Inflammation and Repair — MCQs
On this page
COX-2 primarily inhibits which step in inflammation?
A 59-year-old man experiences acute chest pain and is rushed to the emergency room. Laboratory studies and ECG demonstrate an acute myocardial infarction. Coronary artery angiography performed 2 hours later does not show evidence of thrombosis. Which of the following mediators of inflammation causes relaxation of vascular smooth muscle cells and vasodilation of arterioles at the site of myocardial infarction?
A 9-year-old boy receives a deep laceration over his right eyebrow while playing ice hockey. The wound is cleaned and sutured. Which of the following collagens is deposited first during wound healing?
Which of the following is NOT one of Celsus' cardinal signs of inflammation?
What is the term for the movement of leukocytes across the endothelium?
A 58-year-old woman undergoes lumpectomy for breast cancer. One month following surgery, she notices a firm 0.3-cm nodule along one edge of the surgical incision. Biopsy of this nodule reveals chronic inflammatory cells, multinucleated giant cells, and extensive fibrosis. The multinucleated giant cells in this nodule most likely formed in response to which of the following pathogenic stimuli?
Which enzyme is also known as TACE (TNF converting enzyme)?
What is the most important role of bradykinin in acute inflammation?
Granulomatous inflammatory reaction is caused by all, except?
Scar formation is part of the normal healing process following injury. Which of the following tissues has the ability to heal without scar formation?
Inflammation and Repair Indian Medical PG Practice Questions and MCQs
Question 311: COX-2 primarily inhibits which step in inflammation?
- A. Cell adhesion
- B. Cell differentiation
- C. Cell migration
- D. Platelet aggregation (Correct Answer)
Explanation: **Explanation:** The question focuses on the physiological role of **Cyclooxygenase-2 (COX-2)** in the arachidonic acid pathway. **Why Platelet Aggregation is the Correct Answer:** COX-2 is primarily expressed in vascular endothelial cells, where it is responsible for the synthesis of **Prostacyclin (PGI2)** [1]. Prostacyclin is a potent **vasodilator** and a powerful **inhibitor of platelet aggregation** [1]. When COX-2 is inhibited (e.g., by selective COX-2 inhibitors like Celecoxib), PGI2 levels drop. This tips the homeostatic balance in favor of **Thromboxane A2 (TXA2)**—produced by COX-1 in platelets—which promotes platelet aggregation and vasoconstriction [1]. Therefore, the physiological role of the COX-2 product (PGI2) is to inhibit platelet aggregation. **Analysis of Incorrect Options:** * **A. Cell adhesion:** This is primarily mediated by adhesion molecules like selectins (rolling) and integrins (firm adhesion), which are regulated by cytokines (TNF, IL-1), not directly by COX-2. * **B. Cell differentiation:** This is a long-term process governed by growth factors and transcription factors, unrelated to the acute inflammatory mediators produced by the COX pathway. * **C. Cell migration:** While prostaglandins can influence vascular permeability, the active process of chemotaxis (migration) is primarily driven by leukotrienes (LTB4), C5a, and bacterial products [1]. **High-Yield Clinical Pearls for NEET-PG:** * **The "COX Balance" Theory:** COX-1 produces TXA2 (pro-thrombotic); COX-2 produces PGI2 (anti-thrombotic) [1]. * **Cardiovascular Risk:** Selective COX-2 inhibitors carry a "Black Box Warning" for increased risk of myocardial manifestation because they inhibit the anti-thrombotic PGI2 while leaving the pro-thrombotic TXA2 (COX-1) unopposed [1]. * **Inducibility:** Unlike the constitutive COX-1, COX-2 is **inducible** by inflammatory stimuli (cytokines, endotoxins) in most tissues, except in the kidney and brain where it is constitutive. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 94-97.
