Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 231: Russel bodies are found in which of the following conditions?

A. Multiple myeloma (Correct Answer)
B. Gonadal tumor
C. Parkinsonism
D. Intracranial neoplasms

Explanation: **Explanation:** **Russell bodies** are eosinophilic, large, homogenous immunoglobulin inclusions found within the cytoplasm of activated or neoplastic plasma cells. They represent an accumulation of newly synthesized immunoglobulins in the rough endoplasmic reticulum (RER) that the cell is unable to secrete. * **Multiple Myeloma (Option A):** This is a neoplastic proliferation of plasma cells. Since these cells are "protein factories" producing excessive monoclonal antibodies (M-protein), they often exhibit Russell bodies. When these inclusions are found within the nucleus, they are termed **Dutcher bodies**. A plasma cell packed with multiple Russell bodies is called a **Mott cell** (or grape cell). **Analysis of Incorrect Options:** * **Gonadal tumors (Option B):** Specifically, Yolk Sac tumors are characterized by **Schiller-Duval bodies** and hyaline droplets (alpha-fetoprotein), not Russell bodies. * **Parkinsonism (Option C):** This condition is associated with **Lewy bodies**, which are intracytoplasmic inclusions of alpha-synuclein found in the neurons of the substantia nigra. * **Intracranial neoplasms (Option D):** Various inclusions exist here, such as **Psammoma bodies** in Meningiomas or **Rosenthal fibers** in Pilocytic Astrocytomas, but Russell bodies are not a diagnostic feature. **High-Yield Clinical Pearls for NEET-PG:** * **Mott Cell:** A plasma cell containing multiple Russell bodies (looks like a bunch of grapes). * **Dutcher Bodies:** PAS-positive inclusions in the **nucleus** of plasma cells (seen in Waldenström macroglobulinemia and Multiple Myeloma). * **Councilman Bodies:** Eosinophilic globules seen in the liver due to apoptosis of hepatocytes (common in Yellow Fever and Viral Hepatitis).

Question 232: Hemoglobin functions as an effective buffer primarily due to which of the following characteristics?

A. The presence of histidine residues (Correct Answer)
B. Its protein structure
C. Its acidic nature
D. The presence of iron molecules

Explanation: **Explanation:** Hemoglobin (Hb) is the most important non-bicarbonate buffer in the blood. Its buffering capacity is primarily attributed to the **imidazole groups of histidine residues** within the globin chains [1]. 1. **Why Histidine is Correct:** The pKa of the imidazole group of histidine is approximately **6.8**, which is very close to the physiological pH of blood (7.4) [1]. According to the Henderson-Hasselbalch principle, a buffer is most effective when its pKa is near the pH of the medium. Hemoglobin contains 38 histidine residues per molecule, allowing it to effectively bind or release hydrogen ions ($H^+$) in response to pH changes. Furthermore, **Deoxyhemoglobin** is a better buffer than Oxyhemoglobin because its pKa is higher (approx. 7.9), making it more efficient at picking up $H^+$ ions produced by $CO_2$ transport in tissues (the Bohr effect). 2. **Why Other Options are Incorrect:** * **B. Protein structure:** While the quaternary structure is vital for oxygen transport (allosteric binding), it is the specific amino acid composition (histidine), not the general structure, that provides buffering. * **C. Acidic nature:** Hemoglobin is not inherently acidic; it acts as a weak base/acid conjugate pair. * **D. Iron molecules:** Iron ($Fe^{2+}$) is essential for binding oxygen in the heme group, but it does not participate in the proton exchange required for buffering [4]. **NEET-PG High-Yield Pearls:** * **Bohr Effect:** Increased $H^+$ (acidity) and $CO_2$ shift the oxygen dissociation curve to the **right**, promoting $O_2$ release [3]. * **Haldane Effect:** Oxygenation of Hb in the lungs promotes the release of $CO_2$. * **Intracellular Buffering:** Hemoglobin is responsible for nearly 80% of the non-bicarbonate buffering capacity of the whole blood [2].

Question 233: A 60-year-old male undergoes TURP. After 3 days, the patient develops altered sensorium and drowsiness. What is the most probable diagnosis?

