General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 661: A man dies 5 days after suffering a myocardial infarction. What will a myocardial biopsy show?

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

Explanation: **Explanation:** **1. Why Coagulative Necrosis is Correct:** Coagulative necrosis is the characteristic pattern of cell death seen in all solid organs following **ischemic injury (infarcts)**, with the brain being the only exception [1]. In a myocardial infarction (MI), the sudden loss of blood supply leads to protein denaturation and enzymatic inactivation. This prevents the immediate proteolysis of the dead cells. Microscopically, this results in the "tombstone appearance"—where the cell's structural outline is preserved for several days, but the nuclei are lost (karyolysis) [1]. By day 5, while there is significant neutrophilic and macrophagic infiltration, the underlying tissue architecture still reflects coagulative necrosis [1]. **2. Why Other Options are Incorrect:** * **Liquefactive Necrosis:** Characterized by the complete digestion of dead cells, turning the tissue into a liquid viscous mass (pus). This is typical of bacterial/fungal infections or **CNS infarcts (brain)**. * **Caseous Necrosis:** A "cheese-like" friable appearance seen classically in **Tuberculosis** (granulomatous inflammation). It is a combination of coagulative and liquefactive processes. * **Fibrinoid Necrosis:** Usually seen in **immune-mediated vascular damage** (e.g., Polyarteritis Nodosa, Malignant Hypertension). It involves the deposition of immune complexes and fibrin in arterial walls. **3. NEET-PG High-Yield Pearls:** * **Timeline of MI Pathology:** * **0–4 hours:** No gross changes. * **4–12 hours:** Early coagulative necrosis, edema, and hemorrhage [1]. * **12–24 hours:** Contraction band necrosis [1]. * **1–3 days:** Peak neutrophilic infiltrate [1]. * **3–7 days:** Macrophage infiltration and beginning of **granulation tissue** (highest risk of free wall rupture) [1]. * **7 weeks+:** Dense collagenous scar. * **Exception Rule:** Ischemia in the **Brain** always leads to Liquefactive necrosis, not Coagulative. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, pp. 552-554.

Question 662: Squamous cell carcinoma commonly spreads by which mechanism?

A. Implantation
B. Hematogenous spread
C. Lymphatic spread (Correct Answer)
D. Trancoelomic spread

Explanation: The primary mechanism of spread for **Squamous Cell Carcinoma (SCC)** is **lymphatic spread** [4]. This is a fundamental rule in oncology: **Carcinomas** (malignancies of epithelial origin) typically spread via the lymphatics first, while **Sarcomas** (malignancies of mesenchymal origin) prefer hematogenous (blood-borne) spread [3]. In SCC, tumor cells invade local lymphatic vessels and travel to regional lymph nodes (e.g., cervical nodes in oral SCC or inguinal nodes in penile SCC), which often serve as the first clinical sign of metastasis [2]. **Analysis of Incorrect Options:** * **A. Implantation:** This refers to the "seeding" of a tumor across a surface (e.g., a surgeon’s scalpel or a needle tract). While possible, it is not the *common* or characteristic mode of spread for SCC. * **B. Hematogenous spread:** This is the characteristic route for **Sarcomas** [3]. While carcinomas can spread via blood in later stages (especially to the lungs or liver), it is rarely the initial or primary route for SCC. (Exceptions: Renal cell carcinoma, Hepatocellular carcinoma, Follicular thyroid carcinoma, and Choriocarcinoma) [3]. * **D. Transcoelomic spread:** This occurs when tumors invade a natural body cavity (e.g., the peritoneal or pleural space) [1]. A classic example is **Krukenberg tumor** (gastric cancer spreading to the ovaries). **NEET-PG High-Yield Pearls:** * **The "Rule of Thumb":** Carcinoma = Lymphatic; Sarcoma = Hematogenous. * **Exceptions (Carcinomas that spread via blood):** Remember the mnemonic **"Four He-Man Really Cool"** — **F**ollicular CA of Thyroid, **H**CC, **R**CC, and **C**horiocarcinoma. * **Sentinel Lymph Node:** The first node that receives lymph drainage from a primary tumor; its biopsy is crucial in staging cancers like breast carcinoma and melanoma. **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. 234-235. [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. 233-234. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 282. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Female Genital Tract Disease, pp. 470-471.

