Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 311: Clara cells are present in which part of the respiratory tract?

A. Alveoli
B. Bronchus
C. Bronchioles (Correct Answer)
D. Trachea

Explanation: **Explanation:** **Clara cells** (now officially termed **Club cells**) are non-ciliated, dome-shaped cuboidal cells characterized by apical secretory granules. They are primarily found in the **bronchioles**, specifically the terminal and respiratory bronchioles [1]. **Why Bronchioles is the Correct Answer:** As the respiratory tree branches, the pseudostratified ciliated columnar epithelium of the upper tract transitions into simple cuboidal epithelium. In this transition, goblet cells disappear and are replaced by Club cells [1]. Their primary functions include: 1. **Secretory:** They produce a component of pulmonary surfactant (Surfactant protein A and D) and uteroglobin-like proteins to protect the bronchiolar lining. 2. **Detoxification:** They contain high concentrations of Cytochrome P450 enzymes to metabolize inhaled toxins. 3. **Regeneration:** They act as stem cells, proliferating to replace both ciliated and non-ciliated cells if the airway is damaged. **Why Other Options are Incorrect:** * **Alveoli:** The alveoli are lined by Type I and Type II pneumocytes [2]. While Type II pneumocytes also produce surfactant, they are morphologically and functionally distinct from Club cells [3]. * **Bronchus & Trachea:** These larger airways are lined by pseudostratified ciliated columnar epithelium with numerous **Goblet cells**. Club cells only appear where goblet cells end—at the level of the bronchioles [1]. **High-Yield Facts for NEET-PG:** * **Marker:** Club Cell Secretory Protein (**CC15**) is a clinical marker; decreased levels in lavage fluid are seen in lung injury/COPD. * **Histology Tip:** Look for "dome-shaped" cells without cilia in the bronchiolar lumen. * **Stem Cell Role:** In the event of smoke inhalation or toxic injury, Club cells are the primary source of epithelial repair in the distal airways.

Question 312: Nissl bodies are typically found in which part of a neuron?

A. Cell body (Correct Answer)
B. Axon
C. Dendrites
D. Nerve sheath

Explanation: **Explanation:** **Nissl bodies** (also known as Nissl substance or chromophilic substance) are large granular bodies found in neurons. They are composed of **Rough Endoplasmic Reticulum (RER)** and free ribosomes, serving as the primary site for protein synthesis within the cell [2]. 1. **Why the Cell Body is correct:** The cell body (soma or perikaryon) is the metabolic hub of the neuron [1]. It contains the nucleus and the majority of the protein-synthetic machinery [5]. Nissl bodies are densely packed here to produce neurotransmitters and structural proteins. 2. **Why Dendrites are (partially) incorrect:** While small amounts of Nissl substance can extend into the proximal (basal) portions of large dendrites, they are primarily characteristic of the cell body. In the context of standard medical examinations, the cell body is the definitive primary location. 3. **Why the Axon is incorrect:** The axon is notably devoid of Nissl bodies. The region where the axon originates from the cell body, known as the **Axon Hillock**, is also free of Nissl substance [1]. This is a classic histological landmark used to identify the start of an axon. 4. **Why the Nerve Sheath is incorrect:** The nerve sheath (myelin or connective tissue layers like endoneurium) is an extracellular or supportive structure (formed by Schwann cells or Oligodendrocytes) and does not contain the internal organelles of the neuron itself [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Chromatolysis:** Following an axonal injury, Nissl bodies undergo "chromatolysis"—they disperse and seem to disappear as the cell shifts its metabolic focus to repairing the damaged axon [3]. * **Staining:** Nissl bodies are highly basophilic and are best visualized using basic dyes like **Cresyl Violet** or **Methylene Blue**. * **Key Exclusion:** Always remember: **Axon Hillock = No Nissl bodies.** This is a frequent "trap" in image-based or conceptual questions [1].

