Pathophysiology: Chapter 41: Structure and Function of the Digestive System

Question 1

In the mouth and stomach, salivary Alpha-amylase initiates the digestion of which nutrients?

a. Proteins c. Fats
b. Carbohydrates d. Fiber

Answer 1

ANS: B
Salivary Alpha-amylase is an enzyme that initiates only carbohydrate digestion in the mouth
and stomach.

Question 2

Which elements in saliva protect against tooth decay?

a. Salivary Alpha-amylase and ptyalin
b. Secretin and IgA
c. Endogenous enamelin and salivary Beta-amylase
d. Exogenous fluoride and a pH of 7.4

Answer 2

ANS: D
The bicarbonate concentration of saliva sustains a pH of approximately 7.4, which
neutralizes bacterial acids and prevents tooth decay. Exogenous fluoride (e.g., fluoride in
drinking water) is absorbed and then secreted in the saliva, providing additional protection
against tooth decay. Decay prevention is not associated with any of the other options.

Question 3

Saliva contains which immunoglobulin (Ig)?
a. IgA c. IgG
b. IgE d. IgM
.

Answer 3

ANS: A

Saliva contains only IgA, which helps prevent infection

Question 4

What effect is a result of inhibiting the parasympathetic nervous system with a drug such
as atropine?
a. Salivation becomes thinner. 
b. Salivation decreases. 
c. The pH of saliva changes.
d. Digestive enzymes are inhibited.
.

Answer 4

ANS: B
The sympathetic and parasympathetic divisions of the autonomic nervous system control
salivation. Because cholinergic parasympathetic fibers stimulate the salivary glands,
atropine (an anticholinergic agent) inhibits salivation and makes the mouth dry. None of
the other options is a result of drugs such as atropine

Question 5

Food enters the stomach via which sphincter?

a. Cardiac c. Gastric
b. Upper esophageal d. Fundal

Answer 5

ANS: A
Each end of the esophagus is opened and closed by a sphincter. The upper esophageal
sphincter (cricopharyngeal muscle) prevents entry of air into the esophagus during
respiration. The lower esophageal sphincter (cardiac sphincter) prevents regurgitation
from the stomach. The lower esophageal sphincter is located near the esophageal
hiatus—the opening in the diaphragm where the esophagus ends at the stomach. The
cardiac sphincter is the only option that fulfills the function described in the question.

Question 6

Which gastric cells secrete hydrochloric acid and intrinsic factor?

a. Parietal c. G
b. Chief d. H

Answer 6

ANS: A
Of the available options, only the parietal cells (oxyntic cells) secrete hydrochloric acid
and intrinsic factor.

Question 7

Which cells in the stomach secrete histamine?

a. Oxyntic c. D
b. Chief d. Enterochromaffin-like

Answer 7

ANS: D

Of the available options, only enterochromaffin-like cells secrete histamine.

Question 8

The presence of chyme in the duodenum stimulates which hormones?

a. Motilin and histamine
b. Secretin and cholecystokinin
c. Enteroglucagon and gastric inhibitory peptide
d. Somatostatin and acetylcholine

Answer 8

ANS: B
The movement of chyme from the stomach into the duodenum initiates the intestinal phase
of secretion. This phase represents a slowdown of the gastric secretory response; however,
the presence of digested protein and amino acids in the duodenum continue to stimulate
some gastric secretion. The release of secretin and cholecystokinin stimulate pancreatic
secretions and inhibit gastric secretions. This selection is the only option that correctly
identifies the hormones that are stimulated by the presence of chyme in the duodenum.

Question 9

Which gastric hormone inhibits acid and pepsinogen secretion, as well as decrease the
release of gastrin?
a. Bombesin c. Somatostatin
b. Histamine d. Acetylcholine

Answer 9

ANS: C
Of the options available, only somatostatin inhibits the secretion of acid and pepsinogen
and decreases gastrin release.

Question 10

Which enzyme breaks down protein-forming polypeptides in the stomach?

a. Acetylcholine c. Gastrin
b. Pepsin d. Secretin

Answer 10

ANS: B
Of the options available, only pepsin, a proteolytic enzyme, breaks down protein-forming
polypeptides in the stomach.

Question 11

Exposure to which substance protects the mucosal barrier of the stomach?

a. Prostaglandins c. Helicobacter pylori
b. Aspirin d. Regurgitated bile

Answer 11

ANS: A
Prostaglandins and enterogastrones, such as gastric inhibitory peptide, somatostatin, and
secretin, inhibit acid secretion. This selection is the only option that accurately identifies a
substance that protects the mucosal barrier of the stomach.

Question 12

The ileum and jejunum are suspended by folds of the peritoneum that contain an extensive
vascular and nervous network. What are these folds called?
a. Ligament of Treitz c. Auerbach folds
b. Mesentery d. Lamina propria

Answer 12

ANS: B
The ileum and jejunum are suspended in loose folds from the posterior abdominal wall by
a peritoneal membrane called the mesentery. The mesentery facilitates intestinal motility
and supports blood vessels, nerves, and lymphatics. None of the other options accurately
fills this description.

