Weekly Year 2: GIT Physiology Exam - March 27, 2026 (Section

Question 1

Which of the following statements about Gastrin is TRUE?

Accepted Answer

It stimulates the growth of gastric mucosa. — Gastrin, secreted by G cells, is a potent stimulator of gastric acid secretion and also has a trophic effect, promoting the growth of the gastric mucosa, pancreas, and small intestinal mucosa.

Question 2

Vasoactive Intestinal Peptide (VIP) causes which of the following effects?

Accepted Answer

Relaxation of smooth muscle in the gut wall. — VIP is a neurotransmitter that causes relaxation of gastrointestinal smooth muscle, including sphincters, and also stimulates intestinal and pancreatic fluid and electrolyte secretion, and inhibits gastric acid secretion.

Question 3

Which of the following is a major stimulant for gastrointestinal secretion?

Accepted Answer

Low pH in the small intestine. — Mechanical distension of the gut wall, as well as chemical stimuli (e.g., presence of food components), are primary stimulators of local reflexes and hormone release, leading to increased secretion and motility. Low pH in the small intestine stimulates secretin, which in turn stimulates bicarbonate secretion, but distension is a more general stimulant for overall GI secretion.

Question 4

Regarding the hormone Secretin, which statement is correct?

Accepted Answer

It stimulates the pancreas to secrete a bicarbonate-rich fluid. — Secretin is released from S cells in the duodenum in response to acidic chyme entering the small intestine. Its primary role is to stimulate the pancreas to secrete a large volume of fluid rich in bicarbonate, which neutralizes the gastric acid.

Question 5

Inhibition of the myenteric plexus leads to which of the following?

Accepted Answer

Decreased strength and frequency of contractions. — The myenteric (Auerbach's) plexus is primarily responsible for controlling gastrointestinal motility. Inhibition of this plexus would therefore lead to decreased strength and frequency of contractions, potentially resulting in hypomotility or paralytic ileus.

Question 6

Stimulation of the submucosal plexus results in an increase in which of the following?

Accepted Answer

Gastrointestinal blood flow and local secretions. — The submucosal (Meissner's) plexus primarily controls local gastrointestinal secretion, absorption, and local blood flow. Stimulation would increase these functions.

Question 7

Which of the following hormones inhibits gastric acid secretion?

Accepted Answer

Somatostatin — Somatostatin, released by D cells in the stomach and duodenum, acts locally to inhibit gastrin release and directly inhibits parietal cell acid secretion, thereby decreasing gastric acid output.

Question 8

Cholecystokinin (CCK) has which of the following primary actions?

Accepted Answer

Stimulates gallbladder contraction and pancreatic enzyme secretion. — CCK is released from I cells in the duodenum and jejunum in response to fats and proteins. It potently stimulates gallbladder contraction to release bile and pancreatic acinar cells to secrete digestive enzymes. It also relaxes the sphincter of Oddi and inhibits gastric emptying.

Question 9

The major factor that stimulates the release of Secretin into the bloodstream is:

Accepted Answer

Acidic chyme entering the duodenum. — Secretin is released from S cells in the duodenum specifically in response to a decrease in luminal pH below 4.5, indicating the presence of acidic chyme from the stomach.

Question 10

It is known that gastrin:

Accepted Answer

Stimulates the secretion of intrinsic factor. — Gastrin stimulates enterochromaffin-like (ECL) cells to release histamine, which then acts on parietal cells to stimulate acid secretion. Gastrin also directly stimulates parietal cells.

Question 11

It is known that secretin:

Accepted Answer

Potentiates the action of CCK on pancreatic enzyme secretion. — Secretin primarily stimulates bicarbonate secretion, but it also potentiates the effects of CCK on pancreatic enzyme secretion, meaning that together they have a greater effect than either hormone alone.

Question 12

Concerning the gastrin hormone, which of the following is FALSE?

Accepted Answer

It directly stimulates pepsinogen secretion. — While gastrin indirectly promotes pepsinogen secretion by stimulating acid (which activates pepsinogen to pepsin), gastrin's primary direct action on gastric glands is on acid secretion and mucosal growth. Pepsinogen secretion is more directly stimulated by acetylcholine and secretin.

Question 13

Which single statement below, about the stomach, is correct?

Accepted Answer

Gastric emptying is slowed by the presence of fat in the duodenum. — Fat in the duodenum stimulates CCK and GIP release, which inhibit gastric emptying, allowing more time for fat digestion in the small intestine. The cephalic phase stimulates acid secretion, intrinsic factor is from parietal cells, the fundus/body are main acid sites, and pepsin is active at acidic pH.

