Inflammation and Repair — MCQs
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Which of the following families of glycoproteins plays the most important role in regulating the migration and differentiation of leukocytes and connective tissue cells during wound healing?
A 68-year-old coal miner with a history of smoking and emphysema develops severe air-flow obstruction and expires. Autopsy reveals a "black lung," with coal-dust nodules scattered throughout the parenchyma and a central area of dense fibrosis. The coal dust entrapped within this miner's lung was sequestered primarily by which of the following cells?
Which of the following is NOT responsible for the generation of Reactive Oxygen Species during Ischemia-Reperfusion Injury?
During the early stages of the inflammatory response, histamine-induced increased vascular permeability is most likely to occur in which of the following vascular structures?
Which of the following blood vessels is most likely to be affected by endothelial cell retraction?
Which of the following factors stimulates fibroblast proliferation?
Which of the following is NOT required for wound healing?
Which of the following is NOT a cause of localised idiopathic fibrosis?
What is the most important bactericidal agent?
Which of the following types of collagen is predominant in early granulation tissue?
Inflammation and Repair Indian Medical PG Practice Questions and MCQs
Question 11: Which of the following families of glycoproteins plays the most important role in regulating the migration and differentiation of leukocytes and connective tissue cells during wound healing?
- A. Cadherins
- B. Fibrillins
- C. Integrins (Correct Answer)
- D. Laminins
Explanation: **Explanation:** **1. Why Integrins are Correct:** Integrins are transmembrane heterodimeric glycoproteins (composed of $\alpha$ and $\beta$ subunits) that serve as the primary mechanical link between the intracellular cytoskeleton and the extracellular matrix (ECM) [1]. During wound healing, they play a pivotal role by: * **Migration:** Mediating the firm adhesion of leukocytes to the vascular endothelium (via ICAM-1 and VCAM-1) and facilitating their movement through the interstitial matrix [2]. * **Differentiation & Signaling:** Acting as "mechanotransducers," they relay signals from the ECM to the cell nucleus, triggering cell proliferation, differentiation of fibroblasts into myofibroblasts, and collagen synthesis [1]. **2. Why Other Options are Incorrect:** * **Cadherins (A):** These are calcium-dependent cell-to-cell adhesion molecules (e.g., E-cadherin). They maintain epithelial integrity but do not primarily mediate cell-matrix interactions or the migration of leukocytes through the ECM. * **Fibrillins (B):** These are structural glycoproteins that form the scaffold for elastin deposition. Mutations in Fibrillin-1 lead to **Marfan Syndrome**, but they do not regulate leukocyte migration. * **Laminins (D):** These are the most abundant glycoproteins in the **basement membrane**. While they provide binding sites for integrins, they act more as a structural "glue" rather than the active regulatory sensors that integrins are [1]. **Clinical Pearls for NEET-PG:** * **Leukocyte Adhesion Deficiency (LAD) Type 1:** Caused by a deficiency in **$\beta$2-integrins** (CD18), leading to impaired leukocyte migration, delayed umbilical cord separation, and recurrent bacterial infections without pus formation [3]. * **Platelet Aggregation:** The integrin **GPIIb/IIIa** is essential for platelet aggregation by binding to fibrinogen [1]. * **VLA-4 (Very Late Antigen-4):** An integrin on leukocytes that binds to VCAM-1, crucial for the recruitment of inflammatory cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 36-37. [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. Inflammation and Repair, pp. 87-89.
Question 12: A 68-year-old coal miner with a history of smoking and emphysema develops severe air-flow obstruction and expires. Autopsy reveals a "black lung," with coal-dust nodules scattered throughout the parenchyma and a central area of dense fibrosis. The coal dust entrapped within this miner's lung was sequestered primarily by which of the following cells?
