounts?

A)Vasopressin
B)Thryoid hormone
C)CCK
D)Oxytocin
E)Insulin

Question 61

The pH of the contents of the stomach lumen is considerably higher than that of interstitial fluid.

Question 62

The exact causes of inflammatory bowel diseases continue to be explored,but it is relatively clear that

A)it is equally common among people of all ages and racial groups within the population.
B)it is likely to result from a combination of environmental and genetic factors.
C)individuals suffering from its effects are largely experiencing the consequences of the absence of immune mechanisms in the gastrointestinal tract.
D)it can be easily diagnosed since its symptoms are always very specific and the affected areas are always limited to a very focused area within the small intestine.
E)the cause is allergy to a single particular food,and patients get immediate relief by simply not eating that food.

Question 63

Lactose intolerance

A)is an inability to digest milk sugar.
B)is most common in very young children.
C)results from the inability to secrete insulin.
D)results from removal of the gallbladder.
E)is an inability to digest proteins.

Question 64

The volume of fluids secreted by the gastrointestinal tract in a typical day is far greater than the volume of food and drink ingested.

Question 65

The liver contributes to GI function,although it is not technically part of the gastrointestinal tract.

Question 66

Which of the following would be most likely to cause metabolic acidosis?

A)Severe vomiting
B)Severe diarrhea
C)Hyperventilation
D)Hypoventilation
E)Traveling to high altitude

Question 67

Due to the route of fat absorption and transport in the body,fat-soluble toxins could have a greater effect on the body and brain than water-soluble toxins which are filtered first by the liver.

Question 68

In patients lacking exocrine pancreas secretion,fat digestion is normal provided bile is still produced.

Question 69

The lumen of the gastrointestinal tract is continuous with the external environment.

Question 70

The breakdown products of dietary triglycerides are resynthesized into triglycerides by intestinal cells and pass from these cells into lacteals.

Question 71

Glucose absorption across the luminal membrane of intestinal epithelial cells occurs by secondary active transport.

Question 72

Polysaccharides must be broken down to disaccharides in order to be absorbed.

Question 73

A bacterium that has been associated with ulcers is

A)Eschericia coli.
B)Clostridium difficile.
C)Staphylococcus aureus.
D)Helicobacter pylori.
E)Streptococcus pyogenes.

Question 74

During cholera infection,which causes severe diarrhea,the primary acute danger to one's health is dehydration.In terms of water balance,this is due to the loss of fluids added to the GI tract more than due to a decreased volume of ingested fluids.

Question 75

Barry's children seem to be struggling often with constipation.To help prevent it,their pediatrician recommends

A)avoiding foods that can lead to accumulation of toxins in feces.
B)making the children sit on the toilet until they defecate at least once a day.
C)feeding the children foods with a high proportion of cellulose and other indigestible carbohydrates.
D)feeding the children foods with more lipid content.
E)avoiding milk,the children may be lactose intolerant.

Question 76

Which of the following is NOT characteristic of inflammatory bowel disease (IBD)?

A)Bleeding,edema,and ulceration anywhere along the gastrointestinal tract
B)Pain relief when changing to a diet higher in fiber
C)Perforations in the mucosa and intestinal wall,leading to infection by bacteria,which are normally present and benign
D)Inflammation and thickening of the bowel wall to the point of preventing the usual passage of feces
E)Pain in the lower right abdomen frequently mistaken for appendicitis

Question 77

Amino acids are mainly absorbed across the epithelial wall in the stomach.

Question 78

The products of lipid digestion diffuse into the intestinal epithelium as micelles.

Question 79

The enzyme lactase

A)is involved directly in the digestion of proteins.
B)is necessary for the breakdown of milk fats.
C)is embedded in the luminal plasma membranes of intestinal epithelial cells.
D)promotes the formation of and storage of bile by the gallbladder.
E)is overproduced and released by secretory cells in the small intestine in the condition known as lactose intolerance.

Question 80

Contraction of the circular smooth muscle in the gastrointestinal tract wall decreases the diameter of the lumen,while contraction of the longitudinal smooth muscle shortens the tract.