It is defined as pathological death of cell
living body to the disease , toxins or injury to cell . All the factors
responsible for degeneration , expect in case of sudden death of cells .
The term necrosis means physiological or
gradual death of cell . The cells will pass through various stages of
degeneration and ultimately this will lead to necrosis of thecell . The changes
in Necrobiosis are reversible . the best example of necrosis is the changes in
epidermal cells of the skin . Here , the cells will come to the surface from
the basal layer from dead keratinized cells and subsequently will be
desquamated .
Aetiology of necrosis ….
i)
Necrosis is due to loss of
blood supply – In this type , there will be loss of blood supply or deprivation
of oxygen and nutrition to the tissue . This may be due to the formation of
occluding thrombus , embolus or compression
and stretching of smaller vessels .
ii)
Necrosis is due to the invasion
of bacteria and allied infecting agents –
Bacteria , viruses , rickettsia mand protozoa will produce toxin or
enzyme and damage the cells .
iii)
Necrosis is due to the action
of physical and chemical agents – A cell may be damaged by severe trauma , heat
, and strong acid and alkali , radiant rays and electricity .
Types
of necrosis …..
i)
Coagulative necrosis
ii)
Special type of coagulative
necrosis
a) gaseous necrosis
a) gaseous necrosis
b) Gummatous necrosis
iii)
Colliquative ( Liquefactive )
necrosis –
a.
Primary type
b.
Secondary type
iv)
fat necrosis
a)
generalized fat necrosis in
chronic pancreatitis
b)
Traumatic fat necrosis .
v)
Focal necrosis .
