Cell Death: Necrosis and Apoptosis
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Cell Death: Necrosis and Apoptosis

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Questions and Answers

What defines apoptosis in the context of cell death?

  • A process involving acute inflammation
  • An irreversible process due to injury
  • Enzymatic digestion of cellular structures
  • An internally programmed series of events leading to cell elimination (correct)

    • Which type of necrosis is most commonly associated with ischemia?

  • Liquefactive necrosis
  • Fibrinoid necrosis
  • Coagulative necrosis (correct)
  • Caseous necrosis

    • What is a characteristic morphological feature of necrotic cells?

  • Fragmented nuclear structure (correct)
  • Uniform cell membranes
  • Retention of nuclear details
  • Increased cell membrane integrity

    • What does the term 'karyolysis' refer to in necrotic cells?

    <p>Dissolution of the nucleus</p> Signup and view all the answers

    During coagulative necrosis, what happens to normal cells?

    <p>They lose cytoplasmic and nuclear details but retain outlines</p> Signup and view all the answers

    Which condition is most likely to result in necrosis due to hypoxia?

    <p>Myocardial infarction</p> Signup and view all the answers

    What is the primary cause of necrosis as described?

    <p>Increased intracellular calcium levels</p> Signup and view all the answers

    Which of the following will NOT typically occur in necrotic tissue?

    <p>Vascular permeability decrease</p> Signup and view all the answers

    What is the primary cause of fat necrosis?

    <p>Trauma</p> Signup and view all the answers

    What do the chalky, white areas in fat necrosis result from?

    <p>Calcium deposition</p> Signup and view all the answers

    Which necrosis type is typically associated with immune reactions in blood vessels?

    <p>Fibrinoid necrosis</p> Signup and view all the answers

    Which of the following statements about apoptosis is true?

    <p>Apoptosis requires cellular signals for initiation</p> Signup and view all the answers

    What is the gross appearance of fibrinoid necrosis?

    <p>Changes too small to see grossly</p> Signup and view all the answers

    Which condition can be an example of pathological apoptosis?

    <p>Injury beyond repair</p> Signup and view all the answers

    Which example illustrates physiological apoptosis?

    <p>Excess cell removal during development</p> Signup and view all the answers

    What feature is NOT characteristic of apoptosis?

    <p>Inflammatory reaction</p> Signup and view all the answers

    What is the primary characteristic of coagulative necrosis as observed in kidney infarction?

    <p>Preservation of cell outlines with loss of nuclei</p> Signup and view all the answers

    In which type of necrosis is the necrotic material often creamy yellow and referred to as pus?

    <p>Liquefactive necrosis</p> Signup and view all the answers

    What type of necrosis is described as having a 'cottage cheese-like' appearance?

    <p>Caseous necrosis</p> Signup and view all the answers

    Which inflammatory cells are primarily associated with liquefactive necrosis?

    <p>Neutrophils</p> Signup and view all the answers

    What is the process through which necrotic cells are removed during necrosis?

    <p>Phagocytosis</p> Signup and view all the answers

    Which condition is commonly associated with liquefactive necrosis?

    <p>Cerebral infarction</p> Signup and view all the answers

    What histological feature is observed in caseous necrosis?

    <p>Acellular pink areas of necrosis</p> Signup and view all the answers

    Which of the following best describes the infiltration of inflammatory cells during necrosis?

    <p>Accumulation of leukocytes in the necrosed focus</p> Signup and view all the answers

    What triggers apoptosis when there is an accumulation of misfolded proteins?

    <p>Cell death due to disruptions in protein folding</p> Signup and view all the answers

    Which enzyme is considered an important final executor in the process of apoptosis?

    <p>Caspase-3</p> Signup and view all the answers

    What distinguishes necrosis from apoptosis in terms of cell membrane integrity?

    <p>Necrosis involves membrane fragmentation, while apoptosis does not</p> Signup and view all the answers

    During apoptosis, which morphological feature is typically observed?

    <p>Nuclear condensation and fragmentation</p> Signup and view all the answers

    Which statement accurately reflects the fate of cells undergoing apoptosis?

    <p>They are phagocytosed by neighboring cells without causing inflammation</p> Signup and view all the answers

    Which of the following best describes the circumstances under which apoptosis occurs?

    <p>Both pathological and physiological conditions</p> Signup and view all the answers

    What morphological change occurs to cells undergoing apoptosis?

    <p>Formation of apoptotic bodies</p> Signup and view all the answers

    What defines the biochemical mechanism of apoptosis compared to necrosis?

    <p>Energy-dependent process involving proteases and endonucleases</p> Signup and view all the answers

    Study Notes

    Cell Death: Necrosis and Apoptosis

    • Necrosis: Cell death due to enzymatic digestion of cellular components, causing changes in cell structure.

