Chapter 35: Gastrointestinal Function

The action of bile is to a. emulsify fats. b. digest cellulose. c. convert sucrose. d. release free amino acids.

ANS: A Bile is produced continuously in the liver and is responsible for emulsifying fats. Humans do not secrete an enzyme capable of digesting cellulose. Sucrase converts sucrose to glucose and fructose. Protein digestion involves the release of free amino acids. REF: Pg. 711

Which is associated with contraction of the gallbladder? a. Cholecystokinin b. Morphine c. Norepinephrine d. Gastrin

ANS: A Cholecystokinin has an extremely strong effect on gallbladder contractility. This stimulation of gallbladder activity results in an outpouring of bile, which plays an important role in fat digestion and absorption. REF: Pg. 705

The propulsive movement of the GI tract is called a. peristalsis. b. transmission. c. contraction. d. constriction.

ANS: A The basic propulsive movement of the GI tract is called peristalsis. Peristalsis is an inherent property of any smooth muscle tube that, like the intestine, is a functional syncytium. Segmental contractions do serve to keep the intestinal contents mixed on a constant basis. Nutrients are propelled by the slow advancement of a circular constriction that squeezes the materials in front of the constricted area forward. REF: Pg. 706

Chief cells secrete a. pepsinogen. b. hydrogen chloride. c. intrinsic factor. d. gastrin.

ANS: A pepsinogen In the gastric glands, chief cells secrete pepsinogen. Parietal cells are responsible for secretion of hydrogen chloride. Intrinsic factor enhances vitamin B12 absorption. Gastrin is secreted into the bloodstream and increases gastric motility. REF: Pg. 700

Which are major pairs of salivary glands? (Select all that apply.) a. Parotid b. Parietal c. Submandibular d. Sublingual e. Pituitary

ANS: A, C, D the parotid, submandibular, and sublingual glands. As the food is manipulated and broken down, it is moistened by saliva secreted by three major pairs of salivary glands: the parotid, submandibular, and sublingual glands.

The structure and secretions of the salivary gland most closely resemble those of the a. gastric gland. b. exocrine pancreas. c. liver. d. gallbladder.

ANS: B The salivary gland and the pancreas both secrete amylase. Gastric glands secrete pepsinogen. The gallbladder secretes concentrated bile salts. REF: Pg. 712

Which enzyme assists with protein digestion? a. Amylase b. Chymotrypsin c. Lactase d. Lipase

ANS: B Chymotrypsin Pepsin is neutralized in the duodenum, and pancreatic trypsin, chymotrypsin, and carboxypeptidase take over protein digestion. Amylase initiates carbohydrate digestion. Lactase is an enzyme that stimulates pancreatic secretion. Lipase is secreted in the pancreas. REF: Pg. 716

Which statement regarding pepsin is true? a. It is secreted by parietal cells in gastric pits. b. It is secreted as an inactive proenzyme. c. It accomplishes most of the digestion of dietary protein. d. It is permanently denatured by a pH less than 4.0.

ANS: B It is secreted as an inactive proenzyme. Chief cells produce pepsinogen, the inactive form of the enzyme pepsin. Pepsin reduces most protein to intermediate sized polypeptides. HCl activates pepsinogen to pepsin. REF: Pg. 700

Pancreatic secretions are high in a. hydrochloric acid. b. bicarbonate ions. c. intrinsic factor. d. secretin.

ANS: B bicarbonate ions. The pancreas secretes bicarbonate-rich fluid containing amylase, trypsin, chymotrypsin, and lipase into the duodenum when stimulated by secretin. Intrinsic factor is found in gastric glands. REF: Pg. 712

Most nutrient digestion and absorption occurs in the a. stomach. b. small intestine. c. large intestine. d. cecum.

ANS: B small intestine After intact food entering the mouth has been liquefied and partially digested in the stomach, it enters the small intestine, where the major part of digestion and absorption occurs. Food is liquefied and partially digested in the stomach. Intestinal contents are stored in the cecum. REF: Pg. 708

Carbohydrates are absorbed in the form of a. polysaccharides. b. disaccharides. c. monosaccharides. d. monoglycerides.

