Necrosis: Definition, Causes, Types and MCQs for NEET, GPAT, CSIR NET JRF and NIPER Exam
“Necrosis is defined as a localized area of death of tissue followed later by degradation of tissue by hydrolytic enzymes liberated from dead cells; it is invariably accompanied by inflammatory reaction.”
CAUSES Of NECROSIS: –
Following are the causes of necrosis:
- Hypoxia
- Physical and chemical agents
- Microbial agents
- Immunological injuries etc
The above image is taken for education purpose only from en.wikipedia.org
TYPES OF NECROSIS: –
Based on etiology and morphologic appearance, there are 5 types of necrosis: coagulative, liquefaction (colliquative), caseous, fat, and fibrinoid necrosis.
1.] COAGULATIVE NECROSIS: This is the most common type of necrosis caused by irreversible focal injury, mostly from sudden cessation of blood flow (ischaemic necrosis), and less often from bacterial and chemical agents.
2.] LIQUEFACTION (COLLIQUATIVE) NECROSIS: Liquefaction or colliquative necrosis also occurs commonly due to ischaemic injury and bacterial or fungal infections but hydrolytic enzymes in tissue degradation have a dominant role in causing semi-fluid material. Th e common examples are infarct brain and abscess cavity.
3.] CASEOUS NECROSIS: Caseous (caseous= cheese-like) necrosis is found in the center of foci of tuberculous infections. It combines features of both coagulative and liquefactive necrosis.
4.] FAT NECROSIS: Fat necrosis is a special form of cell death occurring at mainly fat-rich anatomic locations in the body. Th e examples are: traumatic fat necrosis of the breast, especially in heavy and pendulous breasts, and mesenteric fat necrosis due to acute pancreatitis. In the case of acute pancreatitis, there is liberation of pancreatic lipases from injured or inflamed tissue that results in necrosis of the pancreas as well as of the fat depots throughout the peritoneal cavity, and sometimes, even affecting the extra abdominal adipose tissue. In fat necrosis, there is hydrolysis and rupture of adipocytes, causing release of neutral fat which changes into glycerol and free fatty acids. Th e leaked out free fatty acids complex with calcium to form calcium soaps (saponification) dis cussed later under dystrophic calcification.
5.] FIBRINOID NECROSIS: Fibrinoid necrosis is characterized by deposition of fibrin-like material which has the staining properties of fibrin such as phosphotungistic acid haematoxylin (PTAH) stain. It is encountered in various examples of immunologic tissue injury (e.g., in immune complex vasculitis, autoimmune diseases, Arthus reaction etc), arterioles in hypertension, peptic ulcer etc.
MULTIPLE CHOICE QUESTIONS: –
1.] Coagulative necrosis is found in which infection?
a. Tuberculosis
b. Sarcoidosis
c. Gangrene
d. Fungal infection
2.] Liquefactive necrosis is typically seen in?
a. Ischemia necrosis of heart
b. Ischemia necrosis of brain
c. Ischemia necrosis of intestine
d. Tuberculosis
3.] Liquefactive necrosis is seen in?
a. Heart
b. Brain
c. Lung
d. Spleen
4.] Pyogenic infection and brain infection are associated with?
a. Coagulative necrosis
b. Liquefactive necrosis
c. Caseous necrosis
d. Fat necrosis
5.] Coagulative necrosis is seen in?
a. Brain
b. Breast
c. Liver
d. All
6.] Coagulative necrosis as a primary event is most often seen in all except?
a. Kidney
b. CNS
c. Spleen
d. Liver
7.] Following is seen in both necrosis and apoptosis?
a. Both may be physiological
b. Both may be pathological
c. Inflammation
d. Intact cell membrane
8.] Mycobacterium tuberculosis causes the following?
a. Fat necrosis
b. Gangrenous necrosis
c. Caseous necrosis
d. None of the above
9.] Type of repair includes all of the following except?
a. Regeneration
b. Necrosis
c. Fibrosis
d. Gliosis
10.] CNS infarction is a type of?
a. Coagulative necrosis
b. Liquefactive necrosis
c. All of the above
d. None of the above
SOLUTIONS: –
1.] (a) Tuberculosis
2.] (b) Ischemia necrosis of brain
3.] (b) Brain
4.] (b) Liquefactive necrosis
5.] (c) Liver
6.] (b) CNS
7.] (b) Both may be pathological
8.] (c) Caseous necrosis
9.] (b) Necrosis
10.] (b) Liquefactive necrosis
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REFERENCES: –
1.] Textbook of Pathology By Harsh Mohan; 7th edition; Page no.26 – 28.