Question 312: A 59-year-old man experiences acute chest pain and is rushed to the emergency room. Laboratory studies and ECG demonstrate an acute myocardial infarction. Coronary artery angiography performed 2 hours later does not show evidence of thrombosis. Which of the following mediators of inflammation causes relaxation of vascular smooth muscle cells and vasodilation of arterioles at the site of myocardial infarction?
- A. Bradykinin
- B. Histamine
- C. Leukotrienes
- D. Nitric oxide (Correct Answer)
Explanation: **Explanation:** The correct answer is **Nitric Oxide (NO)**. In the context of acute myocardial infarction (MI) and the subsequent inflammatory response, vasodilation is a key early event [1]. Nitric oxide is a potent endogenous gas produced by endothelial cells (eNOs) and macrophages (iNOs). It acts on vascular smooth muscle cells to increase intracellular **cGMP**, leading to dephosphorylation of myosin light chains, which results in smooth muscle relaxation and arteriolar vasodilation. **Why other options are incorrect:** * **Bradykinin:** While it causes vasodilation and increased vascular permeability [2], its primary clinical hallmark in inflammation is the stimulation of pain fibers (nociceptors) [1]. * **Histamine:** Released mainly by mast cells, histamine causes vasodilation and increased permeability of **venules** (not primarily arterioles) [2] and is more characteristic of Type I hypersensitivity and the immediate phase of acute inflammation [1]. * **Leukotrienes:** Specifically $LTC_4, LTD_4,$ and $LTE_4$ (cysteinyl leukotrienes) actually cause **vasoconstriction** and bronchospasm [1]. $LTB_4$ is primarily involved in neutrophil chemotaxis [1]. **NEET-PG High-Yield Pearls:** * **Mechanism of NO:** NO → Guanylyl cyclase activation → ↑ cGMP → Protein Kinase G → Vasodilation. * **Triple Response of Lewis:** Red reaction (capillary dilation), Flare (arteriolar dilation via axon reflex), and Wheal (exudation/edema). * **Vascular Permeability:** The most common mechanism of increased vascular permeability in acute inflammation is **endothelial cell contraction** leading to intercellular gaps in post-capillary venules [2]. * **Clinical Correlation:** In MI, the absence of a thrombus on angiography 2 hours later suggests spontaneous thrombolysis or coronary artery spasm (Prinzmetal angina), but the inflammatory response to the underlying ischemia remains the same. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-101. [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. 187-189.
Question 313: A 9-year-old boy receives a deep laceration over his right eyebrow while playing ice hockey. The wound is cleaned and sutured. Which of the following collagens is deposited first during wound healing?
- A. Type I
- B. Type II
- C. Type III (Correct Answer)
- D. Type IV
Explanation: ### Explanation **Correct Answer: C. Type III Collagen** The process of wound healing by primary intention (sutured wounds) follows a specific chronological sequence of collagen deposition [2]. * **Underlying Concept:** During the **proliferative phase** of wound healing (starting around day 3 to 5), fibroblasts are recruited to the site [1]. These fibroblasts initially synthesize and secrete **Type III collagen** (embryonic/granulation tissue collagen). * **The Transition:** Type III collagen is thin and provides initial structural integrity. However, it lacks significant tensile strength. Starting around the second week, an enzyme called **collagenase** (a Matrix Metalloproteinase) begins to break down Type III collagen, which is then replaced by the much stronger, thicker **Type I collagen** during the remodeling phase. --- ### Why the other options are incorrect: * **Type I Collagen:** This is the most abundant collagen in the body (found in bone, skin, and late scars). While it provides the final tensile strength to a wound, it is deposited **later** during the remodeling phase, replacing Type III [3]. * **Type II Collagen:** This is primarily found in **cartilage** and vitreous humor. It does not play a significant role in the healing of cutaneous lacerations. * **Type IV Collagen:** This is a non-fibrillar collagen that forms the meshwork of the **basal lamina** (basement membrane). It is not the primary structural collagen deposited during the formation of granulation tissue. --- ### NEET-PG High-Yield Pearls: * **Collagen Strength:** At 1 week (suture removal), wound strength is ~10% [3]. It reaches a maximum of **70-80%** of original strength by 3 months; it rarely reaches 100% [3]. * **Cofactors:** Vitamin C and Iron are essential for the **hydroxylation of proline and lysine** residues during collagen synthesis. Deficiency leads to poor wound healing (Scurvy). * **Zinc:** Essential for the action of **Matrix Metalloproteinases (MMPs)** which facilitate the remodeling of Type III to Type I collagen. **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] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121.
