Pathophysiology

Pathophysiology Study Guide

continuously exposed to damaging agents or possess internal abnormality. Cell injury can either be reversible or irreversible and causes cells to die. Reversible Cell Injury During the early and mild phases of the injury of the cell, it is possible to reverse the functional and morphologic change in the cell by removing the stimulus that is causing damage. Cell injury is reversible when the injury has not been caused by nuclear dissolution and severe damage to the membrane. One of the most frequent instances of reversible cell injury is cellular swelling. Cellular swelling occurs when the ionic and fluid homeostasis is disturbed due to a failure of pumping energy- dependent ions into the plasma membrane of the body. Irreversible Cell Injury When cells are damaged for a long time, it becomes impossible to reverse the injury and the cells die, making the cell injury irreversible. Even if the damaging stimulus is removed, it is not possible to reverse the injury. Different types of irreversible cell injuries include: • Necrosis: Necrosis occurs when the cell membrane is damaged to such an extent that enzymes from lysosomes leak, which enters the cytoplasm and digests the cells. A host reaction is also elicited upon the leaking of cellular contents from the damaged plasma membrane. Some instances of these injuries are ischemia, toxin exposure, trauma, and infection. The cell size under Necrosis enlarges due to inflammation and causes swelling of the adjacent cells. It is mostly caused by pathologic parameters. • Apoptosis: Apoptosis occurs when the cell nuclei dissolve due to a lack of growth factors, which damages the DNA or proteins of the cell severely. In this case, the integrity of the membrane is not lost entirely, but is altered so that the cells become vulnerable to phagocytes. Apoptosis does not cause an inflammatory reaction in the host cells as the dead cells are removed before its contents are leaked out. Apoptosis can be caused in physiological, as well as pathological situations. Some instances of physiological apoptosis include programmed destruction during embryogenesis, involution of hormone-dependent tissues, and cell death induced by T- lymphocytes. Examples of pathological apoptosis include damage to DNA due to radiation, cytotoxic anticancer drugs, accumulation of misfolded proteins, and cell injuries in viral injections. • Fatty changes: Fatty changes are predominant in hypoxic, metabolic, or toxic injuries in which lipid vacuoles appear in the cytoplasm of the cell. The cells involved in the metabolism of fat are the targets of fatty changes, like hepatocytes andmyocardial cells. The liver is most affected by fatty changes, but other organs like the heart, kidney, and skeletal muscles may also be affected. In this case, triglycerides are accumulated in abundance in parenchymal cells. Causes of fatty changes include protein malnutrition, toxins, anoxia, diabetes mellitus, and obesity. If the accumulation of triglycerides is mild, it has no effect on the function of the cell. A severe form of fatty change causes malfunctioning of cells, and in extreme cases, the intracellular process gets paired permanently and causes the fatty change to be irreversible, which leads to the death of the cells. An example of irreversible fatty change is nonalcoholic steatohepatitis.

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