Definition and Types of Necrosis
- Necrosis is the premature death of cells in living tissue by autolysis.
- It is caused by external factors such as infection or trauma.
- Necrosis is different from apoptosis, which is a naturally occurring programmed cell death.
- Necrosis is almost always detrimental and can be fatal.
- It results in the loss of cell membrane integrity and the release of cell death products into the extracellular space.
- Types of necrosis include coagulative necrosis, liquefactive necrosis, caseous necrosis, fat necrosis, and gangrenous necrosis.
Causes and Risk Factors of Necrosis
- External factors such as mechanical trauma, electric shock, damage to blood vessels, and ischemia can cause necrosis.
- Thermal effects, such as extremely high or low temperatures, can disrupt cells and result in necrosis.
- Internal factors like low oxygen levels can cause cells to undergo necrosis.
- Specific infections, autoimmune disorders, and certain medications can also cause necrosis.
- Risk factors for necrosis include advanced age, chronic diseases, smoking, and certain medications.
- Ischemic necrosis, also known as avascular necrosis, occurs when blood supply to a tissue is interrupted.
Pathogenesis and Histopathological Changes in Necrosis
- Necrosis can occur through two pathways: oncosis and secondary necrosis.
- Oncosis involves cell swelling, blebbing, pyknosis (nuclear shrinkage), and karyolysis (dissolution of cell nuclei).
- Secondary necrosis occurs after apoptosis and budding, leading to fragmentation of the nucleus (karyorrhexis).
- Necrosis is characterised by various changes in the nucleus, including karyolysis, karyorrhexis, and pyknosis.
- Cytoplasmic hypereosinophilia, seen as a darker stain of the cytoplasm, is a typical change in necrosis.
- The cell membrane appears discontinuous due to cell blebbing and loss of microvilli.
- Pseudopalisading, hypercellular zones surrounding necrotic tissue, indicate aggressive tumors.
- Necrosis in specific organs, such as myocardial infarction, can be diagnosed based on histopathological changes.
Treatment and Complications of Necrosis
- Treatment depends on the underlying cause of necrosis.
- Debridement, the removal of dead tissue, is the standard therapy for necrosis.
- Enzymatic debriding agents can be used to target different components of dead tissue.
- Maggot therapy using larvae has been employed in select cases to remove necrotic tissue and infection.
- Antioxidant treatments can scavenge reactive oxygen species in ischemic conditions.
- Complications of necrosis can include infection, tissue damage, and organ failure.
- Treatment options for necrosis depend on the underlying cause and may include surgical debridement, wound care, antibiotics, and hyperbaric oxygen therapy.
- In some cases, tissue grafting or amputation may be necessary.
Necrosis in Plants and Other Clinical Classifications
- Calcium deficiency can lead to necrosis in plants, causing the necrosis of stem and root tips and leaf edges.
- Plant pathogens can cause tissue necrosis in plants like Arabidopsis thaliana.
- Cacti in the Sonoran Desert regularly experience necrotic patch formation.
- Drosophila mettleri, a species of Dipterans, has developed a detoxification system to utilize exudates released in necrotic patches.
- Necrosis in plants can hinder meristems and affect growth.
- Other clinical classifications of necrosis include gangrene, gummatous necrosis, hemorrhagic necrosis, myonecrosis, and necrosis caused by spider bites.
Necrosis (from Ancient Greek νέκρωσις (nékrōsis) 'death') is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who is often regarded as one of the founders of modern pathology. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the 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.
Cellular death due to necrosis does not follow the apoptotic signal transduction pathway, but rather various receptors are activated and result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the extracellular space. This initiates an inflammatory response in the surrounding tissue, which attracts leukocytes and nearby phagocytes which eliminate the dead cells by phagocytosis. However, microbial damaging substances released by leukocytes would create collateral damage to surrounding tissues. This excess collateral damage inhibits the healing process. Thus, untreated necrosis results in a build-up of decomposing 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 procedure known as debridement.[citation needed]