Question 663: Hemophilia is associated with which chromosome?

A. X chromosome (Correct Answer)
B. Y chromosome
C. Chromosome 3
D. Chromosome 16

Explanation: **Explanation:** **Hemophilia (A and B)** is a classic example of an **X-linked recessive** bleeding disorder [1]. Hemophilia A is caused by a deficiency of Factor VIII, while Hemophilia B (Christmas disease) is caused by a deficiency of Factor IX [1]. The genes encoding both Factor VIII (*F8*) and Factor IX (*F9*) are located on the **long arm of the X chromosome (Xq)** [2]. Because males have only one X chromosome (hemizygous), a single defective gene leads to the disease, whereas females are typically asymptomatic carriers [4]. **Analysis of Incorrect Options:** * **Option B (Y chromosome):** Very few genetic disorders are Y-linked (holandric inheritance), and they primarily affect male fertility (e.g., SRY gene mutations) [4]. * **Option C (Chromosome 3):** This chromosome is associated with conditions like Von Hippel-Lindau (VHL) disease and Alkaptonuria, but not hemophilia. * **Option D (Chromosome 16):** This is the locus for the **alpha-globin chain** genes. Mutations here lead to Alpha-thalassemia, not coagulation factor deficiencies. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance Pattern:** X-linked recessive (Criss-cross inheritance). * **Lab Findings:** Characterized by a **prolonged Activated Partial Thromboplastin Time (aPTT)** with a normal Prothrombin Time (PT) and normal Bleeding Time (BT). * **Most Common Mutation:** The most common cause of severe Hemophilia A is an **intron 22 inversion** [2]. * **Clinical Feature:** Hemarthrosis (bleeding into joints, commonly the knee) is a hallmark of severe hemophilia [3]. * **Note:** **Von Willebrand Disease**, the most common inherited bleeding disorder, is **Autosomal Dominant** (Chromosome 12), unlike Hemophilia. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 622-623. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 670-671. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 623-624. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 151.

Question 664: Karyopyknotic index is a method for?

A. Ovarian carcinoma
B. Hormonal evaluation (Correct Answer)
C. Dysplasia measurement
D. Measurement of cells in active replication

Explanation: **Explanation:** The **Karyopyknotic Index (KPI)** is a cyto-hormonal assessment tool used primarily in vaginal cytology. It is defined as the percentage of **superficial squamous cells** (cells with small, shrunken, and dark "pyknotic" nuclei) compared to intermediate cells in a lateral vaginal wall smear [3]. **Why Hormonal Evaluation is Correct:** The maturation of the vaginal epithelium is directly controlled by steroid hormones [3]. **Estrogen** promotes the maturation of squamous cells into the superficial layer (increasing the KPI), while **Progesterone** (and androgens) leads to a predominance of intermediate cells (decreasing the KPI) [2]. Therefore, KPI serves as a sensitive bioassay to evaluate a patient's estrogenic status, monitor the menstrual cycle, or assess hormonal imbalances. **Analysis of Incorrect Options:** * **A. Ovarian Carcinoma:** While cytology can sometimes detect malignant cells, KPI specifically measures hormonal influence on normal cell maturation, not the presence of malignancy [3]. * **C. Dysplasia Measurement:** Dysplasia is assessed by observing nuclear atypia, loss of polarity, and pleomorphism (e.g., via Bethesda grading in Pap smears), not by calculating the ratio of mature superficial cells [1]. * **D. Cells in Active Replication:** This is typically measured using proliferation markers like **Ki-67** or flow cytometry (S-phase fraction), not by observing terminal differentiation (pyknosis). **High-Yield Clinical Pearls for NEET-PG:** * **Maturation Index (MI):** A more comprehensive hormonal profile expressed as a ratio of Parabasal: Intermediate: Superficial cells. * **Estrogen Effect:** High KPI (Shift to the right in MI). * **Progesterone Effect:** Low KPI; presence of "folded" intermediate cells (Shift to the middle in MI). * **Atrophy:** Predominance of parabasal cells (Shift to the left in MI), seen in post-menopausal women. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Female Genital Tract Disease, pp. 467-468. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1011-1012. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, p. 1010.

Question 665: Amplification of N-myc is associated with which tumour?