Question 314: Which of the following is NOT one of Celsus' cardinal signs of inflammation?
- A. Dolor (Pain)
- B. Tumor (Swelling)
- C. Cyanosis (Correct Answer)
- D. Rubor (Redness)
Explanation: The cardinal signs of inflammation are a high-yield topic in pathology, representing the clinical manifestation of vascular and cellular changes during acute inflammation. **Explanation of the Correct Answer:** **Cyanosis** is the correct answer because it is not part of the classical signs described by Celsus. Cyanosis refers to a bluish discoloration of the skin or mucous membranes due to excessive deoxyhemoglobin, typically associated with hypoxia or circulatory failure, rather than the localized inflammatory process. **The Four Cardinal Signs (Celsus, 1st Century AD):** * **Rubor (Redness):** Caused by vasodilation and increased blood flow (hyperemia) to the injured area [1]. * **Tumor (Swelling):** Results from increased vascular permeability, leading to the accumulation of extravascular fluid (exudate/edema). * **Dolor (Pain):** Triggered by the release of chemical mediators (like bradykinin and prostaglandins) and the physical pressure of edema on nerve endings [1]. * **Calor (Heat):** Caused by increased blood flow and local metabolic activity [1]. **Clinical Pearls for NEET-PG:** 1. **The Fifth Sign:** While Celsus described four signs, **Rudolf Virchow** later added the fifth cardinal sign: **Functio Laesa** (Loss of function) [1]. 2. **Mechanism of Rubor/Calor:** These are primarily due to histamine-mediated vasodilation of arterioles [1]. 3. **Mechanism of Tumor:** This is primarily due to the contraction of endothelial cells in post-capillary venules, creating gaps that allow fluid leakage. 4. **Key Mediator of Pain:** Prostaglandin E2 (PGE2) sensitizes pain receptors to stimuli like bradykinin. **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.
Question 315: What is the term for the movement of leukocytes across the endothelium?
- A. Emigration
- B. Transmigration (Correct Answer)
- C. Margination
- D. Pavementing
Explanation: ### Explanation **Correct Answer: B. Transmigration** **Mechanism:** Transmigration, also known as **diapedesis**, is the process by which leukocytes crawl through endothelial junctions to reach the extravascular space [1]. This occurs primarily in the **post-capillary venules** [2]. The process is mediated by adhesion molecules, most notably **PECAM-1 (CD31)**, which is expressed on both the leukocytes and the endothelial cell junctions [1]. Once through the endothelium, leukocytes secrete collagenases to pierce the basement membrane [1]. **Analysis of Incorrect Options:** * **C. Margination:** This is the initial step where leukocytes move from the central axial column of the blood flow toward the periphery (near the endothelial surface) due to changes in hemodynamics (stasis) [4]. * **D. Pavementing:** This refers to the stage where leukocytes adhere firmly to the endothelial surface, lining it like "cobblestones" or pavement [3]. This is mediated by **Integrins** (on leukocytes) and **ICAM-1/VCAM-1** (on endothelium) [3]. * **A. Emigration:** While often used interchangeably in older texts, emigration is a broader term describing the entire journey of the white blood cell from the vessel lumen to the interstitial tissue [2]. Transmigration specifically refers to the act of crossing the endothelial barrier [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Leukocyte Extravasation:** Margination → Rolling (Selectins) → Adhesion (Integrins) → Transmigration (PECAM-1) → Chemotaxis [4]. * **Leukocyte Adhesion Deficiency (LAD) Type 1:** Caused by a defect in the **CD18 subunit of integrins**, leading to impaired firm adhesion and recurrent infections without pus formation [1]. * **LAD Type 2:** Caused by a defect in **Sialyl-Lewis X** (ligand for selectins), leading to impaired rolling. * **Predominant Cell Type:** Neutrophils dominate the first 6–24 hours; Monocytes/Macrophages take over after 24–48 hours (Exception: *Pseudomonas* infections where neutrophils persist). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89. [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. 188-189. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 87. [4] 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 316: A 58-year-old woman undergoes lumpectomy for breast cancer. One month following surgery, she notices a firm 0.3-cm nodule along one edge of the surgical incision. Biopsy of this nodule reveals chronic inflammatory cells, multinucleated giant cells, and extensive fibrosis. The multinucleated giant cells in this nodule most likely formed in response to which of the following pathogenic stimuli?
