Weekly Year 2: GIT Physiology Exam - August 21, 2026 (Sec...

36 clinical MCQs in Weekly Exam: Year 2: GIT Physiology. Which single statement below, about the stomach, is correct?. Kenya, Africa and global revision.

Questions, Answers & Explanations

1. Q1. Which single statement below, about the stomach, is correct?

   • Acid secretion occurs in response to secretion of the hormone, carbonic anhydrase.
   • Glands called Peyer's patches are responsible for acid secretion.
   • The vagus nerve inhibits acid secretion after a meal has been consumed.
   • Pepsinogen and gastric lipase are secreted into the lumen of the stomach.

   Answer: Pepsinogen and gastric lipase are secreted into the lumen of the stomach.

   Explanation: Pepsinogen (from chief cells) and gastric lipase (from chief cells) are secreted into the stomach lumen to begin protein and fat digestion, respectively. Carbonic anhydrase is an enzyme, not a hormone, involved in acid secretion within parietal cells. Peyer's patches are immune structures in the ileum. The vagus nerve (parasympathetic) stimulates acid secretion.

2. Q2. Water transport can occur from the lumen of the intestine to the bloodstream, or vice versa. Which statement is correct?

   • Water is primarily transported actively against its concentration gradient in the small intestine.
   • The primary driving force for water absorption in the small intestine is an osmotic gradient created by solute absorption.
   • Water secretion into the lumen always occurs when there is an increase in intraluminal hydrostatic pressure.
   • Aquaporins are the sole mechanism for water movement across intestinal epithelial cells.

   Answer: The primary driving force for water absorption in the small intestine is an osmotic gradient created by solute absorption.

   Explanation: Water transport across the intestinal epithelium is largely passive, driven by osmotic gradients. As solutes (like Na+, glucose, amino acids) are actively absorbed, they create an osmotic gradient that draws water from the lumen into the bloodstream. Water can move via paracellular and transcellular (aquaporin-mediated) routes, but the osmotic gradient is the main driving force.

3. Q3. Which statement about fat digestion and absorption is correct?

   • Lingual and gastric lipases are primarily responsible for the complete digestion of triglycerides into monoglycerides and fatty acids.
   • Bile salts emulsify fats in the stomach, preparing them for lipase action.
   • Chylomicrons are formed within intestinal epithelial cells and enter the lacteals.
   • Short-chain fatty acids are incorporated into micelles and transported into lacteals.

   Answer: Chylomicrons are formed within intestinal epithelial cells and enter the lacteals.

   Explanation: Chylomicrons are re-esterified triglycerides packaged with proteins within the intestinal epithelial cells (enterocytes) and are too large to enter capillaries, so they enter the lymphatic system via lacteals. Lingual and gastric lipases initiate triglyceride digestion but are less effective than pancreatic lipase, which, with colipase, completes digestion in the small intestine. Bile salts emulsify fats in the small intestine, not the stomach. Short-chain fatty acids are absorbed directly into the portal blood, not incorporated into micelles or chylomicrons.

4. Q4. Which statement about protein digestion is most correct?

   • Protein digestion begins in the mouth with salivary amylase.
   • Pepsin is primarily responsible for breaking down proteins into individual amino acids in the stomach.
   • Pancreatic proteases (e.g., trypsin, chymotrypsin) are secreted in active forms to immediately digest proteins.
   • Small peptides and amino acids are absorbed by various transporters into intestinal epithelial cells.

   Answer: Small peptides and amino acids are absorbed by various transporters into intestinal epithelial cells.

   Explanation: Protein digestion primarily occurs in the stomach and small intestine. Small peptides (di- and tripeptides) and individual amino acids are absorbed into intestinal epithelial cells via specific transport systems (e.g., Pept1 for di-/tripeptides, various amino acid transporters). Protein digestion begins in the stomach with pepsin, which breaks proteins into large polypeptides. Pancreatic proteases are secreted as inactive zymogens (e.g., trypsinogen, chymotrypsinogen) and activated in the lumen of the small intestine by enteropeptidase and trypsin, respectively.

