 Hello everyone welcome back to another session in dentistry and more today we have a necrosis in pathology. So necrosis as we all know it is a death of cells in an organ or a tissue due to various reasons it could be due to disease could be an injury or failure of the blood supply. So ultimately there will be death of cells in an organ. So let's learn the types of necrosis and its features. So there are two features which are present in all of the types of necrosis that is cell digestion by lytic enzyme cell digestion by lytic enzymes. And the second one is protein denaturation. So this happens in all the types of necrosis but the reason is different and their clinical appearance is also different. So cell digestion by lytic enzyme and protein denaturation is invariably present in all the types of necrosis. So what are the types of necrosis? So we have basically five types. The first one is coagulative necrosis, then liquefaction necrosis, quiesus necrosis, fat necrosis and fibrinoid necrosis. So we will start with coagulative necrosis. So coagulative necrosis it is the form of tissue necrosis in which the component cells are dead but the basic tissue architecture is preserved for at least several days. So if this is the organ, so the structure will be intact but the inside cells will be dead. So that is coagulative necrosis. The inside cells tissues will be dying but the structure will be maintained. So the affected tissue take on a firm texture and the injury, denatures not only the structural proteins but also enzymes and so blocks the proteolysis of the dead cells. So what is happening? The injury, denatures not only the structural proteins but also enzymes. So since the enzymes are dead, the proteolytic enzymes, so these enzymes are not working, it blocks the proteolysis of dead cells. So it is maintaining a structural shape, that shape is not lost. So as a result, the cells that is esophilic and nucleate cells may persist for days, two weeks but ultimately the necrotic cells are removed by phagocytosis of cellular debris but initially the organ will maintain the structural integrity that is the feature of coagulative necrosis. The structural integrity will be retained for a period of time. So most common type of necrosis is, it is the most common type of necrosis and the reasons are one is ischemia, ischemia is nothing but the stoppage of blood flow and it is very rarely this happens due to bacterial and other chemical agents. So in infact, so infact, so infact is nothing but area of ischemic necrosis. So it is a characteristic of infact in all solid organs except brain. So in brain the liquefaction necrosis is happening, so in all solid organs where the infact is present, coagulative necrosis will be there except the brain. So the most common organs affected by coagulative necrosis is heart, kidney and spleen. So in gross morphology the coagulative necrosis foci is present in early stages are pale, firm and slightly swollen with progression they become more yellowish and microscopically we can see tombstone appearances. The normal cells will be converted to tombstone appearance. So that is about coagulative necrosis. Now we have liquefaction or collicative necrosis. This is due to ischemic injury and bacterial or fungal infection. So bacterial and fungal infection is there along with ischemia. So this is most common type and ischemia is a main reason of coagulative necrosis. This is liquefaction necrosis where the degradation of tissue by the action of powerful hydrolytic enzymes. So if the hydrolytic enzymes are very powerful it will completely destroy the area. Here the hydrolytic enzymes were not active so the structural integrity was maintained. So the common examples are in fact cavity of brain. So all the solid organs where coagulative necrosis except brain in brain the liquefaction necrosis is happening. So in the liquefaction necrosis what is happening it completely digest the dead cells resulting in transformation of the tissue into a liquid viscous mass. So there is no structural integrity it becomes a liquid viscous mass. That is the difference between coagulative and liquefactive necrosis. So if this is the structure or this is the organ means it will be completely disorganized and becomes a liquid viscous mass. So if the process was initiated by acute inflammation the material is frequently creamy yellow and there will be pus formation. Okay so the appearance will be the affected area will be soft and liquefied with lots of necrotic debris and later a cyst wall is formed. And there are microscopic features such as cystic space contains necrotic cell debris and macrophages and also the phagocytic material also will be there. Next one is the third one is caseous necrosis. This is found in center of foci of tubercular infection. Okay in tubercular infection at the center the caseous necrosis is there. It combines the feature of both coagulative and liquefactive necrosis. It is a combined one okay the caseous necrosis. And why this name is called caseous it means the cheese like okay cheese like appearance. So it has this peculiar necrosis looks like yellow white appearance of this area look like yellow white cheese like appearance that is why it got that peculiar name caseous necrosis. So the gross morphology is there will be foci of caseous necrosis and it resembles a dry cheese and are very soft and granular and yellowish in color. And microscopically there are isophilic structure less necrotic foci and other epithelioid cells present. So that is caseous necrosis which is a combination of coagulative and liquefactive necrosis. The fourth one is fat necrosis it refers to the focal area of fat destruction. And it is more most commonly seen in acute pancreatic necrosis and the traumatic fat necrosis which is commonly seen in the breast area. So this pancreatic enzymes that I have leaked out of asinine cells and dex and the this they will liquefy the membrane of fat cells in the peritoneum and the lipase enzymes they split the triglycerides esters contained within the fat cells to fatty acid. So these combines calcium to produce a grossly visible chalky white areas which is known as fat saponification. So what is happening? So pancreatic enzymes which are leaked out of this as in our endex cells. So these enzymes liquefy the membrane of fat cells in the peritoneum. Peritoneum is the cavity and the lipase enzymes they split the triglyceride esters which contains within the fat cells. So it becomes fatty acids and these combine calcium to produce a grossly visible chalky white areas and which is known as fat saponification. So that is fat necrosis commonly seen in pancreas and breasts. So fat necrosis appear as a lowest white and firm deposits and there will be calcium presence or calcium soap which imparts a necrosis to foci a firmer and chalky white appearance. So this is a chalky white appearance. Okay. The last one is fibrinoid necrosis. Fibrinoid necrosis is characterized by deposition of fibrin like material which has a staining properties of fibrin. Okay. So it is encountered in various examples of immunological tissue injury such as immune complex vasculitis, arthritis reaction, peptic ulcer, arthritis reaction, peptic ulcers, autoimmune diseases and arterioles in hypertension. So in microscopically this is like a brightly isnophilic hyaline like deposition in the vessel wall and there will be necrotic focus which is surrounded by nuclear debris of neutrophils and there will be local hemorrhage. Okay. So these are the basic five types of necrosis. The common one is coagulating necrosis and the liquefaction, cashews and fat and fibrinoid. The most important one is coagulation and liquefaction. Coagulating is the important point is the structural integrity is maintained for a period of time because that enzymes were not active at the beginning phase at the end of the at the latest stage of acosidus happen and it lost. Liquefaction necrosis is a different one. It is completely destroying and becoming a liquid mass. Cashews is seen in the tuberculosis cavity, achieves like appearance and fat necrosis commonly seen in pancreas and breasts and the fibrino necrosis in peptic ulcer and arterioles in hypertension. So that is the most common five types of necrosis. Necrosis is nothing but the death of cells. And the two features which are the common in all necrosis is protein degeneration and cell digestion by lactic enzyme. So these two implies that the cell is death and it is denatured and necrosed. These are very important for essay question like coagulating and liquefaction could be asked as a separate short note. So I will come up with a new topic in pathology. Thank you.