A. Hypernatremia
B. Hyponatremia (Correct Answer)
C. Stroke
D. Meningitis due to spinal anesthesia

Explanation: ### Explanation **Correct Answer: B. Hyponatremia** The clinical scenario describes **TURP Syndrome**, a classic complication of Transurethral Resection of the Prostate. During the procedure, large volumes of non-conductive irrigation fluids (traditionally **1.5% Glycine**) are used. These fluids can be absorbed into the systemic circulation through opened prostatic venous sinuses [1]. The absorption of this hypotonic, sodium-free fluid leads to **dilutional hyponatremia** and fluid overload [1]. The rapid drop in serum sodium levels causes cerebral edema, manifesting as altered sensorium, drowsiness, confusion, seizures, and potentially coma [1]. **Analysis of Incorrect Options:** * **A. Hypernatremia:** TURP syndrome causes a "dilutional" effect, lowering sodium concentration. Hypernatremia would involve water loss or sodium gain, which is the opposite of the pathophysiology here. * **C. Stroke:** While a stroke can cause altered sensorium in elderly patients, the specific temporal relationship with a TURP procedure strongly points toward a metabolic/electrolyte cause rather than a focal neurological event. * **D. Meningitis:** While spinal anesthesia is used for TURP, meningitis typically presents with fever, nuchal rigidity, and headache. It would not explain the systemic fluid shifts associated with this surgery. **NEET-PG High-Yield Pearls:** * **Irrigating Fluid:** 1.5% Glycine is most common. Others include Mannitol or Sorbitol. * **Triad of TURP Syndrome:** Hypertension (early), Bradycardia, and Altered Mental Status. * **Visual Disturbances:** Glycine is an inhibitory neurotransmitter in the retina; its toxicity can cause transient blindness. * **Prevention:** Limit resection time to <60 minutes and keep the irrigation bag height <60 cm above the patient. * **Treatment:** Fluid restriction and Diuretics (mild cases); **3% Hypertonic saline** (severe symptomatic hyponatremia).

Question 234: Which of the following is NOT a component of the spleen?

A. Red pulp
B. White pulp
C. Subcapsular sinus (Correct Answer)
D. Splenic cords

Explanation: **Explanation:** The correct answer is **C. Subcapsular sinus**. The **subcapsular sinus** is a characteristic feature of **lymph nodes**, not the spleen. In a lymph node, afferent lymphatic vessels drain into the subcapsular sinus, located just beneath the capsule, before the lymph percolates through the cortex and medulla. The spleen, unlike lymph nodes, lacks afferent lymphatics and does not possess a subcapsular sinus. **Analysis of Incorrect Options:** * **White Pulp (B):** This is the lymphoid tissue of the spleen, consisting of the **Periarteriolar Lymphoid Sheath (PALS)**—rich in T-cells—and lymphoid follicles (Malpighian corpuscles) rich in B-cells. * **Red Pulp (A):** This makes up the bulk of the splenic parenchyma. Its primary function is to filter the blood, removing aged or damaged red blood cells [1]. * **Splenic Cords (D):** Also known as **Cords of Billroth**, these are found within the red pulp. They are composed of a reticular meshwork packed with erythrocytes, macrophages, and plasma cells, located between the splenic sinusoids. **High-Yield NEET-PG Pearls:** * **PALS (Periarteriolar Lymphoid Sheath):** A high-yield fact is that PALS is the **T-cell zone** of the spleen, surrounding the central arteriole. * **Open vs. Closed Circulation:** The spleen is unique for its "open circulation," where blood is dumped from penicillar arterioles into the splenic cords before re-entering the venous system via sinusoids. * **Pitting and Culling:** These are the two primary functions of the red pulp, involving the removal of inclusions from RBCs and destroying old RBCs [1]. * **Asplenia:** Patients without a spleen are at high risk for infections by **encapsulated organisms** (e.g., *S. pneumoniae, H. influenzae, N. meningitidis*) [1].

Question 235: Chief cells are found in which part of the gastric gland?

A. Fundus (Correct Answer)
B. Pit
C. Neck
D. Body

Explanation: **Explanation:** The gastric gland (oxyntic gland) is a branched tubular structure divided into three distinct anatomical zones: the **pit**, the **neck**, and the **base (fundus)**. 1. **Why Fundus is Correct:** The **base or fundus** is the deepest part of the gastric gland. It is primarily composed of **Chief cells** (Zymogenic cells), which secrete pepsinogen and gastric lipase [1]. These cells are characterized by their basophilic cytoplasm (due to extensive rough ER) and apical zymogen granules. 2. **Why Other Options are Incorrect:** * **Pit (Foveola):** This is the opening of the gland onto the mucosal surface. It is lined by **Surface mucous cells** which secrete protective insoluble mucus. * **Neck:** This middle segment contains **Mucous neck cells** (secreting soluble mucus) and is the primary site for **Parietal (Oxyntic) cells**, which secrete HCl and Intrinsic Factor [1]. * **Body:** While "Body" refers to a region of the stomach, in the context of a single gastric gland's histology, the term "Body" is often used interchangeably with the neck/isthmus area, but the specific histological niche for Chief cells is always the **base/fundus**. **High-Yield NEET-PG Pearls:** * **Parietal Cells:** Located mostly in the **neck/upper body**; they are eosinophilic (pink) due to numerous mitochondria [1]. * **Chief Cells:** Located in the **base/fundus**; they are basophilic (blue) [1]. * **Stem Cells:** Located in the **isthmus** (between the pit and neck); they replenish all other cell types. * **G-Cells:** Found in the **Antrum** (not the fundic glands), secreting Gastrin [1].

