Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 261: Which of the following is a marker for testicular tumors?

A. Beta hCG (Correct Answer)
B. Acid phosphatase
C. Alkaline phosphatase
D. Alpha fetoprotein

Explanation: **Explanation:** Testicular germ cell tumors (GCTs) often secrete specific proteins into the bloodstream that serve as biochemical markers for diagnosis, staging, and monitoring treatment response. **Beta-hCG (human chorionic gonadotropin)** is a glycoprotein normally produced by syncytiotrophoblasts in the placenta [2]. In the context of testicular cancer, it is classically elevated in **Choriocarcinomas** (100% of cases) and some **Seminomas** (approximately 10–15% containing syncytiotrophoblastic giant cells). **Analysis of Options:** * **Beta-hCG (Correct):** It is the most sensitive marker for choriocarcinoma and helps differentiate between types of germ cell tumors [2]. * **Acid Phosphatase (B):** Specifically, Prostatic Acid Phosphatase (PAP) was historically used as a marker for **Prostate Cancer**, though it has largely been replaced by PSA (Prostate-Specific Antigen) [1]. * **Alkaline Phosphatase (C):** While the Placental-like isoform (PLAP) can be elevated in seminomas, "Alkaline Phosphatase" generally refers to the liver/bone isoenzyme, which is non-specific. * **Alpha-fetoprotein (D):** While AFP is a major marker for **Yolk Sac Tumors** and Embryonal Carcinomas, it is **never** elevated in pure seminomas. In the context of this specific question, Beta-hCG is the most classic "textbook" marker associated with the general category of GCTs. **High-Yield Clinical Pearls for NEET-PG:** * **Seminoma:** Most common testicular tumor; markers are usually normal, but **PLAP** is the most specific, and **hCG** may be mildly elevated. **AFP is always normal.** * **Yolk Sac Tumor:** Characterized by highly elevated **AFP** and presence of **Schiller-Duval bodies** on histology. * **Choriocarcinoma:** Characterized by very high **hCG** and early hematogenous spread (often to lungs) [2]. * **LDH (Lactate Dehydrogenase):** A non-specific marker used to assess tumor burden and prognosis in testicular cancer.

Question 262: The paracortex of a lymph node, located between the cortical follicles and the medulla, is primarily composed of which type of immune cells?

A. Proliferating T cells
B. Antigen-presenting cells
C. Quiescent B cells
D. All of the above (Correct Answer)

Explanation: The **paracortex** is the deep cortical region of the lymph node, situated between the superficial cortex (containing follicles) and the inner medulla. It is functionally known as the **thymus-dependent zone**. 1. **Why "All of the above" is correct:** * **Proliferating T cells:** The paracortex is the primary site for T-cell activation and proliferation [1]. When antigens are presented, T-lymphoblasts undergo rapid clonal expansion here. * **Antigen-presenting cells (APCs):** Specifically, **Interdigitating Dendritic Cells** are abundant in the paracortex. They present processed antigens to naive T cells to initiate the cell-mediated immune response [1]. * **Quiescent B cells:** While B cells primarily reside in the follicles, they must migrate through the paracortex via **High Endothelial Venules (HEVs)** to reach the superficial cortex [1]. Additionally, activated B cells interact with T-helper cells in this zone before forming germinal centers. 2. **Analysis of Options:** * While T cells are the *predominant* cell type, focusing only on them ignores the critical supportive and migratory roles of Dendritic cells and B cells within this histological compartment. **High-Yield Clinical Pearls for NEET-PG:** * **High Endothelial Venules (HEVs):** These specialized post-capillary venules are located in the **paracortex** [1]. They are the site where 90% of lymphocytes enter the lymph node from the blood. * **DiGeorge Syndrome:** Due to thymic hypoplasia, the paracortex of the lymph node will be **depleted/hypoplastic**. * **Dermatopathic Lymphadenopathy:** Characterized by significant expansion of the paracortex due to the accumulation of interdigitating dendritic cells (Langerhans cells). * **Cell-Mediated Immunity:** The paracortex enlarges during systemic viral infections or skin graft rejection [1].

