Lect.no (5)
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Transcript of Lect.no (5)
Outcomes of necrosis:-
1.Inflammation & resolution occurs if the injury is mild & the tissue has the power to proliferate.2.Inflammation & organization (fibrosis). occurs if the injury is severe &/or the tissue do not have the power to proliferate.3. Dystrophic calcification- deposition of Ca++ salts in necrotic tissue.
Myocardial infarction (Posterolateral pale infarct)
22
Inflammation & fibrosis of
severe burn
33
Aortic valve , gross , (calcified aortic stenosis).
44
APOPTOSIS Apoptosis come from the Greek word which means
“falling off”.
ApoptosisApoptosis
• “A programmed active single cell death” that is induced by a tightly regulated intracellular program.Cells actually expend energy in order to die.
• Causes of Apoptosis - Physiologic situations - Pathologic conditions
APOPTOSISAPOPTOSIS•NORMAL (preprogrammed)
•PATHOLOGIC (associated with Necrosis)
Apoptosis in Physiologic SituationsApoptosis in Physiologic Situations
• Programmed destruction of cell during embryogenesis & development
• Hormone-dependent tissue involution - endometrial cells (menstrual cycle)• Cell deletion in proliferating cell population e.g skin• Post-inflammatory clean up- neutrophils.• Cell death induced by cytotoxic T-cells to eliminate
harmful cells - viral infected or tumor cells
Apoptosis in Pathologic ConditionsApoptosis in Pathologic Conditions
• Cell death produced by injurious stimuli – radiation, cytotoxic drug
• Cell injury in certain viral diseases – viral hepatitis
• Pathologic atrophy
• Cell death in tumors .
MORPHOLOGICAL MORPHOLOGICAL FEATURES OF APOPTOSISFEATURES OF APOPTOSIS
• Cell shrinkageCell shrinkage• Chromatin condensation and fragmentation.Chromatin condensation and fragmentation.• Formation of cytoplasmic blebs and apoptotic Formation of cytoplasmic blebs and apoptotic
bodies.bodies.• Phagocytosis of apoptotic bodies by adjacent Phagocytosis of apoptotic bodies by adjacent
healthy cells or macrophages.healthy cells or macrophages.• Lack of inflammation.Lack of inflammation.
Morphology of Apoptosis
Cell shrinkageCell shrinkage
Chromosome Chromosome condensationcondensation
Formation of Formation of cytoplasmic blebs cytoplasmic blebs and apoptotic bodiesand apoptotic bodies
Phagocytosis of Phagocytosis of apoptotic cells or cell apoptotic cells or cell bodiesbodies
normalcellCellular swelling,
chromatin clupingMembrane
damage
Nuclear chromatin condensation and
fragmentation
Cytoplasmic budding and apoptosisi body
Phagocytosisi of apoptosis body
The sequential ultrastructual changes in necrosis and apoptosis
Apotosis of hepatocytes
• Fig 1-18
SHRINKAGE/HYPERCHROMASIASHRINKAGE/HYPERCHROMASIA
PHAGOCYTOSISPHAGOCYTOSIS
APOPTOSIS APOPTOSIS BIOCHEMISTRYBIOCHEMISTRY
• Protein Digestion (Caspases)• DNAbreakdown
(endonucleases)• Phagocytic Recognition
Comparison of cell death by apoptosis and necrosis
Comparison of cell death by apoptosis Comparison of cell death by apoptosis and necrosisand necrosis
Mechanism Mechanism injurious programmed injurious programmed passive cell death active cell death passive cell death active cell death Cell sizeCell size Enlarged Enlarged Reduced Reduced ExtentExtent single cell group of cells single cell group of cellsNucleus Nucleus Pyknosis / karyorrhexis / karyolysis Pyknosis / karyorrhexis / karyolysis condensation & FragmentationFragmentation (Apoptotic bodies)(Apoptotic bodies)
Plasma membranePlasma membrane Disrupted Disrupted Intact Intact
Cellular contentsCellular contents swell& Enzymatic digestion swell& Enzymatic digestion IntactIntact
Feature Necrosis Apoptosis
Comparison of cell death by apoptosis Comparison of cell death by apoptosis and necrosisand necrosis
BiochemistryBiochemistry impairment & cessation of ion homeostasis' Active DNA digestion lysosomes leak lytic enzymes by endonuclease lysosomes intact
Inflammation Inflammation usual Noneusual None
Fate of dead cells phagocytosed by inflammatory phagocytose byphagocytosed by inflammatory phagocytose by cells ( neutrophils & macrophages) macrophagescells ( neutrophils & macrophages) macrophages
CauseCause induced by pathologic stimuli induced by induced by pathologic stimuli induced by physiologic & physiologic & pathologicpathologic stimuli stimuli