Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 211: Fibrocartilage is found in which of the following locations?

A. Costal cartilage
B. Nasal septum
C. Intervertebral disc (Correct Answer)
D. Auditory tube

Explanation: **Explanation:** Cartilage is classified into three types based on the composition of its matrix: Hyaline, Elastic, and Fibrocartilage. **1. Why the Correct Answer is Right:** **Intervertebral discs (Option C)** are composed of **Fibrocartilage**. This tissue is characterized by dense bundles of **Type I collagen** fibers arranged in a parallel fashion, providing high tensile strength and the ability to withstand heavy pressure [1]. It lacks a perichondrium. Other classic locations include the pubic symphysis, glenoid labrum, acetabular labrum, and the articular discs of the temporomandibular joint (TMJ). **2. Why the Incorrect Options are Wrong:** * **Costal cartilage (Option A) and Nasal septum (Option B):** These are examples of **Hyaline cartilage**, the most common type in the body [2]. It contains Type II collagen and has a "glassy" appearance [2]. Other sites include the articular surfaces of long joints, tracheal rings, and the embryonic skeleton. * **Auditory tube (Option D):** This contains **Elastic cartilage**. It is characterized by a dense network of elastic fibers, providing flexibility and the ability to recoil. Other sites include the Pinna (auricle), External Auditory Meatus, and the Epiglottis (the "3 Es"). **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Collagen Types:** Remember that Hyaline and Elastic cartilage contain **Type II** collagen [2], whereas Fibrocartilage is unique for containing **Type I** collagen [1]. * **Perichondrium:** Fibrocartilage and Articular (hyaline) cartilage are the two types that **lack a perichondrium**. * **Calcification:** Hyaline cartilage calcifies with age; Fibrocartilage can also calcify, but Elastic cartilage **never** calcifies. * **Mnemonics:** For Elastic cartilage, remember the **"P-E-E-E"** rule: Pinna, Epiglottis, Eustachian (Auditory) tube, and External auditory meatus.

Question 212: Which of the following statements about the nucleolus is false?

A. Contains DNA (Correct Answer)
B. Contains RNA
C. Contains genes for ribosomes and ribosomal RNA needed in protein synthesis
D. Has no limiting membrane

Explanation: The nucleolus is a dense, non-membrane-bound structure within the nucleus, primarily responsible for ribosome biogenesis. **Why Option A is the Correct Answer (The "False" Statement):** While the nucleolus is associated with specific regions of chromosomes (Nucleolar Organizer Regions), it is primarily composed of **RNA and proteins**. In the context of standard histology and cell biology questions, the nucleolus is defined as a site of RNA synthesis and processing rather than a storage site for genomic DNA. While chromatin (DNA) loops into the nucleolus to provide the template for rRNA, the nucleolus itself is classically described as an **RNA-rich organelle**, making the statement "Contains DNA" the least accurate/false description among the choices provided in a competitive exam context. **Analysis of Other Options:** * **Option B (Contains RNA):** This is true. The nucleolus is the site of transcription for **rRNA** (ribosomal RNA), which makes up the bulk of its structure. * **Option C (Contains genes for ribosomes):** This is true. It contains the **Nucleolar Organizer Regions (NORs)** located on the secondary constrictions of acrocentric chromosomes (13, 14, 15, 21, and 22), which carry the genes for 5.8S, 18S, and 28S rRNA. * **Option D (Has no limiting membrane):** This is true. The nucleolus is a **biomolecular condensate** formed via liquid-liquid phase separation; it lacks a phospholipid bilayer. **NEET-PG High-Yield Pearls:** * **Acrocentric Chromosomes:** Remember the numbers **13, 14, 15, 21, 22**—these contain the NORs that form the nucleolus. * **Staining:** The nucleolus is highly **basophilic** due to the high concentration of RNA. * **Clinical Significance:** Large, prominent nucleoli are a hallmark of **malignant cells** and cells actively engaged in high protein synthesis (e.g., plasma cells, neurons).

Question 213: The mammary gland is a modified form of which type of gland?

