Weekly Year 2: GIT Physiology Exam - March 20, 2026 (Section

Question 1

Which of the following statements about gastrin is TRUE?

Accepted Answer

It stimulates the secretion of pepsinogen from chief cells. — Gastrin, secreted by G cells, is a potent stimulator of gastric acid secretion from parietal cells and also promotes the growth of the gastric mucosa. It stimulates the release of histamine from ECL cells, which in turn stimulates parietal cells. It also has a direct, but weaker, stimulatory effect on pepsinogen secretion from chief cells. Its release is stimulated by amino acids, peptides, gastric distension, and vagal stimulation, and inhibited by low luminal pH (via somatostatin release from D cells).

Question 2

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

Accepted Answer

Relaxation of gastrointestinal smooth muscle. — VIP is a neuropeptide that generally causes relaxation of gastrointestinal smooth muscle, including sphincters. It also stimulates intestinal and pancreatic bicarbonate and fluid secretion, and inhibits gastric acid secretion. Its actions are largely inhibitory to motility and excitatory to secretion of water and electrolytes.

Question 3

Stimulation of gastrointestinal secretion involves all of the following EXCEPT:

Accepted Answer

Sympathetic nervous system activation. — Vagal nerve activity (parasympathetic) and local enteric reflexes are major stimulators of gastrointestinal secretion. Specific hormones like gastrin, secretin, and CCK also play crucial roles. The sympathetic nervous system generally inhibits GI secretion and motility, often diverting blood flow away from the gut.

Question 4

Regarding the hormone Secretin, which statement is TRUE?

Accepted Answer

It promotes bicarbonate secretion from the pancreas and bile ducts. — Secretin is released from S cells in the duodenum in response to low duodenal pH (acid chyme). Its primary role is to stimulate the pancreas and bile ducts to secrete a fluid rich in bicarbonate, which neutralizes the acid and protects the duodenal mucosa. CCK, not secretin, primarily stimulates pancreatic enzyme release in response to fats and proteins.

Question 5

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

Accepted Answer

Decreased gastrointestinal motility. — The myenteric (Auerbach's) plexus is primarily responsible for regulating gastrointestinal motility, including muscle contraction, tone, and peristalsis. Inhibition of this plexus would therefore lead to decreased or absent gastrointestinal motility. The submucosal plexus is more involved in secretion and local blood flow.

Question 6

Stimulation of the submucosal (Meissner's) plexus results in an increase in which of the following?

Accepted Answer

Gastrointestinal blood flow. — The submucosal (Meissner's) plexus primarily regulates intestinal secretion, local blood flow, and absorption. Stimulation would increase these functions. Motility (muscle contraction, frequency, emptying rate, sphincter tone) is predominantly controlled by the myenteric plexus.

Question 7

Which of the following gastrointestinal hormones primarily affects gastric function by inhibiting it?

Accepted Answer

Secretin — Both CCK and Secretin are released from the duodenum in response to chyme, and both inhibit gastric emptying and acid secretion, providing negative feedback to the stomach (part of the intestinal phase of gastric regulation). Gastrin stimulates gastric function. Motilin stimulates motility during fasting.

Question 8

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

Accepted Answer

Promotes gallbladder contraction and pancreatic enzyme secretion. — CCK is released from I cells in the duodenum and jejunum in response to fats and proteins. Its key actions include stimulating gallbladder contraction (releasing bile into the duodenum) and stimulating the pancreas to secrete digestive enzymes. It also inhibits gastric emptying and acid secretion.

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 duodenal mucosa specifically when the pH of the duodenal lumen falls below 4.5, due to the influx of acidic chyme from the stomach. This triggers its bicarbonate-secreting actions to neutralize the acid.

Question 10

It is known that gastrin:

Accepted Answer

Stimulates the growth of the gastric mucosa. — Gastrin, secreted by G cells in the gastric antrum, is a potent trophic hormone for the gastric mucosa, promoting its growth in addition to stimulating acid secretion. Its release is inhibited by low pH and stimulated by peptides, amino acids, and distension. CCK increases gallbladder motility. Secretin and CCK are secreted in the duodenum.

Question 11

It is known that secretin:

Accepted Answer

Reduces gastric acid secretion. — Secretin reduces gastric acid secretion and gastric emptying as part of the negative feedback mechanism initiated by acidic chyme in the duodenum. It stimulates, rather than inhibits, pancreatic bicarbonate secretion. CCK is released in response to fatty acids, not secretin.

Question 12

Concerning the gastrin hormone, which statement is TRUE?

