Inflammation and Repair — MCQs

Inflammation and Repair Indian Medical PG Practice Questions and MCQs

Question 301: A clean incised wound heals by:

A. Primary intention (Correct Answer)
B. Secondary intention
C. Excessive scarring
D. None of the above

Explanation: ### Explanation **Primary Intention (Healing by First Intention)** Healing by primary intention occurs when the wound edges are clean, uninfected, and closely apposed (approximated), typically by surgical sutures, staples, or adhesive tape. A **clean incised wound** is the classic example [4]. Because the tissue loss is minimal, the "gap" to be filled is small. This results in rapid epithelial regeneration, minimal granulation tissue formation, and a very thin, linear scar [1]. **Why other options are incorrect:** * **Secondary Intention:** This occurs when there is extensive tissue loss, irregular wound edges, or infection (e.g., large burns, deep ulcers, or abscesses) [4]. The wound is left open to heal from the bottom up. It involves significant granulation tissue formation, extensive wound contraction (mediated by myofibroblasts), and results in a large, irregular scar [3]. * **Excessive Scarring:** This is a complication of wound healing (like Keloids or Hypertrophic scars) rather than a standard physiological mechanism for a clean incision [4]. It occurs due to an imbalance in collagen synthesis and degradation. **NEET-PG High-Yield Pearls:** * **Day 5:** Neovascularization (angiogenesis) reaches its peak [1]. * **Tensile Strength:** At the end of 1 week (when sutures are usually removed), wound strength is ~10% [2]. It reaches ~70-80% by 3 months but **never** returns to 100% of the original pre-wound strength [2]. * **Type of Collagen:** Initially, Type III collagen is deposited; it is later replaced by the stronger **Type I collagen** during the remodeling phase. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 105-106. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 106-107.

Question 302: Wound contraction is mediated by which of the following cells?

A. Myofibroblasts (Correct Answer)
B. Epithelial cells
C. Collagen
D. Elastin

Explanation: **Explanation:** **Wound contraction** is a critical physiological process that reduces the size of a wound, typically occurring in healing by **secondary union (second intention)** [1]. 1. **Why Myofibroblasts are correct:** The primary cell responsible for this process is the **myofibroblast** [1]. These are modified fibroblasts that acquire features of smooth muscle cells, specifically the expression of **α-smooth muscle actin (α-SMA)**. They form a network at the edge of the wound and exert contractile forces that pull the wound edges together, often reducing the surface area by 5% to 10% of its original size [1], [2]. 2. **Why the other options are incorrect:** * **Epithelial cells:** These are responsible for **re-epithelialization** (covering the wound surface) but do not possess the contractile machinery required to shrink the wound volume [1]. * **Collagen:** This is a structural protein secreted by fibroblasts to provide **tensile strength** to the scar. While it fills the wound gap, it is a passive component and does not actively contract [1], [2]. * **Elastin:** This protein provides elasticity to tissues. In adult skin wounds, elastin is often deficient or poorly organized in scars, which is why scars lack the flexibility of normal skin. **High-Yield NEET-PG Pearls:** * **Timing:** Wound contraction typically begins around day 3 and peaks between weeks 1 and 2. * **Secondary Union:** Contraction is much more pronounced in healing by secondary intention than primary intention [1]. * **Clinical Correlation:** Excessive contraction can lead to **contractures**, commonly seen after severe burn injuries, which can restrict joint mobility [3]. * **Tensile Strength:** At the end of 1 week, wound strength is ~10% of unwounded skin; it reaches ~70-80% by 3 months but rarely recovers 100% of original strength [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 105-106. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 88-89.

Question 303: Rubor in inflammation is due to?

