Cell Injury • cell injury results when cells are stressed so severely that they are no longer able to adapt
• Reversible cell injury. In early stages or mild forms of injury, the functional and morphologic changes are reversible if the damaging stimulus is removed. cellular swelling and fatty change
• Irreversible cell injury With continuing damage the injury becomes irreversible, at which time the cell cannot recover and it dies.
Cell Death
• Two principal types of cell death, necrosis and apoptosis which differ in their morphology, mechanisms, and roles in physiology and disease. • When damage to membranes is severe, lysosomal enzymes enter the cytoplasm and digest the cell, and cellular contents leak out, resulting in necrosis.
• When the cell's DNA or proteins are damaged beyond repair, the cell kills itself by apoptosis
NECROSIS
• Necrosis is the principal outcome in many commonly encountered injuries, such as those following ischemia
• When large numbers of cells die the tissue or organ is said to be necrotic.
• Necrosis of tissues has several morphologically distinct patterns ➢ Coagulative necrosis ➢Liquefactive necrosis ➢Gangrenous necrosis ➢Caseous necrosis ➢Fat necrosis ➢Fibrinoid necrosis coagulative necrosis
• Firm texture
• A localized area of coagulative necrosis is called an infarct
• Ischemia caused by obstruction in a vessel may lead to coagulative necrosis of the supplied tissue in all organs except the brain. kidney infarction kidney infarction
Coagulative necrosis. A, A wedge-shaped kidney infarct (yellow). B, Microscopic view of the edge of the infarct, with normal kidney (N) and necrotic cells in the infarct (I) showing preserved cellular outlines with loss of nuclei and an inflammatory infiltrate pale ghost like glomeruli and tubules , with loss of nuclear detail
Intestine Infarction
Typically transmural colonic necrosis, with nonviable mucosa and edema, hemorrhage and congestion of wall
Hyperemia haemorrhage acute inflammation loss of nuclear detail in the mucosa Testis infarction Testis infarction hemorrhage of parenchyma Ghost outlines of tubules with necrotic germ cells
Liquefactive Necrosis
• The necrotic material is frequently creamy yellow • Presence of dead leukocytes and is called pus • Bacterial or, fungal
• Hypoxic death of cells within the central nervous system
CASEOUS NECROSIS
Caseous necrosis. Tuberculosis of the lung, with a large area of caseous necrosis containing yellow-white and cheesy debris. FAT NECROSIS
Focal area of fat destruction Enzymatic…. Traumatic Fat necrosis. Multinucleated histiocytic giant cells surround a large lipid vacuole formed by fusion of destroyed adipocytes. Scattered lymphocytes and monocytes occupy expanded spaces between cells. intracellular pink amorphous necrotic material with macrophages (foamy cells ) and inflammatory cells
Fibrinoid necrosis
• special form of necrosis usually seen in immune reactions involving blood vessels.
• occurs when complexes of antigens and antibodies are deposited in the walls of arteries. Deposits of these “immune complexes Fibrinoid necrosis in an artery. The wall of the artery shows a circumferential bright pink area of necrosis with inflammation.