Question 313: Endochondral ossification is seen in which of the following bones?

A. Long bones (Correct Answer)
B. Flat bones of the skull
C. Bones of the cranial vault
D. Nasal bones

Explanation: Bone formation (ossification) occurs via two primary mechanisms: **Endochondral** and **Intramembranous** ossification. **1. Why the Correct Answer is Right:** **Endochondral ossification** is the process where a pre-existing hyaline cartilage model is gradually replaced by bone [1]. This mechanism is characteristic of bones that bear weight and require longitudinal growth, such as the **long bones** (e.g., femur, humerus, tibia) and the vertebrae. The process begins at a primary ossification center in the diaphysis, followed by secondary centers in the epiphyses, allowing for growth at the epiphyseal plate. **2. Why the Other Options are Wrong:** * **B, C, and D (Flat bones of the skull, Cranial vault, and Nasal bones):** These bones develop via **Intramembranous ossification** [1]. In this process, mesenchymal (connective tissue) cells differentiate directly into osteoblasts without a cartilaginous precursor [1]. This is typical for the "flat bones" of the body. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mixed Ossification:** Some bones develop using both methods. The most high-yield examples are the **Mandible**, **Clavicle**, and **Occipital bone** [1]. * **The Clavicle:** It is the first bone to start ossifying in the body. It primarily undergoes intramembranous ossification, but its ends ossify endochondrally. * **Achondroplasia:** This clinical condition specifically affects endochondral ossification, leading to short limbs (long bones affected) while the skull (intramembranous) remains relatively normal in size. * **Primary vs. Secondary Centers:** Most primary centers appear before birth; most secondary centers appear after birth (except the distal end of the femur).

Question 314: Which of the following statements is NOT true about carcinoma of the penis?

A. Erythroplasia of Queyrat is a precancerous condition.
B. 40% of patients are under 40 years of age.
C. Circumcision, if performed any time before puberty, provides 100% protection against carcinoma of the penis. (Correct Answer)
D. More than 50% of patients have inguinal lymph node enlargement when they present.

Explanation: **Explanation:** **Why Option C is the correct (False) statement:** While neonatal circumcision significantly reduces the risk of penile carcinoma, it does **not** provide 100% protection. Furthermore, the protective benefit is most pronounced when performed in the **neonatal period**. If circumcision is delayed until puberty, the protective effect against squamous cell carcinoma is substantially diminished because the patient has already been exposed to potential carcinogens (like smegma and HPV) during childhood. **Analysis of other options:** * **Option A:** **Erythroplasia of Queyrat** is a form of Squamous Cell Carcinoma in situ (Bowen’s disease) specifically involving the glans penis or prepuce. It is a well-recognized precancerous lesion. * **Option B:** Penile cancer is primarily a disease of older men (6th–7th decade). It is relatively rare in young individuals; therefore, the statement that 40% are under 40 is statistically incorrect in most clinical contexts, but in the context of this specific MCQ, Option C is the "most" false/definitive error. * **Option D:** Approximately **50-60%** of patients present with palpable inguinal lymphadenopathy. However, only about half of these represent metastatic spread; the rest are often due to secondary infection of the primary tumor. **NEET-PG High-Yield Pearls:** * **Most common type:** Squamous Cell Carcinoma (>95%). * **Risk Factors:** Phimosis (strongest association), HPV 16 and 18, smoking, and poor hygiene. * **Lymphatic Spread:** The primary site of metastasis is the **Inguinal Lymph Nodes** (Vertical group of superficial nodes). * **Sentinel Node:** The **Node of Cloquet** (deep inguinal node) is a critical landmark in staging.

Question 315: Kupffer cells are seen in which organ?