5. Q5. Which statement about dietary fibre is most correct?

   • Dietary fibre is digested by human digestive enzymes in the small intestine.
   • Soluble fibre promotes faster gastric emptying and reduces intestinal transit time.
   • Insoluble fibre increases stool bulk and helps prevent constipation.
   • All types of dietary fibre are fermented by colonic bacteria to produce vitamins.

   Answer: Insoluble fibre increases stool bulk and helps prevent constipation.

   Explanation: Insoluble fibre, such as cellulose, is not digestible by human enzymes, absorbs water, and adds bulk to stool, thereby facilitating bowel movements and preventing constipation. Fibre is not digested by human enzymes. Soluble fibre can delay gastric emptying. While some fibres are fermented by colonic bacteria to produce short-chain fatty acids, not all types are fermented, and the primary production is not vitamins.

6. Q6. Which statement about absorption is most correct?

   • The stomach is the primary site for nutrient absorption due to its highly acidic environment.
   • The small intestine's villi and microvilli significantly decrease its surface area for absorption.
   • Most carbohydrates are absorbed as monosaccharides in the small intestine.
   • Iron absorption is unregulated and directly proportional to dietary intake.

   Answer: Most carbohydrates are absorbed as monosaccharides in the small intestine.

   Explanation: The vast majority of carbohydrates are digested into monosaccharides (glucose, galactose, fructose) and absorbed as such in the small intestine. The stomach absorbs very few substances (e.g., alcohol, aspirin). The villi and microvilli greatly increase the surface area of the small intestine for efficient absorption. Iron absorption is tightly regulated, primarily at the level of intestinal uptake, and is not directly proportional to dietary intake, especially when iron stores are high.

7. Q7. Which statement about the oral phase of digestion is INCORRECT?

   • Salivary amylase begins the chemical digestion of carbohydrates.
   • The chewing of food is a voluntary process.
   • Saliva moistens food and helps form a bolus for swallowing.
   • The oral phase involves significant fat digestion by salivary lipase.

   Answer: The oral phase involves significant fat digestion by salivary lipase.

   Explanation: While lingual lipase (a type of salivary lipase) is secreted in the mouth, its activity is minimal at salivary pH and becomes significant only when it reaches the acidic environment of the stomach. Therefore, the oral phase does not involve significant fat digestion. Salivary amylase begins carbohydrate digestion. Chewing is voluntary, and saliva facilitates bolus formation.

8. Q8. Which statement about stomach lining cells is correct?

   • Parietal cells secrete pepsinogen and gastric lipase.
   • Chief cells produce hydrochloric acid and intrinsic factor.
   • G cells secrete gastrin, which stimulates acid secretion.
   • Mucous neck cells produce the thick alkaline mucus layer protecting the stomach wall.

   Answer: G cells secrete gastrin, which stimulates acid secretion.

   Explanation: G cells, located primarily in the antrum of the stomach, secrete the hormone gastrin, which stimulates parietal cells to secrete hydrochloric acid. Parietal cells secrete HCl and intrinsic factor. Chief cells secrete pepsinogen and gastric lipase. Surface mucous cells (not mucous neck cells) produce the thick, alkaline mucus layer protecting the stomach surface, while mucous neck cells produce a thinner, more acidic mucus.

9. Q9. Which statement about pancreatic enzyme secretion is correct?

   • Secretin is the primary stimulant for pancreatic enzyme secretion.
   • Pancreatic enzymes are synthesized and stored in duct cells.
   • Cholecystokinin (CCK) stimulates the pancreatic acinar cells to secrete digestive enzymes.
   • Pancreatic amylase is responsible for digesting proteins into peptides.

   Answer: Cholecystokinin (CCK) stimulates the pancreatic acinar cells to secrete digestive enzymes.

