necrosis

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necrosis

1. the death of one or more cells in the body, usually within a localized area, as from an interruption of the blood supply to that part
2. death of plant tissue due to disease, frost, etc.

Necrosis

 

the death within the living organism of individual organs or their component tissues or cells.

A necrosis is classified according to the pathological condition that causes it. Thus, frostbite and burns can cause traumatic necrosis; neurotropic necrosis arises with syringomyelia and the nervous form of leprosy; infarcts and gangrene are associated with circulatory, or ischemic, necrosis; caseous necroses occurring in tuberculosis and syphilis are forms of septic necrosis; and fibrinoid necrosis associated with allergic diseases is a type of allergic necrosis.

Necrosis is accompanied by characteristic changes in the cell and in the intercellular substances. The nucleus shrinks and coagulates, a process known as pycnosis, and the cytoplasm breaks up into clumps. The cell eventually lyses, that is, it degenerates and dissolves. The lysis is due to the activation of the lysosomal hydrolytic enzymes, such as ribonuclease, deoxyribonuclease, and acid phosphatase. The activation of the lysosomes occurs as a result of an increase in the permeability of the cell membranes, changes in the osmotic equilibrium, and acidosis—an abnormal increase in the intracellular hydrogen-ion concentration. Fibrinoid changes appear in the connective tissue, and nerve fibers become fragmented and disintegrate into clumps.

The clinical and morphological manifestations and further consequences of necrosis depend on the localization and distribution of the necrosis and on the mechanisms and conditions of origin. The following types of advanced necrotic conditions can develop: dry necrosis, such as Zenker’s degeneration of infected muscles; colliquative, or liquefactive, necrosis, which occurs for example, when a focus of softening arises in the brain in response to cerebral hemorrhage; gangrene; and bed sores. Necrotic tissue tears away; then, either connective tissue grows through it or the necrotic tissue undergoes autolytic or purulent liquefaction. Finally, the necrotic tissue becomes encapsulated and petrified.

The two most serious consequences of necrosis are a loss of function owing to the death of the structural elements of the necrotic tissues or organs and poisoning caused by the actual presence of a necrotic focus and by the inflammation that arises in response to this presence.

V. V. SEROV

necrosis

[nə′krō·səs]
(medicine)
Death of a cell or group of cells as a result of injury, disease, or other pathologic state.
References in periodicals archive ?
Researchers in Madrid, Spain set out to determine the impact of time of day of a heart attack on the size of the dead tissue (infarct) caused in patients with an ST segment elevation myocardial infarction (STEMI) -- a type of heart attack caused by a prolonged period of blocked blood supply.
It is essential that the dead tissue is surgically removed to save a patient's life.
Again, some 7-8 days later she passed more dead tissue, some of it about 5 cm in length and 2-3 cm in width.
There was a small patch of Charlotte where all the leaves are rotting, and ominous chocolate brown patches of dead tissue on leaves elsewhere.
"As well as having effective antibacterial properties, honey has an osmotic action meaning its high sugar content actively draws fluid from the wound helping the body to dissolve and remove dead tissue. It also reduces wound odour and maintains a moist wound healing environment."
Flies lay their eggs in decaying flesh or any moist area with an ample supply of dead tissue. After 8 to 20 hours, the eggs hatch and the flies enter the maggot stage.
D, as in debridement, means removing dead tissue from a wound so it can heal.
They remove the dead tissue and bacteria, leaving the healthy tissue to heal."
Quite simply - and readers of a delicate disposition should skip the next bit - the maggots would eat up all the dead tissue over the blood clot and clean the wound.
However, she said that clinic physician Nicholas Kotopoulos told her that she "had been pregnant and there was dead tissue in her uterus," according to the Star-Ledger.
Claiming the honey has hastened healing in these cases, Kai Sofka, wound specialist at the university's children's clinic said: "Dead tissue is rejected faster, and the wounds heal more rapidly." Bonn's 'medihoneys' include one rich in the enzyme glucose-oxidase, which converts the sugar in honey into hydrogen peroxide.
If blood cannot flow to dead tissue, antibiotics cannot reach the infection.