Microscopic Anatomy of Digestive System — MCQs
Oxyntic cells are present in -
The histological features of celiac disease include all of the following EXCEPT:
Stratified squamous epithelium is seen at all the following sites except which of the following?
Which of the following is least important in the maintenance of normal fecal continence?
The mucosal lining of the vagina is composed of cells:
Anal valve is found in which part of anal canal?
Which of the following is NOT a primary function of histamine antagonists as a drug class?
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
Investigation of choice for Posterior urethral valves?
A patient presents with pulmonary hemorrhage and is P-ANCA positive. What is the most likely diagnosis?
Microscopic Anatomy of Digestive System Indian Medical PG Practice Questions and MCQs
Question 1: Oxyntic cells are present in -
- A. Pylorus
- B. Cardia
- C. Body (Correct Answer)
- D. None of the options
Explanation: ***Body*** - **Oxyntic cells**, also known as **parietal cells**, are predominantly located in the **fundus and body** of the stomach [1], [2]. - These cells are responsible for secreting **hydrochloric acid (HCl)** and **intrinsic factor**, which are crucial for digestion and vitamin B12 absorption [1]. - The gastric glands in the body contain the highest concentration of parietal cells [2]. *Pylorus* - The pylorus is the distal part of the stomach that connects to the duodenum. - It primarily contains **G cells**, which secrete **gastrin**, a hormone that stimulates HCl secretion from parietal cells [3]. - Pyloric glands contain mainly mucus-secreting cells, with few or no parietal cells [2]. *Cardia* - The cardia is the region near the gastroesophageal junction (entrance of the stomach). - This area primarily contains **cardiac glands** with mucus-secreting cells that protect the esophageal lining from gastric acid reflux. - Parietal cells are sparse or absent in the cardia [2]. *None of the options* - This option is incorrect because the **body of the stomach** is the correct location for oxyntic cells.
Question 2: The histological features of celiac disease include all of the following EXCEPT:
- A. Crypt hyperplasia
- B. Increase in intraepithelial lymphocytes
- C. Increase in inflammatory cells in lamina propria
- D. Increase in thickness of the mucosa (Correct Answer)
Explanation: ***Increase in thickness of the mucosa*** - Celiac disease typically causes **villous atrophy**, leading to a **thinner intestinal mucosa**, not an increase in thickness [1]. - The architectural changes in celiac disease primarily involve blunting or absence of villi [2]. *Crypt hyperplasia* - This is a characteristic feature of celiac disease, where the **crypts of Lieberkühn** become elongated and hyperplastic to compensate for the damaged villi [1]. - It reflects increased cell turnover in response to mucosal injury. *Increase in intraepithelial lymphocytes* - An increase in **intraepithelial lymphocytes (IELs)** is a hallmark histological finding in celiac disease, often seen even before significant villous atrophy [1]. - These lymphocytes are typically CD3+ T-cells that infiltrate the epithelial layer. *Increase in inflammatory cells in lamina propria* - The lamina propria in celiac disease shows an increased infiltration of **chronic inflammatory cells**, including plasma cells and lymphocytes [2]. - This reflects the ongoing immune response to gluten peptides in the intestinal wall. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 789-790. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 361-362.
Question 3: Stratified squamous epithelium is seen at all the following sites except which of the following?
- A. Skin
- B. Vagina
- C. Esophagus
- D. Gall bladder (Correct Answer)
Explanation: ***Gall bladder*** - The **gallbladder** is lined by **simple columnar epithelium**, which is specialized for absorption and secretion, not protection against abrasion. - This type of epithelium allows for efficient concentration of bile and mucus secretion. *Skin* - The **epidermis** of the skin is composed of **keratinized stratified squamous epithelium**, which provides a tough, protective barrier against physical trauma, pathogens, and desiccation [1]. - This multi-layered structure is crucial for its role in external protection. *Vagina* - The **vagina** is lined by **non-keratinized stratified squamous epithelium**, which offers protection against mechanical abrasion during intercourse and childbirth [2]. - The non-keratinized nature allows for a moist, flexible surface. *Esophagus* - The **esophagus** is lined by **non-keratinized stratified squamous epithelium**, which protects against the abrasive passage of food boluses. - This protective lining prevents damage from swallowed food as it moves towards the stomach.
