The death of tissue cells. Necrosis can occur as a result of ischaemia (inadequate blood supply), which may lead to gangrene; infection, such as tuberculosis; or damage by extreme heat or cold, noxious chemicals, or excessive exposure to X-rays or other radiation.
In necrosis due to tuberculosis, the dead tissue is soft, dry, and cheese-like. Fatty tissue beneath the skin that has died as a result of damage or infection develops into tough scar tissue that may form a firm nodule.
Death of a limited portion of tissue, the term being most commonly applied to bones when, as the result of disease or injury, a fragment dies and separates. (See BONE, DISEASES OF.)
Death of tissue or cells, either from infection or the loss of normal circulation and autotoxicity.
(mortification) n. the death of some or all of the cells in an organ or tissue, caused by disease, physical or chemical injury, or interference with the blood supply (see gangrene). Caseous necrosis occurs in pulmonary tuberculosis, the lung tissue becoming soft, dry, and cheeselike. Coagulative necrosis – the commonest form of necrosis – occurs in almost all organs (except the brain) and results in a solid mass of dead tissue. Colliquative necrosis occurs in the brain, where the absence of stroma (connective tissue) results in total liquefaction of necrotic tissue. —necrotic adj.
In injury to, or in?ammation of, the PANCREAS, the fat-splitting enzyme in it may escape into the abdominal cavity, causing death of fat-containing cells.... fat necrosis
(ARN) severe inflammation and necrosis of the retina associated with inflammation and blockage of retinal blood vessels, haemorrhage and death of retinal tissue, and retinal detachment. It may affect both eyes (bilateral acute retinal necrosis, BARN), and visual prognosis is poor. ARN is thought to be due to viral infection.... acute retinal necrosis
(ATN) a condition caused by acute renal injury from either ischaemia or toxins and associated with tubular damage that is usually reversible. The earliest feature is *isosthenuria, which may occur while there is still a high urine flow rate. This is followed by a reduction in *glomerular filtration rate. *Oliguria is common and dialysis often needed for survival. If the cause of the initial damage can be removed, recovery of renal function within six weeks can be expected in most cases.... acute tubular necrosis
(TNF) either of two proteins, TNF-? or TNF-?, that function as *cytokines. Produced by macrophages, monocytes, T lymphocytes, and various other cells, they mediate many responses, including inflammation, and have a marked action against tumour cells. Anti-TNF drugs (see cytokine inhibitor) are used in the treatment of several disorders, especially rheumatoid arthritis and ankylosing spondylitis.... tumour necrosis factor
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