Gastrointestinal System — MCQs

Gastrointestinal System Indian Medical PG Practice Questions and MCQs

Question 381: Bilirubin glucuronide in the urine in the absence of urobilinogen suggests which of the following conditions?

A. Hemolytic jaundice
B. Hepatocellular jaundice
C. Obstructive jaundice (Correct Answer)
D. None of the above

Explanation: ### Explanation The presence of **bilirubin glucuronide** (conjugated bilirubin) in the urine without **urobilinogen** is a classic laboratory hallmark of **Obstructive (Post-hepatic) Jaundice**. **1. Why Obstructive Jaundice is Correct:** In obstructive jaundice (e.g., gallstones or pancreatic cancer), the flow of bile into the intestine is physically blocked. * **Bilirubin in Urine:** Conjugated bilirubin (water-soluble) cannot enter the gut, so it regurgitates into the bloodstream and is excreted by the kidneys (bilirubinuria). * **Absence of Urobilinogen:** Urobilinogen is formed by the action of colonic bacteria on bilirubin. Since bile cannot reach the intestine, no urobilinogen is produced. Consequently, none is reabsorbed into the blood or excreted in the urine. **2. Why Incorrect Options are Wrong:** * **Hemolytic Jaundice:** There is an overproduction of unconjugated bilirubin (water-insoluble), which cannot be excreted in urine. However, increased bilirubin reaches the gut, leading to **increased** urinary urobilinogen. * **Hepatocellular Jaundice:** There is both conjugated hyperbilirubinemia and impaired re-excretion of urobilinogen by damaged hepatocytes. Therefore, both bilirubin and urobilinogen are typically **present** in the urine. **3. NEET-PG High-Yield Pearls:** * **Acholuric Jaundice:** Another name for Hemolytic Jaundice (because urine contains no bilirubin). * **Clay-colored stools:** Occurs in obstructive jaundice due to the absence of stercobilin. * **Van den Bergh Reaction:** * Direct Positive = Conjugated Bilirubin (Obstructive). * Indirect Positive = Unconjugated Bilirubin (Hemolytic). * Biphasic = Both (Hepatocellular). * **Urinary Urobilinogen:** It is normally present in trace amounts; its complete absence is the most sensitive indicator of total biliary obstruction.

Question 382: Which is the first part of the gastrointestinal tract to regain motility in paralytic ileus?

A. Stomach
B. Large intestine
C. Rectum
D. Small intestine (Correct Answer)

Explanation: ### Explanation The correct answer is **Small intestine**. **Underlying Medical Concept:** Paralytic ileus is a temporary impairment of gastrointestinal (GI) motility, most commonly occurring after abdominal surgery (postoperative ileus). The recovery of bowel function follows a predictable chronological sequence based on the intrinsic electrical activity and myogenic properties of each segment. The **small intestine** is the first to regain motility, typically within **0 to 24 hours** post-surgery. This is because the small intestine has a higher frequency of basal electrical rhythm (slow waves) and is less sensitive to the inhibitory sympathetic reflexes and inflammatory mediators that cause ileus compared to the stomach and colon. **Analysis of Incorrect Options:** * **Stomach (A):** Gastric motility typically returns within **24 to 48 hours**. The stomach remains "stunned" longer than the small intestine due to its complex vagal innervation and reservoir function. * **Large Intestine (B):** The colon is the **last** part of the GI tract to recover, usually taking **48 to 72 hours** (or up to 5 days). This delay is the primary reason for postoperative constipation and the inability to pass flatus. * **Rectum (C):** While part of the large intestine, the rectum does not regain coordinated propulsive activity until the proximal colon recovers. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Recovery:** Small Intestine (0–24h) → Stomach (24–48h) → Large Intestine (48–72h). * **Clinical Sign of Recovery:** The passage of flatus or a bowel movement is the most reliable clinical indicator that ileus has resolved (reflecting colonic recovery). * **Management:** Early ambulation and gum chewing (sham feeding) are high-yield interventions known to accelerate the return of GI motility. * **Electrolytes:** Hypokalemia is a common metabolic cause that can prolong paralytic ileus.

