Gastrointestinal System — MCQs
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A 4-year-old boy is admitted to the hospital with pneumonia and respiratory distress. The nurses report that the child's bowel movements are greasy and have a pungent odor. A sweat-chloride test is positive. Which of the following mechanisms of disease is the most likely cause of steatorrhea in this child?
In which of the following parts of the gastrointestinal tract is the highest luminal concentration of potassium seen?
Lactose intolerance in a suspected patient is diagnosed by giving an oral load and measuring concentrations of ?
Which of the following has the highest concentration of potassium in a normal individual?
Normal 24-hour gastric acid output in stomach is
Which of the following has the highest pH?
Primary component of nonadrenergic noncholinergic nerve transmission in gut is:
When closure in intercuspal position is attained during mastication, movement stops for about _________ msec before another cycle begins.
Two normal, healthy subjects volunteer for a study on insulin secretion. In Patient 1, blood glucose is increased to 150 mg/dL by direct intravenous infusion. In Patient 2, blood glucose is increased to 150 mg/dL by ingestion of oral glucose. The peak plasma insulin concentration produced in Patient 1 is 70 uU/mL while in Patient 2, it is 95 uU/mL. Which of the following best explains the higher insulin concentration in Patient 2?
Destruction of fat in acute pancreatitis is due to ?
Gastrointestinal System Indian Medical PG Practice Questions and MCQs
Question 491: A 4-year-old boy is admitted to the hospital with pneumonia and respiratory distress. The nurses report that the child's bowel movements are greasy and have a pungent odor. A sweat-chloride test is positive. Which of the following mechanisms of disease is the most likely cause of steatorrhea in this child?
- A. Abnormal dietary intake
- B. Lack of pancreatic enzyme secretion (Correct Answer)
- C. Hyperbilirubinemia with kernicterus
- D. Bacterial overgrowth
Explanation: ***Lack of pancreatic enzyme secretion*** - The clinical picture of **pneumonia**, **respiratory distress**, **greasy/pungent bowel movements (steatorrhea)**, and a **positive sweat chloride test** is classic for **cystic fibrosis (CF)**. - In CF, a defective **CFTR protein** leads to thick, viscous secretions that block pancreatic ducts, causing **pancreatic insufficiency** and leading to inadequate release of digestive enzymes necessary for fat absorption. *Abnormal dietary intake* - While dietary factors can contribute to digestive issues, abnormal intake alone would not explain the other core features like the **positive sweat chloride test** or recurrent respiratory infections characteristic of cystic fibrosis. - This mechanism doesn't account for the fundamental physiological defect seen in this patient. *Hyperbilirubinemia with kernicterus* - **Kernicterus** is a condition caused by very high levels of **bilirubin** in a newborn's blood, leading to brain damage; it is not typically associated with steatorrhea or the respiratory symptoms described. - While CF can sometimes cause liver complications, **kernicterus** is unrelated to the primary mechanism of steatorrhea in this context. *Bacterial overgrowth* - **Bacterial overgrowth** in the small intestine can cause malabsorption and diarrhea, but it does not directly lead to the specific findings of **respiratory distress**, recurrent infections, or the underlying genetic defect indicated by a **positive sweat chloride test** in cystic fibrosis. - This condition is not the primary cause of the systemic and pancreatic issues described.
Question 492: In which of the following parts of the gastrointestinal tract is the highest luminal concentration of potassium seen?
- A. Ileum
- B. Jejunum
- C. Colon (Correct Answer)
- D. Duodenum
Explanation: ***Colon*** - The colon has the **highest luminal concentration of potassium** (90-100 mEq/L) in the gastrointestinal tract. - This is due to **active potassium secretion** by colonic epithelial cells through potassium channels and K+-H+ exchange mechanisms. - As **water is reabsorbed** in the colon, the remaining luminal contents become more concentrated, further increasing potassium concentration. - The colon exchanges **sodium reabsorption for potassium secretion**, maintaining the high luminal K+ levels. *Ileum* - The ileum is the primary site for the absorption of **bile acids** and **vitamin B12**. - While electrolyte exchange occurs, the amount of potassium absorbed or secreted here does not lead to the highest luminal concentration. - Luminal potassium concentration remains lower than in the colon. *Jejunum* - The jejunum is the main site for the absorption of **most nutrients** including carbohydrates, fats, and proteins. - While water and electrolyte absorption also occur, it does not concentrate potassium to the extent seen in the colon. - The jejunum primarily absorbs rather than secretes potassium. *Duodenum* - The duodenum is primarily involved in the **digestion and absorption of minerals** like iron and calcium. - It plays a less significant role in water and electrolyte reabsorption compared to the distal parts of the intestine. - Potassium concentrations remain relatively low as there is minimal active secretion here.
