Necrosis

Necrosis (from the Greek νεκρός, "dead", νέκρωσις, "death, the stage of dying, the act of killing") is a form of cell injury that results in the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma that result unregulated digestion of cell components. In contrast apoptosis is a naturally occurring programmed and targeted cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal.

Cells that die due to necrosis do not follow the apoptotic signal transduction pathway but rather various receptors are activated that result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the intracellular space. This initiates an inflammatory response in the surrounding tissue: Nearby phagocytes are prevented from locating and engulfing the dead cells. The result is a build-up of dead tissue and cell debris at, or near, the site of the cell death. A classic example is gangrene. For this reason, it is often necessary to remove necrotic tissue surgically, a process known as debridement.