Cell injury Flashcards
General causes of injured cells
-Changes in available nutrients (like O2)
-Direct cell damage (microorganisms, toxins, physical forces)
Cell injury susceptibility
-Cells have widely variable resistance
-Metabolic status will influence
-Neurons and cardiac myocytes susceptible to hypoxia
-Fibroblasts or squamous cells can survive absence better
Mechanisms of cell injury
-Loss of membrane integrity
-Loss of ability to produce energy
-Genetic damage
Loss of membrane integrity
Cell membranes breakdown and loose ability to segregate reaction within cell or can loose barrier to environment and loose gradients
Loss of ability to produce energy
ATP is insufficient to support cell functions
Mechanism of loss of membrane integrity
-Free radical-induced damage
-Phospholipase-induced damage
-Direct membrane damage
Free radical injury
Unpaired electrons that readily react with surrounding molecules, causing chain reaction as electron passed to molecule to molecule
Where are free radicals formed
-During oxidation reduction reactions during aerobic respiration
-Biotransformation of chemical substances
-Nitric oxide metabolism
Effects of reactive oxygen metabolites
-Protein and membrane degradation
-DNA damage
-Inflammation
Protective mechanisms against free radical injury
-Vitamins A,C, and E
-Iron and copper binding proteins
-Specific enzymes (superoxide dismutase, catalase etc)
Phospholipase-induced injury
Activated membrane phospholipases cleave phospholipids out of the membrane. Can be because of increased Ca or because of decreased energy
Causes of direct membrane injury
-Bacterial toxins
-Xenobiotics
-Complement
Pathways in which ATP is produces
-Oxidative phosphorylation
-Anaerobic glycolysis
Mechanisms of the loss of ability to produce energy
-Failure of energy dependent membrane pumps
-Decreased intracellular pH
-Decreased protein synthesis
-Cytoskeletal degradation
-Membrane degradation
-Leakage of organelle contents
-Organelle dysfunction
Role of calcium in cell injury
-Mitochondrial injury
-Phospholipase activation
-Protease activation
-Endonuclease activation
Effects of genetic injury
-No effect
-Cell dysfunction leading to disease
-Cell transformation leading to neoplasia
-Cell death
Sublethal injury types
-Cell swelling
-Intracellular accumulations
-Neoplastic transformation
Lethal injury results
-Apoptosis
-Necrosis
Mechanism of cell swelling
Membrane ion pumps fail to maintain osmotic gradients so water enters the cell. Look swollen and vacuolated or hydropic change. Reversible
Intracellular accumulations
Abnormal metabolism, functional demands exceeding capability, or exposure to agents leads to accumulations either endogenous or exogenous. Reversible
Examples of endogenous intracellular accumulations
-Metabolic storage diseases
-Lipidosis
-Glycogenosis
-Intracellular pigments
Lipidosis
Triglyceride accumulation that can be physiological or pathological
Pathologic causes of lipidosis
-Hepatotoxins
-Hypoxia
-Starvation
Morphology of lipidosis
Cytoplasmic vacuoles of variable size
Endogenous accumulations due to glycogenosis
Glycogen accumulates due to abnormal metabolism. Cells look swollen. See in diabetes mellitis
Hemosiderin endogenous accumulations
Intracellular aggregates of ferritin associated with increased rbc senescence or hemolysis
Lipofuscin-ceroid endogenous accumulations
Undegradable remnants of oxidized membrane lipids. It can accumulate from aging or membrane oxidation
Exogenous intracellular accumulations
-Viral inclusions
-Carbon
-Non nutritive minerals (lead)
Sublethal injury leading to transformation
Due to genetic injury can be transformed and are not injured now but detrimentally changed
Morphology of transformed cells
-May be normal or hyperplasia
-Anaplasia
-Pleomorphism
Lethal cell injury
Insult exceeds ability to adapt or responds. Can progress here from sublethal injury
Physiologic Causes of apoptosis
-Patterned death during embryogenesis
-Hormone/cytokine induced
-Maintain balance during proliferation
-Removal of cell no longer needed
-Removal of self reactive lymphocytes
Pathologic causes of apoptosis
-Unrepaired DNA damage
-Heat
-Hypoxia
-Viral infection
-Physical pressure
Necrosis
Death from injury that disrupts the ability to function and happens after it is dead and is a passive process. Autolysis of cell in living animal
Autolysis
Self digestion of cell or tissue
Postmortem autolysis
Self digestion of cells/tissues/organs after animal dies
Causes of necrosis
-Hypoxia
-Direct membrane injury
-Many of same things that initiate apoptosis may cause this if severe enough
Mechanism of necrosis
-Degradation of lytic enzymes can come from same cell (autolysis) or from responding cell (heterolysis)
Necrosis morphology
-Eosinophilia
-Smooth, homogenous cytoplasm
-Vacuolation
-Nuclear degeneration
-Inflammation response
What type of cell destruction is always pathologic and causes inflammation
Necrosis
Post mortem autolysis
Cell and tissue degradation that occurs following death of an animal. Occurs in a predictable fashion
Difference in ante mortem and post mortem autolysis
No inflammation or host response in post mortem and occurs in predictable fashion