Question 493: Lactose intolerance in a suspected patient is diagnosed by giving an oral load and measuring concentrations of ?
- A. CO2
- B. H2 (Correct Answer)
- C. N2
- D. One/two carbon compounds
Explanation: ***H2*** - The **hydrogen breath test** is the most common diagnostic test for lactose intolerance. Unabsorbed lactose in the colon is fermented by bacteria, producing hydrogen gas. - **Hydrogen gas** is then absorbed into the bloodstream and exhaled, allowing its measurement in the breath. *CO2* - While some CO2 is produced during fermentation, it is not specific enough to diagnose lactose intolerance. - **CO2 levels** are significantly influenced by other metabolic processes and respiratory activity, making it a poor marker. *N2* - **Nitrogen** is an inert gas and not produced in significant amounts during lactose fermentation in the gut. - It is not a metabolic byproduct relevant to the diagnosis of carbohydrate malabsorption. *One/two carbon compounds* - While fermentation produces various short-chain fatty acids (SCFAs), which are one or two-carbon compounds, they are absorbed by the colonic mucosa. - Measuring these compounds directly in a non-invasive way to diagnose lactose intolerance is currently not standard clinical practice; breath hydrogen is preferred.
Question 494: Which of the following has the highest concentration of potassium in a normal individual?
- A. Secretions of rectum (Correct Answer)
- B. Ileal secretions
- C. Bile
- D. Pancreatic juice
Explanation: ***Correct: Secretions of rectum*** - **Colonic and rectal secretions** have the highest potassium concentration among all gastrointestinal secretions, typically ranging from **30-90 mEq/L**. - The distal colon and rectum actively **secrete potassium** into the lumen via K+ channels, particularly in exchange for sodium reabsorption. - This active secretion mechanism makes colonic secretions the richest source of potassium in the GI tract. - Chronic diarrhea or villous adenomas of the colon can lead to significant **hypokalemia** due to excessive potassium loss. *Incorrect: Pancreatic juice* - Pancreatic juice has a potassium concentration of approximately **4-10 mEq/L**, which is similar to or slightly higher than plasma levels. - While it does contain potassium, this concentration is significantly lower than that found in colonic/rectal secretions. *Incorrect: Ileal secretions* - Ileal secretions contain potassium at concentrations of approximately **10-15 mEq/L**. - The ileum is primarily involved in **absorption** of nutrients, bile salts, and electrolytes rather than high-level potassium secretion. *Incorrect: Bile* - Bile contains potassium at concentrations similar to plasma (**3.5-5.0 mEq/L**). - The primary role of bile is in **fat emulsification and digestion**, not electrolyte secretion.
Question 495: Normal 24-hour gastric acid output in stomach is
- A. 300-400 mEq
- B. 20-40 mEq
- C. 100-200 mEq (Correct Answer)
- D. 15-20 mEq
Explanation: ***100-200 mEq*** - The normal 24-hour gastric acid output in the stomach is typically within the range of **100-200 mEq**. - This range reflects the baseline secretory activity of **parietal cells** in the absence of significant stimulation. *300-400 mEq* - This range is generally **higher than normal** and might be observed in conditions like **Zollinger-Ellison syndrome**, where there is excessive gastrin production. - Such elevated output would indicate a pathological state of **hypersecretion**. *20-40 mEq* - This range represents a **lower-than-normal** gastric acid output, potentially indicating conditions like **atrophic gastritis** or **achlorhydria**. - Severely reduced acid production can compromise digestion and increase susceptibility to certain infections. *15-20 mEq* - This range is **significantly lower** than the normal gastric acid output. - Such a low level would be considered indicative of **hypochlorhydria** or **achlorhydria**, which can impair nutrient absorption and create an environment susceptible to bacterial overgrowth.
