Microscopic Anatomy — MCQs

Microscopic Anatomy Indian Medical PG Practice Questions and MCQs

Question 141: What are the supporting cells of the testes?

A. Spermatogonia
B. Leydig cells
C. Sertoli cells (Correct Answer)
D. Spermatids

Explanation: **Explanation:** The correct answer is **C. Sertoli cells**. Sertoli cells are the large, columnar "nurse cells" located within the germinal epithelium of the seminiferous tubules [1]. They are considered the **supporting cells** of the testes because they provide structural integrity, nutrition, and protection to developing germ cells [1], [2]. They are also responsible for forming the **blood-testis barrier** via tight junctions, protecting sperm from the immune system [1]. **Analysis of Options:** * **Spermatogonia (A):** These are the undifferentiated male germ cells (stem cells) located on the basement membrane [1]. They are the precursors to sperm, not supporting cells. * **Leydig cells (B):** Also known as interstitial cells, these are found in the connective tissue *between* seminiferous tubules. Their primary function is the endocrine production of **Testosterone** in response to LH [3]. * **Spermatids (D):** These are haploid male germ cells derived from secondary spermatocytes. They represent a late stage of spermatogenesis before undergoing spermiogenesis to become mature spermatozoa [2]. **High-Yield Facts for NEET-PG:** * **Secretions:** Sertoli cells secrete **Inhibin B** (inhibits FSH), **Androgen Binding Protein (ABP)** (maintains high local testosterone), and **Anti-Müllerian Hormone (AMH)** during fetal development [2], [3]. * **Regulation:** Sertoli cells are stimulated by **FSH**, whereas Leydig cells are stimulated by **LH** (Mnemonic: **L**H acts on **L**eydig cells) [3]. * **Phagocytosis:** Sertoli cells phagocytose the excess cytoplasm (residual bodies) shed by spermatids during spermiogenesis. * **Tumor Marker:** Sertoli cells contain **Charcot-Böttcher crystals** (spindle-shaped cytoplasmic inclusions), which are pathognomonic.

Question 142: Which type of cells are not found in the stomach?

A. Chief cells
B. Parietal cells
C. Argentaffin cells
D. Goblet cells (Correct Answer)

Explanation: **Explanation:** The correct answer is **Goblet cells**. The gastric mucosa is lined by a simple columnar epithelium that forms "surface mucous cells," which secrete a protective layer of alkaline mucus. However, true **Goblet cells** (unicellular glands characterized by a constricted base and a distended apical end filled with mucin) are characteristic of the **small and large intestines**, not the stomach. **Analysis of Options:** * **Chief Cells (Peptic/Zymogenic cells):** Found primarily in the base of the gastric glands (body and fundus) [2]. They secrete pepsinogen and gastric lipase [3]. * **Parietal Cells (Oxyntic cells):** Located mainly in the neck and body of gastric glands [2]. They secrete Hydrochloric acid (HCl) and Intrinsic Factor of Castle [3]. * **Argentaffin Cells (Enterochromaffin cells):** These are a type of Enteroendocrine cell found throughout the gastrointestinal tract, including the stomach [1]. They secrete serotonin and histamine to regulate gastric motility and secretion [1]. **High-Yield NEET-PG Pearls:** 1. **Intestinal Metaplasia:** The presence of Goblet cells in the gastric mucosa is a pathological finding (often due to chronic *H. pylori* gastritis) and is considered a pre-cancerous lesion. 2. **Parietal Cell Histology:** They are characterized by an abundance of mitochondria and an intracellular canalicular system [3]. They are stained intensely eosinophilic (pink) on H&E stain. 3. **Vitamin B12:** Destruction of parietal cells (as seen in Atrophic Gastritis) leads to a deficiency of Intrinsic Factor, resulting in **Pernicious Anemia**.

Question 143: Sinusoids are seen in all of the following organs except?

