Histology Practice Questions

Q: Disintegration of Nissl bodies in nerve injury is called:

Chromatolysis. ### Explanation **Correct Option: A. Chromatolysis** **Why it is correct:** Chromatolysis is the histological hallmark of the **axonal reaction**, occurring after a nerve fiber is severed or injured [1]. Nissl bodies are large clusters of rough endoplasmic reticulum (RER) and free ribosomes responsible for protein synthesis in neurons [2]. When an axon is injured, the cell body (soma) undergoes a regenerative response to increase protein production for repair. This causes the Nissl bodies to disperse and disintegrate, leading to a loss of their characteristic granular staining under a light microscope [1], [2]. This process typically begins 2–3 days after injury and is accompanied by swelling of the cell body and displacement of the nucleus to the periphery [1]. **Why other options are incorrect:** * **B. Cytolysis:** This is a general term referring to the dissolution or disruption of a cell, usually due to osmotic imbalance or viral infection leading to cell death. It is not a specific neuroanatomical term for the reaction of Nissl bodies to injury. * **C & D:** Since Chromatolysis is the specific pathological term for this process, these options are incorrect. **NEET-PG High-Yield Pearls:** * **Wallerian Degeneration:** Refers to the degeneration of the **distal** segment of the axon following injury [2]. * **Retrograde Degeneration:** Refers to the degeneration of the **proximal** segment (towards the cell body). * **Nissl Staining:** Nissl bodies are basophilic and stain intensely with dyes like Cresol Violet or Methylene Blue. * **Location:** Nissl bodies are found in the dendrites and soma but are notably **absent in the Axon and Axon Hillock**.

Q: What is the primary function of oligodendrocytes?

Myelin formation. **Explanation:** **1. Why Option A is Correct:** Oligodendrocytes are a type of macroglia found exclusively in the **Central Nervous System (CNS)** [1]. Their primary function is the synthesis and maintenance of the **myelin sheath** around axons [2]. Myelin acts as an electrical insulator, allowing for rapid saltatory conduction of nerve impulses [3]. A single oligodendrocyte is unique because it can extend its processes to myelinate segments of up to 50 different axons simultaneously [2], [4]. **2. Why Other Options are Incorrect:** * **Option B (Blood-Brain Barrier):** This is the primary function of **Astrocytes**. They possess "end-feet" that wrap around capillaries to maintain the integrity of the BBB and regulate the chemical environment [1]. * **Option C (Phagocytosis):** This is the role of **Microglia**. Derived from the monocyte-macrophage lineage (mesoderm), microglia act as the resident immune cells of the CNS [1]. * **Option D (Collagen Synthesis):** Collagen is synthesized by **fibroblasts**. In the CNS, there is minimal collagen; instead, structural support and "scarring" (gliosis) are provided by astrocytes. **3. High-Yield Clinical Pearls for NEET-PG:** * **CNS vs. PNS:** Remember that **Oligodendrocytes** myelinate the CNS, while **Schwann cells** myelinate the Peripheral Nervous System (PNS) [2]. A key difference: one Schwann cell myelinates only *one* axon segment [4]. * **Demyelinating Diseases:** Multiple Sclerosis (MS) involves the autoimmune destruction of oligodendrocytes (CNS), whereas Guillain-Barré Syndrome (GBS) affects Schwann cells (PNS) [2], [3]. * **Origin:** Oligodendrocytes are derived from the **Neural Tube (Ectoderm)**, unlike microglia which are Mesodermal [1].

Q: Which of the following cell types is NOT present in the lungs?