Accepted Answer

It promotes histamine release from ECL cells. — Gastrin is released from G cells and stimulates ECL cells to release histamine, which then acts on parietal cells to stimulate acid secretion. D cells release somatostatin, which inhibits gastrin release. Gastrin also stimulates pepsinogen secretion and its release is stimulated by vagal activity.

Question 13

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

Accepted Answer

Mucus neck cells secrete protective mucus. — Parietal cells secrete HCl and intrinsic factor. Chief cells secrete pepsinogen. G cells are primarily located in the antrum. Mucus neck cells are indeed a type of gastric gland cell that secretes mucus and bicarbonate, contributing to the gastric mucosal barrier.

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 absorption is primarily driven by osmotic gradients created by solute absorption. — Water always moves passively across the intestinal epithelium, primarily following osmotic gradients established by the active transport of solutes (e.g., Na+, glucose, amino acids). While the colon absorbs a significant amount of water, the small intestine absorbs the majority. Water secretion can occur down or against osmotic gradients, but its primary movement is passive.

Question 15

Which statement about fat digestion and absorption is correct?

Accepted Answer

Pancreatic lipase is the primary enzyme for triglyceride digestion in adults. — Lingual and gastric lipases are active in the stomach's acidic environment and initiate triglyceride digestion. Pancreatic lipase, secreted by the pancreas, is indeed the most important enzyme for triglyceride digestion in the small intestine. Short and medium-chain fatty acids are absorbed directly into the portal blood, while long-chain fatty acids are re-esterified and packaged into chylomicrons, which enter lacteals. Bile salts are synthesized in the liver and stored in the gallbladder.

Question 16

Which statement about protein digestion is most correct?

Accepted Answer

Amino acids are absorbed only by passive diffusion into enterocytes. — Protein digestion begins in the stomach with pepsin. Pepsin breaks proteins into smaller polypeptides. Enteropeptidase, a brush border enzyme, activates trypsinogen (from the pancreas) into its active form, trypsin, which then activates other pancreatic proteases. Amino acids and small peptides are absorbed into enterocytes primarily by active transport mechanisms.

Question 17

Which statement about dietary fibre is most correct?

Accepted Answer

Soluble fibre increases transit time and softens stools. — Dietary fibre is largely indigestible by human enzymes and passes into the large intestine. Soluble fibre (e.g., pectins, gums) slows gastric emptying and intestinal transit, helps regulate blood glucose, and can lower cholesterol. Insoluble fibre (e.g., cellulose, lignin) adds bulk to stool and speeds transit time. Soluble fibre is largely fermented by colonic bacteria to produce short-chain fatty acids, which do provide some caloric value (about 2 kcal/g), but insoluble fibre is poorly fermented. The statement about soluble fibre increasing transit time and softening stools is accurate as it forms gels and holds water.

Question 18

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

Accepted Answer

Active transport mechanisms are essential for the absorption of many nutrients. — The small intestine is the primary site for nutrient absorption. Fat-soluble vitamins are absorbed with lipids into lacteals, then into the lymphatic system. Active transport mechanisms (e.g., for glucose, amino acids, some vitamins, and minerals) are crucial for efficient absorption against concentration gradients. Iron absorption is tightly regulated by the body to prevent toxicity, often involving hepcidin.

Question 19

Which statement about the oral phase of digestion is INCORRECT?

Accepted Answer

Lingual lipase is secreted and activated in the mouth. — Lingual lipase is secreted in the mouth, but it is activated by the acidic environment of the stomach, where it initiates fat digestion. The oral phase is indeed both voluntary (chewing, initiating swallow) and reflexive (salivation, initial esophageal phase of swallow). Salivary amylase begins carbohydrate digestion, and mastication is physical breakdown.

Question 20

Which statement about stomach lining cells is correct?

Accepted Answer

Parietal cells secrete hydrochloric acid and intrinsic factor. — Parietal cells secrete HCl and intrinsic factor. G cells secrete gastrin. D cells secrete somatostatin. Chief cells secrete pepsinogen and gastric lipase. ECL cells secrete histamine.

Question 21

Which statement about pancreatic enzyme secretion is correct?

Accepted Answer

CCK stimulates acinar cells to release digestive enzymes. — Pancreatic amylase digests carbohydrates, not proteins. Trypsinogen is secreted in its inactive form and activated by enteropeptidase in the duodenum to prevent autodigestion. Secretin primarily stimulates bicarbonate secretion. Cholecystokinin (CCK) is the primary stimulus for pancreatic acinar cells to release digestive enzymes in response to fats and proteins in the duodenum.

Question 22

Which statement about post-meal motility in the small intestine is correct?

