Digestive System Histology — MCQs
What is the primary function of the myenteric plexus?
A male infant presented with distension of abdomen shortly after birth with delayed passage of meconium. Subsequently a full-thickness biopsy of the rectum was performed. The rectal biopsy is likely to show:
The strongest and thickest layer of the esophagus is
What is the typical length of the anal canal in adults?
Inhibition of myenteric plexus results in
The lower two thirds of the following hematoxylin and eosin stained specimen is similar in appearance to which of the following structures?
Biopsy of the exposed surface of the palatine tonsil reveals which type of tissue?
Identify the structure marked in the image of cardiac myocyte. (AIIMS Nov 2018)
The nasopharynx is primarily lined by which type of epithelium?
Epithelial lining of the urinary bladder is?
Digestive System Histology Indian Medical PG Practice Questions and MCQs
Question 1: What is the primary function of the myenteric plexus?
- A. Regulating GI secretion
- B. Regulating local blood flow
- C. Regulating motility (Correct Answer)
- D. Regulating absorption
Explanation: ***Regulating motility*** - The myenteric plexus, also known as **Auerbach's plexus**, is primarily responsible for coordinating the **rhythmic contractions** and **relaxation of the gastrointestinal (GI) smooth muscle**. - Its strategic location between the **longitudinal and circular muscle layers** allows it to directly influence the strength and frequency of peristalsis, thus regulating the movement of food through the digestive tract. *Regulating GI secretion* - While it has some indirect influence, the **submucosal plexus** (Meissner's plexus) is the primary neural network regulating **secretory functions** of the GI tract. - The myenteric plexus's main role is more directly related to muscle contraction and relaxation rather than glandular secretion. *Regulating local blood flow* - Local blood flow in the GI tract is primarily regulated by the **sympathetic and parasympathetic nervous systems**, along with local metabolic factors and hormones. - The myenteric plexus has a minimal direct role in the control of **GI blood vessel smooth muscle**. *Regulating absorption* - Absorption is primarily a function of the **intestinal epithelial cells** and is regulated by various transport mechanisms, hormones, and local factors. - While the enteric nervous system influences mucosal function indirectly, the myenteric plexus's primary role is **motor control** rather than directly regulating nutrient absorption processes.
Question 2: A male infant presented with distension of abdomen shortly after birth with delayed passage of meconium. Subsequently a full-thickness biopsy of the rectum was performed. The rectal biopsy is likely to show:
- A. Lack of ganglion cells (Correct Answer)
- B. Fibrosis of submucosa
- C. Thickened muscularis propria
- D. Hyalinization of the muscular coat
Explanation: ***Lack of ganglion cells*** - The clinical presentation of **abdominal distension** and **delayed meconium passage** in a neonate is highly suggestive of **Hirschsprung disease** [1]. - **Hirschsprung disease** is characterized by the **absence of ganglion cells** in the myenteric (Auerbach's) and submucosal (Meissner's) plexuses of the distal bowel, starting from the anus and extending proximally to varying degrees [1], [2]. *Fibrosis of submucosa* - While some chronic inflammatory conditions can lead to submucosal fibrosis, it is **not the primary histopathological feature** of Hirschsprung disease. - Submucosal fibrosis is more typically seen in conditions like **Crohn's disease** or chronic infectious colitis. *Thickened muscularis propria* - A **thickened muscularis propria** can be an indirect finding in Hirschsprung disease, occurring as a result of **hypertrophy** of the muscle layers proximal to the aganglionic segment, due to increased effort to propel stool past the obstructed area. - However, the **primary diagnostic feature** on biopsy is the absence of ganglion cells, not muscle thickening, which is a secondary change [2]. *Hyalinization of the muscular coat* - **Hyalinization** refers to a glassy, eosinophilic appearance of tissue, often due to protein accumulation or degeneration. - This is **not a characteristic finding** in Hirschsprung disease and is typically associated with conditions like vascular injury or aging changes. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 94-95. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 759.
Question 3: The strongest and thickest layer of the esophagus is
- A. Muscularis (Correct Answer)
- B. Mucosa
- C. Submucosa
- D. Adventitia
Explanation: ***Muscularis*** The **muscularis propria** (or muscularis externa) is the thickest and strongest layer in the esophagus, responsible for the **peristaltic contractions** that propel food. It consists of an inner layer of circular muscle and an outer layer of longitudinal muscle, with the coordinated action of these two layers being crucial for **swallowing** [1]. *Mucosa* The mucosa is the innermost layer [1], primarily involved in protection and some secretory functions, but it is not the thickest or strongest. It consists of non-keratinized stratified squamous epithelium, lamina propria, and muscularis mucosae. *Submucosa* The submucosa is a layer of connective tissue that contains blood vessels, lymphatics, and nerves (Meissner's plexus). While important for support and nutrient supply, it is structurally weaker and thinner than the muscularis layer. *Adventitia* The adventitia is the outermost layer of the esophagus in the neck and thorax, consisting of loose connective tissue. Its primary role is to anchor the esophagus to surrounding structures, rather than providing strength for peristalsis.