   Explanation: Cholecystokinin (CCK), released in response to fats and proteins in the duodenum, is the primary stimulant for the secretion of digestive enzymes from the pancreatic acinar cells. Secretin primarily stimulates bicarbonate secretion from duct cells. Pancreatic enzymes are synthesized in acinar cells. Pancreatic amylase digests carbohydrates, while proteases like trypsin digest proteins.

10. Q10. Which statement about post-meal motility is correct?

    • The migrating motor complex (MMC) is characteristic of post-meal motility.
    • Peristalsis is the primary motor pattern in the small intestine that mixes chyme with digestive juices.
    • Gastric emptying rate is increased by the presence of fat and acid in the duodenum.
    • Segmentation contractions in the small intestine primarily serve to mix chyme and expose it to the absorptive surface.

    Answer: Segmentation contractions in the small intestine primarily serve to mix chyme and expose it to the absorptive surface.

    Explanation: Segmentation contractions are the primary motor pattern in the small intestine responsible for mixing chyme with digestive juices and exposing it to the absorptive surface. The migrating motor complex (MMC) occurs in the fasting state to clear residual material. Peristalsis is primarily for propelling chyme. Gastric emptying is slowed, not increased, by the presence of fat and acid in the duodenum due to enterogastric reflexes.

11. Q11. Which best describes colonic microbiota functions?

    • They primarily absorb vitamins and minerals from the diet.
    • They synthesize digestive enzymes that break down proteins and fats.
    • They ferment indigestible carbohydrates, producing short-chain fatty acids and vitamins.
    • They are essential for initiating the defecation reflex.

    Answer: They ferment indigestible carbohydrates, producing short-chain fatty acids and vitamins.

    Explanation: Colonic microbiota ferment indigestible dietary carbohydrates (fibre) that reach the large intestine, producing short-chain fatty acids (e.g., butyrate, acetate, propionate) that can be absorbed and used as energy by the host, and also synthesize some vitamins (e.g., K, B vitamins). While some vitamins are produced, they don't primarily absorb all vitamins/minerals from the diet or synthesize digestive enzymes for major nutrients. The defecation reflex is a nervous system function, not directly initiated by microbiota.

12. Q12. What explains fibre's protective effect against colon cancer?

    • Fibre is directly absorbed by colonic epithelial cells, providing anti-cancer nutrients.
    • Fibre reduces colonic transit time, decreasing exposure of the mucosa to potential carcinogens.
    • Fibre enhances the absorption of dietary carcinogens, leading to their rapid excretion.
    • Fibre promotes the growth of pathogenic bacteria that outcompete harmful strains.

    Answer: Fibre reduces colonic transit time, decreasing exposure of the mucosa to potential carcinogens.

    Explanation: Fibre, especially insoluble fibre, increases stool bulk and reduces colonic transit time. This decreased transit time means that potential carcinogens present in the faeces have less time to interact with and damage the colonic mucosa, thereby reducing cancer risk. Fibre is not directly absorbed. Fibre does not enhance absorption of carcinogens; rather, it can bind to them or dilute them. Fibre generally promotes beneficial gut bacteria.

13. Q13. Which of the following statements is FALSE?

    • Sodium is actively reabsorbed in the colon.
    • Approximately 90% of colonic water content is reabsorbed in the large bowel.
    • Water intoxication may result from a large volume of enema.
    • The longest intestinal transit time occurs in the ascending colon.

    Answer: The longest intestinal transit time occurs in the ascending colon.

    Explanation: The longest intestinal transit time occurs in the transverse and descending colon, not the ascending colon, due to its function in storage and dehydration of faeces. Sodium is actively reabsorbed in the colon, drawing water with it. A significant amount of water (up to 90% of colonic content) is reabsorbed in the large bowel. Water intoxication can indeed occur if a large volume of hypotonic enema is rapidly absorbed.

