Necrosis

necrosis is cell injury after infection or pathologically, types of necrosis, Causes and treatment

1. NECROSIS Mrs. Praveen Garg VITS College, Satna

2. Introduction Necrosis is the death of body tissue through disease or injury. It occurs when too little blood flows to the tissue. Necrosis  is the death of cells in living tissue caused by external factors such as infection, trauma, or toxins.  Necrosis is the pattern of cell death that occurs in response to injuries such as hypoxia, extremes of temperature, toxins, physical trauma, and infection with lytic viruses. The injury to a cell is said to be irreversible if it kills the cell.  Necrosis  is a form of cell injury which results in the premature  death of  cells in living tissue by  autolysis. Necrosis cannot be reversed. When large areas of tissue die due to a lack of blood supply, the condition is called gangrene.

3. Pain Redness of the skin Swelling Blisters (is a pocket of fluid between the upper layers of skin) Fluid collection Skin discolouration Sensation Numbness (a loss of sensation or feeling in a part of your body) Symptoms of Necrosis

4. Types of necrosis   Coagulative  necrosis  – eg . Myocardial infarction, renal infarction. Liquefactive  necrosis  – eg . Infarct brain , Abscess . Caseous  necrosis   – eg . Tuberculosis . Fat necrosis  – eg . Acute pancreatitis, traumatic fat necrosis of breast. Fibrinoid   necrosis  – eg . Immune complex deposited in arterial wall. Gangrenous necrosis- Ischemia due to lack of blood supply

5. Classification of Necrosis Co- agulative Necrosis: I t is characterized by the formation of a gelatinous (gel-like) substance in dead tissues. Coagulation occurs as a result of protein  denaturation .  This pattern of necrosis is seen in  hypoxic (low-oxygen) environments, such as  infarction (death of tissue due to failure of blood supply) or infract (dead tissue). Coagulative necrosis occurs primarily in tissues such as the kidney, heart and adrenal glands. Severe  ischemia  most commonly causes necrosis of this form . Ischemia is the reduction in blood flow resulting in decreased oxygen and nutrient supplies to a tissue.  Ischemia  may be reversible, in which case the affected tissue will recover if blood flow is restored, or it may be irreversible, resulting in tissue death.

6. Liquefactive  necrosis: It is characterized by the digestion of dead cells to form a viscous liquid mass. This is occur due to bacterial, or fungal, infections because of their ability to stimulate an inflammatory response. The necrotic liquid mass is frequently creamy yellow due to the presence of dead leukocytes and is commonly known as pus . Hypoxic  infarcts in the brain presents as this type of necrosis, because the brain contains little connective tissue but high amounts of digestive enzymes and lipids, and cells therefore can be readily digested by their own enzymes.

7. Gangrenous necrosis : It can be considered a type of coagulative necrosis that resembles mummified tissue. It is characteristic of ischemia of lower limb and the gastrointestinal tracts. Types of gangrene: Dry gangrene : form of coagulative necrosis and due to peripheral artery disease. Occured in foot and toes. Wet gangrene: tissue infected by m.or ., cause swelling and foul odour , develop due to blockage of arterial blood flow. Occured in moist tissue such as mouth, cervix, lungs, diabetic foot, bed sore. Gas gangrene: produced gas within tissue by bacterial infection. It is fatal.

8. GAS GANGRENE DRY GANGRENE

9. Caseous necrosis:  It can be considered a combination of coagulative and liquefactive necrosis, caused by  mycobacteria  (e.g. tuberculosis), fungi and some foreign substances. The necrotic tissue appears as white and friable, like clumped cheese. Dead cells disintegrate but are not completely digested, leaving granular particles. 

10. Fat necrosis: It  is specialized necrosis of fat tissue, resulting from the action of activated lipases on fatty tissues such as the  pancreas, breast. In the pancreas it leads to acute pancreatitis, a condition where the pancreatic enzymes leak out into the peritoneal cavity, and liquefy the membrane by splitting the triglyceride esters into fatty acids through fat  saponification .  Calcium , magnesium or sodium may bind to these lesions to produce a chalky-white substance .   Sub- c utaneous fat necrosis Facial fat necrosis

11. Fibrinoid necrosis: It is a special form of necrosis usually caused by immune-mediated vascular damage. It is marked by complexes of antigen and antibodies, referred to as immune complexes deposited within arterial walls together with fibrin.

12. There are also very specific forms of necrosis: Gangrene  ( type of tissue death, suffered severe hypoxia ) Treatment of gangrene is the removal of dead tissue by surgery called Debridement, Amputation (Removal of limb by trauma and surgery). Gummatous   necrosis (due to  spirochaetal  infections) Hemorrhagic necrosis (due to the blockage of venous drainage of an organ or tissue).

13. Necrosis may occur due to external or internal factors. External factors External factors may involve mechanical trauma (physical damage to the body which causes cellular breakdown), damage to blood vessels (which may disrupt blood supply to associated tissue), and  ischemia .  Thermal effects can result in necrosis due to the disruption of cells. Internal factors Internal factors causing necrosis include: trophoneurotic disorders (diseases that occur due to defective nerve action in a part of an organ which results in failure of nutrition); injury and paralysis of nerve cells. Pancreatic enzymes (lipases) are the major cause of fat necrosis . Causes

14. Treatment   Treatment  may include surgery to restore blood flow or to remove the damaged tissues, antibiotics to prevent or treat  infection. Debridement, refers to the removal of dead tissue by surgical or non-surgical means , is the standard therapy for necrosis. Depending on the severity of the necrosis, included removal of small patches of skin to complete amputation of affected limbs or organs.

15. Thank You