Question 383: Which of the following cells secrete HCl?

A. Surface Neck Cells
B. Mucous Neck Cells
C. Parietal Cells (Correct Answer)
D. Chief Cells

Explanation: **Explanation:** The secretion of gastric juice is a highly specialized process involving different cell types located within the gastric glands. **Correct Answer: C. Parietal Cells** Parietal cells (also known as **oxyntic cells**) are primarily located in the body and fundus of the stomach. They are responsible for secreting **Hydrochloric Acid (HCl)** and **Intrinsic Factor (IF)**. HCl is essential for activating pepsinogen into pepsin and providing an acidic medium (pH 1.5–3.5) for protein digestion. The secretion of HCl is mediated by the $H^+/K^+$ ATPase pump (proton pump) located on the apical membrane. **Incorrect Options:** * **A & B. Surface and Mucous Neck Cells:** These cells secrete **alkaline mucus** and bicarbonates. This forms the "gastric mucosal barrier," protecting the stomach lining from the corrosive effects of HCl and pepsin. * **D. Chief Cells:** Also known as **peptic or zymogenic cells**, these secrete **pepsinogen** (an inactive precursor) and gastric lipase. Pepsinogen requires the HCl from parietal cells to become active pepsin. **High-Yield Clinical Pearls for NEET-PG:** * **Stimulants of HCl:** Gastrin (via CCK2 receptors), Acetylcholine (via M3 receptors), and Histamine (via H2 receptors). * **Inhibitors of HCl:** Somatostatin, Prostaglandins (PGE2), and Secretin. * **Pernicious Anemia:** Autoimmune destruction of parietal cells leads to a deficiency of Intrinsic Factor, resulting in Vitamin B12 malabsorption. * **Omeprazole:** A Proton Pump Inhibitor (PPI) that irreversibly inhibits the $H^+/K^+$ ATPase in parietal cells.

Question 384: In acute starvation, the feeling of intense hunger typically lasts for approximately how many hours?

A. 12-24 hours
B. 24-36 hours
C. 36-48 hours (Correct Answer)
D. 48-60 hours

Explanation: ### Explanation **Correct Answer: C. 36-48 hours** **Medical Concept:** The sensation of hunger in acute starvation is primarily driven by rhythmic peristaltic contractions of the stomach, known as **hunger contractions**. These occur when the stomach has been empty for several hours. In a state of total food deprivation, these contractions reach their maximum intensity within **36 to 48 hours**. After this peak, the intensity of hunger sensations significantly diminishes or may disappear entirely, even though the body remains in a state of starvation. This physiological adaptation is crucial for survival, as the initial intense drive to find food eventually gives way to metabolic conservation. **Analysis of Options:** * **Option A (12-24 hours):** During this period, glycogenolysis is the primary source of glucose. While hunger contractions begin, they have not yet reached their peak intensity. * **Option B (24-36 hours):** The intensity is increasing as the body transitions toward gluconeogenesis, but the physiological peak of "intense hunger" is typically documented closer to the 48-hour mark. * **Option D (48-60 hours):** By this stage, the sensation of hunger typically begins to wane. The body enters a state of ketosis, and the intense "hunger pangs" are replaced by a general sense of weakness rather than acute abdominal hunger. **High-Yield NEET-PG Pearls:** * **Hunger Contractions:** These are strongest in young, healthy individuals with high gastrointestinal tone and are significantly weaker in the elderly. * **Glucostat Hypothesis:** The hypothalamic satiety center (ventromedial nucleus) and hunger center (lateral hypothalamus) monitor blood glucose levels to regulate these sensations. * **Hormonal Trigger:** **Ghrelin**, secreted by P/D1 cells in the stomach fundus, is the primary "hunger hormone" that peaks before meals and during starvation to stimulate the hunger center.

Question 385: Which of the following increases appetite?

