Microscopic Anatomy Practice Questions

Q: Basement membrane around Schwann cells contains which of the following collagens?

Type XXVIII. **Explanation:** The correct answer is **Type XXVIII**. This question tests your knowledge of the specialized collagen types found in the peripheral nervous system. **1. Why Type XXVIII is correct:** Type XXVIII collagen is a non-fibrillar collagen belonging to the subfamily of **MACITs** (Membrane-Associated Collagens with Interrupted Triple helices). It is specifically expressed by **Schwann cells** and is localized to the **basement membrane** (basal lamina) surrounding the myelin sheath. It plays a crucial role in the stabilization of the nodes of Ranvier and the overall structural integrity of the peripheral nerve fibers. **2. Why other options are incorrect:** * **Type IV:** While Type IV collagen is the classic "network-forming" collagen found in almost all basement membranes (including the endoneurium), it is not the *specific* or unique collagen type associated with the Schwann cell basement membrane in this context. * **Type X:** This is a short-chain collagen found specifically in the **hypertrophic zone of the epiphyseal plate** during endochondral ossification. * **Type XX:** This is a minor collagen type primarily found in corneal epithelium and embryonic tissues, not in the peripheral nervous system. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Type I Collagen:** Most abundant; found in bone, tendon, and dermis. * **Type II Collagen:** Found in hyaline and elastic cartilage ("Type **Two** for **Car-two-lage**"). * **Type III Collagen:** Found in skin, blood vessels, and reticular fibers (granulation tissue). * **Type VII Collagen:** Forms anchoring fibrils in the dermo-epidermal junction (mutated in Epidermolysis Bullosa Dystrophica). * **Schwann Cells vs. Oligodendrocytes:** Remember that Schwann cells myelinate a single internode in the PNS and possess a basal lamina, whereas Oligodendrocytes in the CNS can myelinate multiple axons and lack a basal lamina.

Q: What is the type of cell lining the small intestine?

Simple columnar. The small intestine is primarily designed for **absorption and secretion**. To facilitate these functions, it is lined by a **simple columnar epithelium**. These tall, pillar-like cells provide a large surface area for the placement of transport proteins and enzymes [1]. Furthermore, the apical surface of these cells features **microvilli** (forming the "striated border"), which exponentially increases the surface area for nutrient absorption. Interspersed among these columnar cells are **Goblet cells**, which secrete mucus to lubricate the intestinal wall [1]. **Analysis of Options:** * **Simple Squamous (A):** These are thin, flat cells found where rapid passive diffusion or filtration is required, such as in the **alveoli of lungs** or the **endothelium** of blood vessels. * **Stratified Squamous (B):** This multi-layered epithelium is designed for protection against mechanical stress and abrasion. It lines the **esophagus, oral cavity, and skin**. * **Stratified Columnar (D):** This is a rare type of epithelium found only in specific locations like the **large ducts of salivary glands** and parts of the **male urethra**. It is not suited for the high-absorptive demands of the intestine. **High-Yield Clinical Pearls for NEET-PG:** * **Celiac Disease:** Characterized by the "flattening" or atrophy of these columnar villi, leading to malabsorption. * **Metaplasia:** In **Barrett’s Esophagus**, the stratified squamous epithelium of the esophagus changes to simple columnar epithelium (intestinal metaplasia) due to chronic acid reflux. * **Crypts of Lieberkühn:** These are simple tubular glands located between the bases of the villi, containing Paneth cells (secreting lysozymes) and stem cells [1].

Q: Which of the following is present in Paneth cells?

Zinc. **Explanation:** **Paneth cells** are specialized secretory cells located at the bases of the **Crypts of Lieberkühn** in the small intestine [1]. Their primary role is innate mucosal immunity through the secretion of antimicrobial peptides. **Why Zinc is the Correct Answer:** Paneth cells contain prominent eosinophilic apical granules. These granules are rich in **Zinc**, which acts as a crucial cofactor for the storage and stabilization of antimicrobial enzymes, most notably **Lysozyme** and **alpha-defensins (cryptidins)**. Zinc is essential for the structural integrity of these proteins, ensuring they remain inactive within the cell and become functional only upon secretion into the intestinal lumen. **Analysis of Incorrect Options:** * **B. Copper:** While copper is a vital cofactor for enzymes like cytochrome c oxidase and superoxide dismutase, it is not specifically concentrated or stored within Paneth cell granules. * **C. Molybdenum:** This trace element is a cofactor for enzymes like xanthine oxidase but has no specific association with the secretory machinery of the intestinal crypts. * **D. Selenium:** Selenium is incorporated into selenoproteins (like glutathione peroxidase) for antioxidant defense but is not a characteristic component of Paneth cell secretions. **NEET-PG High-Yield Pearls:** * **Location:** Found only in the **small intestine** (rarely in the cecum/appendix); their absence in the large intestine is a key histological differentiator [1]. * **Function:** They regulate the gut microbiome by secreting Lysozyme, Phospholipase A2, and Defensins. * **Staining:** They are strongly **acidophilic/eosinophilic** due to the high protein content of their granules. * **Clinical Correlation:** Paneth cell metaplasia (appearing in the colon) is a classic histological marker for **Inflammatory Bowel Disease (IBD)**, particularly Crohn’s disease.