Question 14

Water transport can occur from the lumen of the intestine to the bloodstream, or vice versa. Which statement is correct?

Accepted Answer

Water follows the active transport of solutes, primarily sodium. — Water absorption in the GI tract is predominantly passive, occurring down osmotic gradients. These gradients are primarily established by the active transport of solutes, most notably sodium ions, from the lumen into the interstitial space.

Question 15

Which statement about fat digestion and absorption is correct?

Accepted Answer

Micelles are essential for the absorption of fat-soluble vitamins. — Micelles, formed by bile salts, encapsulate fat-soluble vitamins (A, D, E, K) and cholesterol, allowing them to be transported to the brush border for absorption. Long-chain fatty acids are re-esterified into triglycerides and packaged into chylomicrons, which then enter the lymphatic system. Short-chain fatty acids can be absorbed directly into the portal blood.

Question 16

Which statement about protein digestion is most correct?

Accepted Answer

Protein digestion begins in the mouth with salivary amylase. — Aminopeptidases and carboxypeptidases are brush border enzymes (along with dipeptidases and tripeptidases) that cleave small peptides into amino acids, dipeptides, and tripeptides, which are then absorbed. Protein digestion begins in the stomach with pepsin. Pancreatic proteases (e.g., trypsinogen, chymotrypsinogen) are secreted as inactive zymogens.

Question 17

Which statement about dietary fibre is most correct?

Accepted Answer

Dietary fibre can bind to bile acids, increasing their excretion. — Dietary fibre, particularly soluble fibre, binds to bile acids in the intestine, preventing their reabsorption and increasing their excretion. This can lower cholesterol levels as the liver uses more cholesterol to synthesize new bile acids. Soluble fibre is fermented, insoluble fibre increases bulk and decreases transit time. Neither is digested or absorbed in the small intestine. Some are digestible by bacteria.

Question 18

Which statement about absorption in the gastrointestinal tract is most correct?

Accepted Answer

The jejunum is the primary site for absorption of most digested nutrients. — The jejunum has a large surface area due to its folds, villi, and microvilli, making it the primary site for the absorption of most digested carbohydrates, proteins, and fats, as well as many vitamins and electrolytes.

Question 19

Which statement about the oral phase of digestion is INCORRECT?

Accepted Answer

Lipase enzymes are secreted in saliva to start fat digestion. — While lingual lipase is secreted in saliva, its activity is minimal at salivary pH and primarily begins fat digestion once activated by the acidic environment of the stomach. Salivary glands do not secrete significant amounts of lipase that are active in the mouth.

Question 20

Which statement about stomach lining cells is correct?

Accepted Answer

Mucous neck cells secrete bicarbonate. — Parietal cells are responsible for secreting both hydrochloric acid (HCl) and intrinsic factor, which is essential for vitamin B12 absorption. Chief cells secrete pepsinogen, G cells secrete gastrin, and mucous cells secrete mucus and some bicarbonate.

Question 21

Which statement about pancreatic enzyme secretion is correct?

Accepted Answer

Trypsinogen is activated by enteropeptidase in the duodenum. — Trypsinogen, an inactive precursor (zymogen), is converted to active trypsin by the brush-border enzyme enteropeptidase (also known as enterokinase) in the duodenal lumen. Trypsin then activates other pancreatic zymogens.

Question 22

Which statement about post-meal gastrointestinal motility is correct?

Accepted Answer

Mass movements are frequent occurrences in the small intestine after a meal. — The gastrocolic reflex is a physiological reflex that increases motility of the colon in response to stretching of the stomach by food. This prepares the colon for incoming chyme. The MMC occurs during fasting.

Question 23

Which best describes colonic microbiota functions?

Accepted Answer

They produce short-chain fatty acids through fermentation of undigested carbohydrates. — Colonic microbiota ferment undigested carbohydrates (dietary fibre) and some proteins, producing short-chain fatty acids (SCFAs) like acetate, propionate, and butyrate, which can be absorbed and used as energy by the host.

Question 24

What explains fibre's protective effect against colon cancer?

Accepted Answer

It dilutes potential carcinogens and reduces their contact time with the colonic mucosa. — Dietary fibre increases stool bulk and speeds up transit time, which dilutes potential carcinogens in the stool and reduces their contact time with the colonic epithelial cells, thus reducing the risk of cancer.

Question 25

Which of the following statements about GI motility is FALSE?

Accepted Answer

Haustral churning is a type of rapid propulsive movement in the large intestine. — Haustral churning (or haustration) in the large intestine involves slow, mixing movements, not rapid propulsive movements. Mass movements are the strong propulsive contractions in the colon.