Question 4: Which of the following is least important in the maintenance of normal fecal continence?
- A. Anorectal angulation
- B. Rectal innervation
- C. Internal sphincter
- D. Haustral valve (Correct Answer)
Explanation: **Haustral valve** - The **haustral valve** (or redundant mucosal folds within the haustra) primarily functions to *increase surface area* for water absorption and slow the passage of contents through the colon. - While critical for digestive function, it plays a *negligible direct role* in the mechanisms preventing involuntary stool leakage. *Anorectal angulation* - The **anorectal angle**, formed by the pull of the **puborectalis muscle**, creates a sharp bend that acts as a flap valve, significantly contributing to continence. - Loss of this angle (e.g., due to injury or structural changes) substantially impairs continence. *Rectal innervation* - **Intact innervation** of the rectum provides crucial sensory feedback regarding rectal distension and stool consistency, allowing for conscious control of defecation. - It also mediates the **rectoanal inhibitory reflex** and the ability to voluntarily contract external anal sphincters, both vital for continence. *Internal sphincter* - The **internal anal sphincter** is an *involuntary smooth muscle* responsible for approximately 70-80% of the resting anal tone, providing continuous passive continence. - Damage to this sphincter leads to substantial impairment in continence, particularly against flatus and liquid stool.
Question 5: The mucosal lining of the vagina is composed of cells:
- A. Stratified squamous non-keratinized (Correct Answer)
- B. Ciliated columnar epithelium
- C. Pseudostratified columnar epithelium
- D. Transitional epithelium
Explanation: ***Stratified squamous non-keratinized*** - The **vaginal epithelium** is composed of several layers of flattened, nucleated cells that provide **protection against friction** and resist pathogen entry during intercourse and childbirth [1]. - The **non-keratinized nature** ensures the mucosa remains moist and flexible, essential for its function. *Ciliated columnar epithelium* - This type of epithelium is found in locations like the **fallopian tubes** and parts of the **respiratory tract**, where cilia help in moving fluids or particles. - It does not provide the robust protective barrier required for the vagina. *Pseudostratified columnar epithelium* - This epithelium, characterized by nuclei at different levels giving a "pseudostratified" appearance, is typically found in the **trachea** and **bronchi**. In the uterus, however, the endometrial glands are lined by regular, tall, pseudostratified columnar cells during the proliferative phase [2]. - Its primary function is secretion and absorption, not the physical protection needed in the vagina. *Transitional epithelium* - Also known as **urothelium**, this type is specialized to accommodate stretching and is found in the **urinary bladder** and ureters. - It is not suited for the constant friction and protective role of the vaginal lining.
Question 6: Anal valve is found in which part of anal canal?
- A. Lower
- B. At anus
- C. Middle (Correct Answer)
- D. Upper
Explanation: ***Middle*** - The **anal valves** are crescentic folds located at the level of the **pectinate (dentate) line** in the middle portion of the anal canal. - They mark the inferior limit of the **anal columns** and form small recesses called **anal sinuses**. *Lower* - The lower part of the anal canal, below the pectinate line, is lined by **anoderm** and lacks anal valves. - This region is sensitive to pain due to somatic innervation. *At anus* - The anus refers to the external opening and perianal skin, which does not contain anal valves. - The anal canal transitions into the perianal skin at the anocutaneous line. *Upper* - The upper part of the anal canal, above the pectinate line, contains the **anal columns (columns of Morgagni)** but not the anal valves themselves, which are located at the base of these columns. - This region is lined by columnar epithelium and is relatively insensitive to pain.
Question 7: Which of the following is NOT a primary function of histamine antagonists as a drug class?