Q: What is the cell junction marked by the circle?

Zona adherens. ***Zona adherens*** - Part of the **apical junctional complex** located between zonula occludens and macula adherens, forming a **belt-like junction** around epithelial cells. - Contains **cadherin proteins** and **actin filaments** that provide mechanical strength and maintain cell-to-cell adhesion. *Fascia adherens* - Specific to **cardiac muscle cells** at intercalated discs, not found in typical epithelial tissues. - Functions to anchor **actin filaments** and transmit contractile forces between cardiomyocytes. *Macula adherens* - Also called **desmosomes**, these are **spot-like junctions** located more basally in the apical junctional complex. - Contain **desmosomal cadherins** and **intermediate filaments**, providing strong mechanical adhesion but appearing as discrete spots rather than continuous bands. *Zonula occludens* - The most **apical junction** in the terminal bar, also known as **tight junctions**. - Functions to create a **permeability barrier** and prevent paracellular transport, rather than primarily providing mechanical adhesion.

Q: Which one of the following is NOT a component of the filtration slit diaphragm at the glomerulus?

Batin. The **filtration slit diaphragm** is a specialized cell-cell junction between the pedicels (foot processes) of podocytes in the renal glomerulus. It acts as the final physical barrier to protein filtration. [1] **Explanation of the Correct Answer:** * **D. Batin:** This is the correct answer because "Batin" is not a recognized protein component of the glomerular filtration barrier. It is likely a distractor term. The actual proteins forming the diaphragm are complex transmembrane and scaffolding proteins that link the slit to the podocyte cytoskeleton. **Analysis of Incorrect Options:** * **A. Nephrin:** This is a crucial transmembrane glycoprotein of the immunoglobulin superfamily. It forms the "zipper-like" structure of the slit diaphragm. Mutations in the *NPHS1* gene (encoding nephrin) lead to **Finnish-type congenital nephrotic syndrome**. * **B. Podocin:** An integral membrane protein that localizes to the slit diaphragm and interacts with nephrin and CD2AP. Mutations in the *NPHS2* gene (encoding podocin) cause **autosomal recessive steroid-resistant nephrotic syndrome**. * **C. Alpha-actinin 4:** This is an actin-binding protein that anchors the slit diaphragm proteins to the actin cytoskeleton within the podocyte foot process. Mutations in *ACTN4* are associated with **familial Focal Segmental Glomerulosclerosis (FSGS)**. **High-Yield Clinical Pearls for NEET-PG:** * **The Filtration Barrier Layers:** 1. Fenestrated endothelium, 2. Glomerular Basement Membrane (GBM), 3. Slit diaphragm (Podocytes). [1] * **Charge Selectivity:** The barrier is negatively charged due to **heparan sulfate** (in GBM) and **sialoproteins** like podocalyxin, which repel negatively charged albumin. [1] * **Key Protein Summary:** Nephrin (Transmembrane), Podocin (Scaffolding), CD2AP (Linker), and Alpha-actinin 4 (Cytoskeletal anchor).

Question 1

Basement membrane around Schwann cells contains which of the following collagens?

Accepted Answer

Type XXVIII

Answer

Type IV

Answer

Type X

Answer

Type XX

Question 2

What is the type of cell lining the small intestine?

Accepted Answer

Simple columnar

Answer

Simple squamous

Answer

Stratified squamous

Answer

Stratified columnar

Question 3

Which of the following is present in Paneth cells?

Accepted Answer

Zinc

Answer

Copper

Answer

Molybdenum

Answer

Selenium

Question 4

What is the cell junction marked by the circle?

Accepted Answer

Zona adherens

Answer

Fascia adherens

Answer

Macula adherens

Answer

Zonula occludens

Question 5

Which one of the following is NOT a component of the filtration slit diaphragm at the glomerulus?

Accepted Answer

Batin

Answer

Nephrin

Answer

Podocin

Answer

alpha-actinin 4

Microscopic Anatomy — MCQs

Microscopic Anatomy — MCQs

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