- A. Staphylococcal infection
- B. Foreign material (Correct Answer)
- C. Lymphatic obstruction
- D. Neoplastic cells
Explanation: ### Explanation **Correct Answer: B. Foreign material** The clinical presentation describes a **Foreign Body Granuloma**, a specific type of chronic inflammation [2]. In this case, the "firm nodule" appearing at a surgical incision site one month post-surgery is most likely a reaction to **sutures** or other surgical materials. **Why it is correct:** When the body encounters indigestible material (like surgical sutures, talc, or wood splinters) that is too large to be phagocytosed by a single macrophage [3], multiple macrophages fuse together to form **Foreign Body Giant Cells** [2]. Unlike Langhans giant cells (seen in TB) where nuclei are arranged in a horseshoe pattern [1], foreign body giant cells have **nuclei scattered haphazardly** throughout the cytoplasm. The presence of chronic inflammatory cells and extensive fibrosis (scarring) is characteristic of the body's attempt to wall off the irritant [1]. **Why the other options are incorrect:** * **A. Staphylococcal infection:** This typically results in **acute inflammation** characterized by neutrophils, liquefactive necrosis, and abscess formation (pus), rather than a firm, fibrotic granulomatous nodule. * **C. Lymphatic obstruction:** This leads to **lymphedema** (swelling due to fluid accumulation) and potentially "peau d'orange" in breast cancer, but it does not histologically present with multinucleated giant cells. * **D. Neoplastic cells:** While cancer recurrence is a concern post-surgery, the biopsy findings of giant cells and fibrosis specifically point toward an inflammatory reaction rather than malignant cell proliferation. ### NEET-PG High-Yield Pearls * **Giant Cell Types:** * **Langhans Giant Cells:** Nuclei in peripheral "horseshoe" arrangement (e.g., Tuberculosis, Sarcoidosis) [1]. * **Foreign Body Giant Cells:** Nuclei randomly scattered (e.g., Suture reaction) [2]. * **Touton Giant Cells:** Ring of nuclei with peripheral foamy cytoplasm (e.g., Xanthomas). * **Granuloma Components:** Epithelioid histiocytes (activated macrophages), lymphocytes, and often a rim of fibroblasts/fibrosis [1]. * **Suture Granuloma:** A common "spot diagnosis" in pathology for any post-surgical nodule showing giant cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 109. [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. 196-197. [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. 198-200.
Question 317: Which enzyme is also known as TACE (TNF converting enzyme)?