Question 236: What is the principal cell of the epidermis?

A. Melanocytes
B. Langerhan cell
C. Keratinocytes (Correct Answer)
D. Merkel cell

Explanation: **Explanation:** The epidermis is a keratinized stratified squamous epithelium primarily composed of four distinct cell types [1]. **Keratinocytes** are the correct answer because they constitute approximately **90% of the total epidermal cell population**. They originate in the basal layer and undergo a process of maturation (keratinization) as they move toward the surface, providing the essential structural and protective barrier of the skin [1]. **Analysis of Incorrect Options:** * **Melanocytes (A):** These are dendritic cells derived from the **neural crest**. They reside in the *stratum basale* and produce melanin to protect against UV radiation [1]. They make up only about 5–10% of basal cells. * **Langerhans cells (B):** These are bone marrow-derived **antigen-presenting cells** (dendritic cells) located primarily in the *stratum spinosum* [1]. They represent only 2–4% of epidermal cells. * **Merkel cells (C):** These are specialized **mechanoreceptors** for tactile sensation located in the *stratum basale* [1], [2]. They are the least numerous of the epidermal cells. **High-Yield Clinical Pearls for NEET-PG:** * **Layers of Epidermis (Deep to Superficial):** Stratum **B**asale, **S**pinosum, **G**ranulosum, **L**ucidum (only in thick skin), and **C**orneum (Mnemonic: "**B**ritish **S**pies **G**et **L**ow **C**onfidence"). * **Desmosomes:** These are the primary intercellular junctions connecting keratinocytes, particularly prominent in the *stratum spinosum* (giving it a "prickly" appearance). * **Birbeck Granules:** Characteristic "tennis-racket" shaped granules found on electron microscopy in **Langerhans cells**. * **Pemphigus Vulgaris:** An autoimmune condition where antibodies attack desmoglein (in desmosomes), leading to the loss of keratinocyte adhesion (acantholysis).

Question 237: Cystoscopic findings in TB bladder are all except?

A. Thimble bladder
B. Golf hole ureter
C. Whitish efflux from the ureteric holes (Correct Answer)
D. Cobblestone mucosa

Explanation: Explanation: The correct answer is **C (Whitish efflux from the ureteric holes)**. In Genitourinary Tuberculosis (GUTB), the efflux from the ureteric orifice is typically **clear**, even in the presence of sterile pyuria. This is because the "pus" cells in TB are microscopic and do not cause the thick, milky, or "whitish" discharge seen in acute pyogenic infections. **Analysis of Options:** * **Thimble Bladder (Option A):** This is a classic late-stage finding. Chronic inflammation and healing by fibrosis lead to a severely contracted, small-capacity, thick-walled bladder, often referred to as a "thimble bladder." * **Golf Hole Ureter (Option B):** Fibrosis and shortening of the ureter lead to the retraction of the ureteric orifice. This causes the orifice to become dilated, circular, and fixed, resembling a "golf hole." * **Cobblestone Mucosa (Option C):** Early cystoscopic findings include hyperemic patches and the formation of "tubercles" (small yellowish nodules). As these coalesce or become surrounded by edema and granulation tissue, the bladder mucosa takes on a "cobblestone" appearance. **High-Yield Clinical Pearls for NEET-PG:** * **Sterile Pyuria:** The hallmark of GUTB (pus cells in urine but negative routine bacterial culture). * **Putty Kidney:** Refers to autonephrectomy where the kidney is replaced by caseous, calcified material. * **Beaded Vas:** Granulomatous involvement of the vas deferens. * **Investigation of Choice:** Contrast-Enhanced CT (CECT) Urography is the gold standard for diagnosis and staging.

Question 238: Which of the following is the predominant collagen type in bone?

A. Type I (Correct Answer)
B. Type II
C. Type III
D. Type IV

Explanation: **Explanation:** The correct answer is **Type I Collagen**. **1. Why Type I is Correct:** Bone is a specialized connective tissue consisting of an organic matrix (osteoid) and inorganic mineral (hydroxyapatite). Approximately **90% of the organic matrix of bone** is composed of Type I collagen [1]. These fibers provide the structural framework and tensile strength necessary for bone to resist stretching and breakage [2]. It is synthesized by osteoblasts and arranged in a lamellar pattern to facilitate mineralization [1]. **2. Why Other Options are Incorrect:** * **Type II:** This is the predominant collagen in **Hyaline and Elastic cartilage**, as well as the vitreous humor of the eye. It is not found in mature bone. * **Type III (Reticulin):** These fibers form a delicate branching network (reticular fibers) found in highly cellular organs like the **liver, spleen, lymph nodes**, and bone marrow. It is also prominent in early wound healing (granulation tissue). * **Type IV:** This type does not form fibrils; instead, it forms a meshwork that is a key structural component of the **Basal Lamina** (basement membrane). **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Mnemonic:** "Type **One** is in B**one**; Type **Two** is in Car-two-lage (**Cartilage**)." * **Osteogenesis Imperfecta:** A clinical condition caused by mutations in genes encoding Type I collagen, leading to "brittle bone disease" and blue sclera. * **Alport Syndrome:** Associated with defects in **Type IV** collagen (affects kidneys, ears, and eyes). * **Ehlers-Danlos Syndrome (Vascular type):** Often associated with a deficiency in **Type III** collagen.