Question 263: What is the deepest layer of the epidermis?

A. Stratum corneum
B. Stratum spinosum
C. Stratum granulosum
D. Stratum germinatum (Correct Answer)

Explanation: **Explanation:** The epidermis is a keratinized stratified squamous epithelium composed of five distinct layers (in thick skin). The correct answer is **Stratum germinatum** (also known as the **Stratum basale**). **1. Why Stratum germinatum is correct:** The Stratum germinatum is the deepest, single layer of cuboidal or columnar cells resting directly on the basement membrane [1]. It contains stem cells that undergo continuous mitosis to replenish the superficial layers. It is also the site where **melanocytes** and **Merkel cells** are primarily located [1]. **2. Analysis of Incorrect Options:** * **A. Stratum corneum:** This is the most **superficial** layer, consisting of flattened, dead, keratinized cells (corneocytes) without nuclei [1]. * **B. Stratum spinosum:** Located just above the basal layer, it is the thickest layer. Cells here are joined by desmosomes, giving them a "prickle-cell" or spiny appearance. * **C. Stratum granulosum:** This layer sits above the spinosum and is characterized by cells containing dark-staining **keratohyalin granules**. **3. NEET-PG High-Yield Pearls:** * **Mnemonic for layers (Superficial to Deep):** "**C**ome, **L**et's **G**et **S**un **B**urned" (**C**orneum, **L**ucidum, **G**ranulosum, **S**pinosum, **B**asale). * **Stratum Lucidum:** This "clear layer" is found **only in thick skin** (palms and soles), located between the corneum and granulosum. * **Clinical Correlation:** **Basal Cell Carcinoma**, the most common skin cancer, arises from the Stratum germinatum. **Pemphigus vulgaris** involves antibodies against desmosomes in the Stratum spinosum, leading to acantholysis.

Question 264: What is true about the thymus gland?

A. Its size increases after puberty.
B. It is the site of red and white blood cell mass.
C. It consists of Hassall's corpuscles. (Correct Answer)
D. It forms immunoglobulins.

Explanation: ### Explanation **Correct Option: C. It consists of Hassall's corpuscles.** The thymus is a primary lymphoid organ essential for T-cell maturation [1]. Its most characteristic histological feature is the **Hassall’s corpuscle**, found exclusively in the **thymic medulla**. These are concentric arrangements of flattened epithelial reticular cells that may undergo keratinization or calcification. They play a crucial role in the development of regulatory T-cells (Tregs). **Analysis of Incorrect Options:** * **Option A:** The thymus is largest at birth and continues to grow until **puberty**. After puberty, it undergoes **age-involution**, where lymphoid tissue is replaced by adipose and connective tissue. * **Option B:** The thymus is a site for **T-lymphocyte maturation** [1], [2] only. Red blood cells and other white blood cells (granulocytes, B-cells) are primarily produced in the **bone marrow** [1]. * **Option C:** The thymus does **not** produce immunoglobulins (antibodies). Immunoglobulins are produced by **plasma cells** (derived from B-lymphocytes), which mature in the bone marrow and peripheral lymphoid organs like the spleen and lymph nodes [1]. **High-Yield NEET-PG Pearls:** * **Embryology:** The thymus develops from the **3rd pharyngeal pouch** (along with the inferior parathyroid glands). * **Blood-Thymus Barrier:** Located in the **cortex**, it prevents circulating antigens from reaching developing T-cells to avoid premature activation. * **DiGeorge Syndrome:** A microdeletion (22q11.2) resulting in thymic aplasia, leading to severe T-cell deficiency and hypocalcemia. * **Myasthenia Gravis:** Frequently associated with thymic hyperplasia or **thymoma**.

Question 265: What fixative is used for bone histopathology?