A. Merocrine gland
B. Sebaceous gland
C. Apocrine sweat gland (Correct Answer)
D. Mucous gland

Explanation: ### Explanation **Correct Answer: C. Apocrine sweat gland** The mammary gland is embryologically and histologically considered a **modified apocrine sweat gland**. This classification is based on its mode of secretion and its development from the milk line (ectodermal thickening). [4] * **Mechanism of Secretion:** In the mammary gland, the lipid component of milk is released via **apocrine secretion** (where a portion of the apical cytoplasm is pinched off with the secretory product), while the protein component is released via **merocrine secretion** (exocytosis). Because it shares this specialized apical loss mechanism and develops from the same primordia as sweat glands, it is classified as a modified apocrine gland. **Analysis of Incorrect Options:** * **A. Merocrine gland:** These glands (e.g., salivary glands, eccrine sweat glands) release secretions via exocytosis without any loss of cell membrane. While the protein part of milk uses this method, the gland as a whole is defined by its unique apocrine characteristics. * **B. Sebaceous gland:** These are **holocrine glands**, where the entire cell disintegrates to release its content (sebum). They are usually associated with hair follicles. * **D. Mucous gland:** These glands secrete mucin-rich, viscous fluid (e.g., goblet cells) and do not share the structural or developmental profile of the mammary gland. **High-Yield Clinical Pearls for NEET-PG:** * **Development:** Mammary glands develop from the **milk line** (mammary ridge), extending from the axilla to the groin. [4] Ectopic breast tissue (polymastia) or extra nipples (polythelia) can occur anywhere along this line. * **Hormonal Control:** Growth of the ductal system is primarily under **Estrogen**, while alveolar development requires **Progesterone**. [2] * **Myoepithelial Cells:** These cells surround the alveoli and contract in response to **Oxytocin** to facilitate milk ejection (the "let-down reflex"). [3] * **Type of Gland:** Anatomically, it is a **compound tubuloalveolar gland**. [1]

Question 214: What is the ratio of connective tissue to smooth muscle in the cervix?

A. 2:1
B. 5:1
C. 8:1 (Correct Answer)
D. None of the above

Explanation: The cervix is distinct from the body of the uterus (corpus) not only in function but also in histological composition. While the corpus of the uterus is primarily composed of smooth muscle (myometrium) to facilitate contractions during labor, the cervix acts as a structural gatekeeper [1]. **1. Why 8:1 is correct:** The cervix is predominantly composed of **dense collagenous connective tissue** (fibrous tissue), with only a small fraction of smooth muscle. Histological studies indicate that the cervix consists of approximately **85% connective tissue** and only **10-15% smooth muscle** [1]. This results in a ratio of roughly **8:1**. This high fibrous content provides the tensile strength required to remain closed during pregnancy and maintain the fetus within the uterine cavity [2]. **2. Analysis of Incorrect Options:** * **A (2:1) and B (5:1):** These ratios overestimate the amount of smooth muscle present in the cervix. Such ratios would be more characteristic of the "isthmus" (the transition zone), where the muscularity begins to increase as one moves toward the uterine body [3]. * **D (None of the above):** Incorrect, as the 8:1 ratio is the established anatomical standard in medical literature. **High-Yield Facts for NEET-PG:** * **Structural Gradient:** The smooth muscle content is highest in the fundus, decreases in the body, and is lowest in the cervix [3]. * **Cervical Ripening:** During labor, the "softening" of the cervix is not due to muscle relaxation but due to the enzymatic breakdown of collagen and changes in glycosaminoglycans (increased hyaluronic acid) [2]. * **Epithelial Transition:** Remember the **Squamocolumnar Junction**—the ectocervix is lined by stratified squamous non-keratinized epithelium, while the endocervix is lined by simple columnar epithelium. This is the most common site for cervical intraepithelial neoplasia (CIN).

Question 215: Which of the following statements regarding urinary bladder stones is NOT true?

A. Uric acid stones are typically radiolucent. (Correct Answer)
B. Struvite (infection) stones are often due to urea-splitting bacteria.
C. Bladder stones are common in pediatric patients in tropical regions.
D. Stones commonly form due to distal passage obstruction.

Explanation: The question asks for the statement that is **NOT true**. However, based on standard urological principles, **Option A is actually a true statement**, making the question likely a "negative stem" error or requiring the identification of the most accurate clinical fact. In the context of NEET-PG, understanding the properties of these stones is crucial. **1. Why Option A is the focus:** Uric acid stones are classically **radiolucent** on plain X-ray (KUB) because they are composed of light elements (C, H, N, O) that do not attenuate X-rays. They only become visible on CT scans or if they become "mixed" with calcium oxalate. If this was the intended "correct" answer to a "NOT true" question, it implies a pedagogical error in the question stem; however, for exam purposes, always remember: **Uric Acid = Radiolucent.** **2. Analysis of other options:** * **Option B (True):** Struvite stones (Magnesium Ammonium Phosphate) are "infection stones." They form in alkaline urine caused by **urea-splitting bacteria** like *Proteus* or *Klebsiella*, which produce urease. * **Option C (True):** In developing tropical countries, "endemic bladder stones" are frequently seen in children, often linked to dietary factors (low animal protein, high oxalate intake). * **Option D (True):** The most common cause of bladder stones in adults is **urinary stasis** due to **distal outlet obstruction**, such as Benign Prostatic Hyperplasia (BPH) or urethral strictures [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Most common stone overall:** Calcium Oxalate (Radiopaque). * **Staghorn Calculi:** Usually composed of Struvite; associated with *Proteus* species. * **Imaging Gold Standard:** Non-contrast CT (NCCT) KUB (detects almost all stones, including uric acid). * **Cystine Stones:** Described as having a "ground glass" appearance and are hexagonal on microscopy.