Langerhans cells. The correct answer is **Langerhans cells**. These are specialized dendritic (antigen-presenting) cells found primarily in the **stratum spinosum of the epidermis**. [2] While the lungs contain "Alveolar Macrophages" (Dust cells), [3] Langerhans cells are specific to the skin and should not be confused with "Langhans giant cells" (seen in tuberculosis) or "Langerhans islets" (pancreas). **Analysis of Options:** * **Clara Cells (Club Cells):** These are non-ciliated, dome-shaped cells found in the terminal and respiratory bronchioles. They secrete surfactant-like lipoproteins and act as stem cells to regenerate the bronchiolar epithelium. * **Brush Cells (Type III Pneumocytes):** These are chemoreceptor cells found throughout the tracheobronchial tree. They have short, blunt microvilli and are involved in monitoring air quality. * **Kultschitksy Cells (K-cells):** These are enteroendocrine cells of the bronchial tree belonging to the APUD system. They secrete hormones like serotonin and calcitonin. Clinically, they are the cells of origin for **Small Cell Carcinoma** and **Carcinoid tumors** of the lung. [4] **High-Yield Clinical Pearls for NEET-PG:** * **Blood-Air Barrier:** Formed by Type I Pneumocytes, fused basal laminae, and capillary endothelial cells. * **Surfactant:** Produced by **Type II Pneumocytes** (contain lamellar bodies). * **Pneumoconiosis:** Alveolar macrophages (Dust cells) are the primary cells involved in the pathogenesis of occupational lung diseases by phagocytosing silica or asbestos particles. [1] * **Langerhans Cell Histiocytosis (LCH):** While Langerhans cells are skin cells, LCH can involve the lungs in adults (strongly associated with smoking), but these cells are not part of the *normal* lung histology.

Q: The ducts of all the following glands consist of stratified cuboidal epithelium EXCEPT:

Sebaceous glands. **Explanation:** The core concept tested here is the histological classification of glandular ducts. **Stratified cuboidal epithelium** is a relatively rare tissue type in the human body, primarily functioning as a robust lining for the larger excretory ducts of exocrine glands. **Why Sebaceous Glands are the Exception:** Sebaceous glands are **holocrine glands**, meaning the entire cell disintegrates to release its lipid-rich secretion (sebum). Unlike other exocrine glands, sebaceous glands typically lack a long, independent duct system lined by specialized epithelium. Instead, they usually open directly into the upper portion of a hair follicle via a short canal lined by **stratified squamous epithelium** (continuous with the follicular wall and skin surface). **Analysis of Incorrect Options:** * **Sweat Glands:** The secretory portion is simple cuboidal, but the **ductal portion** (specifically the double-layered part in the dermis) is the classic textbook example of **stratified cuboidal epithelium** [1]. * **Salivary Glands & Pancreas:** Both are complex tubuloacinar glands. While their smallest ducts (intercalated) are simple cuboidal, their **larger excretory ducts** (interlobular ducts) are characteristically lined by stratified cuboidal or stratified columnar epithelium to provide structural integrity. **High-Yield NEET-PG Pearls:** 1. **Stratified Cuboidal Locations:** Remember the "Big Three"—Ducts of sweat glands, large ducts of salivary glands, and large ducts of the pancreas [1]. 2. **Holocrine Secretion:** Sebaceous glands are the only major holocrine glands; "Whole cell dies" = Holocrine. 3. **Transitional Epithelium:** Often confused with stratified cuboidal; it is unique to the urinary tract (Urothelium) and allows for distension.

Q: The ureter is lined by which type of epithelium?

Transitional. **Explanation:** The ureter is lined by **Transitional Epithelium** (also known as **Urothelium**). This is a specialized type of stratified epithelium found exclusively in the urinary tract, extending from the renal pelvis to the proximal part of the urethra [1]. **Why Transitional Epithelium is correct:** The primary function of the ureter is to transport urine from the kidneys to the bladder. Transitional epithelium is uniquely adapted for this because it is **distensible**. When the ureter is empty, the surface cells (Umbrella cells) appear large and rounded; when the ureter is distended by urine, these cells flatten out, allowing the tissue to stretch without losing its protective barrier function against toxic urine components [1]. **Why other options are incorrect:** * **Stratified squamous:** Found in areas subject to mechanical friction (e.g., esophagus, skin). It lacks the distensibility required for the urinary tract. * **Cuboidal:** Typically found in glandular ducts or kidney tubules (e.g., PCT/DCT) where secretion or absorption occurs, rather than high-pressure transport. * **Ciliated columnar:** Found in the respiratory tract or fallopian tubes to move mucus or ova; it does not provide the barrier or stretch needed in the ureter. **High-Yield NEET-PG Pearls:** * **Umbrella Cells:** The superficial layer of the urothelium contains large, binucleated "umbrella cells" that possess **uroplakins**, which make the barrier impermeable to water and ions. * **Extent of Urothelium:** It lines the renal pelvis, ureters, urinary bladder, and the prostatic/membranous parts of the male urethra [1]. * **Clinical Correlation:** Transitional Cell Carcinoma (TCC) is the most common primary malignancy of the ureter and bladder.