- A. Antipruritic
- B. Sedation
- C. Inhibition of gastric acid secretion
- D. Antivertigo (Correct Answer)
Explanation: ***Antivertigo*** - While some first-generation **H1-antihistamines** like dimenhydrinate and meclizine have **antivertigo** properties due to their anticholinergic and sedative effects, this is a specific *effect* of certain histamine antagonists, not a general *function* that all antagonists exhibit. - The question asks for an exception to the *general functions* of histamine antagonists. **Antivertigo** is not a primary, universal effect of histamine antagonism in the way the other options describe. *Antipruritic* - **H1-antihistamines** block the action of **histamine** on **H1 receptors**, which are involved in mediating itching (**pruritus**). - This is a common and primary function of **H1-antagonists** in treating allergic reactions and skin conditions. *Sedation* - First-generation **H1-antihistamines** readily cross the **blood-brain barrier** and block **H1 receptors** in the brain, leading to drowsiness and **sedation**. - This is a well-known side effect and, in some cases, a therapeutic use of these drugs. *Inhibition of gastric acid secretion* - **H2-antihistamines** (e.g., ranitidine, cimetidine) specifically block **histamine H2 receptors** on **parietal cells** in the stomach, thereby reducing **gastric acid secretion**. - This is a primary function of a distinct class of histamine antagonists used to treat acid-related disorders.
Question 8: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 9: Investigation of choice for Posterior urethral valves?
- A. Ultrasound
- B. Retrograde urethrography
- C. Micturating Cystourethrography (MCU) (Correct Answer)
- D. Intravenous Pyelography
Explanation: ***Micturating Cystourethrography (MCU)*** - The **Micturating Cystourethrography (MCU)** is the gold standard for diagnosing posterior urethral valves (PUV) as it directly visualizes the posterior urethra during voiding. - It classically shows a **dilated posterior urethra** with a narrow opening at the level of the valves, often accompanied by **vesicoureteral reflux** and bladder wall abnormalities. *Ultrasound* - **Antenatal ultrasound** can suggest PUV by showing bilateral **hydronephrosis**, a dilated bladder, and thick-walled bladder with a "keyhole sign" (dilated posterior urethra). - However, ultrasound alone **cannot definitively diagnose** the valves or rule out other causes of obstruction. *Retrograde urethrography* - **Retrograde urethrography (RGU)** involves injecting contrast against the flow of urine, which can mask the presence of posterior urethral valves, as they are typically obstructive to antegrade flow. - While RGU can highlight urethral strictures and other anterior urethral pathologies, it is **not ideal** for visualizing posterior urethral valves. *Intravenous Pyelography* - **Intravenous Pyelography (IVP)** assesses kidney function and the collecting system, but it provides **limited detailed visualization** of the urethra itself. - While it might show features of obstructive uropathy like **hydronephrosis** or delayed excretion, it cannot directly confirm the presence or location of posterior urethral valves.
Question 10: A patient presents with pulmonary hemorrhage and is P-ANCA positive. What is the most likely diagnosis?
- A. Churg-Strauss syndrome
- B. Microscopic polyangiitis (Correct Answer)
- C. Wegener granulomatosis
- D. Polyarteritis nodosa (PAN)
Explanation: ***Microscopic polyangiitis*** - This condition is characterized by **pulmonary hemorrhage** (often manifesting as diffuse alveolar hemorrhage) and **P-ANCA positivity**, which is typically associated with antibodies against **myeloperoxidase (MPO)**. [1] - It is a **small-vessel vasculitis** that frequently affects the kidneys (glomerulonephritis) and lungs without granuloma formation. *Churg-Strauss syndrome* - While Churg-Strauss syndrome (now known as **Eosinophilic Granulomatosis with Polyangiitis**, EGPA) can be P-ANCA positive, it is typically associated with a history of **asthma**, **allergic rhinitis**, and **eosinophilia**. [1] - Pulmonary involvement often includes **infiltrates** and nodules, but diffuse alveolar hemorrhage with severe pulmonary hemorrhage is less common as the primary presentation compared to MPA. *Wegener granulomatosis* - Wegener granulomatosis (now known as **Granulomatosis with Polyangiitis**, GPA) primarily presents with **upper and lower respiratory tract granulomatous inflammation** and **glomerulonephritis**. - It is typically associated with **C-ANCA positivity** (antibodies against proteinase 3, PR3), not P-ANCA. *Polyarteritis nodosa (PAN)* - Polyarteritis nodosa is a **medium-vessel vasculitis** that typically affects the **kidneys, gastrointestinal tract, skin, and nervous system**. [1] - It is classically **ANCA-negative** and does not typically cause pulmonary hemorrhage or diffuse alveolar hemorrhage.
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