Morphologic changes in reversible and irreversible cell injury. A, Electron micrograph of a normal epithelial cell of the proximal kidney tubule. Note abundant microvilli (mv) lining the lumen (L). N, nucleus; V, apical vacuoles.
B, Epithelial cell of the proximal tubule showing reversible ischemic changes. The microvilli (mv) are lost and have been incorporated in apical cytoplasm; blebs have formed and are extruded in the lumen (L). Mitochondria are slightly dilated. (Compare with A.) C, Proximal tubular cell showing irreversible ischemic injury. Note the markedly swollen mitochondria containing amorphous densities, disrupted cell membranes, and dense pyknotic nucleus.
Subtypes of Necrosis
Coagulitave necrosis Liquefactive necrosis (colliquative necrosis) Caseous necrosis Fat necrosis Fibrinoid necrosis Gangrene
Coagulative necrosis
Irreversible Cell Injury: Cell Death
Stages of the cellular response to stress and injurious stimuli
Irreversiis severe, lysosomal enzymes enter the cytoplasm and digest the cell, and cellular contents leak out, resulting in necrosis
Two large infarctions (areas of coagulative necrosis) are seen in this sectioned spleen. Since the etiology of coagulative necrosis is usually vascular with loss of blood supply, the infarct occurs in a vascular distribution. Thus, infarcts are often wedge-shaped with a base on the organ capsule.
Denaturation of protein is predominant in coagulative necrosis Characteristics: ghost of the dead cells
Coagulative necrosis of the kidney. This is the typical pattern with loss of blood supply and resultant tissue anoxia. There is a wedgeshaped pale area of coagulative necrosis in the renal cortex.
Apoptosis, which is characterized by nuclear dissolution without complete loss of membrane integrity
Morphologic Changes of Irreversible Cell Injury
Necrosis
Definition: Necrosis refers to a sequence of morphologic changes that the death of a group of cells in living tissue
Typical morphologic changes of necrosis depend on the enzyme digestion of dead cells and denaturation of proteins
Autolysis: digestion by the enzyme from the dead cells
Heterolysis: digestion by the enzyme from the invading inflammatory cells
The general features of necrosis: Nuclear changes: pyknosis, karyorrhexis, karyolysis
细胞坏死的核的改变
Pyknosis, Karyorrhexis, and Karyolysis
Microscopic changes of heart infarct.The nuclei of the myocardial fibers are being lost. The cytoplasm is losing its structure, because no well-defined cross-striations are seen.