Accepted Answer

Segmentation contractions primarily mix chyme with digestive juices. — Segmentation contractions are the primary movements in the small intestine during the fed state, responsible for mixing chyme with digestive enzymes and facilitating contact with the absorptive surface. Peristalsis moves chyme forward. The MMC occurs during fasting. Gastric emptying is regulated and slowed by various factors, especially the presence of fat and acid in the duodenum.

Question 23

Which best describes colonic microbiota functions?

Accepted Answer

They ferment undigested carbohydrates, producing short-chain fatty acids. — Colonic microbiota primarily ferment undigested carbohydrates (fiber) that reach the large intestine, producing short-chain fatty acids (like butyrate, propionate, acetate), which are absorbed and provide energy to colonocytes. They also synthesize some vitamins (e.g., K and some B vitamins), but not all essential vitamins, and are not involved in intrinsic factor production or significant protein digestion/absorption.

Question 24

What explains fibre's protective effect against colon cancer?

Accepted Answer

It dilutes carcinogens, binds to bile acids, and produces beneficial short-chain fatty acids. — Dietary fibre contributes to colon cancer protection by increasing stool bulk, which dilutes potential carcinogens. It also speeds up transit time, reducing the duration of contact between carcinogens and the colon mucosa. Furthermore, bacterial fermentation of fibre produces short-chain fatty acids like butyrate, which have anti-proliferative and pro-apoptotic effects on colon cancer cells. It also binds to bile acids, preventing their conversion into secondary bile acids, some of which are carcinogenic.

Question 25

Which of the following statements is FALSE regarding the enteric nervous system?

Accepted Answer

It primarily receives input from the sympathetic nervous system only. — The enteric nervous system (ENS) is often called the 'second brain' because it can indeed function independently. It comprises the myenteric (motility) and submucosal (secretion/blood flow) plexuses. While it can function autonomously, it also receives significant modulating input from both the parasympathetic (e.g., vagus nerve) and sympathetic nervous systems. It contains all three types of neurons.

Question 26

Which tissue layer provides for primary digestive motility, such as peristalsis?

Accepted Answer

Muscularis externa — The muscularis externa (or muscularis propria) is the layer of smooth muscle in the gastrointestinal tract responsible for major movements like peristalsis and segmentation. It typically consists of an inner circular layer and an outer longitudinal layer of muscle.

Question 27

Which statement about bile is true?

Accepted Answer

Bile salts emulsify fats, aiding lipase action. — Bile salts, the most important component of bile for digestion, emulsify large fat globules into smaller micelles, increasing the surface area for pancreatic lipase action. Bile is produced by the liver, stored and concentrated in the gallbladder. Bile does not contain digestive enzymes; those come from the pancreas and intestinal brush border.

Question 28

Which statement regarding the swallowing reflex is false?

Accepted Answer

The upper esophageal sphincter relaxes to propel food into the trachea. — During swallowing, the upper esophageal sphincter (UES) relaxes to allow the bolus to enter the esophagus, not the trachea. The epiglottis covers the glottis (opening to the larynx and trachea) to prevent food from entering the airway (aspiration). Swallowing starts voluntarily but is completed by involuntary reflexes.

Question 29

What is false about tonic contractions in the GI tract?

Accepted Answer

They are primarily involved in mixing chyme. — Tonic contractions are sustained contractions that maintain a constant level of pressure for prolonged periods, typically found in sphincters (e.g., LES, internal anal sphincter) and the fundus of the stomach (accommodating food). They are primarily involved in maintaining luminal pressure or compartmentalization rather than actively mixing chyme; mixing is more characteristic of phasic contractions like segmentation.

Question 30

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

Accepted Answer

They mix chyme with digestive juices and expose it to the mucosal surface. — Segmentation contractions are primarily mixing movements. They involve localized contractions of the circular muscle layer, dividing the intestine into segments and sloshing chyme back and forth, effectively mixing it with enzymes and facilitating nutrient absorption by bringing it into contact with the brush border. Peristalsis propels chyme. The migrating motor complex (MMC) occurs during fasting.

Question 31

Secretion of saliva increases in all of the below except:

Accepted Answer

Sympathetic nervous system activation. — The sight, smell, and presence of food strongly stimulate salivary secretion via parasympathetic pathways. Parasympathetic stimulation (e.g., by vagal and glossopharyngeal nerves) leads to copious, watery saliva. While sympathetic stimulation does produce some saliva, it's typically a small volume of thick, mucus-rich saliva; overall, it's generally considered less significant for digestive secretion and can even inhibit overall fluid secretion in high stress.