ANS: C Carbohydrates are absorbed in the form of monosaccharides. Polysaccharides and disaccharides lack the capacity for absorption. The intestinal epithelium is impermeable to carbohydrates of such high molecular weight. REF: Pg. 715

Which can be absorbed through the intestinal epithelia without further digestion? a. Sucrose b. Lactose c. Glucose d. Glycogen

ANS: C Glucose and galactose are absorbed across the intestinal epithelia by a sodium-dependent cotransporter. Disaccharides are cleaved into monosaccharides by brush border enzymes on the intestinal epithelia. Lactose is a disaccharide which is cleaved into a monosaccharide. Glycogen is not absorbed through the intestinal epithelia without further digestion. REF: Pg. 715

Brush-border enzymes are produced by ________ cells. a. pancreatic acinar b. gastric mucosa c. intestinal epithelial d. goblet

ANS: C The intestinal epithelium secretes brush border enzymes. Bicarbonate-rich fluids are secreted by the pancreas. Gastric glands secrete pepsinogen by the chief cells. Goblet cells throughout the intestinal mucosa secrete large amounts of mucus. REF: Pg. 712

How much fluid is secreted from the intestinal glands daily? a. 1/2 liter b. 1 liter c. 2 liters d. 4 liters

ANS: C 2 liters The intestinal glands secrete about 2 liters of fluid daily into the lumen of the intestine, but most of the fluid is quickly reabsorbed by the villi. REF: Pg. 701

Failure of normal partitioning between the foregut and midgut can lead to a congenital condition known as a. tracheoesophageal fistula. b. esophageal atresia. c. intestinal atresia. d. anal agenesis.

ANS: C intestinal atresia. Failure of normal partitioning between the foregut and midgut can lead to intestinal atresia, a condition in which the lumen of the small intestine is obliterated. Tracheoesophageal fistula is an anomaly characterized by an abnormal connection between the trachea and esophagus. Esophageal atresia is a condition where the esophagus is closed off in a blind pouch. Anal agenesis is a condition in which the rectal pouch ends blindly. REF: Pg. 698

Absorption of glucose and amino acids across the intestinal epithelium occurs by a. endocytosis. b. ATP-driven transporters. c. sodium-dependent carriers. d. passive diffusion.

ANS: C sodium-dependent carriers. The transport of sugars and amino acids across the intestinal epithelial cell occurs through the transport of sodium carriers. REF: Pgs. 715-716

Most of the parasympathetic innervation of the GI tract is supplied by the a. hypoglossal nerves. b. enteric nervous system. c. vagus nerves. d. celiac ganglia.

ANS: C vagus nerves. The parasympathetic supply to the GI tract is divided into cranial and sacral divisions. Cranial parasympathetic stimulation is transmitted almost entirely by the vagus nerves. Vagus nerves provide extensive supply to the esophagus, stomach, pancreas and the first half of the large intestine. REF: Pgs. 704-705

The primary stimulus for pancreatic secretion is a. gastrin. b. histamine. c. acetylcholine. d. secretin.

ANS: D Secretin, which is produced by the mucosa of the duodenum in response to the entry of acidic gastric juice from the stomach, stimulates pancreatic fluid. Gastrin is secreted by endocrine cells of the stomach mucosa in response to food entry. REF: Pg. 705

The portion of the stomach that controls gastric emptying is the a. fundus. b. body. c. antrum. d. pylorus.

ANS: D The pylorus is a muscular sphincter between the stomach and duodenum that serves to control gastric emptying and limit the reflux of bile from the small intestine. The fundus is the part of the stomach that continues lateral to and above the cardia. The body of the stomach extends from the cardia to the antrum. The antrum differs markedly from the rest of the stomach in function and is distinguished by the absence of rugae. REF: Pg. 699

The sympathetic nerve endings in the GI tract secrete a. acetylcholine. b. histamine. c. gastrin. d. norepinephrine.

ANS: D Norepinephrine The sympathetic nerve endings in the GI tract secrete norepinephrine, which promotes the inhibitory effect of the sympathetic nervous system on the GI tract. Histamine stimulates parietal cell secretion. REF: Pg. 705

Older individuals may experience which change in the mouth? a. Increase in salivation b. Increase in taste for salt c. Increase in the number of papillae d. Increased exposure of dentin

ANS: D exposure of dentin As tooth enamel wears away, dentin is exposed, allowing development of caries. Older individuals also experience a decrease in the number of acinar cells in the salivary glands, leading to a reduction in salivary secretion. Of the four basic tastes, the elderly experience a particular decrease in salt and sugar tastes. Elderly people experience a decrease in the number of papillae. REF: Pg. 699

Parasympathetic stimulation of the stomach would a. decrease motility. b. decrease hydrogen chloride secretion. c. inhibit acidity. d. stimulate motility.

ANS: D stimulate motility The GI system has an intrinsic nervous system which controls most GI functions. Input from the sympathetic and parasympathetic nervous systems can strongly affect the activity of the intrinsic nervous system. In general, sympathetic stimulation decreases the activity of the intrinsic nervous system whereas parasympathetic stimulation increases its activity. REF: Pg. 704