Inflammation and Repair — MCQs

A 60-year-old man presents with acute liver failure and undergoes successful orthotopic liver transplantation. For the first 3 days post-transplant, the graft exhibits poor function, characterized by minimal bile production. This poor graft function is attributed to reperfusion injury. Which of the following substances is the most likely cause of reperfusion injury in this transplanted liver?

Inflammation and Repair Indian Medical PG Practice Questions and MCQs

Question 161: Which of the following is true with regards to wound healing?

A. Collagen type I is gradually replaced by collagen type III in wound healing.
B. Wound strength is 70% after 4 weeks of wound healing.
C. Myofibroblasts may lead to large skin defects being reduced to 5% to 10% of their original size within 6 weeks. (Correct Answer)
D. Maximum wound strength is achieved after 2 years.

Explanation: **Explanation:** **Correct Answer: C** Wound contraction is a critical phase of healing by secondary intention. It is mediated by **myofibroblasts**, which are modified fibroblasts containing smooth muscle-like actin filaments [1]. These cells migrate to the wound margins and physically pull the edges together [2]. In large open wounds, this process is highly efficient, often reducing the surface area of the defect to **5% to 10% of its original size within approximately 6 weeks.** [1] **Analysis of Incorrect Options:** * **Option A:** The sequence is reversed. Initially, **Type III collagen** (granulation tissue) is synthesized. During the remodeling phase, it is gradually replaced by the stronger, more mature **Type I collagen**. * **Option B:** At the end of **1 week** (when sutures are removed), wound strength is ~10% [1]. It increases rapidly over the next 4 weeks. By **3 months (12 weeks)**, it reaches approximately **70-80%**. It rarely reaches 70% as early as 4 weeks. * **Option D:** Maximum wound strength is generally achieved by **3 months**. While remodeling continues for months, the strength typically plateaus at about **70% to 80%** of original unwounded skin; it rarely ever returns to 100%. **High-Yield Clinical Pearls for NEET-PG:** * **Collagen Switch:** Type III (Early/Weak) → Type I (Late/Strong). *Mnemonic: "III comes before I in Roman numerals, but I is stronger." * **Vitamin C:** Essential for the hydroxylation of proline and lysine residues during collagen synthesis; deficiency leads to scurvy and poor wound healing. * **Zinc:** A necessary cofactor for **Matrix Metalloproteinases (MMPs)**, which are essential for remodeling the extracellular matrix. * **Steroids:** Inhibit wound healing by reducing TGF-β production and decreasing collagen synthesis. **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 162: Which of the following is NOT an adhesion molecule?

A. Spectrin (Correct Answer)
B. Integrins
C. Selectins
D. Cadherin

Explanation: **Explanation:** The process of leukocyte extravasation and tissue architecture relies on specific **Cell Adhesion Molecules (CAMs)**. **Why Spectrin is the correct answer:** **Spectrin** is not an adhesion molecule; it is a high-molecular-weight **cytoskeletal protein** located on the inner surface of the erythrocyte plasma membrane [1]. It forms a hexagonal meshwork that maintains the structural integrity and biconcave shape of RBCs. Mutations in spectrin lead to **Hereditary Spherocytosis**, where RBCs become fragile and are sequestered by the spleen [1]. **Analysis of other options (CAMs):** * **Selectins (Option C):** These mediate the initial **"rolling"** phase of leukocyte recruitment [2]. Examples include L-selectin (leukocytes), E-selectin (endothelium), and P-selectin (platelets/endothelium). * **Integrins (Option B):** These are transmembrane glycoproteins responsible for **firm adhesion** of leukocytes to the endothelium [3]. They are activated by chemokines and bind to ligands like ICAM-1 and VCAM-1 [2]. * **Cadherins (Option D):** These are calcium-dependent adhesion molecules that maintain **cell-to-cell junctions** (e.g., E-cadherin in epithelial tissues). A loss of E-cadherin is a hallmark of Epithelial-Mesenchymal Transition (EMT) in cancer metastasis. **High-Yield NEET-PG Pearls:** 1. **Leukocyte Adhesion Deficiency (LAD) Type 1:** Caused by a defect in the **CD18 subunit of integrins**, leading to impaired firm adhesion and delayed umbilical cord separation. 2. **LAD Type 2:** Caused by a defect in **Sialyl-Lewis X** (ligand for selectins), impairing the rolling phase. 3. **P-selectin** is stored in **Weibel-Palade bodies** of endothelial cells and alpha-granules of platelets. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 640-641. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 87. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 36-37.