A. Neuroblastoma (Correct Answer)
B. Retinoblastoma
C. Osteosarcoma
D. Neuroma

Explanation: **Explanation:** **N-myc (MYCN)** is a proto-oncogene located on chromosome 2. Its amplification is a classic molecular hallmark of **Neuroblastoma**, the most common extracranial solid tumor of childhood [1]. In neuroblastoma, N-myc amplification (often seen as "double minute chromosomes" or "homogeneously staining regions" on karyotyping) is a critical prognostic marker [1]. High levels of N-myc correlate with advanced stage, rapid tumor progression, and a poor clinical prognosis, regardless of the patient's age or tumor stage [1]. **Analysis of Incorrect Options:** * **Retinoblastoma:** This is primarily associated with the mutation or deletion of the **RB1 tumor suppressor gene** on chromosome 13q14 [2]. While it is a childhood tumor, N-myc is not its primary driver. * **Osteosarcoma:** This bone tumor is most frequently associated with mutations in the **RB1** and **TP53** genes. While c-myc can sometimes be involved, N-myc is not the characteristic marker. * **Neuroma:** These are benign growths of nerve tissue (e.g., Morton’s neuroma or traumatic neuroma) and are not associated with myc gene amplifications, which are features of aggressive malignancies. **High-Yield Clinical Pearls for NEET-PG:** * **C-myc:** Associated with **Burkitt Lymphoma** (t[8;14]) [3]. * **L-myc:** Associated with **Small Cell Carcinoma of the Lung**. * **N-myc:** Associated with **Neuroblastoma** and Small Cell Carcinoma of the Lung. * **Neuroblastoma Marker:** Look for elevated urinary catecholamines (VMA and HVA) and "Homer-Wright rosettes" on histology [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 486-487. [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. 211-212. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 324-325.

Question 666: Dystrophic calcification is seen in which of the following conditions?

A. Paget disease
B. Renal osteodystrophy
C. Atheroma (Correct Answer)
D. Milk alkali syndrome

Explanation: **Explanation:** Pathologic calcification is categorized into two types: **Dystrophic** and **Metastatic**. **Dystrophic Calcification (Correct Option: C)** Dystrophic calcification occurs in **dead, dying, or degenerated tissues** despite **normal serum calcium and phosphate levels** [1]. In **Atheromas** (advanced atherosclerosis), the necrotic core of the lipid plaque undergoes calcification. The process is initiated by membrane-bound vesicles (matrix vesicles) derived from injured cells, which concentrate calcium and phosphate, leading to hydroxyapatite crystal formation [2]. **Metastatic Calcification (Incorrect Options: A, B, D)** Metastatic calcification occurs in **normal tissues** due to **hypercalcemia** (elevated serum calcium) [2], [3]. * **Paget disease:** Characterized by excessive bone remodeling, often leading to hypercalcemia. * **Renal osteodystrophy:** Chronic kidney disease leads to secondary hyperparathyroidism and phosphate retention, causing metastatic calcification. * **Milk-alkali syndrome:** Caused by excessive ingestion of calcium and absorbable antacids. **High-Yield NEET-PG Pearls:** * **Dystrophic Calcification Examples:** Caseous necrosis (TB) [1], Psammoma bodies (Papillary thyroid CA, Meningioma, Serous cystadenocarcinoma of ovary) [3], senile aortic stenosis, and fat necrosis [1]. * **Metastatic Calcification Sites:** Primarily affects interstitial tissues of the **gastric mucosa, kidneys, lungs, and systemic arteries** [2] (sites that lose acid, creating an internal alkaline environment favorable for calcium deposition). * **Morphology:** On H&E stain, both types appear as intracellular or extracellular **basophilic (blue-purple)**, amorphous granular clumps [1], [2]. **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. 55. [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, pp. 76-77. [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. 134-135.

Question 667: The normal cellular counterparts of oncogenes are important for which of the following functions, except?