A. Liver (Correct Answer)
B. Spleen
C. Lung
D. Heart

Explanation: **Explanation:** **Kupffer cells** are specialized, stellate-shaped macrophages located within the **sinusoids of the liver**. They form part of the Mononuclear Phagocyte System (MPS) and are primarily responsible for filtering bacteria, debris, and worn-out red blood cells from the portal circulation. **Analysis of Options:** * **A. Liver (Correct):** Kupffer cells are resident macrophages attached to the endothelial lining of hepatic sinusoids [2]. They play a crucial role in immune surveillance and iron metabolism by recycling hemoglobin. * **B. Spleen:** The resident macrophages in the spleen are simply called **Splenic Macrophages** (found in the red pulp). They are responsible for "pitting" and "culling" of aged erythrocytes [1]. * **C. Lung:** The characteristic macrophages in the lungs are **Alveolar Macrophages** (also known as **Dust Cells**), which clear inhaled particulate matter [2]. * **D. Heart:** While the heart contains cardiac macrophages for tissue repair, they do not have a specific eponymous name like Kupffer cells. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Like all macrophages, Kupffer cells are derived from circulating **monocytes** (which originate in the bone marrow) [2]. * **Staining:** They can be visualized using **India ink** or vital stains (like Trypan blue) because they are highly phagocytic. * **Other Tissue-Specific Macrophages (Must-Know):** * **CNS:** Microglia [2] * **Skin:** Langerhans cells * **Bone:** Osteoclasts * **Kidney:** Mesangial cells * **Connective Tissue:** Histiocytes

Question 316: Which of the following is the least common presentation of multiple myeloma?

A. Anemia
B. Hyperviscocity (Correct Answer)
C. Bone pains
D. Infection

Explanation: **Explanation:** Multiple Myeloma (MM) is a neoplastic proliferation of plasma cells characterized by the "CRAB" features (Calcium elevation, Renal failure, Anemia, and Bone lesions). **Why Hyperviscosity is the correct answer:** While Multiple Myeloma involves the overproduction of monoclonal immunoglobulins (M-protein), **Hyperviscosity Syndrome** is relatively rare, occurring in only about **2–6%** of patients. It is much more characteristic of **Waldenström Macroglobulinemia**, where the large size of IgM pentamers significantly increases blood viscosity. In MM, hyperviscosity usually only occurs if the M-protein concentration is extremely high (typically IgA or IgG3 subtypes). **Analysis of Incorrect Options:** * **Anemia (Option A):** This is the most common hematological finding (present in ~73% of cases) due to bone marrow infiltration by plasma cells and cytokine-mediated suppression of erythropoiesis. * **Bone Pains (Option C):** This is the most common presenting symptom (~58-70%). Plasma cells produce Osteoclast Activating Factors (OAFs) like IL-6 and RANK-L, leading to lytic "punched-out" lesions and pathological fractures. * **Infection (Option D):** This is a leading cause of morbidity and mortality. Patients have functional hypogammaglobulinemia (decreased normal antibodies), making them highly susceptible to encapsulated organisms like *S. pneumoniae*. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of death:** Infection (Sepsis) followed by Renal Failure. * **Radiology:** "Punched-out" lytic lesions; **Bone scans are often negative** because they detect osteoblastic activity, which is absent in MM. * **Blood Film:** **Rouleaux formation** (due to decreased zeta potential between RBCs by paraproteins). * **Urinalysis:** Bence-Jones proteins (free light chains) are detected by heat precipitation test, **not** by standard dipsticks.

Question 317: An open-faced nucleus in a cell signifies what?