14. Q14. Which tissue layer provides for primary digestive motility?

    • Mucosa
    • Submucosa
    • Muscularis externa
    • Serosa

    Answer: Muscularis externa

    Explanation: The muscularis externa (or muscularis propria) consists of an inner circular and an outer longitudinal layer of smooth muscle. These layers are responsible for the major contractile activities of the GI tract, including peristalsis and segmentation, which drive digestive motility.

15. Q15. Which statement about bile is true?

    • Bile is primarily produced by the gallbladder.
    • Bile salts are recycled to the liver via the portal circulation in the enterohepatic circulation.
    • Bile contains digestive enzymes for fat digestion.
    • The main function of bile is to neutralize gastric acid in the duodenum.

    Answer: Bile salts are recycled to the liver via the portal circulation in the enterohepatic circulation.

    Explanation: Bile salts are essential for fat digestion and absorption. After aiding digestion in the small intestine, approximately 95% of bile salts are reabsorbed in the terminal ileum and returned to the liver via the portal vein for reuse, a process known as enterohepatic circulation. Bile is produced by the liver, stored and concentrated by the gallbladder. Bile does not contain digestive enzymes. While it is alkaline, its primary function is fat emulsification, not gastric acid neutralization (which is mainly done by pancreatic bicarbonate).

16. Q16. Which statement regarding the swallowing reflex is false?

    • The pharyngeal phase is involuntary.
    • The soft palate elevates to prevent food from entering the nasopharynx.
    • Respiration is temporarily inhibited during the pharyngeal phase.
    • The esophageal phase is initiated by voluntary relaxation of the upper esophageal sphincter.

    Answer: The esophageal phase is initiated by voluntary relaxation of the upper esophageal sphincter.

    Explanation: The esophageal phase is initiated by the relaxation of the upper esophageal sphincter, which is an involuntary reflex response to swallowing, not a voluntary relaxation. The pharyngeal phase is involuntary and involves the elevation of the soft palate, closure of the epiglottis, and inhibition of respiration to prevent aspiration. The bolus then enters the esophagus.

17. Q17. Which of the following statements is TRUE?

    • Gastric inhibitory peptide (GIP) stimulates gastric acid secretion.
    • Secretin primarily stimulates enzyme secretion from the pancreas.
    • Cholecystokinin (CCK) slows gastric emptying.
    • Motilin is responsible for stimulating mass movements in the colon.

    Answer: Cholecystokinin (CCK) slows gastric emptying.

    Explanation: Cholecystokinin (CCK), released in response to fat and protein in the duodenum, inhibits gastric emptying to allow sufficient time for digestion and absorption in the small intestine. GIP inhibits gastric acid secretion. Secretin primarily stimulates bicarbonate secretion from the pancreas. Motilin stimulates the migrating motor complex in the fasting state, not mass movements in the colon (which are largely stimulated by distension and autonomic reflexes).

18. Q18. What is false about tonic contractions?

    • They are sustained contractions lasting minutes to hours.
    • They occur in sphincters and the stomach to maintain pressure.
    • They are primarily responsible for mixing chyme in the small intestine.
    • They involve sustained depolarization of smooth muscle cells.

    Answer: They are primarily responsible for mixing chyme in the small intestine.

    Explanation: Tonic contractions are sustained contractions that maintain constant pressure (e.g., in sphincters like the lower esophageal sphincter or pylorus) or continuous mixing/storage (e.g., gastric fundus). They last minutes to hours and involve sustained depolarization. Mixing in the small intestine is primarily achieved by phasic (rhythmic) segmenting contractions, not tonic contractions.

19. Q19. Which of the following is characteristic of the segmenting movements in the small intestine?

    • They propel chyme rapidly towards the large intestine.
    • They are responsible for the Migrating Motor Complex (MMC).
    • They involve contractions of circular muscle, primarily for mixing and exposing chyme to mucosa.
    • They are strong, infrequent contractions occurring primarily in the colon.

    Answer: They involve contractions of circular muscle, primarily for mixing and exposing chyme to mucosa.

