Thursday, 6 April 2017

Necrosis and its Types

Necrosis is the type of cell injury, which results in premature death of cells in living tissue, in response to non-stop physiological stress by means of autolysis. It is far an unprogrammed cell loss of life and may be due to factors external to the cell or tissue, together with infection, toxins, or trauma which bring about the unregulated digestion of cell components.

Types of Necrosis

There are six types of necrosis:

  • Coagulative Necrosis
It is an accidental cell death typically caused by ischemia or infarction, which is characterized by the formation of a gelatinous substance in dead tissue and can be observed by light microscope. During coagulation protein ( albumin ) transform into a firm and opaque state, which can be seen in hypoxic conditions. It occurs primarily in tissues such as kidney, adrenal glands, and heart. 

  • Liquefactive Necrosis
It is a type of necrosis, during which the affected cell is completely digested by hydrolytic enzymes, resulting in soft, circumscribed lesion consisting of pus and fluid remains of necrotic tissue. The necrotic fluid is creamy yellowish in appearance, due to the presence of dead leukocytes and commonly known as pus.
  • Gangrenous Necrosis
It is a not communicable disease, caused by a critically an insufficient blood supply.  Smoking and diabetes may increase the risk of gangrenous necrosis. Types of gangrene necrosis may differ in symptoms which include
  1. Dry gangrene
  2. Wet gangrene
  3. Gas gangrene
  4. Internal gangrene
  • Caseous Necrosis
It can be considered a combination of a coagulative and liquefactive necrosis. Typically caused by bacteria, fungi, and some foreign substances. During caseous necrosis, dead cells disintegrate but not completely digested, and a tissue maintains a cheese- like an appearance. 
  • Fat Necrosis
It is a benign condition which is characterized by action upon fat by fat digesting enzymes. During which lipases splits fat into glycerol and fatty acids. Which then combines with alkali metals to form soap, called saponification, which can cause critical conditions.

  • Fibrinoid Necrosis
It is miles a form of necrosis, which is resulting from immune-mediated vascular damage. It's far marked by means of complexes of antigens and antibodies, on occasion known as ''immune complexes'' deposited inside arterial walls together with fibrin.

Cellular Changes during Necrosis

The cellular changes can be classified into following stages.

  • Karyolysis
During which nucleus fades due to loss of DNA by degradation.
  • Pyknosis
The nucleus shrinks and chromatin condensed.
  • Karyorrhexis
The shrunken nucleus fragments to finish dispersal. 

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