A. 10% formalin (Correct Answer)
B. Normal saline
C. Rectified spirit
D. Nothing

Explanation: **Explanation:** The primary goal of fixation in histopathology is to preserve biological tissues from decay (autolysis and putrefaction) while maintaining the structural integrity of cells and extracellular matrix. **Why 10% Formalin is Correct:** 10% Neutral Buffered Formalin (NBF) is the standard "universal fixative" used for most tissues, including bone. It works by forming cross-links between proteins (specifically methylene bridges), which stabilizes the tissue architecture. For bone histopathology, fixation in formalin is a mandatory first step before the specimen undergoes **decalcification** (the removal of calcium salts using acids like EDTA or Nitric acid) to allow for thin sectioning [1]. **Why Incorrect Options are Wrong:** * **Normal Saline:** This is an isotonic solution, not a fixative. It is used for temporary transport of fresh tissue (e.g., for immunofluorescence or frozen sections) but does not prevent autolysis. * **Rectified Spirit (Alcohol):** While alcohol is a fixative, it causes significant tissue shrinkage and hardening. It is primarily used for cytology smears or as a secondary fixative, but not as the primary choice for bone. * **Nothing:** Leaving tissue "dry" leads to rapid enzymatic degradation (autolysis) and bacterial growth, rendering the sample non-diagnostic. **High-Yield Clinical Pearls for NEET-PG:** * **Fixative of choice for Electron Microscopy:** Glutaraldehyde. * **Fixative for Testicular Biopsy:** Bouin’s solution (preserves nuclear detail). * **Fixative for Lipids/Fats:** Osmium tetroxide (also used in EM). * **Decalcifying agent of choice:** EDTA (chelating agent) is preferred for preserving enzyme morphology, though 5-10% Nitric acid is faster. * **Ideal ratio:** The volume of fixative should be **10 to 20 times** the volume of the tissue specimen.

Question 266: Each of the following is true of cadherins and integrins, EXCEPT:

A. They are transmembrane glycoproteins.
B. Both can associate with the actin cytoskeleton.
C. Both represent gene families.
D. Both may be found in zonula adherens junctions. (Correct Answer)

Explanation: This question tests your understanding of **Cell Adhesion Molecules (CAMs)**, which are critical for tissue integrity and cell signaling. [1] ### Why Option D is the Correct Answer (The "Except" Statement) While **Cadherins** are the primary transmembrane proteins found in **Zonula Adherens** (linking to actin filaments via catenins), **Integrins** are typically **not** found there. [1] Integrins are primarily involved in **cell-matrix** interactions (e.g., Hemidesmosomes and Focal Adhesions) rather than cell-to-cell junctions like the zonula adherens. [1] Therefore, the statement that "both" are found in zonula adherens is incorrect. ### Analysis of Other Options * **A. Transmembrane glycoproteins:** Both cadherins and integrins are integral membrane proteins with extracellular domains that bind ligands and intracellular domains that signal to the cytoplasm. * **B. Associate with actin cytoskeleton:** Cadherins (in zonula adherens) and Integrins (in focal adhesions) both link to the actin cytoskeleton to provide mechanical stability. [1] * **C. Represent gene families:** Both are large families. There are over 100 types of cadherins (E-cadherin, N-cadherin, etc.) and at least 24 unique integrin heterodimers formed by different $\alpha$ and $\beta$ subunits. ### High-Yield NEET-PG Pearls * **Cadherins:** Calcium-dependent. **E-cadherin** loss is a hallmark of **Epithelial-Mesenchymal Transition (EMT)** and cancer metastasis. * **Integrins:** Act as "receptors" for the extracellular matrix (binding laminin, fibronectin, and collagen). They facilitate **"Inside-out" and "Outside-in" signaling**. [1] * **Zonula Adherens:** Also known as the "Belt Desmosome." [1] * **Clinical Correlation:** Mutations in integrins can lead to **Glanzmann Thrombasthenia** (defect in Integrin $\alpha_{IIb}\beta_3$ on platelets).

Question 267: Regarding brown adipose tissue, which of the following statements is FALSE?

