Cell Injury 1 PDF

Cell Injury 1 Norhidayah Rosman MSc.(Medicine) Unit of Pathology Learning outcomes 01 List the causes of cell injury with appropriate examples 02 Explain the mechanisms of cell injury Describe 03 the morphologic alterations in reversible and irreversible...

Cell Injury 1 Norhidayah Rosman MSc.(Medicine) Unit of Pathology Learning outcomes 01 List the causes of cell injury with appropriate examples 02 Explain the mechanisms of cell injury Describe 03 the morphologic alterations in reversible and irreversible cell injury Describe 04 the morphology of the patterns of necrosis with suitable examples. 01 List the causes of cell injury with appropriate examples  Hypoxia & Infectious Immunologic Toxins Ischemia agents reactions Causes of Cell Injury Genetic Nutritional Physical abnormalities imbalance agents Aging  Hypoxia & Ischemia Hypoxia: Oxygen deficiency Ischemia: Reduced blood supply Resulting from: Arterial obstruction Disease affecting lung Anaemia Carbon monoxide (CO) poisoning Toxins Infectious agents  Immunologic Reactions Immune responses elicit inflammatory reactions  Genetic Abnormalities Can result in pathologic changes as conspicuous as the congenital malformations Nutritional Imbalance Physical Agents  Aging Results in a diminished ability of cells to respond to stress and, eventually, the death of cells and of the organism. 02 Explain the mechanism of cell injury  General Principles of Cell Injury Cellular response to injury Targets that are suseptible depends on to cell injury Type of injury Cell membranes Duration Production of ATP via aerobic respiration Severity of injury Protein synthesis Type of cell injured DNA Mechanism of Cell Injury  1. Loss of energy (ATP Depletion) Deficiency of oxygen leads to failure of many energy- dependent metabolic pathways, and ultimately to death of cells by necrosis. Associated with both hypoxic and chemical (toxic) injury  1. Loss of energy (ATP Depletion) Hypoxia and Ischemia Persistent or severe hypoxia and ischemia ultimately lead to failure of ATP generation and depletion of ATP in cells. Loss of this critical energy store has deleterious effects on many cellular systems  1. Loss of energy (ATP Depletion) Ischemia-Reperfusion Injury Restoration of blood flow to ischemic but increased cause of cell injury. Mechanisms of cell injury exacerbation New damage may be initiated during reoxygenation by Increased generation of ROS Inflammation due to ischaemic injury may increase with reperfusion because it enhances the influx of leukocytes and plasma proteins 2. Increase oxidative stress Cellular abnormalities that are induced by ROS, which belong to a group of molecules known as free radicals. Produced by two major pathways: Small amounts in all cells during the reduction-oxidation (redox) reactions Phagocytic leukocytes, mainly neutrophils and macrophages  Free radicals They are chemical species with a single unpaired electron in the outer orbit. They are chemically unstable and so they react with other molecules causing damage If they are not neutralized they can damage cells by Lipid peroxidation of membranes DNA fragmentation Protein cross linking  Defects in plasma membrane permeability Can also be damaged directly by certain bacterial toxins, viral proteins, lytic complement components, and a variety of physical and chemical agents. Membrane damage affect the mitochondria, the plasma membrane, and other cellular membranes 3. Accumulation of misfolding protein Can stress compensatory pathways in the ER and lead to apoptosis. May be caused by abnormalities that increase the production of misfolded proteins or reduce the ability to eliminate them May cause disease by creating a deficiency of an essential protein or by inducing apoptosis 4. DNA damage Exposure of cells to: Radiation or chemotherapeutic agents Intracellular generation of ROS Acquisition of mutations Severe may trigger apoptotic death. 