Question 13

Where in the small intestines are lymphocytes, plasma cells, and macrophages produced?

a. Brush border c. Lamina propria
b. Microvilli d. Crypts of Lieberkühn

Answer 13

ANS: C
The lamina propria, which is a connective tissue layer of the mucous membrane, lies
beneath the epithelial cells of the villi and contains lymphocytes, plasma cells, which
produce immunoglobulins, and macrophages. None of the other options performs the
described function.

Question 14

Why are water and electrolytes transported in both directions through tight junctions and
intercellular spaces rather than across cell membranes?
a. The intercellular hydrostatic pressure is inadequate to push the water and
electrolytes across the cell membranes.
b. A balance of cations and ions among the electrolytes on each side of the cell
membranes cannot be maintained.
c. The epithelial cell membranes are formed of lipids that are hydrophobic and
therefore repel water.
d. Receptors on those cell membranes are occupied with a diffusion of amino acids
and monosaccharides.

Answer 14

ANS: C
The epithelial cell membranes of the small intestine are formed of lipids and are
hydrophobic or tend to repel water. Therefore water and electrolytes are transported in
both directions—toward the capillary blood or toward the intestinal lumen—through the
tight junctions and intercellular spaces rather than across cell membranes. This selection is
the only option that accurately describes why water and electrolytes are transported in both
directions.

Question 15

Which statement best describes the gastrointestinal tract?
a. The gastrointestinal tract is a muscular tube that transports food from the mouth to
the stomach.
b. The gastrointestinal tract is a hollow tube that extends from the mouth to the anus.
c. The gastrointestinal tract is a baglike structure that propels partially digested food
(chyme).
d. The structure is 5 m long and consists of three segments.

Answer 15

ANS: B
The gastrointestinal tract is a hollow tube that extends from the mouth to the anus. The
esophagus is a muscular tube that transports food from the mouth to the stomach. The
stomach is a baglike structure that secretes digestive juices, mixes and stores food, and
propels partially digested food (chyme) into the duodenum. The small intestine is 5 m long
and has three segments.

Question 16

Glucose transport enhances the absorption of which electrolyte?

a. Sodium c. Potassium
b. Phosphate d. Chloride

Answer 16

ANS: A
Sodium passes through the tight junctions and is actively transported across cell
membranes. Sodium and glucose share a common active transport carrier (sodium-glucose
ligand transporter 1 [SGLT1]). This statement is not true of any other option.

Question 17

What process is capable of increasing both intrathoracic and intraabdominal pressure,
thereby facilitating defecation?
a. Relaxation of the internal anal sphincter
b. Intestinal peristalsis
c. Valsalva maneuver
d. Ileogastric reflex

Answer 17

ANS: C
Squatting or sitting facilitate defecation; these positions straighten the angle between the
rectum and anal canal and increase the efficiency of straining (increasing intraabdominal
pressure). Initiating the Valsalva maneuver increases intraabdominal pressure. This
maneuver consists of inhaling and forcing the diaphragm and chest muscles against the
closed glottis and increases both intrathoracic and intraabdominal pressure, which is
transmitted to the rectum. None of the other options facilitate defecation as described.

Question 18

Which pancreatic enzyme is responsible for the breakdown of carbohydrates?

a. Trypsin c. Lipase
b. Amylase d. Chymotrypsin

Answer 18

ANS: B
Salivary and pancreatic amylases break down starches to oligosaccharides by splitting
alpha-1,4-glucosidic linkages of long-chain molecules. None of the other options is relevant to
this process.

Question 19

The formation of water-soluble molecules to facilitate the absorption of the by-products of
lipid hydrolysis is accomplished by:
a. Micelles c. Chylomicrons
b. Phospholipase d. Colipase

Answer 19

ANS: A
The products of lipid hydrolysis must be made water soluble if they are to be efficiently
absorbed from the intestinal lumen. The formation of water-soluble molecules known as
micelles (see Figure 40-14) accomplishes this process. This selection is the only option
that accurately identifies the molecule needed to facilitate lipid hydrolysis.

Question 20

What is the primary source of physiologic iron?

a. Transferrin from plasma
b. Pepsin form pepsinogen
c. Bile from bilirubin
d. Heme from animal protein

Answer 20

ANS: D
The primary source of iron is heme from animal protein. The other options are not
considered primary sources of physiologic iron.

Question 21

Which statement is incorrect regarding the characteristics of vitamin B12?

a. Vitamin B12 is absorbed in the terminal ileum.
b. Vitamin B12 is absorbed in its free (unbound) form but only in small amounts.
c. Vitamin B12 is necessary for platelet maturation.
d. Vitamin B12 binds to intrinsic factor.

Answer 21

ANS: C
Vitamin B12 is not necessary for platelet maturation. Most vitamin B12 (cobalamin) is
bound to intrinsic factor (making it resistant to digestion) and is absorbed in the terminal
ileum, although a small amount of the vitamin is absorbed in its free (unbound) form.