Question 163: Which of the following are considered acute phase reactants of inflammation?

A. Haptoglobin
B. C-reactive protein (CRP)
C. Transferrin
D. All of the above (Correct Answer)

Explanation: **Explanation:** Acute Phase Reactants (APRs) are proteins whose plasma concentrations increase or decrease by at least 25% during inflammatory states [1]. This systemic response is primarily mediated by cytokines like **IL-6, IL-1, and TNF-̑**, which stimulate the liver to alter protein synthesis [1][2]. * **C-reactive protein (CRP):** A classic **positive APR** [1]. It acts as an opsonin, binding to phosphocholine on microbes and fixing complement to facilitate phagocytosis. It is a sensitive but non-specific marker of systemic inflammation. * **Haptoglobin:** A **positive APR**. Its primary role is to bind free hemoglobin to prevent iron loss and oxidative damage. Its levels rise during inflammation but decrease during hemolytic anemia. * **Transferrin:** Traditionally classified as a **negative APR** [3]. While positive APRs increase, negative APRs decrease during inflammation to sequester nutrients (like iron) away from microbes. However, in the context of many medical examinations (including some interpretations of this question), all proteins that significantly shift in concentration during the acute phase response are categorized under the broad umbrella of "Acute Phase Reactants." **Clinical Pearls for NEET-PG:** * **Positive APRs (Increase):** "SHARK" mnemonic – **S**erum Amyloid A, **H**aptoglobin, **A**ntitrypsin (̑1), **R**eactive protein (CRP), **K**oagulation factors (Fibrinogen, Ferritin). * **Negative APRs (Decrease):** Albumin, Transferrin, and Transthyretin (Pre-albumin). * **ESR vs. CRP:** CRP rises and falls rapidly (hours), making it a better marker for acute changes, whereas ESR (driven by fibrinogen) changes more slowly (days). * **Ferritin:** Is a positive APR; this is why high ferritin levels in inflammatory states do not always reflect true iron overload. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 111. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 110-111. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 657-658.

Question 164: Which of the following statements about fibrinous exudate is FALSE?

A. It is associated with many types of severe inflammation
B. It has low protein content (Correct Answer)
C. It has fibrin precipitates
D. It induces connective tissue organization

Explanation: ### Explanation **Why Option B is the correct answer (The False Statement):** Fibrinous exudate is a hallmark of **severe inflammation** where vascular permeability increases significantly. This allows large molecular weight proteins, such as **fibrinogen**, to leak out of the blood vessels into the extravascular space. Once outside, fibrinogen is converted into **fibrin** by the activation of the coagulation cascade. Therefore, fibrinous exudate is characterized by **high protein content**, specifically fibrin. A fluid with low protein content and low cellularity is termed a *transudate* or *serous effusion*, not a fibrinous exudate. **Analysis of Incorrect Options:** * **Option A:** True. Fibrinous exudate occurs in more severe inflammatory responses compared to serous inflammation, often involving body cavities like the pericardium, pleura, or meninges [1]. * **Option C:** True. The histological hallmark is the presence of eosinophilic (pink) threads or amorphous clumps of precipitated fibrin [1]. * **Option D:** True. If the fibrin is not removed (fibrinolysis) by macrophages, it serves as a scaffold for the ingrowth of fibroblasts and blood vessels [1], [2]. This process is called **organization**, which leads to the formation of fibrous scar tissue (e.g., pericardial adhesions) [1]. **NEET-PG High-Yield Pearls:** * **Bread and Butter Appearance:** This is the classic gross description of fibrinous pericarditis (e.g., in Rheumatic Heart Disease or Uremia). * **Serous vs. Fibrinous:** Serous exudate is protein-poor (watery); Fibrinous exudate is protein-rich (thick/sticky). * **Outcome:** Resolution (via fibrinolysis) or Organization (via scarring/adhesions). Organization of fibrinous pericarditis can lead to **constrictive pericarditis**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 101-103. [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. 194-195.

Question 165: What is the average time taken for myocardial infarction to heal completely?