Question 32

Defecation is a reflex action involving:

Accepted Answer

Contraction of the rectum and relaxation of both anal sphincters. — Defecation is initiated by distension of the rectum, which triggers an intrinsic defecation reflex (enteric nervous system) and a parasympathetic spinal cord reflex. This causes contraction of the rectum and internal anal sphincter relaxation. The external anal sphincter is under voluntary control, allowing defecation to be delayed or initiated when appropriate. So, for defecation to occur, the rectum contracts, and both sphincters must relax, with the external anal sphincter relaxation being voluntary.

Question 33

In the stomach, which of the following is TRUE?

Accepted Answer

The fundus is the primary site of mixing food. — Intrinsic factor is essential for Vitamin B12 absorption in the ileum. The lower esophageal sphincter (LES) prevents reflux from the esophagus, while the pyloric sphincter regulates emptying into the duodenum. Pepsinogen, secreted by chief cells, is activated to pepsin by HCl (from parietal cells) and by existing pepsin. The antrum, not the fundus, is the primary site for mixing food and generating strong contractions for gastric emptying.

Question 34

Intestinal secretions (succus entericus) contain:

Accepted Answer

Brush border enzymes and mucus. — Succus entericus, the fluid secreted by the small intestine, is primarily composed of water, mucus, and bicarbonate. Crucially, it also contains brush border enzymes (e.g., disaccharidases, peptidases) embedded in the microvilli, which perform the final stages of carbohydrate and protein digestion. Pancreatic enzymes come from the pancreas, HCl and pepsinogen from the stomach, and bile from the liver/gallbladder.

Question 35

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

Accepted Answer

Vitamin B12 deficiency. — Parietal cells secrete intrinsic factor, which is necessary for vitamin B12 absorption in the ileum. Destruction of parietal cells, as seen in atrophic gastritis (which can be associated with chronic alcohol abuse or autoimmune conditions), leads to a lack of intrinsic factor and subsequent Vitamin B12 deficiency (pernicious anemia). Destruction of parietal cells would lead to decreased gastric acid, which in turn can lead to increased gastrin secretion (due to lack of negative feedback). Pepsinogen secretion would likely be normal or decreased depending on the chief cells.

Question 36

Which statement about carbohydrate digestion and absorption is correct?

Accepted Answer

Glucose and galactose are absorbed into enterocytes via SGLT1. — Lactase is a brush border enzyme, not pancreatic, that breaks down lactose. Glucose and galactose are absorbed into enterocytes via the SGLT1 co-transporter (Na+-glucose cotransporter). Fructose is absorbed via GLUT5 by facilitated diffusion, independently of insulin. While most digestible carbohydrates are ultimately absorbed as monosaccharides, some dietary carbohydrates (e.g., fiber) are not absorbed at all.

Question 37

Which of the following hormones is primarily responsible for stimulating the migrating motor complex (MMC) in the small intestine during fasting?

Accepted Answer

Motilin — Motilin is widely recognized as the primary hormonal regulator of the migrating motor complex (MMC), the 'housekeeping' contractions that sweep undigested material through the small intestine during the fasting state. Gastrin, Secretin, and GIP are more active during the fed state.

Question 38

The cephalic phase of gastric secretion is characterized by:

Accepted Answer

Mediated primarily by the vagus nerve. — The cephalic phase occurs before food enters the stomach (e.g., sight, smell, thought of food) and is entirely mediated by vagal nerve stimulation. It prepares the stomach for incoming food by stimulating acid and pepsinogen secretion. Food in the stomach initiates the gastric phase, and duodenal chyme initiates the intestinal phase.

Question 39

Regarding the regulation of gastric emptying, which statement is TRUE?

Accepted Answer

The presence of fat in the duodenum slows emptying. — Gastric emptying is highly regulated to allow proper digestion and absorption in the duodenum. Increased gastric distension (within physiological limits) stimulates emptying. High osmolarity, low pH, and especially the presence of fat in the duodenum trigger neural (enterogastric reflex) and hormonal (CCK, Secretin, GIP) mechanisms that slow gastric emptying. Vagal stimulation generally enhances gastric motility and emptying (though complex, it's not a consistent inhibitor).

Question 40

Which of the following is a key function of intrinsic factor?

Accepted Answer

Facilitating the absorption of Vitamin B12. — Intrinsic factor, secreted by parietal cells in the stomach, is absolutely essential for the absorption of dietary Vitamin B12 (cobalamin) in the terminal ileum. Without it, B12 cannot be absorbed, leading to pernicious anemia.