A. Nucleus of the fat cell is not pushed to the side
B. The fat cell contains one large fat droplet (Correct Answer)
C. Contains numerous mitochondria
D. Serves mainly as a heat generator in animals

Explanation: ### Explanation The correct answer is **B**, as it is a characteristic of **White Adipose Tissue (WAT)**, not Brown Adipose Tissue (BAT). #### 1. Why Option B is False (The Correct Answer) Brown adipose tissue is **multilocular**, meaning each cell contains **numerous small lipid droplets** dispersed throughout the cytoplasm. In contrast, white adipose tissue is unilocular, containing a single large fat droplet that occupies most of the cell volume. #### 2. Analysis of Other Options * **Option A (Nucleus position):** In BAT, because the lipid droplets are small and scattered, the nucleus remains **central or slightly eccentric** but is not flattened or pushed to the extreme periphery. In WAT, the single large droplet pushes the nucleus to the side, creating a "signet ring" appearance. * **Option C (Mitochondria):** BAT is packed with **numerous large mitochondria**. These mitochondria contain high levels of **Cytochrome Oxidase**, which, along with extensive vascularity, gives the tissue its characteristic brown color. * **Option D (Heat generation):** The primary function of BAT is **non-shivering thermogenesis**. It contains a unique protein called **Thermogenin (Uncoupling Protein-1 or UCP-1)** in the inner mitochondrial membrane. This protein uncouples oxidative phosphorylation from ATP production, dissipating energy as heat instead. #### 3. High-Yield Facts for NEET-PG * **Location:** In newborns, BAT is found in the interscapular region, axilla, and around the kidneys/adrenals. In adults, it persists in the cervical, supraclavicular, and paravertebral regions. * **Origin:** Brown adipocytes share a common precursor with **skeletal muscle cells** (Myf5+ lineage), whereas white adipocytes do not. * **Clinical Significance:** On **PET scans**, BAT can show high glucose uptake (FDG-avid), which must be distinguished from metastatic lymph nodes or tumors. * **Key Protein:** **UCP-1 (Thermogenin)** is the most specific marker for Brown Adipose Tissue. (Note: None of the provided references were sufficiently relevant to substantiate this specific histophysiology explanation.)

Question 268: A 60-year-old male presents with a poor stream of urine and a post-void residual volume of 400ml. He has bilateral hydronephrosis and his prostate weighs 70g. His urea is 120 mg/dL and creatinine is 3.5 mg/dL. What is the ideal next immediate step?

A. Catheterize with a Foley catheter (Correct Answer)
B. Bilateral percutaneous nephrostomies
C. CT scan to rule out malignancy
D. MRI pelvis

Explanation: The clinical presentation describes a classic case of **Benign Prostatic Hyperplasia (BPH)** leading to acute-on-chronic urinary retention [1]. The patient has significant bladder outlet obstruction (70g prostate), evidenced by a high post-void residual (400ml) and secondary complications: bilateral hydronephrosis and **post-renal azotemia** (elevated urea and creatinine). **1. Why Option A is Correct:** The immediate priority in post-renal failure is to **relieve the obstruction**. Catheterization with a Foley catheter is the simplest, fastest, and most effective bedside procedure to decompress the bladder. Once the pressure is relieved, the hydronephrosis usually resolves, and renal function (urea/creatinine) typically improves. **2. Why Incorrect Options are Wrong:** * **Option B:** Percutaneous nephrostomies are invasive and reserved for supra-vesical obstructions (e.g., ureteric stones or tumors) where a bladder catheter cannot bypass the blockage. * **Options C & D:** While imaging is useful for staging or ruling out malignancy, they are diagnostic steps. In an emergency setting with deranged renal parameters (azotemia), **therapeutic intervention** (drainage) must precede elective imaging. Furthermore, CT contrast is contraindicated in patients with high creatinine due to the risk of Contrast-Induced Nephropathy. **Clinical Pearls for NEET-PG:** * **Definition of BPH:** Histologically, it involves hyperplasia of both glandular and stromal elements, primarily in the **Transition Zone** of the prostate [1]. * **Post-obstructive Diuresis:** After catheterization, monitor the patient for massive diuresis and electrolyte imbalances. * **Normal Prostate Weight:** ~20g. A 70g prostate is significantly enlarged. * **Management Priority:** Always address the "ABC" and immediate life-threatening complications (like renal failure) before definitive surgical management (e.g., TURP).

