Histology Practice Questions

Q: Prominent eosinophilic secretory granules are seen in Paneth cells of the intestinal crypts. What is secreted from these cells?

Antimicrobial peptides like lysozyme. **Explanation:** **Paneth cells** are specialized secretory cells located at the base of the **Crypts of Lieberkühn** in the small intestine [1]. They are characterized by the presence of large, apical, **eosinophilic (acidophilic) secretory granules**. 1. **Why Option B is Correct:** The primary function of Paneth cells is innate mucosal defense. Their eosinophilic granules contain high concentrations of **antimicrobial peptides**, specifically **Lysozyme**, **Defensins (alpha-defensins/cryptdins)**, and **Phospholipase A2**. These substances degrade bacterial cell walls and maintain the sterility of the intestinal stem cell niche [1]. 2. **Why Other Options are Incorrect:** * **Option A (Mucus):** Mucus is secreted by **Goblet cells**, which are interspersed throughout the intestinal epithelium [1]. Goblet cells contain clear/pale-staining mucinogen granules, not eosinophilic granules. * **Option C (Alkaline fluid):** While the small intestine is alkaline, specific alkaline mucoid secretions are produced by **Brunner’s glands**, which are found exclusively in the **submucosa of the duodenum**. * **Option D (Acidic fluid):** Acidic fluid (HCl) is secreted by **Parietal (Oxyntic) cells** in the gastric glands of the stomach, not in the intestinal crypts. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Paneth cells are most numerous in the **ileum**. * **Zinc Content:** These cells are rich in Zinc, which acts as a cofactor for many of the enzymes they secrete. * **Stem Cell Support:** Paneth cells provide essential growth factors (like Wnt signaling) to the neighboring intestinal stem cells [1]. * **Histology Identification:** On H&E stain, look for "bright red/pink granules" at the very bottom of the intestinal pits.

Q: Which of the following pairs of structures have similar types of epithelium?

Lung alveoli and Bowman's capsule. ### Explanation The correct answer is **D. Lung alveoli and Bowman's capsule**. Both structures are lined by **Simple Squamous Epithelium**. #### 1. Why the Correct Answer is Right Simple squamous epithelium consists of a single layer of flat, scale-like cells [2]. This morphology is ideal for sites where **rapid diffusion or filtration** is required. * **Lung Alveoli:** The thin barrier (Type I pneumocytes) allows for efficient gas exchange between the air and blood [1], [2]. * **Bowman’s Capsule:** The parietal layer is composed of simple squamous cells, facilitating the filtration of blood into the nephron. #### 2. Analysis of Incorrect Options * **A. Alveoli and Olfactory Epithelium:** Alveoli are simple squamous, whereas olfactory epithelium is **Pseudostratified Ciliated Columnar Epithelium** (specialized sensory type) [2]. * **B. Olfactory Epithelium and Skin:** Olfactory epithelium is pseudostratified columnar, while skin (epidermis) is **Keratinized Stratified Squamous Epithelium**, designed for protection against mechanical stress and dehydration. * **C. Esophagus and Urinary Bladder:** The esophagus is lined by **Non-keratinized Stratified Squamous Epithelium** (for protection during swallowing), while the urinary bladder is lined by **Transitional Epithelium (Urothelium)**, which allows for distension. #### 3. High-Yield Clinical Pearls for NEET-PG * **Endothelium vs. Mesothelium:** Both are simple squamous. Endothelium lines blood vessels; Mesothelium lines serous cavities (pleura, pericardium, peritoneum). * **Microvilli vs. Cilia:** Remember that the **Proximal Convoluted Tubule (PCT)** has a "brush border" (microvilli) for absorption, while the **Fallopian tube** has cilia for ovum transport. * **Metaplasia:** In chronic smokers, the ciliated columnar epithelium of the airways can undergo **squamous metaplasia**, a common high-yield pathology concept [2].

Q: Which of the following structures is NOT lined with pseudostratified ciliated columnar epithelium?