      • Causes: Hypoxia, free radicals, cell membrane damage, increased intracellular calcium.
      • Characteristics:
        • Involves a group of cells.
        • Cells become eosinophilic (pink) and glassy.
        • Cell membranes fragment.
        • Nuclear changes:
          • Pyknosis: Nuclear shrinkage.
          • Karyorrhexis: Nuclear fragmentation.
          • Karyolysis: Nuclear dissolution.
        • Presence of inflammatory cells.
      • Types:
        • Coagulative Necrosis: Most common, occurs due to ischemia (loss of blood flow).
          • Grossly: Tissue is firm, often wedge-shaped and pale.
          • Microscopically: Cells retain their outlines, with loss of cytoplasmic and nuclear details.
          • Examples: Kidney infraction, myocardial infarction, splenic infarct.
        • Liquefactive Necrosis: Caused by enzymatic lysis of cells, transforming tissue into a viscous liquid.
          • Causes: Bacterial or fungal infections, brain infarction.
          • Grossly: Tissue is liquidy and creamy yellow (pus).
          • Microscopically: Abundance of neutrophils and cell debris.
          • Examples: Cerebral Infarction.
        • Caseous Necrosis: Necrotic tissue with a "cottage cheese-like" appearance.
          • Grossly: Soft and friable.
          • Microscopically: Loss of cell outlines, acellular pink areas of necrosis surrounded by a granulomatous inflammatory process.
          • Examples: Tuberculosis lesions, fungal infections.
        • Fat Necrosis: Necrosis in adipose tissue induced by lipases.
          • Causes: Trauma, pancreatitis.
          • Grossly: Chalky white areas (saponification).
          • Microscopically: Shadowy outlines of dead fat cells surrounded by calcium deposits and inflammation.
        • Fibrinoid Necrosis: Form of necrosis seen in immune reactions involving blood vessels, where immune complexes and fibrin are deposited in the vessel walls.
          • Grossly: Changes too small to be seen.
          • Microscopically: Vessel walls are thickened and pinkish-red.
          • Examples: Malignant hypertension, vasculitis (polyarteritis nodosa).

    • Apoptosis: Programmed cell death, involves the elimination of unwanted cells without eliciting inflammation.

      • Mechanism:
        • Involves single cells or small groups of cells.
        • Requires cellular signals that activate protein cleavage, leading to cellular death.
        • Energy-dependent process.
      • Characteristics:
        • Cell shrinkage.
        • Membrane blebbing.
        • Chromatin condensation.
        • Nuclear fragmentation.
        • Formation of apoptotic bodies.
        • Phagocytosis of apoptotic bodies by macrophages.
      • Types:
        • Physiological Apoptosis: A normal process to eliminate cells that are no longer needed, maintaining homeostasis.
          • Examples: Removal of excess cells during development, involution of hormone-dependent tissues, endometrial cell breakdown during menstruation, regression of lactating breast.
        • Pathological Apoptosis: Eliminates injured cells without eliciting tissue damage.
          • Examples: DNA damage from radiation or chemotherapy, accumulation of misfolded proteins, infections (particularly viral), atrophy in parenchymal organs following duct obstruction (pancreas, parotid gland, kidney).

    • Apoptotic Pathway:

      • Pro-apoptotic: Cytochrome c.
      • Anti-apoptotic: Bcl-2.
      • Activation of Caspases: Caspases activate proteases and endonucleases that break down the DNA.
        • Caspase-3 is a key final enzyme in this process.

    Differences between Necrosis and Apoptosis

    • Induction: Necrosis is primarily pathological, while apoptosis can be both physiological and pathological.
    • Number of Cells: Necrosis involves groups of cells, while apoptosis affects single cells or small clusters.
    • Cell Membrane: Necrosis leads to loss of membrane integrity, while apoptosis maintains membrane integrity.
    • Cell Size: Necrosis causes cell swelling, while apoptosis results in cell shrinkage and fragmentation.
    • Nucleus: Necrosis features nuclear changes like pyknosis, karyorrhexis, and karyolysis. Apoptosis involves nuclear condensation and fragmentation into apoptotic bodies.
    • Inflammation: Necrosis triggers an inflammatory response, while apoptosis does not cause inflammation.
    • Fate of cells: In necrosis, cells are phagocytosed by neutrophils and macrophages, while in apoptosis, they are phagocytosed by neighboring cells.
    • Biochemical Mechanism: Necrosis is energy-independent, while apoptosis is energy-dependent and involves protease and endonuclease activity.

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    Lecture 4 Cell Death: Necrosis & Apoptosis PDF

    Description

    Explore the mechanisms and characteristics of cell death, focusing on necrosis and apoptosis. Understand the causes, types, and changes that occur during these processes, including the distinct features of coagulative necrosis. This quiz will test your knowledge of essential concepts in cellular biology related to cell death.

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