A. Insulin
B. Leptin
C. a-MSH
D. Neuropeptide Y (Correct Answer)

Explanation: **Explanation:** The regulation of appetite occurs primarily in the **Arcuate Nucleus (ARC)** of the hypothalamus, which contains two distinct sets of neurons: **Orexigenic** (appetite-stimulating) and **Anorexigenic** (appetite-suppressing). **Why Neuropeptide Y (NPY) is correct:** NPY is a potent **orexigenic** neurotransmitter. It is co-released with **Agouti-related peptide (AgRP)** from the ARC neurons. When activated (e.g., during fasting or by the hormone Ghrelin), NPY stimulates the hunger centers in the lateral hypothalamus, leading to increased food intake and decreased energy expenditure. **Analysis of Incorrect Options:** * **Leptin:** Produced by adipose tissue, it is a long-term satiety signal. It inhibits NPY/AgRP neurons and stimulates POMC neurons, thereby **decreasing** appetite. * **$\alpha$-MSH (Alpha-Melanocyte Stimulating Hormone):** This is an **anorexigenic** peptide derived from Pro-opiomelanocortin (POMC). It acts on MC3 and MC4 receptors in the hypothalamus to reduce food intake. * **Insulin:** Similar to leptin, insulin acts as a satiety signal in the CNS. It crosses the blood-brain barrier to inhibit orexigenic neurons, resulting in **decreased** appetite. **High-Yield Clinical Pearls for NEET-PG:** * **Ghrelin:** The only major peripheral hormone that **increases** appetite ("Hunger hormone"). It is secreted by P/D1 cells of the stomach. * **Satiety Center:** Located in the **Ventromedial Nucleus (VMN)** of the hypothalamus. Lesions here lead to hyperphagia and obesity. * **Hunger Center:** Located in the **Lateral Hypothalamus (LHA)**. Lesions here lead to aphagia and weight loss. * **POMC Deficiency:** Can lead to early-onset severe obesity and adrenal insufficiency.

Question 386: In newborns, at which site is the absorption of antibodies maximally achieved?

A. Duodenum
B. Jejunum
C. Ileum (Correct Answer)
D. Colon

Explanation: **Explanation:** The correct answer is **Ileum**. **1. Why the Ileum is the correct answer:** In newborns, passive immunity is acquired through the absorption of intact maternal antibodies (IgG) from colostrum and breast milk. This process occurs via **receptor-mediated endocytosis**. The specialized enterocytes in the **distal small intestine (Ileum)** possess specific neonatal Fc receptors (FcRn) on their apical surface. These receptors bind to the antibodies, which are then internalized in vesicles and transported across the cell to the basolateral membrane (transcytosis) to enter the systemic circulation. The ileum is the primary site for this because it has a higher density of these receptors and specialized endocytic machinery compared to the proximal segments. **2. Why the other options are incorrect:** * **Duodenum & Jejunum:** While these are the primary sites for the absorption of macronutrients (carbohydrates, proteins, and fats) and most electrolytes, they lack the specific density of FcRn receptors required for the bulk transport of intact large proteins like immunoglobulins. * **Colon:** The colon is primarily involved in the absorption of water and electrolytes and the fermentation of undigested carbohydrates. It does not play a significant role in protein or antibody absorption. **3. High-Yield Clinical Pearls for NEET-PG:** * **Gut Closure:** The ability to absorb intact antibodies is time-limited. "Gut closure" typically occurs within the first 24–48 hours of life (though it varies by species), after which the intestinal cells mature and can no longer perform transcytosis of large molecules. * **Low Proteolysis:** To facilitate this absorption, the newborn’s stomach has higher pH (less acidic) and lower pancreatic enzyme activity, preventing the premature digestion of these vital antibodies. * **Vitamin B12:** Remember that in adults, the **terminal ileum** remains the specific site for Vitamin B12-Intrinsic Factor complex absorption.

Question 387: Salivary amylase is inactivated by which of the following?

