Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 351: Transitional epithelium or urothelium lines all of the following structures of the urinary system, EXCEPT:

A. Ureters
B. Minor calyx
C. Urinary bladder
D. Membranous Urethra (Correct Answer)

Explanation: ### Explanation **1. Why Membranous Urethra is the Correct Answer:** The **urothelium (transitional epithelium)** is a specialized stratified epithelium designed to stretch and withstand the toxicity of urine. It lines the urinary tract from the renal pelvis down to the proximal part of the urethra. However, as the urinary tract nears its external opening, the epithelial lining changes to adapt to different mechanical stresses. * The **prostatic urethra** is lined by transitional epithelium. * The **membranous urethra** (the shortest part, passing through the urogenital diaphragm) and the **bulbar/pendulous urethra** are primarily lined by **pseudostratified or stratified columnar epithelium**. * The distal-most part (navicular fossa) transitions into **stratified squamous epithelium**. **2. Why the Other Options are Incorrect:** * **Minor Calyx & Ureters:** The "upper" urinary tract, starting from the renal calyces (major and minor), renal pelvis, and extending through the entire length of the ureters, is consistently lined by transitional epithelium to allow for bolus transport of urine. * **Urinary Bladder:** This is the classic site for transitional epithelium [1]. The presence of **"Umbrella cells"** (dome-shaped surface cells) allows the bladder to distend significantly as it fills without losing its protective barrier. **3. NEET-PG High-Yield Pearls:** * **Umbrella Cells:** These are the superficial cells of the urothelium. They are often binucleated and contain **uroplakin** proteins that form a "blood-urine barrier." * **Histological Transition:** Remember the "Rule of Urethra": Prostatic = Transitional; Membranous = Stratified Columnar; Distal Penile = Stratified Squamous. * **Clinical Correlation:** Transitional Cell Carcinoma (TCC) is the most common malignancy of the bladder, ureters, and renal pelvis because they share this same epithelial lining.

Question 352: Which of the following is an example of hyaline cartilage?

A. Epiglottis
B. Thyroid cartilage (Correct Answer)
C. Apex of arytenoid cartilage
D. Pinna

Explanation: **Explanation:** Cartilage is classified into three types based on the composition of its matrix: Hyaline, Elastic, and Fibrocartilage. **Hyaline cartilage** is the most common type, characterized by a glassy, homogeneous matrix containing Type II collagen fibers [1]. **Why Thyroid Cartilage is Correct:** The majority of the laryngeal skeleton is composed of hyaline cartilage. This includes the **Thyroid**, **Cricoid**, and the **Base of the arytenoid** cartilages. These structures provide a rigid framework for the airway and typically undergo ossification with advancing age. **Analysis of Incorrect Options:** * **A. Epiglottis:** This is composed of **Elastic cartilage**. Elastic cartilage contains a dense network of elastic fibers, allowing for the flexibility required to seal the laryngeal inlet during swallowing. * **C. Apex of arytenoid cartilage:** While the *base* of the arytenoid is hyaline, the **apex** (along with the corniculate and cuneiform cartilages) is made of **Elastic cartilage**. * **D. Pinna (Auricle):** The external ear requires significant flexibility and shape retention, which is provided by **Elastic cartilage**. **High-Yield NEET-PG Pearls:** * **Mnemonic for Elastic Cartilage:** Remember the **6 E’s**: **E**piglottis, **E**xternal Ear (Pinna), **E**xternal Auditory Meatus, **E**ustachian Tube, and the small laryngeal cartilages (**E**xtremity/Apex of arytenoid, Corniculat**e**, and Cun**e**iform). * **Calcification:** Hyaline cartilage has a tendency to calcify and ossify with age (often visible on X-rays), whereas elastic cartilage does not. * **Articular Cartilage:** This is a specialized form of hyaline cartilage that lacks a perichondrium [1].

Question 353: Berbeck's granules are seen in which of the following cell types?

A. Langerhans cells (Correct Answer)
B. Lymphocytes
C. Neutrophils
D. Basophils

Explanation: **Explanation:** **Birbeck granules** (also known as Birbeck bodies) are the pathognomonic ultrastructural hallmark of **Langerhans cells** [1]. These are specialized dendritic cells (antigen-presenting cells) primarily located in the *stratum spinosum* of the epidermis [1]. 1. **Why Langerhans cells are correct:** Under electron microscopy, Birbeck granules appear as unique, rod-shaped or **"tennis racket-shaped"** cytoplasmic organelles with a central striated line. They are formed by the invagination of the cell membrane and are associated with the protein **Langerin (CD207)**, which functions in endocytosis and the trafficking of antigens. 2. **Why other options are incorrect:** * **Lymphocytes:** These are mononuclear leukocytes involved in adaptive immunity. They lack Birbeck granules and are characterized by a large nucleus-to-cytoplasm ratio. * **Neutrophils:** These granulocytes contain primary (azurophilic) and secondary (specific) granules, but not Birbeck granules. * **Basophils:** These contain large, coarse granules filled with histamine and heparin that stain intensely with basic dyes. **High-Yield Clinical Pearls for NEET-PG:** * **Langerhans Cell Histiocytosis (LCH):** A neoplastic proliferation of Langerhans cells. Birbeck granules are the definitive diagnostic marker on electron microscopy. * **Immunohistochemistry (IHC) Markers:** Langerhans cells are positive for **S-100**, **CD1a**, and **Langerin (CD207)**. * **Origin:** Unlike other skin cells, Langerhans cells originate from the **bone marrow** (monocyte-macrophage lineage) [1].