A. 3 weeks
B. 6 weeks (Correct Answer)
C. 12 weeks
D. 12 weeks

Explanation: **Explanation:** The healing of a Myocardial Infarction (MI) is a classic example of **healing by repair (scarring)** because cardiac myocytes are permanent cells and lack the capacity to regenerate. The process follows a predictable chronological sequence of inflammation, granulation tissue formation, and collagen deposition. **Why 6 weeks is correct:** The replacement of necrotic myocardium by a firm, white fibrous scar typically takes **6 to 8 weeks** [1]. By the end of the second week, granulation tissue is well-established. Over the subsequent weeks, there is increased collagen deposition and decreased vascularity. By the 6th week, the infarct area is replaced by dense collagenous connective tissue (mature scar), marking the completion of the healing process. **Analysis of Incorrect Options:** * **3 weeks:** At this stage, the healing is midway. There is prominent collagen deposition and regression of capillaries, but the scar is not yet fully matured or "complete" [1]. * **12 weeks:** While the scar may undergo further contraction and remodeling over several months, the structural healing process is considered complete by 6–8 weeks. 12 weeks is unnecessarily long for the primary repair phase. **NEET-PG High-Yield Pearls:** 1. **Earliest Change:** The first gross change (pallor) is seen at 12–24 hours [1]. The first microscopic change (wavy fibers) can appear within 1–3 hours [2]. 2. **Contraction Band Necrosis:** Occurs due to reperfusion injury (calcium influx) [2]. 3. **Most Common Time for Rupture:** Ventricular free wall rupture, septal rupture, or papillary muscle rupture typically occurs between **3 to 7 days** post-MI, when the tissue is softest (yellow softening) due to maximal macrophage activity and proteolysis [2]. 4. **Staining:** Triphenyltetrazolium chloride (TTC) stain is used to identify infarcted areas macroscopically (infarct remains unstained/pale; viable tissue turns red) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, pp. 552-554. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, p. 552.

Question 166: Which of the following statements regarding wound healing is correct?

A. Wound healing is impaired in anemic patients.
B. Wound healing is not impaired by hypoproteinemia.
C. Wound healing is stimulated by steroids.
D. Wound healing is more rapid in young than in old individuals. (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Wound healing is more rapid in young than in old individuals.** Wound healing is a complex biological process that involves cell proliferation, collagen synthesis, and remodeling. In **younger individuals**, the metabolic rate is higher, the microcirculation is more robust, and the regenerative capacity of stem cells is superior. As age increases, there is a physiological decline in collagen synthesis, slower re-epithelialization, and a delayed inflammatory response, making healing significantly faster in the young. **Analysis of Incorrect Options:** * **A. Wound healing is impaired in anemic patients:** This is generally **incorrect** in the context of pure anemia. Studies show that as long as blood volume is maintained (normovolemia), mild to moderate anemia does not significantly impair wound healing because oxygen dissociation curves shift to maintain tissue oxygenation. However, severe anemia or anemia associated with poor perfusion can have an impact. * **B. Wound healing is not impaired by hypoproteinemia:** This is **incorrect**. Proteins (especially amino acids like methionine and cystine) are essential for collagen synthesis and cellular proliferation. Hypoproteinemia (e.g., in malnutrition or nephrotic syndrome) significantly delays healing and increases the risk of wound dehiscence [1]. * **C. Wound healing is stimulated by steroids:** This is **incorrect**. Glucocorticoids are potent **inhibitors** of wound healing [1]. They suppress the inflammatory phase, inhibit collagen synthesis by fibroblasts, and weaken the resulting scar [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Vitamin C Deficiency (Scurvy):** Leads to defective collagen cross-linking (proline hydroxylation), causing wound dehiscence [1]. * **Zinc Deficiency:** Impairs DNA synthesis and cell division, leading to delayed epithelialization. * **Diabetes Mellitus:** The most common systemic cause of impaired wound healing due to microangiopathy and impaired neutrophil function [1]. * **Tensile Strength:** At the end of 1 week, wound strength is ~10%; it reaches a maximum of **70-80%** of original strength by 3 months. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 116-117.

Question 167: Immune granulomas are not seen in which of the following conditions?