A. Dilation of arterioles (Correct Answer)
B. Increased vascular permeability
C. Increased viscosity of blood
D. Edema

Explanation: **Explanation:** The cardinal signs of inflammation, first described by Celsus [1], include **Rubor** (redness), **Calor** (heat), **Tumor** (swelling), and **Dolor** (pain). **Why Option A is correct:** Rubor (redness) is the earliest clinical sign of acute inflammation [2]. It is primarily caused by **vasodilation of arterioles** [1], mediated by chemical mediators like histamine and nitric oxide [2,3]. This dilation leads to an increased volume of blood flow (hyperemia) to the injured site [1]. Because the blood is oxygenated and flowing through dilated vessels, the area appears clinically red [1]. **Why other options are incorrect:** * **B. Increased vascular permeability:** This leads to the leakage of protein-rich fluid (exudate) into the interstitial space [2]. While it occurs simultaneously, its primary clinical manifestation is **Tumor** (swelling), not Rubor. * **C. Increased viscosity of blood:** As fluid leaves the vessels due to permeability, the concentration of red blood cells increases, leading to **stasis**. Stasis contributes to leukocyte margination but does not cause the initial redness. * **D. Edema:** This is the physical accumulation of fluid in the extravascular space, which results in **Tumor** (swelling). **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Hemodynamic Changes:** Transient vasoconstriction (seconds) → Persistent Vasodilation (Arterioles) → Increased Permeability (Venules) → Stasis. * **Calor (Heat):** Also due to increased blood flow (hyperemia) to the peripheral site [1]. * **Lewis Triple Response:** Includes Flush (capillary dilation), Flare (arteriolar dilation/Rubor), and Wheal (exudation/Edema). * **Fifth Sign:** Virchow later added *Functio Laesa* (loss of function) [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 185-186. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101.

Question 304: Myofibroblasts are typically seen in which of the following locations?

A. Normal connective tissue
B. Muscle septa
C. Wound margin (Correct Answer)
D. Bronchus

Explanation: **Explanation:** **Correct Answer: C. Wound margin** **Underlying Concept:** Myofibroblasts are specialized cells that play a critical role in **wound healing by secondary intention**. They are essentially modified fibroblasts that express **α-smooth muscle actin (α-SMA)**, giving them contractile properties similar to smooth muscle cells [2]. During the proliferative phase of healing (typically appearing around day 3–5), fibroblasts at the **wound margin** differentiate into myofibroblasts under the influence of **TGF-β (Transforming Growth Factor-beta)** and PDGF [1]. Their primary function is to pull the edges of the wound together, a process known as **wound contraction**, which significantly reduces the surface area of the resulting scar [1]. **Analysis of Incorrect Options:** * **A & B (Normal connective tissue / Muscle septa):** In healthy, non-injured tissue, fibroblasts exist in a quiescent state. Myofibroblasts are generally absent in normal physiology; they are "transient" cells that appear only during active repair or pathological fibrosis. * **D (Bronchus):** While smooth muscle is present in the bronchial wall, myofibroblasts are not a constituent of the normal bronchial architecture. However, they may appear pathologically in the subepithelial layers during chronic airway remodeling (e.g., in Asthma). **NEET-PG High-Yield Pearls:** * **Key Marker:** α-Smooth Muscle Actin (α-SMA) is the definitive immunohistochemical marker for myofibroblasts. * **Key Cytokine:** **TGF-β** is the most potent stimulator of myofibroblast differentiation. * **Clinical Correlation:** Excessive myofibroblast activity leads to **pathologic contractures** (commonly seen after severe burns) and is the hallmark of fibrotic diseases like Palmar Fibromatosis (Dupuytren’s contracture). * **Fate:** Once a wound is healed, myofibroblasts typically undergo **apoptosis**. Their persistence is a sign of hypertrophic scarring or keloid formation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 105-106.

Question 305: Which of the following is the gene responsible for Duchenne muscular dystrophy?