Question 354: What are macrophages in the nervous system known as?

A. Schwann cells
B. Oligodendrocytes
C. Astrocytes
D. Microglia (Correct Answer)

Explanation: **Explanation:** **Microglia** are the correct answer because they function as the resident macrophages of the Central Nervous System (CNS) [1]. Unlike other glial cells derived from the neuroectoderm, microglia originate from **mesodermal yolk sac progenitors** that migrate into the brain during early embryonic development. They act as the primary immune defense, performing phagocytosis to clear cellular debris, pathogens, and damaged neurons [1]. **Analysis of Incorrect Options:** * **Schwann cells (A):** These are the myelin-forming cells of the **Peripheral Nervous System (PNS)** [1]. One Schwann cell provides myelin for a single internode of a single axon [2]. * **Oligodendrocytes (B):** These are the myelinating cells of the **CNS** [1]. Unlike Schwann cells, one oligodendrocyte can myelinate segments of multiple axons (up to 50) [2]. * **Astrocytes (C):** These are the most abundant glial cells. They provide structural support, maintain the blood-brain barrier (BBB) via their "end-feet," and regulate the extracellular chemical environment [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Fried Egg Appearance:** Histological characteristic of Oligodendrocytes. * **Blood-Brain Barrier:** Formed by the tight junctions of endothelial cells, the basement membrane, and **astrocyte foot processes**. * **Gitter Cells:** When microglia become activated and laden with lipids after phagocytosing necrotic brain tissue, they are termed "Gitter cells." * **HIV Infection:** Microglia are the primary targets of HIV in the brain; infected microglia fuse to form **multinucleated giant cells**, a hallmark of HIV-associated dementia [1].

Question 355: A 70-year-old male has a pathological fracture of the femur. Radiographs show a lytic lesion with a circumscribed, punched-out appearance. What is the most likely histological finding in curettings from the fracture site?

A. Diminished and thinned trabecular bone
B. Sheets of atypical plasma cells (Correct Answer)
C. Metaplastic prostatic adenocarcinoma
D. Malignant cells forming osteoid bone

Explanation: ### Explanation The clinical presentation of a **70-year-old male** with a **pathological fracture** and **punched-out lytic lesions** on radiography is a classic description of **Multiple Myeloma**. [1] **Why Option B is Correct:** Multiple Myeloma is a plasma cell dyscrasia characterized by the neoplastic proliferation of a single clone of plasma cells. These cells secrete osteoclast-activating factors (like RANKL), leading to bone resorption and the characteristic "punched-out" lesions. Histologically, curettings from these lesions show **sheets of atypical plasma cells** (large cells with eccentric nuclei, "clock-face" chromatin, and a prominent perinuclear halo or Golgi zone). **Why Other Options are Incorrect:** * **Option A:** Diminished and thinned trabeculae are characteristic of **Osteoporosis**. While it causes fractures in the elderly, it presents with generalized osteopenia rather than focal, circumscribed lytic lesions. * **Option C:** Prostatic adenocarcinoma typically causes **osteoblastic (sclerotic)** lesions in the bone, which appear radio-opaque (white) on X-ray, not lytic (dark). * **Option D:** Malignant cells forming osteoid is the hallmark of **Osteosarcoma**. This typically occurs in a younger age group and presents with a "sunburst" appearance or Codman’s triangle on radiography. **High-Yield NEET-PG Pearls:** * **CRAB Criteria:** Calcium elevation, Renal insufficiency, Anemia, and Bone lesions. * **Bence-Jones Proteins:** Immunoglobulin light chains found in urine (not detected by standard dipstick). * **M-Spike:** Found on Serum Protein Electrophoresis (SPEP), usually IgG or IgA. * **Skull X-ray:** Often shows multiple "punched-out" lytic lesions (Raindrop skull).

Question 356: Lichenification occurs in which layer of the skin?