A. Promotion of cell cycle progression
B. Inhibition of apoptosis
C. Promotion of DNA repair (Correct Answer)
D. Promotion of nuclear transcription

Explanation: **Explanation:** The question asks for the function that is **not** associated with proto-oncogenes. **1. Why "Promotion of DNA repair" is the correct answer:** Proto-oncogenes are normal cellular genes that promote cell growth and survival [1]. When mutated or overexpressed, they become **oncogenes**, leading to autonomous cell proliferation [1]. **DNA repair genes**, on the other hand, belong to the category of **Tumor Suppressor Genes (TSGs)** (specifically "caretakers") [3]. Their role is to identify and fix genetic errors. Loss of DNA repair function leads to genomic instability, which predisposes a cell to cancer, but this is a loss-of-function mutation characteristic of TSGs, not a function of proto-oncogenes. **2. Analysis of Incorrect Options:** * **A & D (Cell cycle progression & Nuclear transcription):** Proto-oncogenes code for proteins that act at various levels of the growth signaling pathway [1]. This includes growth factors (e.g., PDGF), growth factor receptors (e.g., HER2), signal transducers (e.g., RAS), and **nuclear transcription factors** (e.g., MYC) that drive the **cell cycle** from G1 to S phase [1], [2]. * **B (Inhibition of apoptosis):** Some proto-oncogenes function by protecting cells from programmed cell death. A classic example is **BCL-2**, which inhibits apoptosis. Overexpression of BCL-2 (as seen in Follicular Lymphoma) leads to cell immortality. **High-Yield Clinical Pearls for NEET-PG:** * **Proto-oncogenes:** Require mutation in only **one allele** (dominant) to promote cancer. * **Tumor Suppressor Genes:** Usually require "two hits" (recessive) according to Knudson’s hypothesis (e.g., RB1, TP53). * **RAS:** The most common mutated proto-oncogene in human tumors. * **MYC:** A nuclear transcription factor associated with Burkitt Lymphoma (t8;14). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 292-293. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 292. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 291-292.

Question 668: A phenotypically normal woman, whose father was color blind, marries a phenotypically normal man. What is the probability of their son being color blind?

A. 25%
B. 50% (Correct Answer)
C. 75%
D. 0%

Explanation: **Explanation:** This question tests your understanding of **X-linked recessive (XLR) inheritance** patterns, a high-yield topic in General Pathology and Genetics [1]. **1. Why 50% is Correct:** * **The Mother’s Genotype:** Color blindness is an XLR disorder. Since the woman’s father was color blind ($X^cY$), he must have passed his only X-chromosome ($X^c$) to her. Although she is phenotypically normal, she is an **obligate carrier** ($X^CX^c$). * **The Father’s Genotype:** He is phenotypically normal, so his genotype is $X^CY$. * **The Cross:** When an $X^CX^c$ mother and $X^CY$ father have children, the possible genotypes for **sons** are $X^CY$ (Normal) and $X^cY$ (Color blind) [2]. * **Probability:** Among the sons, there is a **50% chance** of being color blind. (Note: If the question asked for the probability among *all* children, it would be 25%) [2]. **2. Why Other Options are Wrong:** * **A (25%):** This is the probability of having a color-blind child if the sex is not specified (1 out of 4 total offspring) [2]. * **C (75%):** This ratio is not characteristic of XLR crosses between a carrier and a normal male. * **D (0%):** This would only occur if the mother was not a carrier ($X^CX^C$). **Clinical Pearls for NEET-PG:** * **Criss-cross Inheritance:** XLR traits are typically passed from an affected father to his grandsons through his carrier daughters [1]. * **Common XLR Disorders:** Remember the mnemonic **"CHEDG"**: **C**olor blindness, **H**emophilia A/B, **E**erythroblastosis (G6PD deficiency), **D**uchenne Muscular Dystrophy, and **G**ranulomatous disease (Chronic). * **Rule of Thumb:** In XLR traits, males are never carriers; they are either affected or normal (hemizygous) [1]. Females are usually asymptomatic carriers due to the presence of a second normal X-chromosome. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 151. [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. 53-54.

Question 669: Thymic hypoplasia is seen in which of the following conditions?

