Coagulative necrosis is accidental type of cell death followed by acute inflammation in which underlying tissue architecture is preserved for at least several days. Necrotic tissue remains firm, cell shape and organ structures are preserved by coagulation protein but nucleus disappears.
Before going in details of coagulative necrosis let’s discuss what is necrosis?
Definition of necrosis:
Necrosis is death of large group of cells followed by acute inflammation due to some underlying pathologic process but it is never physiologic that is called apoptosis.
Necrosis is associated with loss of membrane integrity and leakage of cellular contents culminating in dissolution of cells, largely resulting from the degradative action of enzymes on lethally injured cells. The cellular content is leaked and often elicits a local host reaction, called inflammation that attempts to eliminate the dead cells and start the subsequent repair process.
Morphology of necrosis is characterized by changes in the cytoplasm and nuclei of the injured cells. First of all there is cytoplasmic change with increased eosinophilia then there are nuclear changes of breakdown of DNA and chromatin.
Morphology of coagulative necrosis:
Coagulative necrosis is a form of necrosis in which the underlying tissue architecture is preserved. The affected tissues take on a firm texture. Presumably the injury de-natures or coagulate not only structural proteins but also enzymes, thereby blocking the proteolysis of the dead cells; as a result, eosinophilic, anucleate cells may persist for days or weeks. There is lack of lysosomal enzymes allows it to maintain a coagulated morphology for some time. Leukocytes are recruited to the site of necrosis, and the dead cells are digested by the action of lysosomal enzymes of the leukocytes. The cellular debris is then removed by phagocytosis. Coagulative necrosis is characteristic of infarcts (areas of ischemic necrosis) in all of the solid organs except the brain where liquefactive necrosis occors.
Pathology of coagulative necrosis:
Macroscopic appearance of coagulative necrosis is wedge shaped pointing towards the focus of vascular occlusion. Red infarction occurs if blood re-enters a loosely organized tissues, for example testicular infarction or pulmonary infarction. Microscopic appearance is cellular infiltrates with eosinophilia. Nucleus disappears and removed cytoplasmic structure giving small amount of intracellular protein.
Causes of coagulative necrosis:
Hypoxia (lack of oxygen) is most common condition that causes cell death in a localized area that is perfused by blood vessels. When these vessels fail to deliver oxygen and other important nutrients there is ischemic infarction in that tissue and result in coagulative necrosis. There is reduced blood flow result in reduced oxygen and nutrients to that cells which results in hydrolytic lysis of that cells. When this ischemia occurs in central nervous system it causes liquefactive necrosis. It is caused by conditions that do not involve trauma, toxin or immune response.
Regeneration of coagulative necrosis:
Some of the structural remnant of necrotic tissue remains labile and adjacent tissue near affected tissue replicate and replaces the dead necrotic cells. Labile cells undergo mitosis and help in replacing the affected tissue. Fibroblast migrates to the affected area depositing fibrous tissue causing fibrosis and scaring in that area where viable cells cannot replicate.
Examples of coagulative necrosis:
There are many examples of coagulative necrosis, let discuss few examples of coagulative necrosis.
Myocardial infarction and coagulative necrosis:
The gross and microscopic appearance of an MI depends on the age of the injury. Areas of damage progress through a highly characteristic sequence of morphologic changes occurs from coagulative necrosis, to acute and then chronic inflammation to fibrosis. Typical features of coagulative necrosis become detectable within 4 to 12 hours of infarction. “Wavy fibers” also can be present at the edges of an infarct.
Pulmonary embolism, hemorrhages and coagulative necrosis:
Characteristically, they are wedge-shaped, with their base at the pleural surface and the apex pointing toward the hilus of the lung. Pulmonary infarcts typically are hemorrhagic and appear as raised, red-blue areas in the early stages On histological examination, the hallmark of fresh infarcts is coagulative necrosis of the lung parenchyma and hemorrhage.
Syphilis and coagulative necrosis:
The pathognomonic microscopic lesion of syphilis is a proliferative endarteritis with an accompanying inflammatory infiltrate rich in plasma cells. On microscopic examination, the gumma contains a central zone of coagulative necrosis surrounded by a mixed inflammatory infiltrate composed of lymphocytes, plasma cells, activated macrophages (epithelioid cells), occasional giant cells, and a peripheral zone of dense fibrous tissue.
Also see from our site..