A. Stratum malpighi (Correct Answer)
B. Stratum corneum
C. Stratum lucidum
D. Stratum granulosum

Explanation: **Explanation:** **Lichenification** is a clinical term describing skin that has become thickened, leathery, and exaggerated in its surface markings, usually due to chronic rubbing or scratching. 1. **Why Stratum Malpighi is correct:** Histologically, lichenification is characterized by **acanthosis**, which is the hyperplasia (increased thickness) of the **Stratum Malpighi**. The Stratum Malpighi (also known as the Malpighian layer) consists of the **Stratum Basale** and the **Stratum Spinosum**. In response to chronic mechanical irritation, the keratinocytes in these layers undergo increased proliferation to provide a protective barrier, leading to the clinical appearance of thickened skin. 2. **Why other options are incorrect:** * **Stratum corneum:** While chronic friction also leads to *hyperkeratosis* (thickening of this layer), the primary structural "body" of the skin thickening in lichenification is attributed to the cellular expansion of the Malpighian layer. * **Stratum lucidum:** This is a thin, clear layer found only in thick skin (palms and soles). It is not the primary site of pathological thickening in generalized lichenification. * **Stratum granulosum:** Though this layer may be prominent in certain skin conditions (like Lichen Planus), its thickening alone does not define the clinical entity of lichenification. **High-Yield Clinical Pearls for NEET-PG:** * **Acanthosis:** Specifically refers to the thickening of the Stratum Spinosum. * **Lichen Simplex Chronicus:** The classic clinical example of localized lichenification caused by the "itch-scratch cycle." * **Layers of Epidermis (Deep to Superficial):** Basale → Spinosum → Granulosum → Lucidum → Corneum (Mnemonic: **B**ritish **S**pelling **G**ives **L**oose **C**onstruction). * **Stratum Malpighi** is the "germinal layer" where active mitosis occurs. (Note: While provided references discuss related dermatological pathologies like Lichen Planus and Epidermal Hyperplasia, none provide a specific definition of lichenification in the Stratum Malpighi for citation.)

Question 357: Paneth cells secrete which of the following substances?

A. Antibacterial substances (Correct Answer)
B. Lipase
C. Maltase
D. Secretin

Explanation: ### Explanation **Paneth cells** are specialized secretory cells located at the **base of the Crypts of Lieberkühn** in the small intestine [2]. Their primary role is innate immunity and the maintenance of the gastrointestinal mucosal barrier. **1. Why Option A is Correct:** Paneth cells contain large, eosinophilic apical granules filled with **antibacterial substances**. The most significant of these is **Lysozyme**, an enzyme that digests the cell walls of certain bacteria. They also secrete **alpha-defensins** (cryptdins), which create pores in bacterial membranes, and **Zinc**, which is essential for the activity of various antibacterial enzymes. By secreting these agents, Paneth cells regulate the gut microbiome and protect intestinal stem cells from pathogens [2]. **2. Why the Other Options are Incorrect:** * **B. Lipase:** Primarily secreted by the **Pancreas** (pancreatic lipase) [1], [3] and the stomach (gastric lipase) [3] for fat digestion. * **C. Maltase:** This is a **brush-border enzyme** produced by the enterocytes of the small intestine to break down maltose into glucose. * **D. Secretin:** An enteroendocrine hormone secreted by **S-cells** in the duodenum in response to low pH, stimulating pancreatic bicarbonate secretion [1]. **3. NEET-PG High-Yield Pearls:** * **Location:** Most numerous in the **Ileum**; absent in the large intestine (except in pathological states like "Paneth cell metaplasia" in IBD). * **Staining:** They are highly **acidophilic/eosinophilic** due to the protein-rich nature of their granules. * **Life Span:** They have a longer turnover rate (approx. 30 days) compared to regular enterocytes (3–5 days). * **Clinical Correlation:** Dysfunction of Paneth cells is strongly linked to the pathogenesis of **Crohn’s Disease**.

Question 358: What is the histological appearance of the vaginal mucosa?

A. Stratified squamous (Correct Answer)
B. Glandular
C. Simple squamous
D. Cuboidal

Explanation: The vaginal mucosa is lined by **Non-keratinized Stratified Squamous Epithelium**. This histological structure is essential for its function: the multiple layers of cells provide protection against mechanical friction during intercourse and offer a barrier against pathogens [1]. Under the influence of estrogen, these cells accumulate **glycogen**. When these cells are shed, the resident flora (*Lactobacillus acidophilus* or Doderlein’s bacilli) ferment the glycogen into lactic acid, maintaining an acidic vaginal pH (3.8–4.5) which inhibits the growth of pathogenic bacteria. **Analysis of Incorrect Options:** * **B. Glandular:** The vagina is unique because its mucosa **lacks glands**. Lubrication is provided by cervical mucus and transudation from the subepithelial capillaries. * **C. Simple Squamous:** This single-layered epithelium is found in areas requiring rapid diffusion (e.g., alveoli, endothelium) and would be too fragile to withstand the mechanical stress of the vaginal canal. * **D. Cuboidal:** Simple cuboidal epithelium is typically found in secretory or absorptive organs, such as the thyroid follicles or renal tubules. **High-Yield Clinical Pearls for NEET-PG:** * **Embryology:** The upper 1/3rd of the vagina is derived from the **Müllerian ducts** (Mesoderm), while the lower 2/3rd is derived from the **Urogenital sinus** (Endoderm) [1]. * **Vaginal Adenosis:** This is a condition where glandular (columnar) epithelium is found in the vagina instead of squamous epithelium, often seen in daughters of women who took **Diethylstilbestrol (DES)** during pregnancy. It is a precursor to Clear Cell Adenocarcinoma. * **Cytology:** In a Pap smear, the presence of "Clue cells" (squamous cells covered in bacteria) is diagnostic of Bacterial Vaginosis.