A. Liver
B. Kidney (Correct Answer)
C. Lymph nodes
D. Spleen

Explanation: ### Explanation **Conceptual Overview** Sinusoids are a specialized type of **discontinuous capillary** characterized by a wide, irregular lumen, a fenestrated endothelium with large gaps, and a partial or absent basement membrane [1]. These features allow for the free exchange of large molecules (like proteins) and even whole cells between the blood and the surrounding tissue [2]. **Why Kidney is the Correct Answer** The kidney contains **fenestrated capillaries** (specifically in the glomerulus and peritubular network), but it does **not** contain sinusoids [1]. Unlike sinusoids, fenestrated capillaries in the kidney have a **thick, continuous basement membrane** that acts as a critical filtration barrier to prevent the passage of large proteins and blood cells into the primary urine [1]. **Analysis of Incorrect Options** * **Liver (A):** The liver is the classic example of sinusoidal architecture [2]. Hepatic sinusoids allow plasma to come into direct contact with hepatocytes in the Space of Disse for metabolic processing [3]. * **Lymph nodes (C):** These contain lymphatic sinusoids (subcapsular, cortical, and medullary) which facilitate the slow flow of lymph, allowing macrophages to filter antigens. * **Spleen (D):** The red pulp of the spleen contains splenic sinusoids (venous sinusoids). These are essential for "pitting" and "culling" of aged or abnormal red blood cells. **NEET-PG High-Yield Pearls** * **Locations of Sinusoids:** Remember the mnemonic **"LBS"** (Liver, Bone marrow, Spleen) + Adrenal cortex, Anterior Pituitary, and Lymph nodes. * **Basement Membrane:** The defining difference between a fenestrated capillary (Kidney/Endocrine glands) and a sinusoid is the **continuity of the basement membrane** (Continuous in fenestrated; Discontinuous/Absent in sinusoids) [1]. * **Spleen Specifics:** Splenic sinusoids are lined by long, rod-shaped endothelial cells called **Stave cells**.

Question 144: Which of the following is NOT true about terminal bronchioles?

A. Absence of cartilage
B. Presence of Clara cells
C. Absence of smooth muscles (Correct Answer)
D. Absence of submucous glands

Explanation: To understand the histology of the respiratory tree, one must identify the transition points between the conducting zone and the respiratory zone. [1] ### **Explanation of the Correct Option** **C. Absence of smooth muscles** is the correct answer because it is a **false** statement. Terminal bronchioles actually possess a well-developed, continuous layer of smooth muscle. In fact, as the respiratory tree branches and loses its cartilaginous support, the relative amount of smooth muscle increases to maintain airway patency and regulate airflow. It is only at the level of the alveolar sacs that smooth muscle finally disappears. ### **Analysis of Incorrect Options** * **A. Absence of cartilage:** This is a true statement. Cartilage disappears at the level of the bronchiole. The absence of cartilage is the primary histological feature that distinguishes a bronchiole from a bronchus. * **B. Presence of Clara cells:** This is a true statement. Clara cells (now called Club cells) are non-ciliated, dome-shaped cells that first appear in the bronchioles. They secrete surfactant-like lipoproteins and play a role in detoxification. [1] * **C. Absence of submucous glands:** This is a true statement. Submucous glands and goblet cells are present in the trachea and bronchi but are absent in the terminal bronchioles to prevent mucus from plugging the small airways. [1] ### **High-Yield NEET-PG Pearls** * **Terminal vs. Respiratory Bronchiole:** The terminal bronchiole is the **last part of the conducting zone**. Once alveoli appear in the wall, it becomes a respiratory bronchiole (the start of the respiratory zone). [1] * **Epithelium Shift:** The epithelium transitions from pseudostratified ciliated columnar (trachea/bronchi) to **simple ciliated columnar/cuboidal** in the terminal bronchioles. [1] * **Clinical Correlation:** In **Asthma**, the smooth muscle in the bronchioles undergoes bronchospasm. Since there is no cartilage to hold these small airways open, the muscle contraction leads to significant airway obstruction.