A. Wiskott-Aldrich syndrome
B. DiGeorge syndrome (Correct Answer)
C. IgA deficiency
D. Agammaglobulinemia

Explanation: **Explanation:** **DiGeorge Syndrome (Correct Answer):** DiGeorge syndrome is a T-cell immunodeficiency caused by the **maldevelopment of the 3rd and 4th pharyngeal pouches** [1]. This results in **thymic hypoplasia or aplasia**, leading to deficient T-cell maturation and cell-mediated immunity [1]. It is most commonly associated with a **22q11.2 microdeletion** [1], [2]. The clinical spectrum is often remembered by the mnemonic **CATCH-22**: **C**ardiac defects (Truncus arteriosus/Tetralogy of Fallot), **A**bnormal facies, **T**hymic hypoplasia, **C**left palate, and **H**ypocalcemia (due to parathyroid hypoplasia) [1]. **Analysis of Incorrect Options:** * **Wiskott-Aldrich Syndrome:** This is an X-linked recessive disorder characterized by the triad of **thrombocytopenia (small platelets), eczema, and recurrent infections**. It is caused by a mutation in the *WASP* gene, affecting actin cytoskeleton remodeling, not primary thymic development [4]. * **IgA Deficiency:** This is the most common primary immunodeficiency. It involves a failure of B-cells to differentiate into IgA-secreting plasma cells [5]. The thymus and T-cell counts are typically normal. * **Agammaglobulinemia (Bruton’s):** This is an X-linked condition caused by a mutation in **Bruton Tyrosine Kinase (BTK)**, leading to a failure of pre-B cells to differentiate into mature B cells [3]. While B-cell zones in lymph nodes are depleted, the thymus develops normally [3]. **High-Yield NEET-PG Pearls:** * **Chest X-ray finding:** Look for the **"Absent Thymic Shadow"** in DiGeorge syndrome and SCID. * **Diagnostic Test:** FISH (Fluorescence In Situ Hybridization) is the gold standard to detect the 22q11.2 deletion [2]. * **Parathyroid involvement:** Hypocalcemia presenting as neonatal tetany is a classic clue for DiGeorge syndrome [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. 167-168. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 173. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 248-249. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 250-251. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 249-250.

Question 670: Venous thrombi most commonly embolize to which organ?

A. Heart
B. Lung (Correct Answer)
C. Brain
D. Kidneys

Explanation: **Explanation:** The correct answer is **Lung**. This is a fundamental concept in hemodynamic disorders regarding the pathway of systemic venous circulation. **1. Why Lung is Correct:** Venous thrombi most commonly originate in the deep veins of the lower extremities (Deep Vein Thrombosis or DVT). Once a thrombus dislodges, it becomes an embolus and travels through progressively larger vessels: from the **iliac veins** to the **inferior vena cava (IVC)**, into the **right atrium**, and then the **right ventricle**. From the right heart, the embolus is pumped into the **pulmonary arteries** [1], [3]. Because the pulmonary arterial tree narrows into a capillary bed, it acts as a "sieve," trapping the embolus. This sequence results in **Pulmonary Embolism (PE)** [1], [2]. **2. Why Incorrect Options are Wrong:** * **Heart:** While the embolus passes *through* the right chambers of the heart, it rarely lodges there unless there is a structural abnormality (e.g., a large saddle embolus straddling the bifurcation or a clot adhering to a prosthetic valve) [1]. * **Brain & Kidneys:** These are common sites for **arterial emboli** (usually originating from the left heart or carotid arteries) [1]. For a venous thrombus to reach the brain or kidneys, it must bypass the pulmonary circulation via a right-to-left shunt (e.g., Patent Foramen Ovale), a phenomenon known as **Paradoxical Embolism** [1], [2]. **High-Yield NEET-PG Pearls:** * **Most common source of PE:** Deep veins of the leg above the knee (Popliteal, Femoral, and Iliac veins). * **Lines of Zahn:** Morphologic feature of thrombi formed in flowing blood (alternating layers of platelets/fibrin and RBCs); helps distinguish a pre-mortem clot from a post-mortem clot. * **Virchow’s Triad:** Endothelial injury, Stasis, and Hypercoagulability are the three primary influences on thrombus formation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 137-138. [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. 144-145. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 705-706.

Practice by Chapter

Cell Injury and Cell Death

Practice Questions

Adaptations of Cellular Growth

Practice Questions

Accumulations and Deposits

Practice Questions

Acute and Chronic Inflammation

Practice Questions

Tissue Repair and Wound Healing

Practice Questions

Hemodynamic Disorders

Practice Questions

Genetic Disorders

Practice Questions

Environmental Pathology

Practice Questions

Nutritional Diseases

Practice Questions

Molecular Basis of Disease

Practice Questions

Want unlimited practice?

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

Start For Free