Question 26

Which tissue layer provides for primary digestive motility?

Accepted Answer

Muscularis externa — The muscularis externa (or muscularis propria) consists of inner circular and outer longitudinal smooth muscle layers. Contractions of these layers are responsible for the major propulsive (peristalsis) and mixing (segmentation) movements of the GI tract.

Question 27

Which statement about bile is true?

Accepted Answer

Bile acids are recycled through the enterohepatic circulation. — Bile acids (a component of bile) are highly conserved and undergo enterohepatic recirculation, where they are reabsorbed from the ileum and returned to the liver for reuse. Bile is produced in the liver, stored in the gallbladder, and contains bile salts/acids, cholesterol, bilirubin, and electrolytes, but not digestive enzymes.

Question 28

Which statement regarding the swallowing reflex is false?

Accepted Answer

The pharyngeal phase is involuntary. — Primary peristalsis in the esophagus is a reflex initiated by swallowing and is a wave of muscle contraction that propels food towards the stomach, independent of gravity. Gravity can assist, but the reflex itself is muscular.

Question 29

Which of the following statements about GI regulation is TRUE?

Accepted Answer

The enteric nervous system can function completely independently of the CNS. — The enteric nervous system (ENS), often called the 'gut brain,' is capable of independent function (e.g., controlling motility, secretion, and blood flow through local reflexes) even if extrinsic neural input from the CNS is severed. Sympathetic stimulation generally inhibits, parasympathetic stimulates. Gastrin is a hormone, not a neurotransmitter.

Question 30

What is false about tonic contractions in the GI tract?

Accepted Answer

They are important for maintaining pressure against flow. — Tonic contractions are sustained contractions, often lasting minutes to hours, and are characteristic of sphincters (maintaining closure) and the orad (proximal) stomach (maintaining pressure for receptive relaxation). Phasic contractions (like segmentation or peristalsis) are rhythmic and of shorter duration. Tonic contractions are sustained, not rhythmic.

Question 31

Which of the following is characteristic of the segmenting movements in the small intestine?

Accepted Answer

They are responsible for thoroughly mixing chyme with digestive juices. — Segmenting movements are localized contractions of the circular muscle that divide the small intestine into segments. Their primary function is to mix the chyme with digestive enzymes and expose it to the absorptive surface of the mucosa, rather than rapid propulsion.

Question 32

Secretion of saliva increases in all of the below except:

Accepted Answer

Fear and anxiety. — Fear and anxiety are associated with increased sympathetic activity, which generally inhibits salivary secretion, leading to a dry mouth. The other options are stimuli that typically increase salivary flow, primarily through parasympathetic pathways.

Question 33

Defecation is a reflex action:

Accepted Answer

Initiated by distension of the rectum. — The defecation reflex is initiated when feces enter the rectum, causing distension of the rectal wall. This triggers local and spinal cord reflexes. While the internal anal sphincter relaxes involuntarily, the external anal sphincter is under voluntary control, allowing for conscious control over defecation, though not indefinitely.

Question 34

In the stomach, which of the following is true?

Accepted Answer

Carbohydrate digestion is completed here. — Parietal cells secrete HCl, which provides the acidic environment necessary for pepsin activation and for denaturing proteins, making them more accessible to enzymatic breakdown. Intrinsic factor is for B12 absorption, not iron.

Question 35

Intestinal secretions contain:

Accepted Answer

Bile salts for emulsification. — The brush border of the small intestine contains integral membrane enzymes such as disaccharidases (e.g., lactase, sucrase, maltase) and peptidases (e.g., aminopeptidases, dipeptidases) that are responsible for the final stages of carbohydrate and protein digestion.

Question 36

A 55-year-old man with chronic alcohol consumption presents with nonspecific complaints of dyspepsia. Examination reveals destruction of gastric glands, particularly parietal cells. This predisposes him to:

Accepted Answer

Pernicious anemia. — Parietal cells secrete intrinsic factor, which is necessary for vitamin B12 absorption in the ileum. Destruction of parietal cells leads to a lack of intrinsic factor, resulting in pernicious anemia (a type of megaloblastic anemia). Low acid also leads to increased gastrin (loss of negative feedback) but the primary direct consequence of parietal cell loss is B12 malabsorption.

Question 37

Regarding the regulation of gastric acid secretion, which statement is TRUE?

Accepted Answer

Histamine, released from ECL cells, is a potent stimulator of parietal cells. — Histamine, released from enterochromaffin-like (ECL) cells in response to gastrin and acetylcholine, acts on H2 receptors on parietal cells, strongly stimulating HCl secretion.