A. Tuberculosis
B. Syphilis
C. Silicosis (Correct Answer)
D. Berylliosis

Explanation: **Explanation:** Granulomas are classified into two types based on their pathogenesis: **Immune granulomas** and **Foreign body granulomas**. [1] **1. Why Silicosis is the correct answer:** Silicosis is characterized by **foreign body granulomas**. These form when inert particles (like silica) are too large or indigestible for a single macrophage to eliminate [1], but do not necessarily incite a specific T-cell mediated immune response. In silicosis, macrophages ingest silica, which then causes lysosomal rupture and macrophage death, leading to the release of fibrogenic cytokines. Under polarized light, silica particles appear birefringent, and the granuloma typically lacks the organized "cuff" of T-lymphocytes seen in immune types. **2. Why the other options are incorrect:** * **Tuberculosis (A):** The classic example of an immune granuloma. It involves a **Type IV Hypersensitivity** reaction [2] where macrophages present antigens to T-cells, leading to the formation of caseating granulomas. * **Syphilis (B):** Forms a specific type of immune granuloma called a **Gumma**. It is characterized by a central necrotic area (rubbery) surrounded by plasma cells and lymphocytes. * **Berylliosis (D):** Unlike other inorganic dusts, beryllium acts as a hapten and induces a **cell-mediated immune response** [1], resulting in non-caseating immune granulomas (similar to Sarcoidosis). **NEET-PG High-Yield Pearls:** * **Immune Granuloma Key:** Requires a persistent T-cell mediated immune response (IL-2, IFN-γ). [2] * **Foreign Body Granuloma Key:** Lacks a significant T-cell response; characterized by "foreign body giant cells" with haphazardly arranged nuclei (unlike the peripheral horseshoe arrangement in Langhans giant cells). * **Schistosoma haematobium:** A classic cause of immune granulomas in response to parasite eggs. **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. 198-200. [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. 173-174.

Question 168: A wedge-shaped area in the adrenal gland is affected. On histopathology, the nucleus is not seen but cellular outlines are intact. Which type of necrosis is being described?

A. Coagulative (Correct Answer)
B. Liquefactive
C. Fibrinoid
D. Caseous

Explanation: **Explanation:** The description provided is the classic histopathological hallmark of **Coagulative Necrosis**. **1. Why Coagulative Necrosis is correct:** Coagulative necrosis typically occurs due to sudden ischemia (infarction) in solid organs (except the brain) [3]. The "wedge-shaped" area indicates a vascular territory supplied by a single artery [1,2]. The key pathological feature is the **denaturation of structural proteins and enzymes**. Because digestive enzymes are also denatured, proteolysis is delayed. This results in **"Tombstone cells"**—where the nucleus is lost (karyolysis), but the basic **cellular architecture and outlines are preserved** for several days [3]. **2. Why other options are incorrect:** * **Liquefactive Necrosis:** Characterized by complete digestion of dead cells, resulting in a liquid viscous mass (pus). It is typical of brain infarcts and bacterial/fungal infections [2]. Cellular outlines are **never** preserved. * **Fibrinoid Necrosis:** Usually seen in immune-mediated vascular damage (e.g., Polyarteritis Nodosa). It involves the deposition of immune complexes and fibrin in arterial walls, appearing as bright pink, amorphous material. * **Caseous Necrosis:** Characteristic of Tuberculosis. It presents as a "cheese-like" friable white appearance macroscopically. Microscopically, it shows a granuloma with a central area of **amorphous debris** where cellular outlines are completely lost. **Clinical Pearls for NEET-PG:** * **Exception Rule:** Ischemia to all solid organs causes coagulative necrosis **EXCEPT the brain** (which undergoes liquefactive necrosis) [2]. * **Mechanism:** Acidosis denatures proteins and blocks proteolysis. * **Adrenal Infarction:** Often associated with Waterhouse-Friderichsen syndrome (though usually hemorrhagic). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, p. 140. [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. 148-149. [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. 53-55.

Question 169: What is the first change seen in acute inflammation?