- A. Matrix metalloproteinase
- B. Serine proteinase
- C. ADAM-17 (Correct Answer)
- D. Interstitial collagenase
Explanation: **Explanation:** **Correct Answer: C. ADAM-17** ADAM-17 (A Disintegrin and Metalloproteinase 17) is a membrane-bound enzyme responsible for the proteolytic cleavage of membrane-bound Tumor Necrosis Factor-alpha (TNF-α) into its soluble, active form. Because of this specific function, it is widely known as **TACE (TNF-alpha Converting Enzyme)**. This process, called "ectodomain shedding," is a critical regulatory step in the inflammatory response, as soluble TNF-α acts as a potent systemic mediator of inflammation. **Analysis of Incorrect Options:** * **A. Matrix metalloproteinases (MMPs):** While ADAMs belong to the broader metalloproteinase superfamily, "MMP" usually refers to enzymes like gelatinases or stromelysins that primarily degrade extracellular matrix (ECM) components rather than specific cytokine processing. * **B. Serine proteinases:** These include enzymes like elastase and cathepsin G. They are involved in protein degradation and neutrophil action but do not possess the specific TACE activity required to release TNF-α. * **D. Interstitial collagenase:** Specifically refers to **MMP-1**, which cleaves Type I, II, and III collagen. It is essential for wound healing and remodeling but is not involved in TNF-α conversion. **High-Yield Facts for NEET-PG:** * **ADAM-17** also cleaves other important molecules, including the **EGFR ligand (TGF-α)** and **L-selectin**. * **TNF-α** is primarily produced by activated macrophages and is the "master regulator" of inflammation. * **Clinical Correlation:** Inhibitors of TACE/ADAM-17 are researched as potential anti-inflammatory therapies for conditions like Rheumatoid Arthritis and Crohn’s disease, similar to TNF-α blockers (e.g., Infliximab, Etanercept) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1212.
Question 318: What is the most important role of bradykinin in acute inflammation?
- A. Increase in vascular permeability (Correct Answer)
- B. Vasodilation
- C. Mediation of pain
- D. Bronchoconstriction
Explanation: **Explanation:** **1. Why Option A is Correct:** Bradykinin is a potent vasoactive peptide derived from the kinin system (activated by Hageman factor/Factor XII) [3]. Its primary and most significant role in the context of acute inflammation is the **increase in vascular permeability** [1], [2]. It acts on endothelial cells to cause contraction, leading to the formation of intercellular gaps in post-capillary venules [2]. This allows for the leakage of protein-rich fluid (exudate) into the extravascular space, contributing to inflammatory edema. **2. Analysis of Incorrect Options:** * **Option B (Vasodilation):** While bradykinin does cause vasodilation, it is not its *most important* role in the inflammatory cascade [1]. Prostaglandins (PGI2, PGE2) and Nitric Oxide (NO) are the primary mediators responsible for the sustained vasodilation seen in acute inflammation [4]. * **Option C (Mediation of Pain):** Bradykinin is indeed a mediator of pain (along with Prostaglandin E2), but this is a sensory effect rather than a primary vascular driver of the inflammatory process [1], [4]. * **Option D (Bronchoconstriction):** Bradykinin causes contraction of non-vascular smooth muscle (bronchial and intestinal), but this is a secondary physiological effect and not the hallmark of the acute inflammatory response in tissues [1]. **3. NEET-PG High-Yield Pearls:** * **The "Kinin Trio":** Remember that Bradykinin causes **Vasodilation, Increased Permeability, and Pain.** [1] * **Short Half-life:** Bradykinin is rapidly inactivated by **Angiotensin-Converting Enzyme (ACE)** (also known as kininase) [1]. This explains why ACE inhibitors can cause a dry cough and angioedema (due to accumulation of bradykinin). * **Sequence of Activation:** Factor XII (Hageman Factor) → Prekallikrein to Kallikrein → HMWK (High Molecular Weight Kininogen) to Bradykinin [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 100-101. [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. 187-188. [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. 189-190. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101.
Question 319: Granulomatous inflammatory reaction is caused by all, except?