    Explanation: Segmenting movements are localized contractions of the circular muscle layer that divide the small intestine into segments, effectively mixing the chyme with digestive juices and bringing it into contact with the absorptive surface of the mucosa. They are not primarily propulsive (that's peristalsis) or responsible for the MMC (that's motilin in the fasting state), nor are they strong, infrequent contractions characteristic of the colon (mass movements).

20. Q20. Secretion of saliva increases in all of the below except:

    • Sight or smell of food.
    • Chewing a dry cracker.
    • Fear or anxiety.
    • Stimulation of parasympathetic nerves to salivary glands.

    Answer: Fear or anxiety.

    Explanation: Fear or anxiety typically decreases salivary secretion, leading to a 'dry mouth' sensation, due to sympathetic nervous system activation. The sight or smell of food (cephalic phase), chewing, and parasympathetic stimulation all increase saliva production.

21. Q21. Defecation is a reflex action...

    • that is entirely voluntary and under conscious control.
    • primarily initiated by the presence of chyme in the rectum.
    • involving both involuntary spinal reflexes and voluntary control.
    • that results from relaxation of the internal anal sphincter only.

    Answer: involving both involuntary spinal reflexes and voluntary control.

    Explanation: Defecation is a reflex initiated by distension of the rectum, which triggers an involuntary spinal reflex that causes contraction of the rectum and relaxation of the internal anal sphincter. However, the external anal sphincter is under voluntary control, allowing a conscious decision to delay or facilitate defecation. It's not entirely voluntary or involuntary.

22. Q22. In the stomach,

    • the primary role is nutrient absorption.
    • gastric motility is primarily characterized by segmentation.
    • intrinsic factor is secreted by chief cells to aid vitamin B12 absorption.
    • protein digestion begins with the action of pepsin.

    Answer: protein digestion begins with the action of pepsin.

    Explanation: Protein digestion begins in the stomach with the enzyme pepsin, secreted by chief cells in its inactive form, pepsinogen, and activated by HCl. The stomach's primary role is food storage, mixing, and initial protein digestion, not nutrient absorption. Gastric motility includes receptive relaxation, mixing, and emptying, not primarily segmentation. Intrinsic factor is secreted by parietal cells, not chief cells.

23. Q23. Intestinal secretions contain...

    • a wide array of digestive enzymes for all macronutrients, including pepsin.
    • bicarbonate to neutralize acidic chyme, primarily from Brunner's glands and enterocytes.
    • intrinsic factor for Vitamin B12 absorption.
    • mainly water and mucus, with enzymes primarily bound to the brush border.

    Answer: mainly water and mucus, with enzymes primarily bound to the brush border.

    Explanation: Intestinal secretions (succus entericus) are primarily composed of water and mucus, which lubricate and protect the mucosa. While the brush border of enterocytes contains many digestive enzymes (e.g., disaccharidases, peptidases), the lumenal secretions themselves contain few freely secreted enzymes. Bicarbonate is primarily from the pancreas. Intrinsic factor is gastric.

24. Q24. A 55-year-old man with chronic alcohol consumption presents with nonspecific complaints of dyspepsia. Examination reveals destruction of gastric glands. This predisposes him to...

    • increased gastrin secretion.
    • an increased risk of peptic ulcers.
    • vitamin B12 deficiency.
    • rapid gastric emptying.

    Answer: vitamin B12 deficiency.

    Explanation: Destruction of gastric glands, particularly parietal cells, would lead to reduced intrinsic factor secretion. Intrinsic factor is crucial for the absorption of vitamin B12 in the ileum. Chronic deficiency leads to pernicious anemia and neurological issues. It would lead to decreased acid (hypochlorhydria/achlorhydria) and thus increased gastrin (due to reduced negative feedback) and potentially slower digestion/gastric emptying, and reduced peptic ulcers (less acid). However, the most direct and severe consequence related to a specific secretion from gastric glands is B12 deficiency due to lack of intrinsic factor.