Question 269: A young man presents with primary infertility, and semen analysis reveals low volume, fructose-negative ejaculate with azoospermia. Which of the following is the most useful imaging modality to evaluate the cause of his infertility?

A. Colour duplex ultrasonography of the scrotum
B. Transrectal ultrasonography (Correct Answer)
C. Retrograde urethrography
D. Spermatic venography

Explanation: ### Explanation The clinical presentation of **azoospermia** (absence of sperm) combined with **low-volume, fructose-negative ejaculate** is a classic indicator of **Ejaculatory Duct Obstruction (EDO)** or congenital bilateral absence of the vas deferens (CBAVD). **1. Why Transrectal Ultrasonography (TRUS) is correct:** Fructose is produced by the **seminal vesicles**. If the ejaculate is fructose-negative and low volume, it suggests that the secretions from the seminal vesicles are not reaching the urethra. TRUS is the gold standard imaging modality to visualize the prostate, seminal vesicles, and ejaculatory ducts [1]. It can identify midline prostatic cysts, dilated seminal vesicles (>15mm width), or calcifications obstructing the ejaculatory ducts, which are surgically correctable causes of infertility. **2. Why the other options are incorrect:** * **A. Colour duplex ultrasonography of the scrotum:** This is the investigation of choice for **varicoceles** or testicular pathology [1]. While it can detect absence of the vas deferens in the scrotum, it cannot visualize the ejaculatory ducts or seminal vesicles. * **C. Retrograde urethrography (RGU):** This is used to visualize urethral strictures or trauma, not the internal male reproductive tract. * **D. Spermatic venography:** This was historically used to diagnose subclinical varicoceles but has been largely replaced by Doppler ultrasound [1]. It plays no role in evaluating obstructive azoospermia. ### High-Yield Clinical Pearls for NEET-PG: * **Fructose-negative semen:** Pathognomonic for EDO or CBAVD (since seminal vesicles provide 70% of semen volume and all the fructose). * **CBAVD Association:** Often associated with mutations in the **CFTR gene** (Cystic Fibrosis). * **Normal Semen pH:** Alkaline (>7.2). In EDO/CBAVD, the semen becomes **acidic** because the alkaline seminal vesicle fluid is missing, leaving only the acidic prostatic fluid. * **Treatment of EDO:** Transurethral resection of the ejaculatory ducts (TURED).

Question 270: Simple cuboidal epithelium is typically found in which of the following locations?

A. Skin epidermis
B. Trachea lining
C. Oesophageal lining
D. Thyroid gland follicles (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Thyroid gland follicles** **Reasoning:** Simple cuboidal epithelium consists of a single layer of cube-shaped cells with centrally located, spherical nuclei. This tissue is specialized for **secretion and absorption**. In the thyroid gland, these cells surround the follicular cavity and are responsible for the synthesis of thyroid hormones (T3 and T4) and the secretion of thyroglobulin into the colloid [1], [2]. **Analysis of Incorrect Options:** * **A. Skin epidermis:** This is composed of **Keratinized Stratified Squamous Epithelium**, which provides a tough, water-resistant barrier against mechanical friction and pathogens. * **B. Trachea lining:** The respiratory tract is primarily lined by **Pseudostratified Ciliated Columnar Epithelium** (often called "Respiratory Epithelium"), which functions in trapping and moving mucus. * **C. Oesophageal lining:** This is lined by **Non-keratinized Stratified Squamous Epithelium**, designed to protect the underlying tissue from the abrasive effects of swallowed food. **High-Yield Clinical Pearls for NEET-PG:** * **Cuboidal Epithelium Locations:** Remember the mnemonic **"R-T-G"**: **R**enal tubules (PCT/DCT), **T**hyroid follicles, and **G**erminal epithelium of the ovary. * **Functional Change:** In the thyroid, the height of the epithelium reflects activity. Under TSH stimulation (active state), the cells become **columnar**; in an inactive state (colloid goiter), they may flatten into **simple squamous** [2]. * **Microvilli:** Simple cuboidal cells in the PCT of the kidney possess a "brush border" (microvilli) to maximize surface area for reabsorption.

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Histology — MCQs

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