Q: From which of the following layers does the regeneration of the endometrium take place?

Zona basalis. The endometrium is divided into two primary functional layers: the **Stratum Functionalis** and the **Stratum Basalis** [5]. ### Why Zona Basalis is Correct The **Zona basalis (Stratum basalis)** is the deep, permanent layer of the endometrium. It does not undergo significant changes during the menstrual cycle and is **not shed** during menstruation. It contains the blind ends of the uterine glands and is supplied by the **straight arteries**. Following menses, the epithelial cells and stromal cells from this layer proliferate to regenerate the entire functional layer [2], [3]. ### Why Other Options are Incorrect * **Zona compacta & Zona spongiosum:** These two layers together constitute the **Stratum Functionalis**. The *compacta* is the superficial layer of dense stroma, while the *spongiosum* is the middle layer containing edematous stroma and dilated glands [1]. These are the layers that respond to hormones, undergo secretory changes, and are **shed during menstruation**. * **Zona pellucidum:** This is a physiological misnomer in this context. The *Zona pellucida* is the glycoprotein membrane surrounding the plasma membrane of an oocyte; it has no role in endometrial regeneration [4]. ### NEET-PG High-Yield Pearls * **Blood Supply:** The Stratum basalis is supplied by **straight arteries**, while the Stratum functionalis is supplied by **spiral arteries**. The constriction of spiral arteries leads to ischemic necrosis and menstruation. * **Hormonal Control:** Regeneration occurs during the **Proliferative Phase**, which is dominated by **Estrogen** [2]. * **Clinical Correlation:** If the Zona basalis is damaged (e.g., by over-vigorous curettage), it leads to intrauterine adhesions and secondary amenorrhea, known as **Asherman Syndrome**.

Q: The mammary gland is which type of gland?

Apocrine. The mammary gland is classified as an **apocrine gland** based on its mode of secretion. In apocrine secretion, the apical portion of the secretory cell cytoplasm is pinched off along with the secretory product [1]. In the case of the mammary gland, while the protein component (casein) is secreted via exocytosis (merocrine), the **lipid/fat component** is released via the apocrine mechanism. For competitive exams like NEET-PG, the mammary gland is the classic textbook example of an apocrine gland. **Analysis of Options:** * **A. Apocrine (Correct):** The secretory process involves the loss of the apical cell membrane. Other examples include modified sweat glands in the axilla, areola, and perianal region. * **B. Merocrine:** This is the most common type of secretion where products are released via exocytosis without any loss of cell substance (e.g., salivary glands, pancreas, and most eccrine sweat glands). * **C. Holocrine:** The entire cell disintegrates to release its secretion. The classic example is the **Sebaceous gland**. * **D. Endocrine:** These are ductless glands that secrete hormones directly into the bloodstream (e.g., Thyroid, Adrenal glands). The mammary gland is an exocrine gland as it uses a duct system. **High-Yield Clinical Pearls for NEET-PG:** * **Embryology:** Mammary glands are modified **apocrine sweat glands** [1]. They develop from the **milk line** (ectodermal thickening). * **Histology:** The functional unit is the Terminal Duct Lobular Unit (TDLU) [2]. * **Hormonal Control:** Prolactin stimulates milk production (alveolar cells), while Oxytocin stimulates milk ejection (contraction of myoepithelial cells).