Question 145: Which of the following organs does NOT contain sinuses?

A. Kidney (Correct Answer)
B. Spleen
C. Endocrine gland
D. Liver

Explanation: The correct answer is **Kidney**. In histology, **sinusoids** (or sinuses) are specialized, wide-diameter, thin-walled capillaries with large fenestrations and a discontinuous basement membrane [1]. They allow for the exchange of large molecules and cells between the blood and the surrounding tissue. 1. **Why Kidney is the correct answer:** The kidney contains **fenestrated capillaries** (specifically in the glomerulus and peritubular network), but it does **not** contain sinusoids [1]. The renal "sinus" is an anatomical space containing the renal pelvis and vessels, but it is not a vascular sinusoid. 2. **Why the other options are incorrect:** * **Spleen:** Contains prominent **venous sinusoids** in the red pulp, lined by "stave cells" that filter aged red blood cells. * **Endocrine Glands:** Many endocrine glands (like the pituitary and adrenal glands) contain sinusoids to facilitate the rapid entry of large hormone molecules into the bloodstream [1]. * **Liver:** The liver is the classic example of an organ with **discontinuous sinusoids**, where blood from the portal vein and hepatic artery mixes before reaching the central vein [2], [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Locations of Sinusoids:** Remember the mnemonic **"L-B-S-E"** (Liver, Bone marrow, Spleen, Endocrine glands) [4]. * **Liver Sinusoids:** Contain **Kupffer cells** (fixed macrophages) and are separated from hepatocytes by the **Space of Disse** [2]. * **Spleen:** The splenic sinusoids act as a "mechanical filter"; RBCs must be flexible to squeeze through the stave cell gaps. * **Capillary Types:** * *Continuous:* Muscle, Lung, CNS (Blood-Brain Barrier). * *Fenestrated:* Kidney (Glomerulus), Intestine, Endocrine glands [1]. * *Sinusoidal:* Liver, Spleen, Bone Marrow [4].

Question 146: All of the following statements are true except?

A. Microglial cells are modified macrophages in the brain.
B. Hofbauer cells are modified macrophages in the placenta.
C. Stellate cells are modified macrophages in the liver. (Correct Answer)
D. Osteoclasts are modified macrophages.

Explanation: ### **Explanation** The question asks to identify the incorrect statement regarding the **Mononuclear Phagocyte System (MPS)**. **1. Why Option C is the Correct (Incorrect) Statement:** In the liver, the resident macrophages are **Kupffer cells**, which are located within the hepatic sinusoids [3]. **Stellate cells** (also known as Ito cells), located in the space of Disse [1], are not macrophages; they are specialized cells responsible for **Vitamin A storage**. In pathological states (like chronic alcohol use), they transform into myofibroblasts and produce collagen, leading to liver fibrosis and cirrhosis. **2. Analysis of Other Options:** * **Option A:** **Microglial cells** are the resident macrophages of the Central Nervous System (CNS) [3]. They are unique because they are derived from the yolk sac (mesoderm), unlike other brain cells which are ectodermal. * **Option B:** **Hofbauer cells** are mesenchymal macrophages found in the chorionic villi of the placenta. They play a role in preventing vertical transmission of pathogens. * **Option C:** **Osteoclasts** are multinucleated giant cells in the bone derived from the fusion of monocyte-macrophage precursors [3]. They are responsible for bone resorption [2], [4]. **3. NEET-PG High-Yield Pearls:** * **Dust Cells:** Alveolar macrophages in the lungs [3]. * **Langerhans Cells:** Antigen-presenting macrophages in the skin (contain Birbeck granules). * **Mesangial Cells:** Specialized macrophages in the kidney glomerulus. * **Littoral Cells:** Macrophages found in the splenic sinusoids. * **Heart Failure Cells:** Siderophages (hemosiderin-laden macrophages) found in the alveoli during left heart failure.