Question 4: What is the typical length of the anal canal in adults?
- A. 10 - 15 mm
- B. 15 - 20 mm
- C. 25 - 30 mm
- D. 35 - 40 mm (Correct Answer)
Explanation: ***35 - 40 mm*** - The **anal canal** in adults typically measures between **3.5 to 4.0 cm** (35 to 40 mm) in length. - This length is measured from the **anorectal ring** to the **anal verge**. *10 - 15 mm* - This length is too short for the **adult anal canal**; it's approximately one-third of the actual length. - Such a short measurement would be anatomically incorrect and clinically significant for various colorectal conditions. *15 - 20 mm* - This measurement is still significantly shorter than the average length of the **adult anal canal**. - A canal this short would likely be pathological or developmental in origin. *25 - 30 mm* - While closer, this range is still generally below the accepted average length of the **adult anal canal**. - Precise anatomical measurements are crucial for diagnostic and surgical procedures in proctology.
Question 5: Inhibition of myenteric plexus results in
- A. Hyperacidity
- B. Diarrhea
- C. Decreased gut motility (Correct Answer)
- D. Increased secretions
Explanation: ***Decreased gut motility*** - The **myenteric plexus** (Auerbach's plexus) is primarily responsible for regulating **gastrointestinal motility**, including peristalsis and muscle contraction. - Its inhibition would therefore lead to **reduced peristaltic movements** and **decreased gut motility**. *Hyperacidity* - **Gastric acid secretion** is mainly regulated by the vagus nerve (via acetylcholine), gastrin, and histamine, not directly by the myenteric plexus. - While gut motility can indirectly affect acid exposure, a primary and direct consequence of myenteric plexus inhibition is not hyperacidity. *Diarrhea* - **Diarrhea** is typically caused by increased gut motility, increased secretion, or decreased absorption. - Inhibition of the myenteric plexus would lead to **decreased motility**, making diarrhea an unlikely outcome. *Increased secretions* - **Gastrointestinal secretions** are largely controlled by the submucosal plexus (Meissner's plexus) and hormonal factors. - While the myenteric plexus has some indirect influence, its primary role is motility, and its inhibition would not directly lead to increased secretions.
Question 6: The lower two thirds of the following hematoxylin and eosin stained specimen is similar in appearance to which of the following structures?
- A. Articular disk
- B. Pinna
- C. Epiphyseal growth plate
- D. Intervertebral disk (Correct Answer)
Explanation: ***Intervertebral disk*** - The lower two-thirds of the specimen shows **hyaline-like cartilage** that histologically resembles the **transition zone** of the intervertebral disk, where the inner annulus fibrosus transitions from the nucleus pulposus. - While the nucleus pulposus itself is gelatinous and notochordal in origin, the **inner annulus fibrosus** contains fibrocartilage with regions that can appear similar to hyaline cartilage, particularly in the transitional zones. - The specimen's appearance, with **chondrocytes in lacunae** within a relatively homogeneous matrix, matches the cartilaginous components found in intervertebral disk structure. *Articular disk* - Articular disks are composed predominantly of **fibrocartilage**, characterized by **dense parallel collagen fiber bundles** clearly visible in the matrix and chondrocytes arranged in linear rows between collagen bundles. - The homogeneous matrix appearance in the specimen lacks the prominent fibrous architecture typical of articular disks. *Pinna* - The pinna (external ear) is supported by **elastic cartilage**, which contains abundant **elastic fibers** in its extracellular matrix providing flexibility and resilience. - With H&E staining, elastic cartilage would show a more textured matrix, and special stains would demonstrate extensive elastic fiber networks not present in this specimen. *Epiphyseal growth plate* - While the epiphyseal growth plate consists of **hyaline cartilage**, it exhibits highly characteristic **zonal organization**: resting zone, proliferative zone (with columnar arrangement), hypertrophic zone, and zone of calcification. - The specimen lacks the distinct columnar arrangement and zonal stratification that defines an active epiphyseal growth plate.
Question 7: Biopsy of the exposed surface of the palatine tonsil reveals which type of tissue?