A. STK11 gene
B. PTCH gene
C. DMPK gene
D. Dystrophin gene (Correct Answer)

Explanation: **Explanation:** **Duchenne Muscular Dystrophy (DMD)** is an X-linked recessive disorder caused by a mutation in the **Dystrophin gene**, located on the short arm of the X chromosome (Xp21) [1], [3]. This gene is the largest known human gene, making it highly susceptible to spontaneous mutations. Dystrophin is a vital structural protein that links the intracellular cytoskeleton (actin) to the extracellular matrix via the dystroglycan complex. Its absence leads to membrane instability, myofiber necrosis, and progressive muscle weakness [1]. **Analysis of Incorrect Options:** * **STK11 gene (Option A):** Mutations in this tumor suppressor gene are associated with **Peutz-Jeghers Syndrome**, characterized by hamartomatous polyps and mucocutaneous hyperpigmentation. * **PTCH gene (Option B):** Mutations in the Patched (PTCH1) gene are linked to **Gorlin Syndrome** (Basal Cell Nevus Syndrome), which presents with multiple basal cell carcinomas and odontogenic keratocysts. * **DMPK gene (Option C):** A CTG trinucleotide repeat expansion in this gene causes **Myotonic Dystrophy Type 1**, the most common adult-onset muscular dystrophy [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** X-linked recessive (primarily affects males) [3]. * **Clinical Signs:** **Gower’s sign** (using hands to "climb up" the body to stand) and **Pseudohypertrophy** of the calves (muscle replaced by fat and connective tissue). * **Diagnosis:** Markedly elevated **Creatine Kinase (CK)** levels; Gold standard is genetic testing or muscle biopsy showing absent dystrophin [1]. * **Becker Muscular Dystrophy (BMD):** Also involves the dystrophin gene but results from *in-frame* mutations, leading to a truncated but functional protein (milder phenotype) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1244-1245. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1245-1246. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 58-59.

Question 306: In the lipoxygenase pathway, which of the following arachidonic acid products helps in vasoconstriction and increased vascular permeability?

A. C5a
B. Thromboxane A2
C. Leukotriene D4 (Correct Answer)
D. C, activators

Explanation: ### Explanation **Correct Answer: C. Leukotriene D4** **Mechanism and Concept:** Arachidonic acid is metabolized via two main pathways: the Cyclooxygenase (COX) pathway and the **Lipoxygenase (LOX)** pathway [1]. In the LOX pathway, 5-lipoxygenase converts arachidonic acid into 5-HPETE, which is then transformed into **Leukotriene A4 (LTA4)**. LTA4 is further processed into the cysteinyl-containing leukotrienes: **LTC4, LTD4, and LTE4** [1]. These specific leukotrienes are potent mediators of inflammation that cause: 1. **Intense Vasoconstriction** (unlike prostaglandins like PGI2/PGE2 which cause vasodilation). 2. **Increased Vascular Permeability** (via contraction of post-capillary venule endothelial cells) [1]. 3. **Bronchospasm** (making them central to the pathogenesis of asthma). **Analysis of Incorrect Options:** * **A. C5a:** This is a component of the Complement system (Anaphylatoxin). While it increases vascular permeability and is a potent chemotactic agent, it is **not** a product of the lipoxygenase pathway. * **B. Thromboxane A2 (TXA2):** This is a product of the **Cyclooxygenase (COX)** pathway [1]. While it causes vasoconstriction and platelet aggregation, it does not belong to the LOX pathway. * **D. C, activators:** This likely refers to complement activators or C-reactive protein, which are plasma-derived mediators, not lipid-derived arachidonic acid metabolites. **NEET-PG High-Yield Pearls:** * **LTC4, LTD4, LTE4** are collectively known as the **Slow-Reacting Substance of Anaphylaxis (SRS-A)**. * **LTB4** is the "Chemotactic Leukotriene" (mnemonic: LTB4 **B**rings neutrophils). * **Lipoxins (LXA4, LXB4)** are also LOX products but serve to **inhibit** inflammation (anti-inflammatory), acting as "stop signals." * **Zileuton** inhibits 5-lipoxygenase, while **Montelukast/Zafirlukast** are LTD4 receptor antagonists used in asthma management. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 95.

Question 307: Arrange the vascular events in the correct chronological order during acute inflammation:

A. Vasoconstriction, Vasodilation, Increased vascular permeability, Increased blood viscosity, Stasis (Correct Answer)
B. Vasodilation, Increased blood viscosity, Increased vascular permeability, Stasis, Vasoconstriction
C. Vasodilation, Stasis, Increased vascular permeability, Vasoconstriction, Increased blood viscosity
D. Increased vascular permeability, Stasis, Increased blood viscosity, Vasoconstriction, Vasodilation