Vocal cords. The respiratory tract is predominantly lined by **pseudostratified ciliated columnar epithelium** (often referred to as "Respiratory Epithelium"). This specialized lining contains goblet cells that secrete mucus to trap particles, while the cilia move the mucus toward the pharynx [2]. **Why Vocal Cords are the Correct Answer:** The **true vocal cords** (vocal folds) are a notable exception in the respiratory tract. They are lined by **non-keratinized stratified squamous epithelium**. This structural adaptation is essential because the vocal cords undergo constant mechanical stress and high-frequency vibration during phonation. Squamous epithelium is more durable and better suited to withstand this friction than the delicate respiratory epithelium. **Analysis of Incorrect Options:** * **Nasal Cavity:** The majority of the nasal cavity (respiratory region) is lined with respiratory epithelium to warm and humidify air [1]. * **Paranasal Air Sinuses:** These are continuous with the nasal cavity and are lined by a thinner layer of pseudostratified ciliated columnar epithelium. * **Trachea:** This is the classic example of respiratory epithelium, featuring a thick basement membrane and numerous goblet cells [2]. **High-Yield NEET-PG Pearls:** 1. **Transition Zones:** The epithelium changes from respiratory to stratified squamous at areas of high friction: the **vestibule of the nose**, the **oropharynx**, and the **true vocal cords**. 2. **False Vocal Cords:** Unlike the true vocal cords, the false vocal cords (vestibular folds) are lined by **respiratory epithelium**. 3. **Metaplasia:** In chronic smokers, the respiratory epithelium of the trachea can undergo **squamous metaplasia**, transforming into stratified squamous epithelium to survive the irritation [2].

Q: Which of the following is NOT a type of microglia?

Spirocytes. **Explanation:** The question asks to identify which option is **NOT** a type of neuroglia (glial cells). The term "microglia" in the question stem is likely used as a broad reference to glial cells, though technically, microglia are a specific subtype of immune cells in the CNS [1]. **1. Why "Spirocytes" is the correct answer:** **Spirocytes** do not exist in human neuroanatomy. They are a fictional or non-anatomical term in this context. Therefore, they are not classified as neuroglia. **2. Analysis of Incorrect Options (Types of Neuroglia):** * **Oligodendrocytes (Option A):** These are macroglia of the **Central Nervous System (CNS)**. Their primary function is to provide myelination to multiple axons simultaneously [2]. * **Schwann cells (Option B):** These are the functional equivalents of oligodendrocytes but are located in the **Peripheral Nervous System (PNS)**. One Schwann cell myelinates only a single segment of one axon [2]. * **Astrocytes (Option D):** These are the most numerous glial cells in the CNS [1]. They form the **Blood-Brain Barrier (BBB)**, provide structural support, and regulate the chemical environment (K+ metabolism). **High-Yield NEET-PG Clinical Pearls:** * **Origin:** Microglia are derived from the **Mesoderm** (monocyte-macrophage lineage), whereas all other glial cells (Astrocytes, Oligodendrocytes, Schwann cells) are derived from the **Ectoderm** (Neural tube/crest) [1]. * **Blood-Brain Barrier:** Formed by the foot processes of **Astrocytes** along with capillary endothelial cells (tight junctions). * **Pathology:** In Multiple Sclerosis, **Oligodendrocytes** are destroyed (CNS demyelination); in Guillain-Barré Syndrome, **Schwann cells** are targeted (PNS demyelination) [2]. * **Fried Egg Appearance:** Histological hallmark of Oligodendrogliomas.

Q: What are the cells responsible for bone resorption?