Question 41

A patient with liver cirrhosis and portal hypertension may experience ascites due to:

Accepted Answer

Increased capillary hydrostatic pressure and decreased plasma oncotic pressure. — Ascites (fluid accumulation in the peritoneal cavity) in liver cirrhosis is primarily caused by two factors: increased capillary hydrostatic pressure due to portal hypertension, which pushes fluid out of the splanchnic circulation, and decreased plasma oncotic pressure due to impaired albumin synthesis by the diseased liver, which reduces the osmotic pull of fluid back into the capillaries. This leads to net fluid movement into the peritoneal cavity.

Question 42

Which statement best describes the role of the ileocecal valve?

Accepted Answer

It prevents reflux of colonic contents into the ileum. — The ileocecal valve (or sphincter) primarily functions to prevent the reflux of bacteria-rich colonic contents back into the sterile small intestine, and to regulate the passage of undigested chyme from the ileum into the cecum.

Question 43

Regarding the enterohepatic circulation, which of the following is TRUE?

Accepted Answer

It ensures that most bile salts are returned to the liver. — The enterohepatic circulation describes the process by which bile salts are secreted into the duodenum, facilitate fat digestion and absorption, and are then reabsorbed primarily in the terminal ileum, transported via the portal vein back to the liver, and re-secreted. This efficient recycling ensures that the body's limited bile salt pool can be used multiple times for fat digestion.

Question 44

Which hormone has a primary role in decreasing gastric acid secretion when chyme enters the duodenum?

Accepted Answer

Somatostatin — When acidic chyme enters the duodenum, D cells in the gastric antrum and duodenum are stimulated to release somatostatin. Somatostatin acts to inhibit gastrin release from G cells, histamine release from ECL cells, and directly inhibits parietal cells, thereby decreasing gastric acid secretion as part of the negative feedback mechanism for the intestinal phase.

Question 45

The primary mechanism for chloride secretion into the intestinal lumen is:

Accepted Answer

Secretion through the CFTR channel. — Chloride secretion into the intestinal lumen, particularly in crypt cells, is critically dependent on the cystic fibrosis transmembrane conductance regulator (CFTR) channel. This channel allows chloride ions to move from the cell into the lumen, driving water secretion. Na+/K+ ATPase is involved in maintaining ion gradients, and other transporters are involved, but CFTR is central to Cl- secretion.

Question 46

A patient presents with severe diarrhea after consuming a meal containing fatty foods. This could be due to a deficiency in which of the following?

Accepted Answer

Pancreatic lipase. — A deficiency in pancreatic lipase would impair the digestion of fats, leading to steatorrhea (fatty stools) and diarrhea, especially after consuming fatty foods. Undigested fats in the colon can also stimulate secretion and motility. Salivary amylase and pepsin digest carbohydrates and proteins respectively. Lactase deficiency causes diarrhea after consuming lactose.

Question 47

Which reflex is responsible for the urge to defecate after a meal?

Accepted Answer

Gastrocolic reflex. — The gastrocolic reflex is a physiological reflex that stimulates mass movements in the colon after a meal, leading to the urge to defecate. It is mediated by both extrinsic nerves and hormones (e.g., gastrin, CCK). The enterogastric reflex inhibits gastric emptying and secretion. The intestino-intestinal reflex inhibits intestinal motility in response to overdistension.

Question 48

The parietal cells of the stomach are characterized by all of the following EXCEPT:

Accepted Answer

They contain numerous zymogen granules for enzyme storage. — Parietal cells are indeed rich in mitochondria (due to high energy demand for acid secretion), secrete intrinsic factor, and possess an extensive system of intracellular canaliculi that rapidly expand to increase the surface area for acid secretion. Zymogen granules are characteristic of chief cells (for pepsinogen storage) and pancreatic acinar cells (for digestive enzymes).

Question 49

What is the primary function of the longitudinal muscle layer in the muscularis externa?

Accepted Answer

To cause shortening of segments of the GI tract. — The muscularis externa consists of an inner circular layer and an outer longitudinal layer. Contraction of the longitudinal muscle layer shortens sections of the GI tract, contributing to propulsive movements (peristalsis). The circular muscle layer constricts the lumen and is involved in segmentation and sphincter formation. Regulation of blood flow is primarily by the submucosal plexus and local arterioles.

Question 50

Which of the following would be expected to increase bile flow from the liver?

Accepted Answer

Secretin release. — Secretin, released in response to duodenal acid, stimulates the secretion of bicarbonate and water from bile duct epithelial cells, thereby increasing bile flow (the aqueous component). Increased reabsorption of bile salts in the ileum would eventually lead to their increased secretion by the liver, but Secretin directly stimulates ductal secretion. Vagal stimulation can increase bile production; sympathetic activity generally decreases it.

Weekly Year 2: GIT Physiology Exam - March 20, 2026 (Section

Questions, Answers & Explanations