- A. Endothelial cells
- B. Fibroblasts
- C. Lymphocytes
- D. Macrophages (Correct Answer)
Explanation: **Explanation:** The correct answer is **D. Macrophages**. The clinical presentation describes **Coal Worker's Pneumoconiosis (CWP)**. When coal dust (carbon pigment) is inhaled, particles smaller than 1–5 μm reach the terminal alveoli. Here, they are phagocytosed by **alveolar macrophages**, which act as the primary defense mechanism of the lung parenchyma. These macrophages ingest the dust but are often unable to digest it, leading to the accumulation of "dust cells." These cells then aggregate to form **coal macules** and **nodules** [1]. In severe cases (Progressive Massive Fibrosis), the death of these macrophages releases lysosomal enzymes and cytokines (like TNF and IL-1), triggering extensive collagen deposition and dense fibrosis [1]. **Why other options are incorrect:** * **A. Endothelial cells:** These line the blood vessels. While they are involved in leukocyte recruitment during inflammation, they do not have a primary phagocytic role in sequestering inhaled particulate matter. * **B. Fibroblasts:** These cells are responsible for secreting collagen and forming the "dense fibrosis" mentioned in the stem, but they do not engulf or sequester the coal dust itself. * **C. Lymphocytes:** These are mediators of adaptive immunity (B and T cells). While they may be present in chronic inflammation, they are not phagocytic cells. **NEET-PG High-Yield Pearls:** * **Anthracosis:** The simplest form of carbon deposition in the lungs (seen in smokers/urban dwellers); it is asymptomatic. * **Caplan Syndrome:** The combination of rheumatoid arthritis and pneumoconiosis (characteristically seen in coal miners) presenting with large pulmonary nodules. * **Centrilobular Emphysema:** The specific type of emphysema most commonly associated with coal dust inhalation and smoking. * **Stain:** Carbon pigment is easily identified as it is **non-refractile** and does not stain with Prussian Blue (unlike hemosiderin). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 331-332.
Question 13: Which of the following is NOT responsible for the generation of Reactive Oxygen Species during Ischemia-Reperfusion Injury?
- A. Incomplete redox reactions by damaged mitochondria
- B. Compromised cellular antioxidant defense mechanisms
- C. Infiltrating leukocytes
- D. Activation of the complement system (Correct Answer)
Explanation: ### Explanation **Ischemia-Reperfusion Injury (IRI)** occurs when blood flow is restored to tissues after a period of ischemia. While restoration of flow is essential, it paradoxically exacerbates tissue damage through the sudden burst of **Reactive Oxygen Species (ROS)** and inflammation [1,5]. **Why Option D is the Correct Answer:** While the **Activation of the complement system** is a hallmark of reperfusion injury [1], it is a mediator of the **inflammatory response**, not a direct source of ROS generation. Complement proteins (like C3a and C5a) act as chemoattractants for neutrophils and cause cell lysis via the Membrane Attack Complex (MAC). Although complement activation *recruits* cells that produce ROS, the biochemical process of complement activation itself does not generate free radicals [1]. **Analysis of Incorrect Options (Sources of ROS):** * **A. Damaged Mitochondria:** During ischemia, the electron transport chain is disrupted. Upon reperfusion, oxygen returns to these "leaky" mitochondria, leading to incomplete reduction of $O_2$ and the formation of superoxide radicals ($O_2^{\bullet-}$) [3,4,5]. * **B. Compromised Antioxidant Defenses:** Ischemia depletes cellular antioxidants like glutathione and superoxide dismutase (SOD) [3,4]. When reperfusion occurs, the cell cannot neutralize the sudden influx of free radicals. * **C. Infiltrating Leukocytes:** Reperfusion triggers an influx of neutrophils. These cells utilize the enzyme **NADPH oxidase** (phagocyte oxidase) to produce ROS during the "respiratory burst" to eliminate perceived threats [2,4]. **High-Yield Clinical Pearls for NEET-PG:** * **Xanthine Oxidase:** A major source of ROS in IRI. During ischemia, ATP breakdown leads to hypoxanthine accumulation; upon reperfusion, xanthine oxidase uses $O_2$ to convert hypoxanthine to uric acid, releasing superoxide as a byproduct. * **Mitochondrial Permeability Transition Pore (MPTP):** ROS and calcium overload cause this pore to open, leading to ATP depletion and apoptosis [5]. * **Key ROS:** Superoxide ($O_2^{\bullet-}$), Hydrogen peroxide ($H_2O_2$), and the highly reactive Hydroxyl radical ($OH^\bullet$) [2,4]. **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, pp. 62-63. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 91. [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. 100-101. [4] 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. [5] 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. 102-103.
