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Questions and Answers
In necrosis, the cell membrane remains intact.
In necrosis, the cell membrane remains intact.
False
Apoptosis is always a pathological process.
Apoptosis is always a pathological process.
False
High motility group box 1 protein (HMBG-1) inhibits the movement of macrophages and neutrophils to the site of injury.
High motility group box 1 protein (HMBG-1) inhibits the movement of macrophages and neutrophils to the site of injury.
False
Coagulative necrosis is characterized by the complete digestion of dead tissue leaving a fluid-filled space.
Coagulative necrosis is characterized by the complete digestion of dead tissue leaving a fluid-filled space.
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Karyolysis, karyorrhexis, and pyknosis are types of plasma membrane changes associated with necrosis.
Karyolysis, karyorrhexis, and pyknosis are types of plasma membrane changes associated with necrosis.
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Coagulative necrosis is characterized by the digestion of dead cells, resulting in a viscous liquid.
Coagulative necrosis is characterized by the digestion of dead cells, resulting in a viscous liquid.
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Dry gangrene results from liquefactive necrosis.
Dry gangrene results from liquefactive necrosis.
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Caseous necrosis is characterized by a bright pink appearance of the walls of involved arteries.
Caseous necrosis is characterized by a bright pink appearance of the walls of involved arteries.
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Apoptosis always involves spillage of cellular contents into the surrounding environment leading to inflammation.
Apoptosis always involves spillage of cellular contents into the surrounding environment leading to inflammation.
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Accumulation of unfolded proteins is not a cause of apoptosis.
Accumulation of unfolded proteins is not a cause of apoptosis.
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Study Notes
Cell Death
- Cell death is the endpoint of normal cell physiology, resulting in the irreversible termination of cellular functions like growth, division, and homeostasis.
- It's crucial for maintaining healthy cell physiology and removing dysfunctional, worn-out, or damaged cells.
- Cell death, survival, proliferation, and differentiation are fundamental processes of life.
- Cell death can occur as a component of a physiological process or as a response to a pathological condition, like injury.
- Homeostatic mechanisms maintain cells within a narrow metabolic window allowing minimal deviation from equilibrium.
- Stressors exceeding homeostatic capabilities lead to reversible then irreversible injury, potentially causing cell death.
- Irreversible injury results in the endpoint of cell death.
- Apoptosis and necrosis are the two primary types of cell death.
Types of Cell Death
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Apoptosis (Type 1): A genetically controlled, synchronized programmed cell death characterized by the orderly breakdown of the cell without spilling contents into the surrounding environment.
- Physiological causes: removal of excess cells in embryonic development, hormone withdrawal-related tissue involution, and cell turnover in rapidly dividing tissues.
- Pathological causes: DNA damage, misfolded proteins, and viral infections.
- Morphological changes: cell shrinkage, chromatin condensation, nuclear fragmentation (karyorrhexis), plasma membrane blebbing, and formation of apoptotic bodies intensely eosinophilic
- The process is characterized by the absence of inflammation and efficient phagocytosis of apoptotic bodies.
- Identification methods: microscopy, annexin V stain, DNA fragmentation assays, and flow cytometry.
- Mechanisms: intrinsic mitochondrial and extrinsic death receptor pathways converge to activate caspase executioner caspases, inducing programmed cell death.
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Necrosis (Type II): The pathological endpoint of severe cellular injury, including denaturation of proteins, leakage of cellular contents through damaged membranes, local inflammation due to enzymatic digestion of the lethally injured cell, and swelling.
- Causes: toxins, infections, trauma, inflammation
- Morphological Changes: necrotic cells exhibit increased eosinophilia, a glassy homogeneous appearance, vacuolated cytoplasm, and myelin figures, with karyolysis, karyorrhexis, and pyknosis of the nucleus.
- Types:
- Coagulative: denaturation of proteins, preserving cell structure, typically caused by ischemia.
- Liquefactive: digestion converts tissue to a liquid; often seen in bacterial or fungal infections.
- Gangrenous: coagulative or liquefactive necrosis in extremities, often due to ischemia.
- Caseous: characteristic in TB infections, with a white, cheese-like appearance.
- Fat necrosis: adipose tissue damage, often featuring inflammatory cells, and calcification.
- Fibrinoid: depositions of immune complexes and plasma proteins, causing a bright pink appearance in arteries.
- Damage-associated molecular patterns (DAMPs) elicit inflammation.
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Autophagy: A self-digestive process that delivers cytoplasmic material to lysosomes for degradation, which may serve as a mechanism of cell killing.
- Forms: Macro-autophagy Micro-autophagy and Chaperone-mediated autophagy.
- Initiated due to cellular stress and may lead to excessive autophagy resulting in cell death.
Other Cell Death Types
- Anoikis: Programmed cell death that occurs due to the lack of attachment to the extracellular matrix (ECM). ECM attachment is essential for cell survival.
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Necroptosis: Regulated necrosis facilitated by death receptors.
- It resembles necrosis but involves the activation of receptor-interacting protein kinase 3 (RIPK3) in the extrinsic pathway and consequent mixed lineage kinase domain-like protein (MLKL) phosphorylation.
- Pyroptosis: A form of apoptosis accompanied by the release of fever-inducing cytokine IL-1, triggered by excessive intracellular levels of iron or reactive oxygen species (ROS).
- Ferroptosis: A distinct cell death that is triggered when excessive intracellular levels of iron or reactive oxygen species overwhelm the body's glutathione-dependent antioxidant defenses, potentially leading to inflammation.
- Entosis: A cell-to-cell internalization mechanism, potentially defining a “cell-in-cell” structure.
- Parthanatos: Mitochondrial-linked but caspase-independent cell death characterized by the hyperactivation of poly(ADP-ribose) polymerase, known as PARP, which mediates the synthesis of poly(ADP-ribose) and may cause apoptosis.
- NETosis: Neutrophil extracellular trap-associated cell death mainly occurs in immune cells, particularly neutrophils, triggered by pathogens or components;
- Methuosis: Programmed cell death characterized by the displacement of cytoplasm by large fluid-filled vacuoles derived from macropinosomes.
- Cuproptosis: Programmed cell death triggered by copper.
- Oxeiptosis: Caspase-independent, ROS-sensitive, and non-inflammatory cell death pathway.
- Erebosis: A novel form of cell death during the natural turnover of gut enterocytes, marked by a loss of cell adhesion.
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Description
Explore the critical processes of cell death, including apoptosis and necrosis. Understand how cell death is essential for maintaining healthy cell physiology and the implications of pathological conditions. This quiz covers the mechanisms, types, and significance of cell death in biological systems.