Q: Respiratory epithelium (i.e., ciliated pseudostratified columnar) is found in all of the following structures, EXCEPT:

Alveoli. The respiratory tract is lined by different types of epithelium depending on the function of the specific segment. **Respiratory epithelium** is defined as **ciliated pseudostratified columnar epithelium with goblet cells** [1]. Its primary role is to warm, humidify, and filter air (the mucociliary escalator) [1]. **1. Why Alveoli is the Correct Answer:** The alveoli are the primary sites of gas exchange. For efficient diffusion of oxygen and carbon dioxide, the barrier must be extremely thin. Therefore, the thick respiratory epithelium is replaced by **Simple Squamous Epithelium** (Type I pneumocytes) and surfactant-secreting Type II pneumocytes [2], [3]. Cilia and goblet cells are absent here to prevent fluid accumulation and obstruction of gas exchange. **2. Analysis of Incorrect Options:** * **Nasal Cavity:** Most of the nasal cavity (except the vestibule and olfactory region) is lined by respiratory epithelium to filter incoming dust [1]. * **Trachea:** This is the classic site for ciliated pseudostratified columnar epithelium, containing numerous goblet cells and a thick basement membrane [1]. * **Extrapulmonary Bronchi:** These structures maintain the same histological profile as the trachea before entering the lungs. **High-Yield NEET-PG Pearls:** * **Transition Point:** The epithelium gradually thins as we move down the tract: Pseudostratified Columnar (Trachea/Bronchi) → Simple Columnar (Large Bronchioles) → Simple Cuboidal (Terminal Bronchioles) → Simple Squamous (Alveoli) [2]. * **Goblet Cells:** These disappear first (at the level of terminal bronchioles), followed by cilia. * **Kartagener Syndrome:** A high-yield clinical correlation where dynein arm defects lead to immobile cilia, causing recurrent respiratory infections and situs inversus [2].

Question 1

Disintegration of Nissl bodies in nerve injury is called:

Accepted Answer

Chromatolysis

Answer

Cytolysis

Answer

Both

Answer

None

Question 2

What is the primary function of oligodendrocytes?

Accepted Answer

Myelin formation

Answer

Blood brain barrier maintenance

Answer

Phagocytosis

Answer

Collagen synthesis

Question 3

From which structure are fibroblasts derived?

Accepted Answer

Local mesenchyme

Answer

Macrophage

Answer

Endothelium

Answer

Vessels

Question 4

Which of the following cell types is NOT present in the lungs?

Accepted Answer

Langerhans cells

Answer

Clara cells

Answer

Brush cells

Answer

Klutischky cells

Question 5

The ducts of all the following glands consist of stratified cuboidal epithelium EXCEPT:

Accepted Answer

Sebaceous glands

Answer

Sweat gland

Answer

Salivary glands

Answer

Pancreas

Question 6

The ureter is lined by which type of epithelium?

Accepted Answer

Transitional

Answer

Stratified squamous

Answer

Cuboidal

Answer

Ciliated columnar

Question 7

From which of the following layers does the regeneration of the endometrium take place?

Accepted Answer

Zona basalis

Answer

Zona pellucidum

Answer

Zona compacta

Answer

Zona spongiosum

Question 8

The mammary gland is which type of gland?

Accepted Answer

Apocrine

Answer

Merocrine

Answer

Holocrine

Answer

Endocrine

Question 9

Maximum amount of smooth muscle, in relation to wall thickness, is present in which part of the respiratory tract?

Accepted Answer

Terminal bronchioles

Answer

Trachea

Answer

Bronchi

Answer

Respiratory bronchioles

Question 10

Respiratory epithelium (i.e., ciliated pseudostratified columnar) is found in all of the following structures, EXCEPT:

Accepted Answer

Alveoli

Answer

Nasal cavity

Answer

Trachea

Answer

Extrapulmonary bronchi

Histology — MCQs

Histology — MCQs

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