Question 14: During the early stages of the inflammatory response, histamine-induced increased vascular permeability is most likely to occur in which of the following vascular structures?
- A. Arteries
- B. Precapillary arterioles
- C. Capillaries
- D. Postcapillary venules (Correct Answer)
Explanation: ### Explanation The hallmark of acute inflammation is increased vascular permeability, leading to the formation of an exudate. **Why Postcapillary Venules are the Correct Answer:** Histamine is the primary mediator of the **immediate transient response** (occurring 30–60 minutes after injury) [1]. It acts by binding to H1 receptors on endothelial cells, causing **endothelial cell contraction** [1]. This contraction creates intercellular gaps that allow fluid and proteins to leak out. This specific mechanism occurs almost exclusively in the **postcapillary venules** because these vessels have the highest density of histamine receptors and a unique cytoskeletal structure that facilitates gap formation compared to other segments of the microvasculature [1]. **Analysis of Incorrect Options:** * **Arteries and Precapillary Arterioles (A & B):** These vessels are primarily involved in vasodilation (mediated by Nitric Oxide and Prostaglandins) to increase blood flow (rubor and calor) [2]. Their thick smooth muscle layer and tight endothelial junctions make them resistant to the gap formation induced by histamine. * **Capillaries (C):** While capillaries can become leaky in cases of **direct endothelial injury** (e.g., severe burns or bacterial toxins), they are generally not the primary site for mediator-induced (histamine) leakage [1]. **NEET-PG High-Yield Pearls:** * **Immediate Transient Response:** Mediated by Histamine, Bradykinin, and Leukotrienes; affects only **postcapillary venules** [1]. * **Delayed Prolonged Leakage:** Occurs 2–12 hours later (e.g., sunburn); involves **capillaries and venules**. * **Leukocyte Adhesion:** The postcapillary venule is also the primary site for leukocyte extravasation (margination, rolling, and adhesion) [3]. * **Mechanism:** Remember that histamine causes **contraction** (active) of endothelial cells, not "retraction" (which is a slower reorganization of the cytoskeleton mediated by cytokines like TNF and IL-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. 187-188. [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. Migration in the tissues toward a chemotactic stimulus, pp. 86-87.
Question 15: Which of the following blood vessels is most likely to be affected by endothelial cell retraction?
- A. Venules (Correct Answer)
- B. Capillaries
- C. Arterioles
- D. None of the above
Explanation: **Explanation:** The correct answer is **Venules**. **1. Why Venules are the correct answer:** Endothelial cell retraction is the most common mechanism of increased vascular permeability in acute inflammation [1]. It is mediated by chemical mediators like **histamine, bradykinin, and leukotrienes**. These mediators bind to specific receptors located predominantly on the endothelial cells of **post-capillary venules** [1][2]. This binding triggers a signaling cascade (involving phosphorylation of contractile proteins like myosin), causing the cells to contract and create intercellular gaps [1]. Because the receptor density for these primary inflammatory mediators is highest in the venules, this is the primary site of "immediate transient leakage" [1]. **2. Why other options are incorrect:** * **Capillaries:** While capillaries can leak due to direct endothelial injury (e.g., burns or toxins), they generally lack the specific receptor-mediated contractile machinery required for "retraction" in response to histamine [1]. * **Arterioles:** Arterioles are resistance vessels with a thick smooth muscle layer. Their primary role in inflammation is vasodilation (mediated by nitric oxide and prostaglandins) to increase blood flow (hyperemia), rather than increasing permeability through endothelial retraction. **3. High-Yield Facts for NEET-PG:** * **Immediate Transient Response:** Endothelial retraction occurs rapidly (within minutes) and is short-lived (15–30 minutes) [1]. * **Immediate Sustained Response:** Caused by direct endothelial cell necrosis (e.g., severe burns); affects **all** levels of microvasculature (venules, capillaries, and arterioles). * **Delayed Prolonged Leakage:** Occurs 2–12 hours after injury (e.g., sunburn); involves capillaries and venules. * **Key Mediator:** Histamine is the classic prototype mediator for venular endothelial retraction [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. 187-188. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101.