- A. Stratified squamous epithelium (Correct Answer)
- B. Simple squamous epithelium
- C. Simple columnar epithelium
- D. Pseudostratified columnar ciliated epithelium
Explanation: The palatine tonsils are part of the **oropharynx**, which is subjected to mechanical abrasion from food and drink. **Stratified squamous epithelium** provides robust protection against such friction and is characteristic of surfaces needing high wear resistance. *Simple squamous epithelium* - This type of epithelium is found in areas where **diffusion** or **filtration** is important, such as the lining of blood vessels (endothelium) and alveoli of the lungs. - It would not provide adequate protection for the exposed surface of the tonsil that is subject to frequent mechanical stress. *Simple columnar epithelium* - Characterized by cells taller than they are wide, often found in the **gastrointestinal tract** for absorption and secretion. - It lacks the multi-layered structure needed for protection against the abrasive forces typical in the oropharynx. *Pseudostratified columnar ciliated epithelium* - This epithelium is primarily found in the **respiratory tract**, where its cilia help move mucus and trapped particles. - While it offers some protection, its primary function is not mechanical resistance, and it is not found on the exposed surfaces of the palatine tonsils.
Question 8: Identify the structure marked in the image of cardiac myocyte. (AIIMS Nov 2018)
- A. Lipofuscin granules (Correct Answer)
- B. Lysosomes
- C. Phagolysosome
- D. Inflammasome
Explanation: ***Lipofuscin granules*** - The image displays electron-dense, irregular structures, characteristic of **lipofuscin granules**, which are wear-and-tear pigments accumulating in aging cardiac myocytes. - They are typically located near the nucleus and appear dark due to their complex lipid-protein composition. *Lysosomes* - Lysosomes are typically smaller, more uniformly shaped, and contain hydrolytic enzymes, which is not clearly depicted. - While involved in cellular waste breakdown, they do not typically accumulate as large, intensely electron-dense, irregular aggregates like those shown. *Phagolysosome* - A phagolysosome forms when a phagosome fuses with a lysosome, containing engulfed material often of foreign or cellular debris origin. - The image does not show evidence of recently engulfed material or the typical morphology of a phagocytic vesicle. *Inflammasome* - An inflammasome is a multi-protein intracellular complex involved in the inflammatory response, not a visibly distinct organelle with this characteristic electron microscopic appearance. - It is a signaling platform, not a storage granule, and would not appear as dense, granular deposits in a routine electron micrograph.
Question 9: The nasopharynx is primarily lined by which type of epithelium?
- A. Stratified squamous keratinized
- B. Ciliated columnar (Correct Answer)
- C. Cuboidal
- D. Stratified squamous nonkeratinized
Explanation: ***Ciliated columnar*** - The **nasopharynx** is lined by **pseudostratified ciliated columnar epithelium** with goblet cells, also known as respiratory epithelium [2]. - This specialized epithelium is crucial for **warming**, **humidifying**, and **filtering** inhaled air before it reaches the lungs [1]. *Stratified squamous nonkeratinized* - This type of epithelium is found in areas subject to **abrasion** and needing protection, such as the **oral cavity**, pharynx (oropharynx and laryngopharynx), and esophagus. - It is not primary in the nasopharynx, which requires ciliary action for particle removal. *Stratified squamous keratinized* - This robust epithelium is characteristic of areas that require significant **protection against friction** and **drying**, such as the **epidermis of the skin**. - It is not found in the nasopharynx due to its lack of flexibility and ciliary function. *Cuboidal* - **Cuboidal epithelium** is typically found in glands and kidney tubules, where its function includes **secretion** and **absorption**. - It lacks the specialized cilia and goblet cells necessary for the respiratory function of the nasopharynx [2].
Question 10: Epithelial lining of the urinary bladder is?
- A. Squamous epithelium
- B. Transitional epithelium (Correct Answer)
- C. Cuboidal epithelium
- D. Columnar epithelium
Explanation: ***Transitional epithelium*** - The urinary bladder is lined by **transitional epithelium**, also known as **urothelium** [1]. - This specialized epithelium can stretch and flatten when the bladder fills with urine, and then contract when it empties, a crucial adaptation for its function. *Squamous epithelium* - **Stratified squamous epithelium** is typically found in areas subject to abrasion, such as the skin, esophagus, and vagina. - It does not possess the unique distensibility required for the urinary bladder's function. *Cuboidal epithelium* - **Cuboidal epithelium** is commonly found in glands and kidney tubules, where it is involved in secretion and absorption. - It is not specialized for the significant stretching and recoiling seen in the urinary bladder. *Columnar epithelium* - **Columnar epithelium** is primarily involved in secretion and absorption and is found in regions like the gastrointestinal tract and some glandular ducts. - It lacks the necessary structural characteristics to accommodate the large volume changes of the urinary bladder.
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