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Questions and Answers
What is the primary cause of caseous necrosis?
In which organ is caseous necrosis most commonly observed?
What characterizes the appearance of fat necrosis microscopically?
Which type of necrosis is associated with the deposition of pinkish substance in blood vessels?
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What is a major event that leads to fat necrosis in cases of acute pancreatitis?
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What feature distinguishes caseous necrosis grossly?
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What is the consequence of ruptured blood vessels in fat necrosis?
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In which tissues is fat necrosis most likely to occur?
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What primarily causes gangrenous necrosis?
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Which type of gangrene primarily affects the distal parts of the extremities?
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How does moist gangrene typically arise?
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What is a distinguishing feature of gas gangrene?
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Which of the following statements about the appearance of dry gangrene is correct?
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What is the primary cause of necrosis in cells?
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What is a characteristic gross feature of necrotic tissue?
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Which nuclear change is associated with necrosis characterized by a shrunken, deeply basophilic nucleus?
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What happens to the cytoplasm of a cell undergoing necrosis?
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What process occurs to a small necrotic area in the body?
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What are the microscopic changes seen in necrosis that involve the nucleus breaking into fragments?
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In the context of necrosis, what does the term 'infarct' refer to?
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What type of inflammatory response surrounds necrotic tissue?
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What is the most common form of necrosis?
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What is a significant feature of coagulative necrosis?
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Which organ is primarily affected by liquefactive necrosis?
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What best characterizes the necrotic area in coagulative necrosis as seen grossly?
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Which cell type predominates in the inflammatory response associated with liquefactive necrosis initially?
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What process leads to the formation of a liquid mass in liquefactive necrosis?
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Which necrotic tissue pattern is specifically related to ischemia in the brain?
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In coagulative necrosis, what happens to the cell outlines microscopically?
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Study Notes
Irreversible Cell Injury
- Necrosis is when groups of cells die within a living body.
- Necrosis can occur directly or as a result of reversible cell injury.
- When cells die through necrosis, the membrane integrity is lost, and the contents leak out, causing inflammation.
Morphologic Changes in Necrosis
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Gross features:
- Necrotic tissue appears opaque, whitish, or yellowish
- The surrounding tissue is red due to inflammation.
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Microscopic picture:
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Nuclear changes:
- Pyknosis: Shrunken, deeply basophilic nucleus
- Karyorrhexis: Pyknotic nucleus breaks up into numerous small fragments
- Karyolysis: Dissolved nucleus
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Cytoplasmic changes:
- Cytoplasm becomes swollen, deeply eosinophilic, due to denaturation of cytoplasmic proteins by its own enzymes.
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Nuclear changes:
Coagulative Necrosis
- Most common form of necrosis
- Cause: Sudden and complete ischemia
- Organs involved: Solid organs (heart, kidney, spleen, liver)
- Major event: Denaturation and coagulation of proteins
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Features:
- Grossly: Necrotic area is initially firm, white, and slightly swollen (called an infarct)
- With progression, the affected area becomes yellowish, softer, and shrunken
- Microscopically: Cellular outlines are preserved but details are lost, so the cell type can be recognized.
Liquefactive Necrosis
- Cause: Ischemia (brain) or bacterial infections (abscess)
- Organs involved: Brain (Infarct brain) and abscess
- Major event: Enzymatic digestion of necrotic area
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Features:
- The necrotic area is converted into a liquid mass, which undergoes cystic change later
- Example: Infarct of the brain
- G/A (Gross Anatomy): The affected area of the brain is soft with a liquefied center containing necrotic debris. Later, a cyst wall is formed.
Caseous Necrosis
- Cause: Mycobacterium tuberculosis
- Organs involved: Lung, lymph node, skin, and other tissues
- Major event: A combination of protein denaturation and liquefactive necrosis, due to an immune-mediated delayed hypersensitivity reaction to mycobacterium.
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Features:
- The necrotic area appears firm, dry, and cheesy with amorphous, granular debris
- The structure of the necrotic tissue is completely lost.
Fat Necrosis
- Cause: Acute pancreatitis or trauma (breast)
- Organs involved: Pancreas, breast, subcutaneous tissue
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Major event:
- Enzymatic digestion of peritoneal fat by released lipase (in acute pancreatitis).
- Non-enzymatic rupture of fat cells (in trauma). Fatty acids combine with Ca+2 to form Ca salt precipitates.
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Features:
- Grossly: The necrotic area is firm, white (due to calcification).
- Microscopically: Cellular outlines are preserved but with no details, so the cell type can be recognized.
- Grossly: Necrotic fat appears as chalky white, opaque deposits in the adipose tissue surrounding the pancreas and in the omentum.
Fibrinoid Necrosis
- Cause: Immune-mediated (Antigen-antibody reaction)
- Organs involved: Blood vessels
- Major event: Collagen fibers and media of blood vessels are affected by fibrinoid deposition.
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Features:
- Deposition of pinkish substance in the blood vessels
- Microscopically: Fibrinoid necrosis is identified by brightly eosinophilic, hyaline-like deposition in the vessel wall. The necrotic focus is surrounded by nuclear debris of neutrophils (leucocytoclasis).
Gangrenous Necrosis
- It is tissue necrosis followed by putrefaction.
- Caused by: Certain bacterial infections (saprophytic)
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Types:
- Dry Gangrene: Occurs in limbs (e.g., senile) due to ischemia (arterial occlusion). Gradual onset, dry, shrunken, dark brown to black, with a line of demarcation between gangrenous and non-gangrenous parts.
- Moist Gangrene: Occurs mostly in moist organs like the small bowel and lung due to obstruction to the venous outflow in addition to arterial supply. Rapid onset, swollen, dark brown to black, with an ill-defined line of demarcation.
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Gas Gangrene: A special type of moist gangrene due to infection with anaerobic bacteria (Clostridia). The most common predisposing factor is lacerated wounds contaminated with spores of the bacteria. The bacteria secretes powerful exotoxins, causing muscle necrosis.
- Muscle carbohydrate is fermented into lactic acid, hydrogen, and CO2 which accumulates in the affected tissue.
- The affected organ appears swollen, tense, greenish-black, crepitant (due to gas accumulation), and foul-smelling (due to the formation of H2S).
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Description
Explore the details of irreversible cell injury and necrosis, including its definitions and morphologic changes. This quiz focuses on the gross and microscopic features of necrotic tissue, as well as the most common form: coagulative necrosis. Test your understanding of these essential concepts in cellular pathology.