Question 16: Which of the following factors stimulates fibroblast proliferation?
- A. TGF-β (Correct Answer)
- B. IFN-γ
- C. TNF-α
- D. IL-10
Explanation: **Explanation:** **Correct Answer: A. TGF-̢ (Transforming Growth Factor-beta)** TGF-̢ is the most important cytokine involved in tissue repair and fibrosis [1]. It acts as a potent **fibrogenic agent** by stimulating fibroblast chemotaxis, inducing fibroblast proliferation, and increasing the synthesis of collagen and fibronectin [1]. Simultaneously, it inhibits the degradation of the extracellular matrix (ECM) by decreasing the activity of metalloproteinases. In chronic inflammation, persistent TGF-̢ signaling leads to excessive deposition of collagen, resulting in organ fibrosis. **Analysis of Incorrect Options:** * **B. IFN-̣ (Interferon-gamma):** This is a major macrophage activator (M1 pathway). Crucially, it is **antifibrotic**; it inhibits fibroblast proliferation and collagen synthesis. * **C. TNF-̡ (Tumor Necrosis Factor-alpha):** While TNF-̡ is a potent pro-inflammatory cytokine that activates endothelial cells and leukocytes, its primary role is in acute inflammation and apoptosis rather than direct fibroblast proliferation. * **D. IL-10:** This is an **anti-inflammatory** cytokine produced by M2 macrophages and Th2 cells [1]. It serves to downregulate the inflammatory response rather than stimulate the proliferative phase of repair. **High-Yield Clinical Pearls for NEET-PG:** * **TGF-̢ Dual Role:** It is anti-inflammatory (terminates the inflammatory response) but pro-fibrotic (stimulates scarring). * **M2 Macrophages:** These are the primary source of TGF-̢ and IL-10 during the repair phase of inflammation [1]. * **Scar Formation Sequence:** Angiogenesis → Migration and proliferation of fibroblasts → Deposition of ECM → Remodeling (maturation) [1]. * **Vitamin C:** Essential for the hydroxylation of proline and lysine residues during collagen synthesis; deficiency leads to poor wound healing. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 113-116.
Question 17: Which of the following is NOT required for wound healing?
- A. Vitamin C
- B. Copper
- C. Methionine
- D. Sodium (Correct Answer)
Explanation: **Explanation:** Wound healing is a complex process involving inflammation, proliferation (granulation tissue formation), and remodeling [2]. This process requires specific vitamins, minerals, and amino acids as cofactors for collagen synthesis and cross-linking [3]. **Why Sodium is the Correct Answer:** **Sodium** is the primary extracellular cation responsible for maintaining osmotic pressure and fluid balance. While essential for general cellular homeostasis and nerve conduction, it plays **no direct biochemical role** in the synthesis of collagen, the migration of fibroblasts, or the enzymatic reactions specific to wound repair. **Analysis of Incorrect Options:** * **Vitamin C (Ascorbic Acid):** Essential for the **hydroxylation of proline and lysine** residues during collagen synthesis [3]. Deficiency leads to scurvy, characterized by poor wound healing and capillary fragility. * **Copper:** A vital cofactor for the enzyme **lysyl oxidase**, which facilitates the cross-linking of collagen and elastin fibers, providing tensile strength to the healing tissue [1]. * **Methionine:** An essential sulfur-containing amino acid. It is a precursor to **cysteine**, which is crucial for connective tissue synthesis and serves as a methyl donor in various metabolic pathways required for cell proliferation. **High-Yield Clinical Pearls for NEET-PG:** * **Zinc:** Often tested; it is a cofactor for **collagenase** (Matrix Metalloproteinases), essential for remodeling and epithelialization [1]. * **Tensile Strength:** At the end of 1 week, wound strength is ~10% [4]. It reaches a maximum of **70-80%** by 3 months; it never returns to 100%. * **Glucocorticoids:** These inhibit wound healing by reducing TGF-β production and decreasing collagen synthesis [3]. * **Vitamin A:** Can counteract the inhibitory effects of steroids on wound healing. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Central Nervous System Synapse, pp. 450-451. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 116-117. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121.