Question 496: Which of the following has the highest pH?
- A. Bile in the gallbladder
- B. Saliva
- C. Gastric juice
- D. Pancreatic juice (Correct Answer)
Explanation: ***Pancreatic juice*** - **Pancreatic juice** has the highest pH among the options, typically ranging from 7.5 to 8.8, due to its high concentration of **bicarbonate**. - This **alkaline fluid** is crucial for neutralizing acidic chyme from the stomach in the duodenum, creating an optimal environment for pancreatic enzymes. *Bile in the gallbladder* - **Bile** in the gallbladder has a pH that is slightly alkaline to neutral, usually between 7.0 and 8.0, but generally lower than pancreatic juice. - Its primary role is **fat emulsification**, not significant acid neutralization. *Saliva* - **Saliva** has a pH that is typically close to neutral, ranging from 6.2 to 7.6. - Its main functions include **lubrication**, initiating **carbohydrate digestion**, and oral hygiene, with limited buffering capacity compared to pancreatic juice. *Gastric juice* - **Gastric juice** is highly acidic, with a pH ranging from 1.5 to 3.5, due to the secretion of **hydrochloric acid** by parietal cells. - This extreme acidity is essential for **protein denaturation** and activating pepsin.
Question 497: Primary component of nonadrenergic noncholinergic nerve transmission in gut is:
- A. VIP and Substance P
- B. VIP and CCK
- C. VIP and NO (Correct Answer)
- D. VIP and Motilin
Explanation: ***VIP and NO*** - **Vasoactive Intestinal Peptide (VIP)** and **Nitric Oxide (NO)** are the primary neurotransmitters mediating the **nonadrenergic noncholinergic (NANC) transmission** in the gut. - The NANC system is crucial for **gut motility, secretion, and relaxation of smooth muscle** beyond the actions of adrenergic and cholinergic systems. *VIP and substance* - While **VIP** is a key NANC neurotransmitter, **Substance P** primarily mediates excitatory effects, particularly in pain transmission and inflammatory responses in the gut, rather than being a primary NANC inhibitory transmitter. - Substance P is often co-released with acetylcholine or acts independently to **stimulate smooth muscle contraction** and secretion, not relaxation. *VIP and CCK* - Although **VIP** is a significant NANC neurotransmitter, **Cholecystokinin (CCK)** is a peptide hormone primarily involved in stimulating gallbladder contraction and pancreatic enzyme secretion, and it acts as a neuromodulator rather than a primary NANC neurotransmitter. - CCK plays a significant role in **digestion and satiety**, but its role in NANC transmission is not as central as NO for smooth muscle relaxation. *VIP and Motilin* - **VIP** is a critical NANC neurotransmitter, but **Motilin** is a peptide hormone that primarily stimulates **gastric and intestinal motility** during fasting (migrating motor complex). - Motilin's main function is related to cyclical contractions of the gut, and it is not considered a primary direct neurotransmitter in the NANC system.
Question 498: When closure in intercuspal position is attained during mastication, movement stops for about _________ msec before another cycle begins.
- A. 94 msec
- B. 594 msec
- C. 194 msec (Correct Answer)
- D. 394 msec
Explanation: ***194 msec*** - This duration represents the brief pause in mandibular movement during the **power stroke** of mastication when the teeth are in the **intercuspal position**. - This short **isometric contraction** phase allows for effective food comminution and acts as a transition before the next opening cycle. *94 msec* - This duration is **too short** for the typical isometric phase observed during the intercuspal closure in mastication. - An excessively short pause might indicate compromised chewing efficiency or neuromuscular control. *594 msec* - This duration is **too long** for the normal physiological pause at intercuspal occlusion during a single masticatory cycle. - A prolonged pause could suggest abnormal masticatory patterns or muscle fatigue. *394 msec* - While longer than the correct duration, this still represents a significant deviation from the typically observed pause after intercuspal closure. - Such a lengthy pause might interrupt the rhythmic nature of mastication.