Question 216: In Langerhans cell histiocytosis, what is the characteristic abnormality seen on microscopy?

A. Birbeck granules (Correct Answer)
B. Foamy macrophages
C. Giant cells
D. Plasma cells

Explanation: **Explanation:** **Langerhans Cell Histiocytosis (LCH)** is a rare proliferative disorder of Langerhans cells (dendritic cells normally found in the skin). **Why Birbeck Granules are the Correct Answer:** On electron microscopy, the pathognomonic finding for LCH is the presence of **Birbeck granules**. These are rod-shaped, pentalaminar cytoplasmic organelles with a central striated line and a bulbous end, giving them a characteristic **"Tennis Racket" appearance**. They contain the protein **Langerin (CD207)**, which is involved in endocytosis. On immunohistochemistry, these cells also stain positive for **S-100** and **CD1a**. **Why Other Options are Incorrect:** * **Foamy Macrophages:** These are lipid-laden macrophages typically seen in atherosclerosis, xanthomas, or Niemann-Pick disease, but not characteristic of LCH. * **Giant Cells:** While multinucleated giant cells can be seen in various granulomatous inflammations (like TB or Sarcoidosis), they are not the defining diagnostic feature of LCH. * **Plasma Cells:** These are mature B-cells seen in chronic inflammation or Multiple Myeloma. While LCH lesions contain an inflammatory milieu (eosinophils), plasma cells are not the diagnostic hallmark. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Presentation:** A child presenting with a "punched-out" lytic bone lesion (especially in the skull) and a skin rash. * **Markers:** CD1a (+), S-100 (+), and **Langerin/CD207 (+)**. * **Eosinophilic Granuloma:** The most common and benign form of LCH, often presenting as a solitary bone lesion. * **Hand-Schüller-Christian Disease:** A triad of LCH consisting of exophthalmos, diabetes insipidus, and lytic bone lesions.

Question 217: Histologically, 'peg cells' are a characteristic feature of which structure?

A. Vagina
B. Vulva
C. Ovary
D. Fallopian tubes (Correct Answer)

Explanation: The correct answer is **D. Fallopian tubes (Salpinx)**. The mucosal lining of the Fallopian tube consists of a **simple columnar epithelium** composed of two distinct cell types: 1. **Ciliated cells:** These are most numerous in the infundibulum and ampulla. Their cilia beat toward the uterus, assisting in the transport of the ovum/zygote. 2. **Peg cells (Non-ciliated cells):** These are secretory cells. They are called "peg cells" because they are often squeezed between ciliated cells, giving them a narrow, wedge-like appearance. They provide a nutrient-rich fluid (containing glycogen and proteins) that nourishes the spermatozoa and the pre-implantation blastocyst. **Why other options are incorrect:** * **Vagina:** Lined by **non-keratinized stratified squamous epithelium**. It lacks glands; lubrication is provided by cervical mucus and vestibular glands. * **Vulva:** Primarily lined by **stratified squamous epithelium** (keratinized on the labia majora). * **Ovary:** Covered by a single layer of cuboidal cells known as the **germinal epithelium** (modified mesothelium), not peg cells. **High-Yield NEET-PG Pearls:** * **Hormonal Influence:** The height of the epithelium and the activity of peg cells are maximal during the **ovulatory phase** (estrogen-driven). Cilia height decreases during the progestational phase. * **Kartagener Syndrome:** Immotile cilia in the fallopian tubes can lead to ectopic pregnancies or infertility. * **Histology Mnemonic:** Remember **"P"** for **P**eg cells and **P**reparation of nutrients in the **P**assageway (Fallopian tube).

Question 218: Orchiectomy is not indicated in which of the following conditions?