Question 18: Which of the following is NOT a cause of localised idiopathic fibrosis?
- A. Riedel's struma
- B. Hypertrophic scar (Correct Answer)
- C. Sclerosing cholangitis
- D. Panniculitis
Explanation: **Explanation:** The core concept behind this question is the distinction between **Idiopathic Localised Fibrosis** (often grouped under the umbrella of IgG4-related diseases or fibroinflammatory disorders) and **Reactive Fibrosis**. **Why Hypertrophic Scar is the correct answer:** A **hypertrophic scar** is not idiopathic; it is a known, reactive process resulting from an exaggerated physiological response to **cutaneous injury** (trauma, surgery, or burns) [1]. It is characterized by excessive collagen deposition (primarily Type III) that remains within the boundaries of the original wound. Since the inciting cause (trauma) is known, it cannot be classified as "idiopathic." **Analysis of Incorrect Options:** * **Riedel’s Struma:** A rare form of chronic thyroiditis where the thyroid parenchyma is replaced by dense fibrous tissue. It is considered a localized idiopathic fibrotic process and is now often linked to IgG4-related disease. * **Sclerosing Cholangitis:** Primary Sclerosing Cholangitis (PSC) involves idiopathic inflammation and obliterative fibrosis of the bile ducts. It is a classic example of localized idiopathic fibrosis. * **Panniculitis:** Specifically, **Mesenteric Panniculitis** (Sclerosing Mesenteritis) is an idiopathic primary fibrotic process affecting the adipose tissue of the mesentery. **High-Yield Clinical Pearls for NEET-PG:** * **IgG4-Related Disease (IgG4-RD):** Many conditions previously called "idiopathic fibrosis" (e.g., Ormond’s disease/Retroperitoneal fibrosis, Riedel’s thyroiditis, Mikulicz syndrome) are now recognized as part of this systemic spectrum. * **Histology of IgG4-RD:** Look for "Storiform" fibrosis, obliterative phlebitis, and dense lymphoplasmacytic infiltrate. * **Hypertrophic Scar vs. Keloid:** Hypertrophic scars stay within wound boundaries and may regress; Keloids extend beyond boundaries, contain thick "glassy" collagen, and rarely regress [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121.
Question 19: What is the most important bactericidal agent?