A. Increased permeability
B. Vasodilation
C. Neutrophil migration
D. Vasoconstriction (Correct Answer)

Explanation: **Explanation:** In acute inflammation, the vascular response follows a highly specific chronological sequence. **1. Why Vasoconstriction is the Correct Answer:** The **immediate** response to tissue injury is **transient vasoconstriction** of the arterioles. This is a neurogenic reflex mediated by the autonomic nervous system and lasts only for a few seconds to minutes. While it is the very first change to occur, it is often fleeting and is quickly superseded by the more clinically significant phase of vasodilation. **2. Analysis of Incorrect Options:** * **B. Vasodilation:** This is the **first clinically significant** or "functional" change [1]. It follows vasoconstriction and is mediated by histamine and nitric oxide. It leads to increased blood flow (hyperemia), causing the classic signs of redness (*rubor*) and heat (*calor*) [2]. * **A. Increased Permeability:** This occurs after vasodilation [1]. It is the hallmark of acute inflammation, leading to the formation of protein-rich exudate (edema/swelling) [3]. * **C. Neutrophil Migration:** This is a cellular event that occurs later in the sequence (peaking at 6–24 hours) after the initial vascular changes have facilitated leukocyte margination and rolling. **3. NEET-PG High-Yield Pearls:** * **Sequence of Vascular Changes:** Transient vasoconstriction → Persistent vasodilation → Increased vascular permeability → Stasis → Leukocyte margination. * **Hallmark of Acute Inflammation:** Increased vascular permeability (leading to exudate) [1]. * **Most Common Mechanism of Permeability:** Endothelial cell contraction (mediated by histamine, bradykinin, and leukotrienes), primarily affecting **post-capillary venules** [3]. * **Key Distinction:** If the question asks for the "first change," the answer is **Vasoconstriction**. If it asks for the "first hemodynamic/functional change," the answer is **Vasodilation** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85. [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. 185-186. [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. 187-188.

Question 170: A 60-year-old man presents with acute liver failure and undergoes successful orthotopic liver transplantation. For the first 3 days post-transplant, the graft exhibits poor function, characterized by minimal bile production. This poor graft function is attributed to reperfusion injury. Which of the following substances is the most likely cause of reperfusion injury in this transplanted liver?

A. Cationic proteins
B. Free ferric iron
C. Hydrochlorous acid
D. Reactive oxygen species (Correct Answer)

Explanation: **Explanation:** **Correct Answer: D. Reactive Oxygen Species (ROS)** Reperfusion injury occurs when blood flow is restored to tissues that have undergone a period of ischemia (as seen in organ transplantation). During the ischemic phase, cells accumulate breakdown products of ATP (like hypoxanthine). Upon restoration of blood flow, the sudden influx of oxygen reacts with these metabolites via enzymes like xanthine oxidase, leading to a "burst" of **Reactive Oxygen Species (ROS)** such as superoxide radicals ($O_2^-$), hydrogen peroxide ($H_2O_2$), and hydroxyl radicals ($OH^•$) [1]. These ROS cause lipid peroxidation of membranes, protein oxidation, and DNA damage, leading to graft dysfunction [1]. **Analysis of Incorrect Options:** * **A. Cationic proteins:** These are found in neutrophil granules (e.g., MBP) and are primarily involved in killing parasites or extracellular bacteria, not the primary mediation of reperfusion injury. * **B. Free ferric iron:** While iron ($Fe^{2+}$) can facilitate the **Fenton reaction** to produce hydroxyl radicals, it is a catalyst rather than the primary substance generated during the reperfusion burst. * **C. Hypochlorous acid (HOCl):** This is produced by the enzyme **Myeloperoxidase (MPO)** in neutrophils. While it contributes to inflammation, the initial and most significant damage in reperfusion is driven by the broader category of ROS. **NEET-PG High-Yield Pearls:** * **The "Oxygen Paradox":** Reintroducing oxygen to ischemic tissue can paradoxically cause more damage than the ischemia itself. * **Mitochondrial Role:** Ischemia damages mitochondria, leading to incomplete reduction of oxygen and further ROS leakage during reperfusion [1]. * **Antioxidant Defense:** Enzymes like **Superoxide Dismutase (SOD)**, **Catalase**, and **Glutathione Peroxidase** are the body’s primary defenses against ROS-mediated injury [1]. * **Clinical Correlation:** Reperfusion injury is a major cause of "primary non-function" or "delayed graft function" in solid organ transplants. **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. 100-101.

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

Practice Questions

Systemic Effects of Inflammation

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Wound Healing

Practice Questions

Tissue Regeneration

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Fibrosis and Repair

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Resolution of Inflammation

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