A. Enteropeptidase
B. Low pH of the stomach (Correct Answer)
C. High pH of the intestine
D. None of the above

Explanation: **Explanation:** Salivary amylase (also known as **ptyalin**) is an enzyme secreted by the salivary glands that initiates the digestion of dietary starches into maltose and dextrins. **Why the correct answer is right:** Salivary amylase functions optimally at a near-neutral pH (approximately **6.7 to 7.0**). When the food bolus reaches the stomach, it encounters gastric juice, which has a very **low pH (1.5 to 2.5)** due to the presence of hydrochloric acid (HCl). This high acidity denatures the protein structure of salivary amylase, rendering it completely inactive. While some starch digestion continues within the center of a food bolus for a short period, the enzyme is eventually inactivated as the bolus mixes with gastric secretions. **Why the incorrect options are wrong:** * **A. Enteropeptidase:** Also known as enterokinase, this enzyme is located in the duodenal brush border. Its specific role is to convert trypsinogen into active trypsin; it has no inhibitory effect on amylase. * **C. High pH of the intestine:** The intestine actually has a slightly alkaline pH (around 7.0 to 8.0), which is favorable for amylase activity. In fact, starch digestion is completed in the small intestine by **pancreatic amylase**, which functions optimally in this environment. **High-Yield Facts for NEET-PG:** * **Chloride ions ($Cl^-$):** These are essential activators for salivary amylase. * **Site of action:** Salivary amylase accounts for only about 5% of total starch digestion in the mouth but can contribute up to 30-40% before being fully inactivated in the stomach. * **Lingual Lipase:** Unlike amylase, lingual lipase is acid-stable and remains active in the stomach, beginning lipid digestion.

Question 388: Kupffer cells in the liver are:

A. Endothelial cells
B. Secretory cells
C. Phagocytic cells (Correct Answer)
D. Phagocytic cells

Explanation: **Explanation:** **Kupffer cells** are specialized, resident macrophages located within the hepatic sinusoids. They form part of the **Mononuclear Phagocyte System (MPS)** and are the most abundant population of tissue macrophages in the body. **1. Why the Correct Answer is Right:** Kupffer cells are primarily **phagocytic cells**. Their main physiological role is to filter the portal blood arriving from the gastrointestinal tract. They engulf and digest particulate matter, aged red blood cells, and, most importantly, bacteria (such as *E. coli*) and endotoxins. This prevents systemic bacteremia and protects the body from gut-derived pathogens. **2. Why the Other Options are Wrong:** * **Endothelial cells:** While Kupffer cells are located within the sinusoids, they are distinct from the sinusoidal endothelial cells. Endothelial cells form the lining of the blood vessels and possess "fenestrations" (pores), whereas Kupffer cells are immune cells attached to the luminal surface of these endothelia. * **Secretory cells:** Although Kupffer cells can secrete cytokines (like TNF-alpha and Interleukins) during an inflammatory response, their primary anatomical classification and functional definition in physiology is as phagocytes. * **Note on Options C & D:** Both options provided the same answer; in a standard exam, the primary functional classification remains phagocytic. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** They are found on the luminal side of the sinusoidal endothelium, protruding into the **Space of Disse**. * **Origin:** They are derived from yolk-sac progenitors and maintained by local proliferation (though they can be replenished by blood monocytes during injury). * **Staining:** They can be identified using **CD68** markers or by their ability to take up vital dyes like India ink or Trypan blue. * **Clinical Significance:** In conditions like alcoholic liver disease, Kupffer cell activation by endotoxins leads to the release of inflammatory mediators that activate **Stellate cells** (Ito cells), leading to liver fibrosis.

Question 389: Which class of carbohydrates is absorbed fastest in the intestine?

