Necrosis – the exact causes and types of necrosis

Cell death is one of the most crucial events in pathology, affecting every cell type and being a major consequence of ischemia, infection, toxin, and immune reaction. There are two types of a pattern of cell injury and deaths, necrosis and apoptosis. Necrosis refers to a spectrum
of morphologic changes that follow cell death in living organisms. Necrosis is characterized denaturation of cytoplasmic proteins, failure of membrane integrity, break down of cell organelles and swelling of lethally injured cells.

 

Types of necrosis 

Necrotic cells have different morphological types. It can be classified into a total of five types

Coagulative Necrosis

Coagulative necrosis is the most common type of necrosis in which cells death happen after exogenous or endogenous stimuli, occurring after such stresses as ischemia, virus toxin, physical and chemical injury. It is manifested by severe cell rupture, denaturation, and coagulation of cytoplasmic proteins.

In coagulative necrosis, the texture of the tissue will be normal or firm, but later it may become soft as a result of digestion by macrophages. The myocardial infarction is the typical example of coagulative necrosis. 

Caseous necrosis

Caseous necrosis is a distinctive form of coagulative necrosis in tuberculosis infection. The term caseous is derived from the gross appearance of the area of necrosis. On microscopic examination, the necrotic focus appears as amorphous coarsely granular eosinophilic debris, without any original outline of cells and tissues. This distinctive types of necrosis are generally attributed to the toxic effect of the unusual cell wall of Mycobacterium, which contains complete waxes. 

Liquefactive necrosis

Liquefactive necrosis is a characteristic of focal bacterial or occasionally fungal infections because these agents constitute powerful stimuli to the accumulation of inflammatory cells. The polymorphonuclear leukocytes in the acute inflammatory reactions are endowed with potent hydrolases, capable of completely digesting dead cells. For the reasons of the presence of more abundant lysosomal enzymes or different hydrolases and the lack of any substantial supporting stroma specific to the nerve cells, hypoxic death of cells within the central nervous system often evokes liquefactive necrosis. 

Fibroid necrosis

Fibroid necrosis refers to an alteration of injured tissues which are homogenous, deeply eosinophilic in necrosis. For example, malignant hypertension, the wall of the arterioles is under such necrosis, because of the insulation and accumulation of immunoglobulins, plasma proteins and especially the consequences deposition of fibrin.  

Gangrenous necrosis

Gangrenous necrosis is necrosis putrefaction of the tissues as a result of the action of the saprophytic bacteria, mainly clostridium. There are three types of gangrenous necrosis:

1.       Dry gangrenous

2.       Wet gangrenous

3.       Gas gangrenous