Question 38

Which hormone primarily inhibits gastric emptying?

Accepted Answer

Cholecystokinin (CCK) — Cholecystokinin (CCK) and Secretin are both released from the duodenum in response to chyme and act to inhibit gastric emptying, allowing more time for digestion and absorption in the small intestine. CCK is more potent in this role, especially in response to fat.

Question 39

The primary role of the migrating motor complex (MMC) is:

Accepted Answer

To clear undigested material and bacteria from the small intestine during fasting. — The MMC is a pattern of electrical and motor activity that occurs in the gastrointestinal tract during periods between meals (fasting state). Its primary function is to sweep undigested food, bacteria, and debris from the stomach and small intestine into the large intestine, often referred to as the 'housekeeping' function.

Question 40

Regarding carbohydrate digestion and absorption, which of the following is correct?

Accepted Answer

SGLT1 is a transporter responsible for glucose and galactose absorption. — SGLT1 (sodium-glucose cotransporter 1) is a secondary active transporter on the apical membrane of enterocytes that absorbs glucose and galactose along with sodium. Fructose uses GLUT5 for facilitated diffusion. Salivary amylase is inactivated by gastric acid.

Question 41

The enterogastric reflex functions to:

Accepted Answer

Inhibit gastric emptying and acid secretion when chyme enters the duodenum. — The enterogastric reflex is a short reflex that occurs when the duodenum becomes distended or receives acidic, fatty, or hypertonic chyme. It inhibits gastric motility and gastric acid secretion, thereby slowing gastric emptying and allowing the small intestine more time to process the chyme.

Question 42

Which of the following describes the role of bile salts in fat digestion?

Accepted Answer

They emulsify large fat globules into smaller micelles. — Bile salts do not digest fats; they are detergents that emulsify large fat globules into smaller fat droplets, increasing the surface area for pancreatic lipase to act upon. These smaller droplets are then incorporated into micelles for transport.

Question 43

Which statement about the exocrine pancreas is FALSE?

Accepted Answer

Secretin primarily stimulates the acinar cells. — Secretin primarily acts on the pancreatic duct cells to stimulate the secretion of a bicarbonate-rich fluid to neutralize acid. CCK primarily acts on the acinar cells to stimulate enzyme secretion.

Question 44

Regarding the regulation of pancreatic enzyme secretion, which neurotransmitter is a major stimulant?

Accepted Answer

Acetylcholine — Acetylcholine, released from vagal nerve endings and enteric neurons, is a potent stimulant of pancreatic enzyme secretion from acinar cells.

Question 45

The final products of carbohydrate digestion absorbed by the small intestine are primarily:

Accepted Answer

Monosaccharides — Carbohydrates are digested by amylase and brush border disaccharidases into their simplest forms, monosaccharides (glucose, galactose, fructose), which are then absorbed into the enterocytes.

Question 46

Which of the following factors would inhibit gastric emptying?

Accepted Answer

Acid in the duodenum. — Acid (low pH), fat, and hypertonicity in the duodenum are strong inhibitors of gastric emptying. They trigger enterogastric reflexes and release of hormones like CCK and secretin that slow gastric emptying.

Question 47

The primary function of the large intestine is:

Accepted Answer

Absorption of water and electrolytes, and storage of feces. — The large intestine's main functions are to absorb most of the remaining water and electrolytes from indigestible food matter, store fecal matter before defecation, and compact it.

Question 48

Which type of motility is responsible for moving chyme over long distances in the colon?

Accepted Answer

Mass movements — Mass movements are strong, sustained contractions that occur infrequently (1-3 times per day) and are responsible for propelling fecal matter over long distances in the colon, typically into the rectum.

Question 49

Regarding salivary glands, which statement is true?

Accepted Answer

Saliva is hypotonic to plasma. — Saliva is hypotonic (lower solute concentration) compared to plasma because ductal cells reabsorb more NaCl than they secrete water. Saliva is primarily regulated by the autonomic nervous system, not hormones.

Question 50

Which of the following best describes the function of GIP (Gastric Inhibitory Peptide/Glucose-dependent Insulinotropic Peptide)?

Accepted Answer

Stimulates insulin release from the pancreas in response to glucose. — GIP is released from K cells in the duodenum and jejunum in response to glucose and fat. Its primary role is to stimulate insulin secretion from pancreatic beta cells, particularly after a carbohydrate-rich meal, and it also weakly inhibits gastric acid secretion and motility.

Weekly Year 2: GIT Physiology Exam - March 27, 2026 (Section

Questions, Answers & Explanations