A. Hexoses (Correct Answer)
B. Disaccharides
C. Oligosaccharides
D. Polysaccharides

Explanation: **Explanation:** The absorption of carbohydrates in the small intestine is a highly specific process that occurs only in the form of **monosaccharides**. **1. Why Hexoses are correct:** Hexoses (6-carbon monosaccharides) like **Glucose and Galactose** are absorbed the fastest because they are the final products of carbohydrate digestion. They do not require further enzymatic breakdown. They are rapidly transported across the apical membrane of enterocytes via **SGLT-1** (Secondary active transport with Sodium) and across the basolateral membrane via **GLUT-2** (Facilitated diffusion). Fructose, another hexose, is absorbed via GLUT-5. Since they are already in their simplest absorbable form, their uptake is immediate. **2. Why other options are incorrect:** * **Disaccharides (e.g., Lactose, Sucrose):** These cannot be absorbed directly. They must first be hydrolyzed into monosaccharides by "brush border enzymes" (Lactase, Sucrase) before transport can occur. * **Oligosaccharides & Polysaccharides (e.g., Starch, Glycogen):** These are complex molecules that require extensive luminal digestion by salivary and pancreatic **alpha-amylase** followed by brush border enzymes. This multi-step process makes their overall absorption rate significantly slower than that of free hexoses. **High-Yield Clinical Pearls for NEET-PG:** * **Rate of Absorption:** Galactose > Glucose > Fructose. * **SGLT-1:** This transporter is the physiological basis for **Oral Rehydration Therapy (ORT)**; sodium absorption is enhanced in the presence of glucose. * **Diagnostic Test:** The **D-Xylose test** is used to distinguish between malabsorption due to mucosal disease (low absorption) and pancreatic deficiency (normal absorption), as D-xylose is a pentose that does not require pancreatic enzymes for breakdown.

Question 390: Which of the following inhibits the gastric phase of gastric secretion?

A. Amino acids in the stomach
B. Vagus effect
C. Distension of the stomach
D. Low gastric pH (Correct Answer)

Explanation: **Explanation:** The regulation of gastric secretion occurs in three phases: Cephalic, Gastric, and Intestinal. The **Gastric Phase** is responsible for the majority (about 60%) of total acid secretion and is primarily mediated by the hormone **gastrin**. **Why "Low gastric pH" is correct:** The gastric phase is regulated by a **negative feedback mechanism**. When the pH of the gastric contents falls below 3.0, it stimulates **D-cells** in the antrum to release **Somatostatin**. Somatostatin acts directly on G-cells to inhibit the release of gastrin. Once gastrin levels drop, parietal cells decrease HCl production. This "acid brake" prevents the stomach environment from becoming excessively acidic, which could damage the gastric mucosa. **Analysis of Incorrect Options:** * **A. Amino acids in the stomach:** These are potent stimulators of the gastric phase. They directly stimulate G-cells to release gastrin. * **B. Vagus effect:** Vagal stimulation (via the Cephalic phase and vago-vagal reflexes) increases acid secretion by releasing Acetylcholine (ACh) and Gastrin-Releasing Peptide (GRP). * **C. Distension of the stomach:** Mechanical stretching of the stomach wall triggers local enteric reflexes and long vago-vagal reflexes, both of which stimulate gastrin release and acid secretion. **High-Yield Clinical Pearls for NEET-PG:** * **Somatostatin** is the "universal inhibitor" of the GI tract. * **pH < 1.5** almost completely shuts down gastrin secretion. * **Gastrin-Releasing Peptide (GRP)** is the neurotransmitter used by the Vagus nerve to stimulate G-cells; notably, this pathway is **not blocked by Atropine**. * The **Intestinal Phase** is primarily inhibitory, mediated by "Enterogastrones" like Secretin and CCK.

Practice by Chapter

Gastrointestinal Motility

Practice Questions

Gastrointestinal Secretions

Practice Questions

Digestion and Absorption

Practice Questions

Gastrointestinal Hormones

Practice Questions

Hepatobiliary Physiology

Practice Questions

Pancreatic Exocrine Function

Practice Questions

Gastrointestinal Circulation

Practice Questions

Intestinal Immune System

Practice Questions

Gut Microbiome

Practice Questions

Regulation of Food Intake

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free