Osteoclasts. **Explanation:** The correct answer is **B. Osteoclasts**. **1. Why Osteoclasts are correct:** Osteoclasts are large, multinucleated giant cells derived from the **monocyte-macrophage lineage** (hematopoietic stem cells) [1]. Their primary function is **bone resorption** [1, 3]. They achieve this by adhering to the bone surface and creating a sealed "Howship’s lacuna." They secrete hydrogen ions (via proton pumps) to dissolve hydroxyapatite crystals and lysosomal enzymes (like Cathepsin K) to digest the organic collagen matrix [1]. **2. Why other options are incorrect:** * **A. Osteoblasts:** These are bone-forming cells derived from mesenchymal stem cells [1, 3]. They synthesize the organic matrix (osteoid) and regulate mineralization [2]. * **C. Stem cells:** While osteoblasts arise from Mesenchymal Stem Cells (MSCs) and osteoclasts from Hematopoietic Stem Cells (HSCs), "stem cells" is a generic term and not the functional cell responsible for resorption [1]. * **D. Cytotoxic T cells:** These are immune cells involved in destroying virus-infected or tumor cells; they do not play a direct physiological role in bone remodeling. **3. High-Yield Facts for NEET-PG:** * **Origin:** Osteoblasts = Mesenchymal; Osteoclasts = Monocyte-Macrophage lineage (HSC) [1]. * **Markers:** Osteoclasts are characterized by **TRAP** (Tartrate-Resistant Acid Phosphatase) positivity. * **Regulation:** **Parathyroid Hormone (PTH)** stimulates bone resorption indirectly by acting on Osteoblasts, which then release **RANK-L**. RANK-L binds to receptors on Osteoclasts to activate them. * **Calcitonin:** Directly inhibits osteoclast activity, decreasing bone resorption. * **Howship’s Lacunae:** The microscopic pits on the bone surface where active resorption occurs [1].

Q: All of the following are cellular components of taste buds except?

Zymogenic Cells. **Explanation:** Taste buds are specialized ovoid sensory organs located primarily within the papillae of the tongue. They are composed of approximately 50–150 modified epithelial cells categorized into four distinct types based on their morphology and function. **Why Zymogenic Cells is the correct answer:** **Zymogenic cells** (also known as Chief cells) are found in the **stomach lining** (gastric glands), where they secrete pepsinogen. They are not a component of the sensory system or taste buds. **Analysis of other options:** * **Gustatory Cells (Type III):** These are the actual sensory receptors. They contain synaptic vesicles and release neurotransmitters (like serotonin) to stimulate the gustatory nerves. * **Sustentacular Cells (Type I & II):** These are support cells. Type I (Dark cells) act like glia, while Type II (Light cells) contain G-protein coupled receptors for sweet, bitter, and umami tastes. * **Basal Cells (Type IV):** These are undifferentiated stem cells located at the base of the taste bud. They continuously proliferate and differentiate to replace older taste cells every 10–14 days. **High-Yield Facts for NEET-PG:** * **Turnover:** Taste bud cells have a high turnover rate, being replaced every **10 to 14 days**. * **Innervation:** The anterior 2/3 of the tongue is supplied by the **Chorda Tympani** (CN VII); the posterior 1/3 by the **Glossopharyngeal nerve** (CN IX); and the epiglottis/pharynx by the **Vagus nerve** (CN X). * **Location:** Taste buds are most numerous in **circumvallate** and **foliate** papillae. Note that **filiform papillae** do NOT contain taste buds (they are purely mechanical).

Q: Dense regular collagen is found in all of the following tissues EXCEPT:

Periosteum. The classification of connective tissue depends on the arrangement and density of collagen fibers. **Dense regular connective tissue** consists of collagen fibers arranged in parallel bundles, providing maximum tensile strength in a single direction. **Why Periosteum is the Correct Answer:** The **periosteum** is composed of **dense irregular connective tissue**. Its collagen fibers are arranged in a haphazard, multidirectional network. This structural arrangement allows the bone to withstand mechanical stresses and tension applied from multiple different directions, rather than just one. It consists of an outer fibrous layer (dense irregular) and an inner osteogenic layer. **Analysis of Incorrect Options:** * **Tendons:** These connect muscle to bone. They consist of dense regular collagen fibers packed parallel to each other to resist the unidirectional pull of muscle contraction. * **Ligaments:** These connect bone to bone. Like tendons, they are composed of dense regular connective tissue to provide stability and resist strain along the axis of the fiber. * **Aponeuroses:** These are broad, sheet-like tendons. Despite their flat shape, the collagen fibers within them are organized in a highly regular, parallel fashion, classifying them as dense regular tissue. **High-Yield NEET-PG Pearls:** * **Dense Regular:** Tendons, Ligaments, Aponeuroses, and Corneal stroma. * **Dense Irregular:** Periosteum, Perichondrium, Dermis of skin, and Organ capsules (e.g., Glisson’s capsule of the liver). * **Type I Collagen** is the predominant collagen type found in all the structures mentioned in this question [1], [2]. * **Sharpey’s Fibers:** These are specific collagen fibers from the periosteum that penetrate into the bone tissue to anchor it firmly.

