Cell Injury-3 Pathology PDF

Cell injury-3 Dr.Gehan Abdelmenam  Intended Learning Objectives Recall types of cell death. Describe types, examples, morphological features of necrotic cells. Describe morphologic appearance and types of apoptotic cells. Comparison between necrotic and apoptotic cell. * Types...

Cell injury-3 Dr.Gehan Abdelmenam  Intended Learning Objectives Recall types of cell death. Describe types, examples, morphological features of necrotic cells. Describe morphologic appearance and types of apoptotic cells. Comparison between necrotic and apoptotic cell. * Types of cell death: Necrosis: local death of a group of cells within the living body. Apoptosis: genetically controlled programmed 3 single cell death.  Necrosis 4 * Morphological features of necrosis * Grossly: The necrotic area is well- defined, swollen, opaque, pale yellow or pale red and surrounded by a red zone of inflammatory hyperemia. Red Inflammatory zone Yellow Area of infarction 5 *Microscopically: Immediately the cells appear normal, then a series of changes occur: 1. Cell membrane: disappear & the cells become indistinct from each other. 2. Cytoplasm: swollen & coagulated, appears homogenous and deeply eosinophilic. 3. Nucleus: Pyknosis: shrunken & deeply basophilic. Karyorrhexis: fragmented. Karyolysis: disappear due to chromatin hydrolysis. 6 7  Nuclear pyknosis Karyorrhexis Karyolysis 8 * Types of necrosis: 1. Coagulation necrosis. 2. Liquefactive necrosis. 3. Caseation necrosis. 4. Fat necrosis. 5. Fibrinoid necrosis. 9  Coagulative necrosis * Mechanism: – Denaturation and coagulation of structural and enzymatic proteins. – Preserving cell outlines and tissue architecture. – Examples: myocardial infarction due to coronary artery occlusion. 10 Coronary artery Myocardial thrombosis infarction 11  Coagulative necrosis of renal tubules Ghosts of renal tubules with preserved outlines but lost cellular details 12  Liquifactive necrosis * Definition: necrosis with complete loss of cell and tissue structure due to liquefaction by hydrolytic enzymes. * Mechanism: – Enzymes derived from either cell’s own lysosomes (autolysis) or from Neutrophils and macrophages (heterolysis). Examples: A- ischemic necrosis of brain (infarction) B- pyogenic abscess. 13  Necrotic material Lung Abscesses with loss of cellular architecture Neutrophils Necrotic tissue  Coagulative versus Liquefactive necrosis Coagulative necrosis Focus of liquefactive necrosis  Caseation necrosis It is a combination of coagulative and liquefaction necrosis. The tissue is firm (grossly) and without cellular details or tissue outline (microscopically). Examples: Tuberculosis 17 Caseous necrosis of tuberculosis Inflammatory cells of the tuberculous granuloma Caseous necrosis 18 Fat necrosis 19  Fat necrosis is a form of necrosis characterized necrosis of fat cells by either trauma to fatty tissue or by the action of lipase enzyme. Examples: 1. Traumatic fat necrosis of the breast due to trauma. 2. Enzymatic fat necrosis of the pancreas and omentum in case of acute hemorrhagic pancreatitis. fat necrosis The pancreas contains numerous whitish yellow nodules corresponding to foci which undergo.saponification 21  Fibrnoid necrosis Definition: it is the death of cells in the inner layer of small blood vessels. It can lead to bleeding and internal damage throughout the body Causes : 1-Malignant hypertension extremely high blood pressure, such as can cause fibrinoid necrosis in the blood vessels of the heart, brain, kidneys. 2- Autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus. 3- Subacute bacterial endocarditis, an infection of the heart. 4- Vasculitis :such as polyarteritis nodosa. 22  Apoptosis 23 * Morphologic appearance of apoptotic cells: 1. Cell shrinkage. 2. The cytoplasm becomes deeply esinophilic. 3. The nucleus becomes pyknotic then fragments. 4. The cell membrane does not rupture. 5. Formation of cytoplasmic buds. 6. Each nuclear fragment go with a cytoplasmic bud and breaking off to form apoptotic bodies. 7. Phagocytosis of apoptotic bodies by adjacent cells or macrophages. 8. A lack of inflammatory response. 24  * Physiologic examples of apoptosis: 1. Embryogenesis. Development of lumen within hollow organs (e.g. bowel and heart). 2. Hormone-dependent involution in adults. – Post-lactational change in breast size. – Uterine involution after delivery. 3. Removal of self reacting T-lymphocytes in Thymus. 25 * Pathologic examples of apoptosis: 1. Councilman bodies = apoptotic hepatocytes in viral hepatitis. 2. Tumor cell death. 3. Neurons that are lost in Alzheimer's disease. 4. HIV-positive T-lymphocytes die by apoptosis. 26 Apoptosis of epidermal Apoptotic cell in liver cells Apoptosis vs. Necrosis  Feature Necrosis Apoptosis Cell size Enlarged (swelling) Reduced (shrinkage) Nucleus Pyknosis  Fragmentation karyorrhexis  karyolysis Cellular contents Enzymatic Intact, may be digestion; may leak released in out of cell apoptotic bodies. 29 Feature Necrosis Apoptosis Adjacent inflammation Frequent No Physiologic or Always pathologic Often physiologic, may pathologic role be pathologic 30 31  REFERENCES Robbins and Cotran Pathologic Basis of Disease, 9th edition, 2014 ( Kumar, Abbas, Aster) Robbins Basic Pathology 10th edition, 2017 ( Kumar, Abbas, Aster) Good luck