Question 359: Laminin is seen in:

A. Basement membrane (Correct Answer)
B. Lens
C. Bone
D. Cartilage

Explanation: **Explanation:** **Laminin** is a large, cross-shaped glycoprotein that serves as a primary structural component of the **basement membrane** (specifically the *lamina lucida*) [1]. It plays a crucial role in anchoring the overlying epithelial cells to the underlying connective tissue by binding to cell surface receptors like integrins, as well as to Type IV collagen and heparan sulfate proteoglycans [1]. **Analysis of Options:** * **A. Basement membrane (Correct):** Laminin is the most abundant glycoprotein in the basal lamina [1]. It facilitates cell adhesion, differentiation, and migration. * **B. Lens:** While the lens capsule is a specialized thick basement membrane containing Type IV collagen and laminin, the lens fibers themselves are primarily composed of **Crystallins**. * **C. Bone:** The organic matrix of bone (osteoid) is predominantly composed of **Type I Collagen** and non-collagenous proteins like Osteocalcin and Osteonectin. * **D. Cartilage:** The primary structural component of hyaline and elastic cartilage is **Type II Collagen**, along with proteoglycans like Aggrecan. **NEET-PG High-Yield Pearls:** * **Structure:** Laminin is a heterotrimer composed of $\alpha$, $\beta$, and $\gamma$ chains [1]. * **Type IV Collagen + Laminin:** These are the "signature" molecules of the basement membrane [1]. * **Clinical Correlation:** **Junctionals Epidermolysis Bullosa** is often caused by genetic mutations in laminin (specifically Laminin-332), leading to severe skin blistering due to the failure of dermo-epidermal adhesion. * **Goodpasture Syndrome:** Involves antibodies against the non-collagenous domain of Type IV collagen in the basement membranes of lungs and kidneys.

Question 360: A gastric biopsy is taken from a 42-year-old man. The pathologist observes numerous, normal cuboidal-to-columnar cells with apical membrane-bound secretion granules in the gastric glands. From which area of the stomach was the biopsy most likely taken?

A. Cardiac region
B. Columns of Morgagni
C. Fundic region (Correct Answer)
D. Greater omentum

Explanation: The question describes **Chief cells (Zymogenic cells)**, which are characterized by their cuboidal-to-columnar shape and the presence of apical membrane-bound secretion granules containing **pepsinogen**. **1. Why the Fundic Region is Correct:** The gastric glands of the **fundus and body** (corpus) are the most complex in the stomach. They contain four primary cell types: Mucous neck cells, Parietal (oxyntic) cells, Chief (zymogenic) cells, and Enteroendocrine cells [1]. Chief cells are predominantly located in the lower third (base) of these fundic glands. Their apical granules (zymogen granules) are a hallmark histological feature required for the synthesis and secretion of the proenzyme pepsinogen. **2. Analysis of Incorrect Options:** * **Cardiac region:** Glands here are primarily mucus-secreting (tubular and coiled) to protect the esophagus from acid reflux [1]. They lack a significant population of chief cells. * **Columns of Morgagni:** These are longitudinal mucosal folds found in the **anal canal**, not the stomach. * **Greater omentum:** This is a double fold of peritoneum (serosa and adipose tissue) and does not contain gastric mucosal glands. **3. NEET-PG High-Yield Pearls:** * **Parietal Cells:** Located in the neck/body of fundic glands; secrete HCl and **Intrinsic Factor**. They are characterized by an abundance of mitochondria and intracellular canaliculi. * **Pyloric Glands:** Contain deep gastric pits and primarily secrete mucus and **Gastrin (G-cells)** [1]. * **Staining:** Chief cells are **basophilic** (due to extensive RER), while Parietal cells are intensely **acidophilic/eosinophilic** (due to mitochondria). * **Pepsinogen Activation:** Pepsinogen is a proenzyme converted to active pepsin by the low pH (HCl) in the gastric lumen.

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Histology — MCQs

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