Question 22

Which water-soluble vitamin is absorbed by passive diffusion?

a. Vitamin B6 c. Vitamin K
b. Vitamin B1 d. Folic acid

Answer 22

ANS: A
Of the options available, only Vitamin B6 is the water-soluble vitamin absorbed by passive
diffusion.

Question 23

Which vitamin facilitates the absorption of iron by the epithelial cells of the duodenum
and jejunum?
a. B6 c. E
b. C d. B12

Answer 23

ANS: B
Of the options available, only vitamin C reduces ferric iron to ferrous iron, which is the
form more easily absorbed by the epithelial cells of the duodenum and jejunum.

Question 24

What is the role of the normal intestinal bacterial flora?

a. Metabolizing bile salts, estrogens, and lipids
b. Breaking down proteins into amino acids
c. Facilitating the motility of the colon
d. Metabolizing aldosterone and insulin

Answer 24

ANS: A
The intestinal bacteria play a role in the metabolism of bile salts, contributing to the
intestinal reabsorption of bile and the elimination of toxic bile metabolites. These bacteria
also play a role in the metabolism of estrogens, androgens, and lipids, as well as in the
conversion of unabsorbed carbohydrates to absorbable organic acids, the synthesis of
vitamin K2, and the metabolism of various nitrogenous substances and drugs. This
selection is the only option that accurately describes the role of normal intestinal bacterial
flora.

Question 25

Kupffer cells are best described as:

a. Natural killer cells that produce interferon-gamma (IFN-gamma)
b. Contractile and therefore capable of regulating the sinusoid blood flow
c. Bactericidal and therefore central to innate immunity
d. Able to metabolize estrogen, progesterone, and androgens

Answer 25

ANS: C
The sinusoids are lined with phagocytic cells, known as Kupffer cells, which are part of the
mononuclear phagocyte system and are the largest population of tissue macrophages in the
body. They are bactericidal and central to innate immunity. None of the other options
accurately describe Kupffer cells.

Question 26

Bilirubin is a by-product of the destruction of which aged cells?

a. Platelets c. Leukocytes
b. Protein d. Erythrocytes

Answer 26

ANS: D

Bilirubin is a by-product of only the destruction of aged red blood cells or erythrocytes.

Question 27

The process of conjugation of bilirubin in the liver is best described as which
transformation?
a. Unconjugated (fat-soluble) bilirubin into urobilinogen
b. Unconjugated (fat-soluble) bilirubin into conjugated (water-soluble) bilirubin
c. Conjugated (water-soluble) bilirubin into unconjugated (fat-soluble) bilirubin
d. Conjugated (water-soluble) bilirubin into urobilinogen

Answer 27

ANS: B
In the liver, unconjugated bilirubin moves from plasma in the sinusoids into the
hepatocytes. Within hepatocytes it joins with glucuronic acid to form conjugated bilirubin,
which is water-soluble. This selection is the only option that accurately describes the
transformation associated with the conjugation of bilirubin.

Question 28

Which statement is incorrect regarding gallbladder function?

a. Within 30 minutes of eating, the gallbladder forces bile into the stomach.
b. Cholinergic branches of the vagus nerve mediate gallbladder contraction.
c. Cholecystokinin provides hormonal regulation of gallbladder contraction.
d. The sphincter of Oddi controls the flow of bile from the gallbladder.

Answer 28

ANS: A
Within 30 minutes after eating, the gallbladder begins to contract and the sphincter of Oddi
relaxes, forcing bile into the duodenum through the major duodenal papilla. The other
options are correct statements regarding the functioning of the gallbladder.

Question 29

Which structure synthesizes clotting factors and the vitamin K necessary for hemostasis?

a. Colon c. Gallbladder
b. Spleen d. Liver

Answer 29

ANS: D
The liver has hemostatic functions. It synthesizes prothrombin, fibrinogen, and factors I,
II, VII, IX, and X, all of which are necessary for effective clotting. Vitamin K, a
fat-soluble vitamin, is essential for the synthesis of other clotting factors. Because bile
salts are needed for the absorption of fats, vitamin K absorption depends on adequate bile
production in the liver. Impairment of vitamin K absorption diminishes the production of
clotting factors and increases the risk of bleeding. The other structures mentioned are not
associated with synthesizing of clotting factors and vitamin K.

Question 30

How many days does it take for the entire epithelial population of the small intestines to be
replaced?
a. 30 to 45                   c. 7 to 15
b. 15 to 25                   d. 4 to 7
ANS: D

Answer 30

The entire epithelial population is replaced approximately every 4 to 7 days.

Question 31

Which statement is true regarding the state of the intestinal tract at birth?

a. The intestinal tract is colonized by Escherichia coli.
b. The intestinal tract is sterile.
c. Clostridium welchii is present in the intestinal tract but in very small numbers.
d. Streptococcus colonization in the intestinal tract has begun.

Answer 31

ANS: B
The intestinal tract is sterile at birth but becomes colonized with Escherichia coli,
Clostridium welchii, and Streptococcus within a few hours.