5. Inflammation Elicited by pathogens, necrotic cells, and dysregulated immune responses (autoimmune diseases and allergies) Inflammatory cells secrete products that evolved to destroy microbes but also may damage host tissues (Hypersensitivity) 03 Describe the morphologic alterations in reversible and irreversible cell injury  Reversible vs irreversible cell injury Reversible injury : Within limits, the cell can compensate for the derangements and, if the injurious stimulus stops , will return to normalcy Irreversible : Persistent or excessive injury, causes irreversible injury And when does the cell actually die? 1. The inability to reverse mitochondrial dysfunction 2. The development of profound disturbances in membrane function.  Morphology – Reversible Injury On light microscopy Hydropic Swelling Fatty Change Ultrastructural changes: Changes are seen by EM  Morphology – Irreversible Injury On light microscopy Plasma membrane damage Lysosomal rupture Autolysis Increase mitochondrial permeability Changes of the nucleus Pyknosis (Nuclear shrinkage) Karyorrhexis (Nucleus undergoes fragmentation) Karyolysis (Chromatin fade) 03 Describe the morphology of the patterns of necrosis with suitable examples  Necrosis Spectrum of morphologic changes that follow cell death in living tissues , resulting from the progressive degradative action of enzymes on the lethally injured cells which then invokes inflammatory response TYPES OF NECROSIS Coagulative Liquefactive necrosis necrosis 1 2 Gangrenous Fat necrosis 6 3 necrosis Fibrinoid 5 4 Caseous necrosis necrosis  1. COAGULATIVE NECROSIS Most common necrosis Form of tissue necrosis where the component cells are dead but underlying tissue architecture is preserved for at least several days All solid organs except the brain. Gross Morphology: Firm texture, pale, & slightly swollen. With progression: more yellowish, softer & shrunken  COAGULATIVE Protein NECROSIS (Cont.) structure & Blocking the enzymes proteolysis of the denatured dead cells Leukocytes are recruited to the site of MAY PERSIST FOR DAYS/WEEKS necrosis Cellular debris removed Digested by the action by phagocytosis of lysosomal enzymes WHICH ONE IS COAGULATIVE NECROSIS? B A Microscopic view of coagulative necrosis  2. LIQUEFACTIVE NECROSIS Due to bacterial and, occasionally, fungal infections acute inflammation (bacterial Dead cells are completely digested. infection) Transform of tissue into liquid viscous mass. frequently creamy yellow (pus) Remove by phagocytes  Gross Morphology Microscopical Morphology The affected area is soft with liquefied Demonstrates many macrophages at centre containing necrotic debris the right which are cleaning up the necrotic cellular debris Cyst wall is performed 3. GANGRENOUS NECROSIS Body part lost blood supply/serious bacterial infection Undergo coagulative necrosis (multiple tissue layers) Superimposed bacterial infection Change morphologic appearance to liquefactive necrosis Destructive contents of the bacteria Attracted leukocytes Example: DM, Frost bite, Raynaud’s disease, Escharotic drugs  Gross Morphology Microscopical Morphology Dry gangrenous necrosis Wet gangrenous Inflammation extending beneath the necrosis skin involve soft tissue (fat and connective tissue at the right) and bone (at the left). 4. CASEOUS NECROSIS Coagulative necrosis + Liquefactive necrosis  Gross Morphology Microscopical Morphology Foci of caseous necrosis, friable Collection of fragmented or lysed cells yellow-white appearance of the area with an amorphous granular pink of necrosis. appearance in H&E stained tissue sections.  5. FAT NECROSIS Acinar cell LIPASES injury Saponification Calcium Split (Chalky features) + triglyceride Fatty acid ester  Gross Morphology Microscopical Morphology A B Soft and chalky white areas Microscopical Morphology A B  6. FIBRINOID NECROSIS A special form of necrosis. Associated with vascular damage & the exudation of plasma. Characterised by deposition of fibrin-like material which has the staining properties of fibrin. Cannot be identified grossly. Example of immunologic tissue injury: 1. Immune complex vasculitis 2. Autoimmune diseases 3. Arthus reaction  Microscopical Morphology The wall of the artery is surrounded by a (intensely pink) fibrinoid necrosis (large bright ring of necrosis with inflammation. blood vessel - right of image) in a case of vasculitis. H&E stain was used.  + Cmd A Thanks! Does anyone have any questions? 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