Pathology CAT 1: Cell Injury, Metaplasia & OmpathStudy

MOUNT KENYA UNIVERSITY — MEDICAL SCHOOL Programme: Bachelor of Medicine and Bachelor of Surgery, Year 3 Assessment: Mid Semester 1 — CAT 1 Unit Code: MBPA 3411 — Introduction to Pathology Date: 13th October 2025 Time: 22 minutes Reg No: BMS/2023/.. --- Q1. Which of the following best describes the primary mechanism underlying cellular metaplasia? A. Irreversible genetic mutation in somatic cells B. Reversible reprogramming of stem cells or undifferentiated cells C. Direct transformation of fully differentiated cells D. Failure of DNA repair mechanisms E. Accumulation of misfolded proteins Answer: B Metaplasia is a reversible adaptive change driven by reprogramming of stem/reserve cells to a different differentiated phenotype in response to a chronic stimulus — not a mutation (A) or direct conversion of mature cells (C). Q2. In pathological hypertrophy of cardiac muscle, which molecular pathway is most commonly activated? A. p53-mediated cell cycle arrest B. mTOR signaling pathway C. Caspase-dependent apoptosis D. Autophagy-lysosomal pathway E. NF-κB inflammatory pathway Answer: B mTOR signalling drives the protein synthesis and cell growth underlying cardiomyocyte hypertrophy in response to increased workload. The others (A, C, D) relate to cell death/degradation, not growth. Q3. Barrett's esophagus represents which type of cellular adaptation, and what is its primary clinical significance? A. Hyperplasia; increased risk of squamous cell carcinoma B. Atrophy; decreased digestive function C. Metaplasia; increased risk of adenocarcinoma D. Hypertrophy; improved acid resistance E. Dysplasia; immediate malignant transformation Answer: C Chronic acid reflux causes squamous epithelium to convert to columnar (intestinal-type) epithelium — classic metaplasia — which predisposes to esophageal adenocarcinoma, not squamous carcinoma (A). Q4. Which cellular organelle is most critically involved in maintaining cellular energy homeostasis and is first affected during hypoxic injury? A. Rough endoplasmic reticulum B. Golgi apparatus C. Mitochondria D. Lysosomes E. Peroxisomes Answer: C Mitochondria generate ATP via oxidative phosphorylation; hypoxia halts this immediately, making them the first organelle affected. Others (A, B, D, E) are affected secondarily as ATP depletion progresses. Q5. Oncosis differs from apoptosis primarily in which of the following characteristics? A. Nuclear fragmentation pattern B. Cell membrane integrity C. Energy requirement D. Inflammatory response E. DNA ladder formation Answer: B Oncosis (necrotic cell swelling) involves early loss of membrane integrity and cell lysis, while apoptosis preserves membrane integrity until late (apoptotic bodies are phagocytosed intact). D and E are also differences, but membrane integrity is the most fundamental distinguishing feature. Q6. Which of the following best explains why neurons are particularly vulnerable to hypoxic injury compared to other cell types? A. Higher metabolic rate and dependence on aerobic respiration B. Larger cell size requiring more nutrients C. Inability to undergo cellular adaptation D. Lack of antioxidant mechanisms E. Higher concentration of mitochondria Answer: A Neurons have very high oxidative metabolic demand and rely almost entirely on aerobic respiration for ATP, making them exquisitely sensitive to even brief hypoxia. Q7. Which mechanism is primarily responsible for the removal of damaged organelles during cellular stress? A. Proteasomal degradation B. Exocytosis C. Macroautophagy D. Apoptosis E. Necroptosis Answer: C Macroautophagy specifically engulfs and degrades damaged organelles via autophagosomes. Proteasomal degradation (A) targets individual misfolded proteins, not whole organelles. Q8. Free radical injury to cells primarily affects which cellular components first? A. Nuclear DNA B. Mitochondrial DNA C. Cell membrane lipids D. Cytoplasmic proteins E. Ribosomal RNA Answer: C Lipid peroxidation of membrane lipids is the earliest and most characteristic effect of free radical damage, disrupting membrane integrity before DNA/protein damage becomes significant. Q9. In reversible cell injury, which morphological change is typically observed first? A. Nuclear pyknosis B. Cell membrane blebbing C. Cellular swelling D. Mitochondrial fragmentation E. Chromatin condensation Answer: C Cellular (hydropic) swelling from ATP-dependent sodium pump failure is the earliest, classic sign of reversible injury. A and E are late/irreversible changes. Q10. Necroptosis is characterized by all of the following EXCEPT: A. RIP1 and RIP3 kinase activation B. Caspase-independent mechanism C. Inflammatory response D. ATP preservation E. Plasma membrane rupture Answer: D Necroptosis, like necrosis, is an energy (ATP)-depleting process with membrane rupture and inflammation — not ATP-preserving. A, B, C, E are all correct hallmarks of necroptosis. Q11. Which type of necrosis is most commonly seen in brain infarction? A. Coagulative necrosis B. Li