25. Q25. Which statement about some GIT hormones is true?

    • Gastrin is released as a result of stomach distension and vagal stimulation.
    • Secretin stimulates the pancreatic acinar cells to secrete enzymes.
    • Pancreozymin is a distinct hormone from Cholecystokinin (CCK).
    • Secretin causes excessive gastric secretion and accelerates gastric emptying.

    Answer: Gastrin is released as a result of stomach distension and vagal stimulation.

    Explanation: Gastrin secretion from G cells is stimulated by stomach distension, peptides/amino acids, and vagal stimulation. Secretin stimulates pancreatic duct cells to secrete bicarbonate, not acinar cells for enzymes (that's CCK). Pancreozymin was an earlier name for CCK, so they are the same. Secretin inhibits gastric secretion and motility, thus slowing gastric emptying.

26. Q26. VIP (Vasoactive Intestinal Peptide) causes which of the following?

    • Increased gastric acid secretion.
    • Contraction of GI smooth muscle.
    • Relaxation of GI smooth muscle and stimulation of intestinal secretion.
    • Increased absorption of water and electrolytes in the small intestine.

    Answer: Relaxation of GI smooth muscle and stimulation of intestinal secretion.

    Explanation: VIP is a neuropeptide that causes relaxation of GI smooth muscle (e.g., sphincters), vasodilation, and stimulation of intestinal and pancreatic secretion (water and electrolytes). It generally inhibits gastric acid secretion and motility, and promotes secretion rather than absorption of water/electrolytes.

27. Q27. Stimulation of Gastrointestinal Secretion can include:

    • Reduced parasympathetic activity.
    • Decreased luminal pH in the small intestine.
    • Distension of the stomach.
    • Release of somatostatin.

    Answer: Distension of the stomach.

    Explanation: Distension of the stomach (gastric phase) stimulates secretion of acid and pepsinogen via local reflexes and vagal stimulation. Increased parasympathetic activity stimulates secretions. Decreased luminal pH in the duodenum stimulates secretin release, which in turn stimulates pancreatic bicarbonate secretion. Somatostatin inhibits many GI secretions.

28. Q28. The Secretin hormone:

    • is released in response to high fat content in the duodenum.
    • primarily stimulates the secretion of pancreatic bicarbonate.
    • increases gastric motility and acid production.
    • acts mainly on the gallbladder to cause contraction.

    Answer: primarily stimulates the secretion of pancreatic bicarbonate.

    Explanation: Secretin is released from S cells in the duodenum in response to low pH (acidic chyme). Its primary action is to stimulate the pancreas to secrete a bicarbonate-rich fluid to neutralize the acid. It inhibits gastric motility and acid production and has little direct effect on gallbladder contraction (that's CCK).

29. Q29. The GIT is controlled by:

    • Only the central nervous system.
    • Only the enteric nervous system (ENS).
    • A combination of the enteric nervous system, autonomic nervous system, and hormones.
    • Hormones exclusively.

    Answer: A combination of the enteric nervous system, autonomic nervous system, and hormones.

    Explanation: The gastrointestinal tract is controlled by a complex interplay of systems: the intrinsic enteric nervous system (ENS), extrinsic autonomic nervous system (parasympathetic and sympathetic), and various GI hormones and paracrine factors. These systems work together to regulate motility, secretion, digestion, and absorption.

30. Q30. Inhibition of the myenteric plexus leads to which of the following?

    • Increased intestinal motility.
    • Enhanced secretion of digestive enzymes.
    • Decreased intestinal motility.
    • Stronger segmentation contractions.

    Answer: Decreased intestinal motility.

    Explanation: The myenteric (Auerbach's) plexus is primarily responsible for regulating GI motility. Inhibition of this plexus would therefore lead to decreased intestinal motility, potentially causing conditions like ileus or constipation. Enhanced secretion is largely regulated by the submucosal plexus and hormones.