- A. M. Tuberculosis
- B. M. Leprae
- C. Yersinia pestis
- D. Mycoplasma (Correct Answer)
Explanation: **Explanation:** **1. Why Mycoplasma is the Correct Answer:** Granulomatous inflammation is a specific pattern of chronic inflammation characterized by the formation of **granulomas**—aggregates of activated macrophages (epithelioid cells), lymphocytes, and multinucleated giant cells. It is typically triggered by agents that are difficult to eradicate (persistent intracellular pathogens or non-degradable foreign bodies) [1], [2]. **Mycoplasma pneumoniae** causes an acute respiratory infection characterized by interstitial inflammation and a mononuclear infiltrate, but it **does not** induce a granulomatous response. **2. Analysis of Incorrect Options:** * **M. Tuberculosis (A):** The classic cause of granulomatous inflammation [1]. It produces **caseating granulomas** (central necrosis) due to the delayed-type hypersensitivity (Type IV) response. * **M. Leprae (B):** Causes Leprosy. Depending on the immune status, it forms well-defined granulomas (Tuberculoid leprosy) or diffuse histiocytic infiltrates (Lepromatous leprosy). * **Yersinia pestis (C):** While primarily known for the plague, certain species of *Yersinia* (like *Y. pseudotuberculosis* and occasionally *Y. pestis* in specific chronic forms) can cause **necrotizing granulomas** in lymph nodes (Stellate abscesses). **3. High-Yield Clinical Pearls for NEET-PG:** * **Definition of Epithelioid Cell:** These are activated macrophages with abundant pink cytoplasm and slipper-shaped nuclei; they are the hallmark of a granuloma [2]. * **Non-Infectious Granulomas:** Remember **Sarcoidosis** (non-caseating), Berylliosis, and Crohn’s disease [2]. * **Stellate Granulomas:** Classically seen in **Cat Scratch Disease** (*Bartonella henselae*), Lymphogranuloma Venereum (LGV), and Yersinia. * **Schistosomiasis:** The most common cause of granulomas worldwide (parasitic). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 360. [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. 196-200.
Question 320: Scar formation is part of the normal healing process following injury. Which of the following tissues has the ability to heal without scar formation?
- A. Liver
- B. Skin
- C. Bone (Correct Answer)
- D. Muscle
Explanation: **Explanation:** The correct answer is **Bone (Option C)**. Healing in most adult tissues occurs through a combination of regeneration (replacement by the same cell type) and repair (replacement by connective tissue, leading to a scar) [1]. **Bone** is unique because it is one of the few tissues in the human body capable of healing by **regeneration** rather than repair. Following a fracture, the body produces a procallus which is eventually replaced by lamellar bone through remodeling [3]. This results in the restoration of the original skeletal structure and strength without the formation of a permanent fibrous scar. **Why the other options are incorrect:** * **Liver (Option A):** While the liver has a high regenerative capacity, this only occurs if the reticulin framework is preserved [2]. In cases of chronic injury or massive necrosis (e.g., cirrhosis), the framework collapses, leading to collagen deposition and permanent scarring (fibrosis) [3]. * **Skin (Option B):** Cutaneous wounds that extend beyond the epidermis into the dermis heal by secondary intention or primary intention, both of which involve the formation of a fibrous scar (collagen type I replacement). Only fetal skin (early gestation) has the ability to heal without scarring. * **Muscle (Option D):** Skeletal and cardiac muscles have very limited regenerative capacity. Injury to these tissues is typically repaired by the proliferation of fibroblasts and the deposition of dense connective tissue (scarring), as seen in a healed myocardial infarction. **NEET-PG High-Yield Pearls:** * **Tissues with high regenerative capacity:** Bone, Liver (limited), and Epithelia [1]. * **Tissues that always heal by scar:** Cardiac muscle and Nerve cells (CNS). * **Key Growth Factor:** TGF-β is the most important cytokine involved in stimulating synthesis and deposition of connective tissue proteins (fibrosis). * **Bone Healing Sequence:** Hematoma → Soft Callus → Hard Callus (Woven bone) → Remodeling (Lamellar bone). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 112-115. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 113. [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. 108-109.
Practice by Chapter
Acute Inflammation: Vascular Events
Practice Questions
Acute Inflammation: Cellular Events
Practice Questions
Chemical Mediators of Inflammation
Practice Questions
Chronic Inflammation
Practice Questions
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
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free