A. that the cell is resting
B. that the cell is active (Correct Answer)
C. nothing
D. that the cell is in a transition phase

Explanation: ### Explanation **1. Why the Correct Answer is Right:** An **"open-faced" nucleus** (also known as a vesicular nucleus) is a histological hallmark of a **metabolically active cell**. In such cells, the DNA is primarily in the form of **euchromatin** (extended, loosely packed chromatin). Because euchromatin is less dense, it allows light to pass through during microscopy, making the nucleus appear pale or "clear." This state indicates that the DNA is being actively transcribed into RNA for protein synthesis. A prominent nucleolus is often seen within an open-faced nucleus, further signifying active ribosomal RNA synthesis. **2. Why the Other Options are Wrong:** * **Option A (Resting):** In resting or inactive cells, the DNA is tightly coiled into **heterochromatin**. This dense packing makes the nucleus appear dark and shrunken (**pyknotic**), rather than open-faced. * **Option C (Nothing):** Nuclear morphology is a critical diagnostic tool in histology and pathology; it directly reflects the functional state of the cell. * **Option D (Transition phase):** While cells change during transition phases (like mitosis), the term "open-faced" specifically describes the interphase state of high transcriptional activity, not the transition process itself. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Classic Examples:** Open-faced nuclei are characteristically seen in **neurons** (large motor neurons), **hepatocytes**, **plasma cells**, and **active endocrine cells**. * **Pathology Link:** In **Papillary Carcinoma of the Thyroid**, the nuclei have a very distinct open appearance called **"Orphan Annie Eye" nuclei** due to finely dispersed chromatin. * **Contrast:** Remember the rule—**Euchromatin = Active (Pale/Open)** vs. **Heterochromatin = Inactive (Dark/Dense).** * **Nucleolus:** A prominent nucleolus within an open-faced nucleus is a sign of intense protein synthesis (e.g., in malignant cells or silk-producing glands).

Question 318: Which of the following statements regarding Paneth cells is true?

A. Absence of lysosomes
B. High concentration of zinc (Correct Answer)
C. No role in innate immunity
D. Abundant in esophagus and stomach

Explanation: Paneth cells are specialized secretory cells located at the **base of the Crypts of Lieberkühn** in the small intestine [1]. They play a pivotal role in maintaining the mucosal barrier and regulating the gut microbiome [1]. **Why Option B is Correct:** Paneth cells contain prominent eosinophilic apical granules. These granules have a **high concentration of Zinc**, which acts as a critical cofactor for various enzymes and antimicrobial peptides stored within the cell. Zinc is essential for the structural stability and biological activity of these secretions. **Analysis of Incorrect Options:** * **Option A:** Paneth cells are rich in **lysosomes** and secretory granules containing **Lysozyme**, an enzyme that digests bacterial cell walls. * **Option C:** They are primary mediators of **innate immunity**. They secrete antimicrobial peptides like **alpha-defensins (cryptidins)** and TNF-alpha, which neutralize pathogens. * **Option D:** Paneth cells are characteristic of the **small intestine** (most abundant in the ileum) [1]. They are normally **absent** in the esophagus and stomach; their presence in the stomach or esophagus usually indicates intestinal metaplasia. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Base of Crypts of Lieberkühn (Small Intestine) [1]. * **Secretions:** Lysozyme, Alpha-defensins (Cryptidins), Zinc, and Phospholipase A2. * **Staining:** They are acidophilic/eosinophilic due to the nature of their granules. * **Clinical Correlation:** Dysfunction of Paneth cells is implicated in the pathogenesis of **Crohn’s Disease**, where a decrease in alpha-defensins leads to impaired mucosal defense.

Question 319: Fibrous cartilage is located in all of the following structures except?

A. Intervertebral discs
B. Temporomandibular joint (TMJ)
C. Pubic symphysis
D. None of the above is an exception (Correct Answer)