Explanation: ### Explanation The vascular events in acute inflammation follow a highly specific hemodynamic sequence designed to facilitate the movement of leukocytes from the blood into the injured tissue. **1. Why Option A is Correct:** The sequence begins with **transient vasoconstriction** of arterioles, a neurogenic reflex lasting only seconds. This is immediately followed by **vasodilation** (induced by histamine and nitric oxide), which increases blood flow (causing redness and heat) [3]. Next, **increased vascular permeability** occurs, leading to the escape of protein-rich fluid (exudate) into the extravascular space [1]. This loss of fluid results in **increased blood viscosity** (hemoconcentration). Finally, the combination of dilated vessels and viscous blood leads to **stasis**, allowing leukocytes to marginate and exit the vessel [2]. **2. Why Other Options are Incorrect:** * **Options B & C:** These incorrectly place vasodilation before vasoconstriction. While vasoconstriction is fleeting and often missed clinically, it is physiologically the first event. * **Option D:** This suggests permeability changes occur before diameter changes. Without initial vasodilation, the hydrostatic pressure would not be sufficient to drive the inflammatory exudate effectively [3]. **3. NEET-PG High-Yield Pearls:** * **Earliest Event:** Transient vasoconstriction (seconds). * **Most Characteristic Feature:** Increased vascular permeability (leads to edema). * **Mechanism of Permeability:** The most common mechanism is **endothelial cell contraction**, primarily affecting **post-capillary venules** [4]. * **Triple Response of Lewis:** Flush (capillary dilation), Flare (arteriolar dilation), and Wheal (exudation/edema) mirrors this hemodynamic sequence. * **Stasis:** This is the critical prerequisite for **leukocyte margination**, the first step of the cellular stage [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Migration in the tissues toward a chemotactic stimulus, pp. 86-87. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 187-188.

Question 308: Empyema is a term given for:

A. Collection of pus in the tissue spaces (Correct Answer)
B. Collection of blood in the tissue spaces
C. Collection of air in the tissue spaces
D. Collection of serous fluid in the tissue spaces

Explanation: **Explanation:** **Empyema** is defined as a localized collection of **pus** within a naturally occurring anatomical cavity or tissue space [1]. It is a form of suppurative (purulent) inflammation, most commonly occurring in the pleural space (pleural empyema) as a complication of pneumonia, but it can also occur in the gallbladder [1], joints, or subdural space. **Analysis of Options:** * **Option A (Correct):** Empyema specifically refers to the accumulation of purulent exudate (pus), which consists of neutrophils, necrotic debris, and edema fluid, within a body cavity [1]. * **Option B (Incorrect):** A collection of blood in a tissue space or cavity is termed a **Hematoma** (in tissues) or prefixed with "hemo-" (e.g., Hemothorax in the pleural cavity). * **Option C (Incorrect):** A collection of air in a body cavity is termed **Pneumatosis** or prefixed with "pneumo-" (e.g., Pneumothorax). * **Option D (Incorrect):** A collection of serous fluid is termed an **Effusion** (e.g., Serous pleural effusion) or **Ascites** (in the peritoneal cavity) [1]. **NEET-PG High-Yield Pearls:** * **Empyema vs. Abscess:** While both contain pus, an **abscess** is a localized collection of pus in a *newly formed* cavity caused by tissue destruction, whereas **empyema** occurs in a *pre-existing* anatomical space. * **Common Organisms:** *Staphylococcus aureus* is a frequent cause of empyema. * **Morphology:** In pathology, this falls under **Suppurative Inflammation**, characterized by liquefactive necrosis [1]. * **Clinical Note:** Empyema of the gallbladder is a surgical emergency often resulting from cystic duct obstruction followed by bacterial superinfection [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 191-193.

Question 309: Which of the following enzymes helps in generating reactive oxygen species intermediates in neutrophils?