- A. Cationic basic protein
- B. Lactoferrin
- C. Lysozyme
- D. Reactive oxygen species (Correct Answer)
Explanation: **Explanation:** The killing of microorganisms within phagocytes occurs primarily through two mechanisms: oxygen-dependent and oxygen-independent. [1] **Why Reactive Oxygen Species (ROS) is the correct answer:** The **oxygen-dependent mechanism** is the most potent and important bactericidal system in neutrophils. [1] It involves the "Respiratory Burst," where oxygen is rapidly converted into the **Superoxide radical ($O_2^\bullet-$)** by NADPH oxidase. [2] This is further converted to **Hydrogen peroxide ($H_2O_2$)**. In the presence of the enzyme **Myeloperoxidase (MPO)** and a halide (like Chloride), $H_2O_2$ is converted into **Hypochlorite ($HOCl^\bullet$)**. [1] Hypochlorite is the most powerful bactericidal agent in the neutrophil’s arsenal, acting via lipid peroxidation and protein oxidation. [1] **Analysis of Incorrect Options:** * **A. Cationic basic proteins:** These include defensins and major basic protein (MBP). While they damage microbial membranes, they are part of the oxygen-independent pathway and are less potent than ROS. * **B. Lactoferrin:** An iron-binding protein found in specific granules. It inhibits bacterial growth by sequestering iron (nutritional immunity) but is bacteriostatic rather than a primary bactericidal agent. * **C. Lysozyme:** An enzyme that degrades the glycopeptide coat of bacterial cell walls (muramidase). It is effective mainly against specific gram-positive bacteria and is less versatile than ROS. **Clinical Pearls for NEET-PG:** * **Chronic Granulomatous Disease (CGD):** Caused by a deficiency in **NADPH oxidase**. Patients cannot produce ROS, leading to recurrent infections with catalase-positive organisms (e.g., *S. aureus*). [2] * **Nitroblue Tetrazolium (NBT) Test:** Used to diagnose CGD. Normal cells turn blue (positive), while CGD cells remain colorless (negative). * **MPO Deficiency:** Most patients are asymptomatic because the $H_2O_2$ system remains intact, though it takes longer to kill microbes. [3] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 91. [2] 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. [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. 100-101.
Question 20: Which of the following types of collagen is predominant in early granulation tissue?
- A. Type 1 and 2
- B. Type 1 and 3 (Correct Answer)
- C. Type 2 and 3
- D. Type 1 and 4
Explanation: ### Explanation **Correct Answer: B. Type 1 and 3** **Understanding the Concept:** Granulation tissue is the hallmark of early wound healing (repair by secondary union). It consists of new thin-walled capillaries (angiogenesis), fibroblasts, and a provisional extracellular matrix [1, 2]. * **Type 3 Collagen:** This is the "embryonic" or "early" collagen. It is synthesized rapidly by fibroblasts during the initial phases of wound healing because its structure allows for flexibility and rapid remodeling [2]. * **Type 1 Collagen:** This is the most abundant collagen in the body and provides high tensile strength. As the wound matures, Type 3 collagen is replaced by Type 1 collagen through the action of **matrix metalloproteinases (MMPs)** [2]. While Type 3 is the *characteristic* collagen of early granulation tissue, Type 1 is also present as the primary structural component of the dermis and surrounding tissue. Therefore, the combination of Type 1 and 3 represents the collagenous profile of a healing wound. **Why Other Options are Wrong:** * **Type 2:** Found primarily in **cartilage** and vitreous humor. It is not a significant component of skin repair or granulation tissue. * **Type 4:** Found in **basement membranes**. While present in the basement membranes of the new capillaries within granulation tissue, it is not the "predominant" structural collagen of the matrix. **High-Yield Clinical Pearls for NEET-PG:** * **Collagen Switch:** In wound healing, the ratio of Type 3 to Type 1 is high initially. In a mature scar, Type 1 predominates (providing 80% of skin strength). * **Vitamin C:** Essential for the hydroxylation of proline and lysine residues; deficiency leads to scurvy and poor wound healing. * **Zinc:** A necessary cofactor for **MMPs**, which are required for the remodeling of Type 3 collagen into Type 1 [2]. * **Keloids:** Characterized by an excess of Type 1 and Type 3 collagen (disorganized thick bundles) [1, 3]. **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. 117-119. [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. 106-107.
Practice by Chapter
Acute Inflammation: Vascular Events
Practice Questions
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
Practice Questions
Wound Healing
Practice Questions
Tissue Regeneration
Practice Questions
Fibrosis and Repair
Practice Questions
Resolution of Inflammation
Practice Questions
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