Question 147: What is the positive zone of enamel caries?

A. Translucent zone
B. Dark zone (Correct Answer)
C. Body of the lesion
D. Surface zone

Explanation: ### Explanation In the histopathology of enamel caries, the lesion is divided into four distinct zones based on the degree of demineralization and the size of the resulting pores. **Why the Dark Zone is correct:** The **Dark Zone** is referred to as the "positive zone" because it appears dark under a polarizing microscope when mounted in quinoline. This occurs because the zone contains very small "micropores" (2–4% mineral loss) that are too small for the large molecules of quinoline to enter. These pores remain filled with air or vapor, which scatters light, resulting in a dark appearance. It is considered a zone of active remineralization and is a hallmark of a progressing lesion. **Analysis of Incorrect Options:** * **A. Translucent Zone:** This is the advancing front of the lesion. It is called "translucent" because its pores (1% mineral loss) are large enough to be completely filled by quinoline, making it appear clear. * **C. Body of the Lesion:** This is the area of maximum demineralization (5–25% mineral loss). It has the largest pores, which are easily filled by the mounting medium, making it appear relatively clear compared to the dark zone. * **D. Surface Zone:** This is the relatively intact outer layer (1% mineral loss). It remains mineralized due to constant exposure to fluoride and minerals from saliva. **High-Yield NEET-PG Pearls:** * **Order of zones (from deep to superficial):** Translucent zone → Dark zone → Body of the lesion → Surface zone. * **The Dark Zone** is a "dynamic" zone; its presence indicates that remineralization is occurring. * **The Translucent Zone** is the first recognizable histological change in enamel caries. * **Pore Volume:** Translucent (1%) < Dark (2-4%) < Body of lesion (5-25%).

Question 148: Serous demilunes are present in large numbers in which gland?

A. Parotid
B. Submandibular (Correct Answer)
C. Sublingual
D. Pituitary

Explanation: The correct answer is **Submandibular gland**. **1. Why Submandibular is Correct:** Salivary glands are classified based on their secretion type: serous, mucous, or mixed. The **submandibular gland** is a **mixed gland** with a predominant serous component. Serous demilunes (also known as **Giannuzzi's crescents**) are characteristic histological features of mixed glands. They consist of cap-like clusters of serous cells situated at the periphery of mucous acini. During traditional histological preparation, the swelling of mucous cells pushes the serous cells outward, creating the "half-moon" or demilune appearance. **2. Analysis of Incorrect Options:** * **Parotid Gland:** This is a **purely serous** gland. Since it lacks mucous acini, it does not contain serous demilunes. * **Sublingual Gland:** This is a mixed gland but is **predominantly mucous**. While it may contain some demilunes, they are significantly more numerous and characteristic in the submandibular gland. * **Pituitary Gland:** This is an endocrine gland composed of cords of epithelial cells (acidophils, basophils, and chromophobes) and does not contain exocrine acini or demilunes. **3. NEET-PG High-Yield Pearls:** * **Secretory Ratio:** Submandibular (80% serous, 20% mucous); Sublingual (predominantly mucous). * **Staining:** Serous cells are protein-secreting (basophilic cytoplasm due to RER); Mucous cells contain mucin (pale/vacuolated appearance). * **Myoepithelial cells:** Located between the basal lamina and acinar cells; they contract to expel secretions into the duct system. * **Ducts:** The submandibular gland has the most prominent **striated ducts**, which are involved in ion reabsorption.

Question 149: The juxtaglomerular apparatus is located in relation to which renal structure?