Q: What type of cartilage is found in the trachea?

Hyaline. ### Explanation **1. Why Hyaline Cartilage is Correct:** The trachea contains 16–20 C-shaped rings of **hyaline cartilage**. This type of cartilage is characterized by a glassy, translucent matrix rich in Type II collagen and chondroitin sulfate [1]. Its primary function in the trachea is to provide structural rigidity, ensuring the airway remains patent (open) despite the negative pressure generated during inspiration, while still allowing for flexibility during neck movement [1]. **2. Why the Other Options are Incorrect:** * **Elastic Cartilage:** Contains abundant elastic fibers. It is found in structures requiring high flexibility and shape retention, such as the **epiglottis**, pinna of the ear, and Eustachian tube. * **Articular Cartilage:** While this is a subtype of hyaline cartilage, it specifically refers to the cartilage covering the **ends of long bones** in synovial joints [1]. It lacks a perichondrium, whereas tracheal hyaline cartilage possesses one. * **Fibrocartilage:** Contains thick bundles of Type I collagen. It is designed to withstand heavy pressure and tension. Examples include **intervertebral discs**, pubic symphysis, and the TMJ. **3. NEET-PG High-Yield Pearls:** * **The "C-shape" Rule:** Tracheal rings are incomplete posteriorly. This gap is bridged by the **trachealis muscle** (smooth muscle), which allows the esophagus to expand during swallowing. * **Laryngeal Cartilages:** Remember the "3P" rule for Elastic cartilage: **P**inna, **P**haryngotympanic tube, and **P**liable laryngeal parts (Epiglottis, Corniculate, Cuneiform). The rest (Thyroid, Cricoid, and base of Arytenoid) are **Hyaline**. * **Calcification:** Hyaline cartilage has a tendency to calcify with age, whereas elastic cartilage does not.

Q: Why is the regeneration of nerve fibres possible in the peripheral nervous system but more limited in the central nervous system?

Presence of neurilemmal sheath in peripheral nerves. The regenerative capacity of nerve fibers depends primarily on the presence of the **neurilemma (Sheath of Schwann)** [1]. **1. Why Option A is Correct:** In the Peripheral Nervous System (PNS), axons are myelinated by **Schwann cells** [1], [4]. The outermost layer of the Schwann cell cytoplasm forms the **neurilemmal sheath**. When a peripheral nerve is injured, this sheath remains intact as a hollow tube (forming the *Bands of Büngner*). It produces neurotrophic factors and provides a physical scaffold that guides the sprouting axon toward its target organ, facilitating successful regeneration [1]. **2. Why the Other Options are Incorrect:** * **Option B:** The CNS lacks a neurilemmal sheath. Myelination in the CNS is performed by **oligodendrocytes**, which do not form a continuous basement membrane or neurilemma [3]. * **Option C:** The CNS is heavily myelinated; however, CNS myelin contains inhibitory proteins (like **Nogo-A**) that actively prevent axonal regrowth. * **Option D:** While vascularity is vital for tissue health, the primary limiting factor for nerve regeneration is the cellular environment (glial scarring and lack of neurilemma), not blood supply. **High-Yield NEET-PG Pearls:** * **Wallerian Degeneration:** The process of antegrade degeneration of the distal segment of an axon following injury [1]. * **Glial Scarring:** In the CNS, **astrocytes** proliferate at the injury site, forming a physical and chemical barrier that prevents regeneration [2]. * **Key Difference:** One Schwann cell myelinates only **one** internode of a single axon, whereas one oligodendrocyte can myelinate up to **50** different axons [3], [4].