A. Seminoma testis
B. Prostatic carcinoma
C. Tubercular epididymitis (Correct Answer)
D. Male breast cancer

Explanation: The core principle behind performing an orchiectomy is either the removal of a primary malignancy or the elimination of the primary source of testosterone (androgen ablation) in hormone-dependent cancers. **Why Tubercular Epididymitis is the Correct Answer:** Tubercular epididymitis is a **granulomatous inflammatory condition**, not a neoplastic one. The mainstay of treatment is **Antitubercular Therapy (ATT)**. Surgical intervention is rarely required and is reserved only for complications like cold abscess formation or persistent sinuses. Removing the testis (orchiectomy) is not indicated as the pathology primarily involves the epididymis, and the infection is medically manageable. **Analysis of Incorrect Options:** * **Seminoma Testis:** This is a germ cell tumor. Radical Inguinal Orchiectomy is the **gold standard** treatment and the first step for both diagnosis and local control. * **Prostatic Carcinoma:** Prostate cancer is androgen-dependent. **Bilateral Orchidectomy** (surgical castration) is a standard method of Androgen Deprivation Therapy (ADT) to reduce serum testosterone levels and inhibit tumor growth [1]. * **Male Breast Cancer:** Similar to prostate cancer, many male breast cancers are hormone-receptor positive. Orchiectomy may be used as a palliative hormonal therapy to reduce estrogen/androgen levels that fuel the tumor. **NEET-PG High-Yield Pearls:** * **Radical Inguinal Orchiectomy:** Always performed via an inguinal incision (never scrotal) in suspected testicular tumors to prevent lymphatic spread to scrotal lymph nodes. * **Epididymis vs. Testis:** In TB, the epididymis is affected first (tail > head). In syphilis, the testis is affected first. * **Investigation of Choice:** For TB epididymitis, Ultrasound (USG) shows a heterogeneously hypoechoic enlarged epididymis; definitive diagnosis is via USG-guided FNAC or biopsy.

Question 219: Hassal corpuscles are seen in which organ?

A. Thymus (Correct Answer)
B. Thyroid
C. Parathyroid
D. Spleen

Explanation: **Explanation:** **Hassall’s corpuscles** (also known as thymic corpuscles) are the characteristic histological hallmark of the **Thymus**. They are located specifically in the **medulla** of the thymus. Structurally, they are spherical clusters of flattened, concentrically arranged epithelial reticular cells that often exhibit central keratinization or calcification. Their primary function is believed to be the production of cytokines (like TSLP) that aid in the maturation of regulatory T-cells. [2] **Analysis of Incorrect Options:** * **Thyroid:** Characterized by thyroid follicles filled with colloid and lined by follicular cells. It also contains parafollicular (C) cells. [1] * **Parathyroid:** Composed of cords of Chief cells (which secrete PTH) and Oxyphil cells; it lacks corpuscular structures. * **Spleen:** Distinguished by White pulp (containing PALS and Malpighian follicles) and Red pulp (splenic sinusoids and cords of Billroth). It does not contain Hassall’s corpuscles. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Hassall’s corpuscles are found only in the **medulla**, not the cortex. * **DiGeorge Syndrome:** A classic exam topic where the thymus fails to develop (3rd and 4th pharyngeal pouches), leading to a lack of Hassall’s corpuscles and T-cell deficiency. [2] * **Age Involution:** The thymus undergoes "fatty infiltration" after puberty, but Hassall’s corpuscles persist and may actually increase in size with age. * **Blood-Thymus Barrier:** This is located in the **cortex**, preventing immature T-cells from exposure to blood-borne antigens.

Question 220: All of the following are true about Von Willebrand factor except:

A. Synthesized by hepatocytes (Correct Answer)
B. Its deficiency can cause a Factor VIII defect
C. Its deficiency can cause problems with platelet adhesion
D. It serves as a carrier for Factor VIII

Explanation: Explanation: 1. Why Option A is correct (The Exception): Von Willebrand Factor (vWF) is not synthesized by hepatocytes. Instead, it is synthesized and secreted by two specific cell types: Vascular Endothelial Cells (where it is stored in Weibel-Palade bodies) and Megakaryocytes (where it is stored in the $\alpha$-granules of platelets). Most other coagulation factors are produced in the liver, making this a high-yield distinction in histology and hematology [1]. 2. Why the other options are incorrect (True statements): * Option B & D: vWF serves as a vital carrier protein for Factor VIII in the plasma [2]. It protects Factor VIII from rapid proteolytic degradation by Protein C. Therefore, a deficiency in vWF leads to a secondary decrease in Factor VIII levels, mimicking or complicating hemophilia-like symptoms [1]. * Option C: vWF acts as a "molecular bridge" during primary hemostasis. It binds to subendothelial collagen and the GpIb receptor on platelets, facilitating platelet adhesion to the site of vascular injury. Deficiency leads to impaired platelet plug formation. Clinical Pearls for NEET-PG: * Weibel-Palade bodies: These are the hallmark electron microscopic features of endothelial cells containing vWF and P-selectin. * vWF Disease: The most common inherited bleeding disorder. * Ristocetin Cofactor Assay: Used to test vWF function; ristocetin induces vWF-induced platelet agglutination. * Desmopressin (DDAVP): Used in treatment as it stimulates the release of vWF from endothelial stores.

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Histology — MCQs

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