Question 239: Myelofibrosis leading to a dry tap on bone marrow aspiration is seen with which of the following conditions?

A. Burkitt's lymphoma
B. Acute erythroblastic leukemia
C. Acute megakaryocytic leukemia (Correct Answer)
D. Acute undifferentiated leukemia

Explanation: **Explanation:** The correct answer is **Acute megakaryocytic leukemia (AML-M7)**. **Underlying Medical Concept:** A "dry tap" occurs when bone marrow cannot be aspirated despite multiple attempts, usually due to extensive **myelofibrosis** (replacement of marrow space by collagen/fibrous tissue). In Acute Megakaryocytic Leukemia (AML-M7), the malignant megakaryoblasts release potent fibrogenic cytokines, specifically **Transforming George Factor-beta (TGF-β)** and **Platelet-Derived George Factor (PDGF)**. These cytokines stimulate marrow fibroblasts to deposit excessive reticulin and collagen, leading to rapid and severe fibrosis. **Analysis of Options:** * **Acute Megakaryocytic Leukemia (Correct):** It is the classic cause of acute myelofibrosis among the leukemias. It is also notably associated with Down Syndrome in children under the age of 5. * **Burkitt’s Lymphoma:** This is a high-grade B-cell lymphoma characterized by a "starry sky" appearance on histology. While it can involve the marrow, it typically presents with hypercellularity rather than primary fibrosis. * **Acute Erythroblastic Leukemia (AML-M6):** This involves the proliferation of erythroid precursors. While the marrow is hypercellular, it does not typically induce the cytokine-mediated fibrotic response seen in M7. * **Acute Undifferentiated Leukemia:** These are rare leukemias lacking lineage-specific markers. They do not have a specific association with early-onset myelofibrosis. **High-Yield Clinical Pearls for NEET-PG:** * **Common causes of Dry Tap:** Myelofibrosis (Primary or Secondary), Hairy Cell Leukemia, Aplastic Anemia, and Metastatic carcinoma. * **AML-M7 Association:** Strongly associated with **Trisomy 21 (Down Syndrome)**. * **Diagnosis:** When a dry tap occurs, a **Trephine Biopsy** is mandatory to visualize the architecture and confirm fibrosis using Silver (Reticulin) stain.

Question 240: The type of epithelium associated with the vermilion zone of the lips is:

A. Stratified squamous non-keratinized
B. Pseudostratified ciliated columnar
C. Stratified squamous keratinized (Correct Answer)
D. Stratified cuboidal

Explanation: The lip is divided into three distinct zones: the outer skin, the inner mucous membrane, and the transitional **vermilion zone** (the red margin). **1. Why Option C is Correct:** The vermilion zone is covered by **stratified squamous keratinized epithelium**. Although it is a transition zone, it remains a modified form of skin. The keratin layer here is very thin (parakeratinized or orthokeratinized), and the underlying connective tissue papillae are tall, narrow, and highly vascular. This proximity of blood vessels to the surface, combined with the thinness of the epithelium, gives the lips their characteristic red color. Notably, this zone lacks sweat glands and hair follicles, making it prone to drying. **2. Why Incorrect Options are Wrong:** * **Option A (Non-keratinized):** This is found on the **internal/oral aspect** of the lip (labial mucosa). It is kept moist by minor salivary glands. * **Option B (Pseudostratified ciliated columnar):** This is "respiratory epithelium," found in the nasal cavity, trachea, and bronchi, not in the oral region. * **Option C (Stratified cuboidal):** This rare epithelium is typically found in the larger ducts of exocrine glands (e.g., sweat gland ducts). **3. High-Yield Clinical Pearls for NEET-PG:** * **Fordyce Spots:** These are ectopic sebaceous glands (not associated with hair follicles) sometimes seen as yellowish specks in the vermilion or oral mucosa. * **Eleidin:** The vermilion zone contains a clear protein called eleidin, which contributes to its translucency. * **Clinical Correlation:** Squamous cell carcinoma of the lip most commonly affects the lower lip at the vermilion border due to chronic sun exposure.

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Histology — MCQs

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