Necrosis and Gangrene: Double trouble
Necrosis is the death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply.
- It is the process of nuclear fading.
- Chromatin dissolution due to action of DNAases and RNAases.
- It is the process of nuclear shrinkage
- DNA condenses into shrunken basophilic mass
- It is the process of cell fragmentation
- Pyknotic nuclei membrane ruptures and nucleus undergo fragmentation
Types of necrosis
- Occurs when a lytic (dissolving) enzyme liquefies necrotic cells
- It is generally associated with abscess formation.
- Typically, liquefication necrosis occurs in brain infarcts and pancreatic necrosis.
- Liquefaction by leukocytic enzymes is called suppuration and the resultant fluid is called pus.
- Liquefaction or colliquative necrosis occurs commonly due to ischemic injury and bacterial or fungal infections.
- It occurs due to degradation of tissue by the action of powerful hydrolytic enzymes.
- The common examples are infarct brain and abscess cavity
- The necrotic cells disintegrate but the cellular pieces remain undigested for months or years.
- This type of necrotic tissue gets its name from its crumbly, cheese- like (caseous) appearance.
- It commonly occurs in lung tuberculosis.
- Accumulation of amorphous (no structure) debris within an area of necrosis.
- Tissue architecture is abolished, and viable cells are no longer recognizable.
- Characteristically associated with the granulomatous inflammation of tuberculosis. Also seen in some fungal infection.
- In fat necrosis enzymes called lipases break down intracellular triglycerides into free fatty acids.
- These free fatty acids combine with sodium, magnesium, or calcium ions to form soaps.
- The tissue becomes opaque and chalky white.
- It is characteristic of tissues adjacent to pancreatic necrosis.
- Grossly, fat necrosis appears as yellowish-white and firm deposits
- Microscopically, the necrosed fat cells have cloudy appearance and are surrounded by an inflammatory reaction.
- It is the most common form of necrosis in cells without large number of lysosomes.
- Commonly occur when the blood supply to any organ (except the brain is interrupted
- It typically affects the kidney, heart and adrenal glands.
- Lytic (lysosomal) enzyme activity in the cells is inhibited, so that the necrotic cells maintain their shape, at least temporarily.
- Grossly, foci of coagulative necrosis in the early stage are pale, firm, and slightly swollen.
- Microscopically, the hall mark of coagulative necrosis is the conversion of normal cells into their ‘tombstones’.
- The outlines of the cells are retained so that the cell types can still be recognized but their cytoplasmic and nuclear details are lost.
- It is due to deposition of fibrin like material.
- It is seen in immunologic cell injury, hypertension, peptic ulcer.
- Microscopically, fibrinoid necrosis is identifies by brightly eosinophilic, hyaline like deposition in the vessel wall
It is a form of coagulative necrosis, typically results from lack of blood flow and is complicated by an overgrowth and invasion of bacteria. It commonly occurs in the lower legs as a result of arteriosclerosis or in the gastrointestinal tract.
Gangrene can occur in three forms,
- Dry gangrene
- Moist or wet gangrene
- Gas gangrene
- Occurs when bacterial invasion is minimal.
- It is marked by dry, wrinkled, dark brown or blackened tissue on an extremity.
- Develops with liquefactive necrosis that includes extensive lytic activity from bacteria and white blood cells to produce a liquid center in area of tissue.
- It occurs in the internal organs as well as the extremities.
- It develops when anaerobic bacteria of the genus clostridium infect tissue.
- Its more likely to occur with severe trauma and may be fatal.
- The bacteria release toxins that kill nearby cells and the gas gangrene rapidly spreads.
- Release of gas bubbles from affected muscle cells indicates that gas gangrene is present.
The art of medicine consists in amusing the patient while the nature cures the illness...
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