Explanation: Explanation: Fibrocartilage is a unique histological tissue that combines the tensile strength of dense connective tissue with the resilience of cartilage. It is characterized by thick bundles of Type I collagen fibers (unlike hyaline cartilage, which primarily contains Type II [1]) and a lack of a perichondrium. In medical scenarios such as bone repair, activated mesenchymal cells differentiate into chondrocytes that produce fibrocartilage as part of the bony callus [2]. 1. Intervertebral Discs (Option A): The annulus fibrosus of the intervertebral disc is a classic example of fibrocartilage. Its concentric lamellae of collagen fibers are designed to withstand heavy pressure and shear forces. 2. Temporomandibular Joint (Option B): While most synovial joints are lined by hyaline cartilage [1], the TMJ is a notable exception. Both the articular surfaces and the intra-articular disc are composed of fibrocartilage, which provides better repair potential and resistance to the complex loading forces of mastication. 3. Pubic Symphysis (Option C): This is a secondary cartilaginous joint (amphiarthrosis). The midline disc connecting the two pubic bones is made of fibrocartilage, allowing for slight movement and significant shock absorption. Why "None of the above" is correct: Since all three structures listed (A, B, and C) are primary anatomical locations for fibrocartilage, there is no exception among the choices. High-Yield Clinical Pearls for NEET-PG: * Collagen Type: Remember: Fibrocartilage = Type I (mnemonic: "F-I-rst"). * Perichondrium: Fibrocartilage lacks a perichondrium (similar to articular hyaline cartilage [1]). * Other Locations: Also found in the Glenoid labrum, Acetabular labrum, and the Menisci of the knee. * Transition Zone: It often acts as a transition tissue between tendons/ligaments and bone.

Question 320: Large pulp chambers are characteristic of all the following conditions except?

A. Shell teeth
B. Taurodontism
C. Dentin dysplasia
D. Dentinogenesis imperfecta (Correct Answer)

Explanation: ### Explanation The key to answering this question lies in understanding how different genetic dental disorders affect the formation of dentin and the subsequent volume of the pulp chamber. **Why Dentinogenesis Imperfecta (DI) is the correct answer:** In **Dentinogenesis Imperfecta**, there is an overproduction of irregular secondary dentin. This rapid and excessive deposition leads to the **obliteration of the pulp chambers** and root canals shortly after eruption. Therefore, DI is characterized by **small or absent pulp chambers**, not large ones. Radiographically, these teeth also show a "bulbous crown" with a constricted cervical neck. **Analysis of Incorrect Options (Conditions with Large Pulp Chambers):** * **Shell Teeth:** This is a severe expression of Dentinogenesis Imperfecta (Type III) where dentin formation is extremely thin, leaving a **massive, hollow pulp chamber**. * **Taurodontism:** Known as "bull-like" teeth, this condition involves the failure of Hertwig’s epithelial root sheath to invaginate at the proper level. This results in a vertically elongated body and a **pulp chamber that is apically displaced and enlarged**. * **Dentin Dysplasia (Type II):** While Type I (Radicular) shows "half-moon" pulp remnants, **Type II (Coronal)** is characterized by **large, flame-shaped or "thistle-tube" pulp chambers** in the permanent dentition. **High-Yield Clinical Pearls for NEET-PG:** * **Dentinogenesis Imperfecta:** Often associated with **Osteogenesis Imperfecta** (Type I) due to mutations in Type I collagen. Look for "Blue Sclera" in clinical vignettes. * **Taurodontism:** Frequently associated with **Klinefelter Syndrome (47, XXY)** and Tricho-dento-osseous syndrome. * **Regional Odontodysplasia:** Also known as **"Ghost Teeth,"** characterized by thin enamel and dentin with very large pulp chambers.

Practice by Chapter

Basic Tissue Types

Practice Questions

Cell Biology and Organelles

Practice Questions

Epithelial Tissue

Practice Questions

Connective Tissue

Practice Questions

Muscular Tissue

Practice Questions

Nervous Tissue

Practice Questions

Cardiovascular System Histology

Practice Questions

Lymphoid Organs and Immune System

Practice Questions

Endocrine System Histology

Practice Questions

Respiratory System Histology

Practice Questions

Digestive System Histology

Practice Questions

Urinary and Reproductive System Histology

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Histology — MCQs

Histology — MCQs

On this page

Practice by Chapter

Want unlimited practice?