Q: What best describes myoepithelium?

Epithelial cells with contractile units. **Explanation:** **Myoepithelial cells** are unique cells found in glandular epithelium. Despite their name, they are **epithelial in origin** (derived from the ectoderm) but possess functional characteristics of smooth muscle cells. **1. Why Option C is Correct:** Myoepithelial cells contain **contractile units** consisting of actin and myosin filaments (specifically alpha-smooth muscle actin) [2]. They are located between the basal plasma membrane of the secretory cells and the basal lamina. When these cells contract, they squeeze the acini or ducts of glands, facilitating the expulsion of secretory products into the ductal system. **2. Why Other Options are Incorrect:** * **Option A:** Epithelial cells covering muscle tissue refers to general connective tissue sheaths (like endomysium) or serous membranes, not a specific cell type with contractile properties. * **Option B:** While they share contractile proteins with muscle cells, myoepithelial cells are histologically distinct. They are joined by desmosomes and contain cytokeratin filaments, which are hallmarks of epithelial cells, not myocytes. **3. NEET-PG High-Yield Facts & Clinical Pearls:** * **Location:** Commonly found in the **mammary glands** (stimulated by oxytocin), **salivary glands**, **sweat glands**, and **lacrimal glands**. * **Staining:** They are identified immunohistochemically using markers like **p63**, **S-100**, and **Smooth Muscle Actin (SMA)**. * **Clinical Significance:** In breast pathology, the presence of a preserved myoepithelial layer is a key diagnostic feature used to differentiate **benign/in-situ lesions** from **invasive carcinoma** (where the myoepithelial layer is typically lost) [1]. * **Origin:** Unlike most muscle (mesodermal), myoepithelial cells are **ectodermal** in origin.

Question 1

Prominent eosinophilic secretory granules are seen in Paneth cells of the intestinal crypts. What is secreted from these cells?

Accepted Answer

Antimicrobial peptides like lysozyme

Answer

Mucus

Answer

Alkaline fluid

Answer

Acidic fluid

Question 2

Which of the following pairs of structures have similar types of epithelium?

Accepted Answer

Lung alveoli and Bowman's capsule

Answer

Alveoli and olfactory epithelium

Answer

Olfactory epithelium and skin

Answer

Esophagus and urinary bladder

Question 3

Which of the following structures is NOT lined with pseudostratified ciliated columnar epithelium?

Accepted Answer

Vocal cords

Answer

Nasal cavity

Answer

Paranasal air sinuses

Answer

Trachea

Question 4

Which of the following is NOT a type of microglia?

Accepted Answer

Spirocytes

Answer

Oligodendrocyte

Answer

Schwann cells

Answer

Astrocytes

Question 5

What are the cells responsible for bone resorption?

Accepted Answer

Osteoclasts

Answer

Osteoblasts

Answer

Stem cells

Answer

Cytotoxic T cells

Question 6

All of the following are cellular components of taste buds except?

Accepted Answer

Zymogenic Cells

Answer

Basal Cell

Answer

Sustentacular Cells

Answer

Gustatory Cells

Question 7

Dense regular collagen is found in all of the following tissues EXCEPT:

Accepted Answer

Periosteum

Answer

Ligament

Answer

Aponeurosis

Answer

Tendon

Question 8

What type of cartilage is found in the trachea?

Accepted Answer

Hyaline

Answer

Elastic

Answer

Articular

Answer

Fibro

Question 9

Why is the regeneration of nerve fibres possible in the peripheral nervous system but more limited in the central nervous system?

Accepted Answer

Presence of neurilemmal sheath in peripheral nerves

Answer

Presence of neurilemmal sheath in the central nervous system

Answer

Absence of myelin sheath in the central nervous system

Answer

Disturbed vascular supply in the central nervous system

Question 10

What best describes myoepithelium?

Accepted Answer

Epithelial cells with contractile units

Answer

Epithelial cells covering muscle tissue

Answer

Muscle cells

Answer

None of the above

Histology — MCQs

Histology — MCQs

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