A. NADPH Oxidase (Correct Answer)
B. Superoxide dismutase (SOD)
C. Catalase
D. Glutathione peroxidase

Explanation: ### Explanation **Correct Option: A. NADPH Oxidase** The generation of Reactive Oxygen Species (ROS) in neutrophils occurs via a process called the **Respiratory Burst**. The key enzyme initiating this process is **NADPH oxidase** (also known as phagocyte oxidase) [1][2]. It converts molecular oxygen ($O_2$) into the **superoxide anion** ($O_2^{ullet-}$). This superoxide is the precursor for other potent microbicidal ROS, such as hydrogen peroxide ($H_2O_2$) and the highly reactive hydroxyl radical ($OH^ullet$) [1]. **Analysis of Incorrect Options:** * **B. Superoxide Dismutase (SOD):** This enzyme actually acts as an antioxidant. It converts the superoxide anion into hydrogen peroxide ($H_2O_2$) [1][4]. While it is part of the pathway, it is considered a protective mechanism to neutralize the highly reactive superoxide. * **C. Catalase:** This is a protective antioxidant enzyme found in peroxisomes [1]. It breaks down $H_2O_2$ into water and oxygen, thereby limiting ROS-induced damage [4]. * **D. Glutathione Peroxidase:** This enzyme protects the cell from oxidative damage by reducing lipid hydroperoxides and free hydrogen peroxide using reduced glutathione [3]. **Clinical Pearls for NEET-PG:** 1. **Chronic Granulomatous Disease (CGD):** This is a high-yield clinical correlation. It is caused by a genetic deficiency in **NADPH oxidase**. Patients cannot generate a respiratory burst, leading to recurrent infections with **catalase-positive organisms** (e.g., *S. aureus*, *Aspergillus*, *Serratia*). 2. **MPO-Halide System:** Neutrophil granules contain **Myeloperoxidase (MPO)**, which converts $H_2O_2$ and $Cl^-$ into **HOCl (Hypochlorite/Bleach)**, the most potent bactericidal system in neutrophils [2]. 3. **Nitroblue Tetrazolium (NBT) Test:** Historically used to diagnose CGD; a positive test (blue color) indicates functional NADPH oxidase, while a negative test (no color change) indicates deficiency. (Note: Dihydrorhodamine/DHR flow cytometry is now the preferred test). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, p. 59. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 91. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 59-60. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 100-101.

Question 310: Activation of fibroblasts and deposition of connective tissue are orchestrated by all of the following except:

A. PDGF
B. FGF-2
C. TGF-β
D. HGF (Correct Answer)

Explanation: **Explanation:** The process of **fibrosis (scarring)** involves the migration and proliferation of fibroblasts, followed by the deposition of extracellular matrix (ECM). This is primarily driven by specific growth factors secreted by inflammatory cells (especially M2 macrophages) [1]. **Why HGF is the Correct Answer:** **HGF (Hepatocyte Growth Factor)**, despite its name, is a potent **mitogen for hepatocytes** and most epithelial cells. Crucially, in the context of tissue repair, HGF acts as an **anti-fibrotic** agent. It antagonizes the pro-fibrotic effects of TGF-β and promotes the degradation of the extracellular matrix. Therefore, it does not orchestrate the deposition of connective tissue; rather, it aids in epithelial regeneration. **Analysis of Incorrect Options:** * **TGF-β (Transforming Growth Factor-beta):** The most important cytokine involved in fibrosis. It stimulates fibroblast chemotaxis, enhances the synthesis of collagen/fibronectin, and inhibits collagen degradation by decreasing metalloproteinase (MMP) activity [1]. * **PDGF (Platelet-Derived Growth Factor):** Causes migration and proliferation of fibroblasts and smooth muscle cells [1]. It is a potent mitogen used in early wound healing. * **FGF-2 (Basic Fibroblast Growth Factor):** Promotes angiogenesis and stimulates the proliferation of fibroblasts and epithelial cells. **High-Yield Clinical Pearls for NEET-PG:** * **TGF-β** is the "master regulator" of fibrosis and is also involved in limiting the inflammatory response (anti-inflammatory) [1]. * **VEGF** is the primary driver of angiogenesis (not fibrosis). * **M2 Macrophages** are the main source of growth factors (TGF-β, PDGF) required for tissue repair and fibrosis [1]. * **Vitamin C deficiency** leads to poor collagen cross-linking (scurvy) because it is a cofactor for the hydroxylation of proline and lysine. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 115-116.

Practice by Chapter

Acute Inflammation: Vascular Events

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Acute Inflammation: Cellular Events

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Chemical Mediators of Inflammation

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Chronic Inflammation

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Granulomatous Inflammation

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Systemic Effects of Inflammation

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Wound Healing

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Tissue Regeneration

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Fibrosis and Repair

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Resolution of Inflammation

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