Question 499: Two normal, healthy subjects volunteer for a study on insulin secretion. In Patient 1, blood glucose is increased to 150 mg/dL by direct intravenous infusion. In Patient 2, blood glucose is increased to 150 mg/dL by ingestion of oral glucose. The peak plasma insulin concentration produced in Patient 1 is 70 uU/mL while in Patient 2, it is 95 uU/mL. Which of the following best explains the higher insulin concentration in Patient 2?
- A. Ingested glucose increases duodenal secretion of gastric inhibitory peptide (GIP), increasing beta cell release of insulin (Correct Answer)
- B. Intravenous glucose increases islet cell secretion of somatostatin, inhibiting beta cell release of insulin
- C. Intravenous glucose increases islet cell secretion of glucagon, inhibiting beta cell release of insulin
- D. Ingested glucose activates a sympathetic reflex that increases beta cell release of insulin
Explanation: ***Ingested glucose increases duodenal secretion of gastric inhibitory peptide (GIP), increasing beta cell release of insulin*** - **Oral glucose ingestion** stimulates the release of **incretin hormones** like **GIP (glucose-dependent insulinotropic polypeptide)** and GLP-1 (glucagon-like peptide-1) from the small intestine. - These **incretins amplify glucose-stimulated insulin secretion** from pancreatic beta cells, explaining the **higher insulin response** in Patient 2 compared to Patient 1, who received intravenous glucose and thus bypassed the intestinal incretin release. *Intravenous glucose increases islet cell secretion of somatostatin, inhibiting beta cell release of insulin* - While somatostatin does inhibit insulin secretion, its release is typically stimulated by high nutrient levels or certain hormones, not directly by **intravenous glucose** in a way that would explain the difference between the two patients. - The primary physiological difference between oral and intravenous glucose administration regarding insulin response is the **incretin effect**, not differential somatostatin secretion. *Intravenous glucose increases islet cell secretion of glucagon, inhibiting beta cell release of insulin* - **Glucagon** is generally secreted in response to **low blood glucose** and works to raise it, not inhibit insulin release in this specific context. - Furthermore, **glucose stimulation typically suppresses glucagon secretion**, so an increase in glucagon with intravenous glucose is unlikely and wouldn't explain the lower insulin. *Ingested glucose activates a sympathetic reflex that increases beta cell release of insulin* - The **sympathetic nervous system** generally **inhibits insulin secretion** (via alpha-adrenergic receptors) and stimulates glucagon secretion, particularly during stress or exercise. - Therefore, an activation of a sympathetic reflex due to ingested glucose would more likely *decrease* or have a minimal effect on insulin release, rather than increasing it.
Question 500: Destruction of fat in acute pancreatitis is due to ?
- A. Lipase (Correct Answer)
- B. Trypsin
- C. Secretin
- D. Elastase
Explanation: ***Lipase*** - **Lipase** is the primary enzyme responsible for **fat necrosis** in acute pancreatitis. - It hydrolyzes triglycerides into **fatty acids and glycerol**. - The released fatty acids combine with calcium to form **soap (saponification)**, visible as chalky white areas of fat necrosis. - This is a characteristic pathological finding in acute pancreatitis. *Trypsin* - **Trypsin** is a proteolytic enzyme that breaks down **proteins**, not fats. - While trypsin activation is central to the pathogenesis of pancreatitis (it activates other pancreatic enzymes), **it does not directly destroy fat**. - Its primary role is in the autodigestion of pancreatic tissue and activation of the enzymatic cascade. *Secretin* - **Secretin** is a hormone that regulates pancreatic bicarbonate secretion and gastric acid secretion. - It plays **no role** in the enzymatic destruction of fat in acute pancreatitis. *Elastase* - **Elastase** is a protease that digests elastin in blood vessel walls and other proteins. - It contributes to vascular damage and hemorrhage in pancreatitis but **does not directly destroy fat**. - Fat necrosis is specifically caused by lipolytic enzymes, not proteases.
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