31. Q31. The secretion of gastrin ceases (stops) when:

    • The stomach is distended with food.
    • Peptides and amino acids are present in the stomach.
    • The pH of the stomach lumen falls below 3.
    • Vagal stimulation is increased.

    Answer: The pH of the stomach lumen falls below 3.

    Explanation: Gastrin secretion is strongly inhibited when the pH of the stomach lumen becomes highly acidic (typically below pH 3). This negative feedback mechanism ensures that acid secretion does not become excessive. Stomach distension, peptides, amino acids, and vagal stimulation all stimulate gastrin release.

32. Q32. Stimulation of the submucosal plexus results in an increase in which of the following?

    • Intestinal wall contraction for peristalsis.
    • Secretion of digestive juices.
    • Blood flow to the muscles of the GI tract.
    • Rate of gastric emptying.

    Answer: Secretion of digestive juices.

    Explanation: The submucosal (Meissner's) plexus is primarily involved in regulating glandular secretions and local blood flow. Therefore, its stimulation would result in an increase in the secretion of digestive juices. Peristalsis is mainly controlled by the myenteric plexus. Blood flow to the mucosa (rather than muscles) is also regulated by this plexus, but secretion is a more direct and prominent effect.

33. Q33. Cholecystokinin (CCK):

    • is released in response to carbohydrates in the duodenum.
    • stimulates gastric acid secretion and motility.
    • causes gallbladder contraction and pancreatic enzyme secretion.
    • is primarily involved in regulating intestinal water absorption.

    Answer: causes gallbladder contraction and pancreatic enzyme secretion.

    Explanation: Cholecystokinin (CCK) is released from I cells in the duodenum in response to fats and proteins. It has multiple effects, including stimulating contraction of the gallbladder (to release bile for fat emulsification) and stimulating pancreatic acinar cells to secrete digestive enzymes (for fat and protein digestion). It also inhibits gastric emptying and acid secretion. It is not primarily involved in water absorption or released due to carbohydrates.

34. Q34. A major part of gallbladder contractions are due to:

    • Secretin.
    • Gastrin.
    • Vagal stimulation and Cholecystokinin (CCK).
    • Somatostatin.

    Answer: Vagal stimulation and Cholecystokinin (CCK).

    Explanation: Gallbladder contraction is primarily stimulated by Cholecystokinin (CCK), released in response to fats and proteins in the duodenum. Vagal (parasympathetic) stimulation also contributes to gallbladder contraction. Secretin primarily stimulates bicarbonate secretion. Gastrin stimulates gastric acid. Somatostatin is inhibitory.

35. Q35. Which of the following statements about GIT hormones affecting gastric function is correct?

    • Gastrin is the only hormone that stimulates gastric acid secretion.
    • Secretin, CCK, and GIP all inhibit gastric acid secretion and/or motility.
    • Somatostatin acts primarily to stimulate gastrin release.
    • Histamine directly inhibits parietal cell acid secretion.

    Answer: Secretin, CCK, and GIP all inhibit gastric acid secretion and/or motility.

    Explanation: Secretin, Cholecystokinin (CCK), and Gastric Inhibitory Peptide (GIP) are all enterogastrones, hormones released from the small intestine that inhibit gastric acid secretion and/or gastric motility, to allow the small intestine time to process incoming chyme. Gastrin is a major stimulant, but not the only one (e.g., histamine, ACh). Somatostatin inhibits gastrin release and acid secretion. Histamine stimulates, not inhibits, parietal cell acid secretion.

36. Q36. Brunner’s glands in the duodenum primarily secrete:

    • digestive enzymes.
    • hydrochloric acid.
    • alkaline mucus.
    • intrinsic factor.

    Answer: alkaline mucus.

    Explanation: Brunner’s glands are located in the submucosa of the duodenum and secrete a thick, alkaline mucus. This mucus helps to neutralize the acidic chyme entering from the stomach and protect the duodenal mucosa from acid erosion. Digestive enzymes are primarily pancreatic or brush border; HCl and intrinsic factor are gastric secretions.