A. Proximal convoluted tubule
B. Ascending loop of Henle
C. Descending loop of Henle
D. Glomerulus (Correct Answer)

Explanation: **Explanation:** The **Juxtaglomerular Apparatus (JGA)** is a specialized structure located at the **vascular pole of the renal corpuscle (Glomerulus)** [1]. It serves as a critical regulatory unit that monitors systemic blood pressure and glomerular filtration rate (GFR). The JGA is formed by the anatomical contact between the **afferent arteriole** (and sometimes the efferent arteriole) and the **thick ascending limb/distal convoluted tubule** of the same nephron [1]. Because it is physically situated at the entry and exit point of the glomerular capillaries, it is considered anatomically and functionally related to the **Glomerulus** [4]. **Analysis of Options:** * **Proximal Convoluted Tubule (A):** This is located at the urinary pole of the glomerulus, opposite the JGA [2]. * **Ascending Loop of Henle (B):** While the *thick* ascending limb returns to touch the glomerulus (forming the Macula Densa), the JGA as a complex is defined by its relationship to the glomerular hilum. * **Descending Loop of Henle (C):** This segment is located deep in the medulla and has no physical contact with the vascular pole of the nephron. **NEET-PG High-Yield Pearls:** 1. **Components of JGA:** * **Juxtaglomerular (JG) Cells:** Modified smooth muscle cells of the afferent arteriole; they secrete **Renin** [1][3]. * **Macula Densa:** Specialized columnar cells of the distal tubule; they act as **chemoreceptors** for sodium chloride (NaCl) levels. * **Lacis Cells (Extraglomerular Mesangial Cells):** Located in the triangular space between the arterioles and the macula densa. 2. **Function:** It regulates the **Renin-Angiotensin-Aldosterone System (RAAS)** and mediates **Tubuloglomerular Feedback** [3].

Question 150: Node of Ranvier is seen in which part of a neuron?

A. Cell body
B. Dendrites
C. Axons (Correct Answer)
D. Terminal buttons

Explanation: The **Node of Ranvier** refers to the periodic gaps (approximately 1 μm wide) in the myelin sheath along the length of an **axon**. [1] These gaps are essential for **saltatory conduction**, where the action potential "jumps" from one node to the next, significantly increasing the speed of nerve impulse transmission. [1] * **Why Axon is correct:** Myelination is a specific feature of axons. [1] In the Peripheral Nervous System (PNS), Schwann cells wrap around the axon, while in the Central Nervous System (CNS), oligodendrocytes perform this function. [1] The segments between nodes are called internodes. The nodal membrane is highly enriched with **voltage-gated sodium (Na+) channels**, which are necessary for regenerating the action potential. [1] * **Why other options are incorrect:** * **Cell body (Soma):** Contains the nucleus and organelles (like Nissl bodies) but lacks a myelin sheath; therefore, no nodes are present. [1] * **Dendrites:** These are typically unmyelinated processes that receive signals. [1] * **Terminal buttons:** These are the distal ends of axon branches that form synapses; they are specialized for neurotransmitter release, not impulse propagation via myelin gaps. [1] **High-Yield Clinical Pearls for NEET-PG:** * **Saltatory Conduction:** This mechanism is energy-efficient as it localizes metabolic activity (Na+/K+ ATPase pump) primarily to the nodes. * **Demyelinating Diseases:** In **Multiple Sclerosis** (CNS) and **Guillain-Barré Syndrome** (PNS), the myelin sheath is damaged, disrupting conduction at these nodes and leading to neurological deficits. [1] * **Caspr Protein:** A specific molecular marker found in the paranodal regions adjacent to the Node of Ranvier.

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Cellular Ultrastructure

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Microscopic Anatomy of Epithelial Tissues

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Microscopic Anatomy of Connective Tissues

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Microscopic Anatomy of Muscle Tissues

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Microscopic Anatomy of Nervous Tissues

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Microscopic Anatomy of Blood and Immune System

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Microscopic Anatomy of Endocrine Glands

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Microscopic Anatomy of Digestive System

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Microscopic Anatomy of Respiratory System

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Microscopic Anatomy of Urinary System

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Microscopic Anatomy of Reproductive System

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Techniques in Microscopic Anatomy

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