Necrosis

Question 1

What is necrosis?

Answer 1

Necrosis is a pathologic process that is the consequence of severe injury.

Question 2

What are the main causes of necrosis?

Answer 2

The main causes of necrosis include loss of oxygen supply (ischemia), exposure to microbial toxins, burns and other forms of chemical and physical injury, and unusual situations in which active proteases leak out of cells.

Question 3

What leads to irreparable damage in necrosis?

Answer 3

All initiating triggers of necrosis lead to irreparable damage of numerous cellular components.

Question 4

What are the characteristics of necrosis?

Answer 4

Necrosis is characterized by denaturation of cellular proteins, leakage of cellular contents through damaged membranes, local inflammation, and enzymatic digestion.

Question 5

What happens when membranes are severely damaged?

Answer 5

Lysosomal enzymes enter the cytoplasm and digest the cell. Cellular contents leak into the extracellular space, eliciting a host reaction (inflammation).

Question 6

What are damage-associated molecular patterns (DAMPs)?

Answer 6

Specific substances released from injured cells, such as ATP and uric acid, which indicate severe cell injury.

Question 7

What triggers phagocytosis and cytokine production in response to DAMPs?

Answer 7

DAMPs are recognized by receptors in macrophages and other cell types.

Question 8

What is the role of inflammatory cells in response to necrosis?

Answer 8

Inflammatory cells produce proteolytic enzymes, leading to clearance of necrotic cells through phagocytosis and enzymatic digestion.

Question 9

How does necrosis affect blood tests for tissue-specific injury?

Answer 9

Necrosis leads to leakage of intracellular proteins into circulation, which can be detected in blood tests.

Question 10

What are some examples of tissue-specific proteins used as biomarkers?

Answer 10

Cardiac-specific troponin, alkaline phosphatase from bile duct epithelium, and transaminases from hepatocytes.

Question 11

How quickly can cardiac-specific troponins be detected after myocardial cell necrosis?

Answer 11

Cardiac-specific troponins can be detected in the blood as early as 2 hours after necrosis.

Question 12

What is the significance of serial measurement of serum cardiac troponins?

Answer 12

It plays a central role in the diagnosis and management of patients with myocardial infarction.

Question 13

What is the appearance of necrotic cells in H&E stains?

Answer 13

Necrotic cells show increased eosinophilia due to loss of cytoplasmic RNA and accumulation of denatured cytoplasmic proteins.

Question 14

What causes the glassy homogeneous appearance of necrotic cells?

Answer 14

The glassy homogeneous appearance is mainly due to the loss of glycogen particles.

Question 15

What happens to the cytoplasm of necrotic cells?

Answer 15

The cytoplasm becomes vacuolated and appears moth-eaten after organelle digestion.

Question 16

What are myelin figures?

Answer 16

Myelin figures are large whorled phospholipid precipitates that may replace dead cells.

Question 17

How are necrotic cells characterized by electron microscopy?

Answer 17

Necrotic cells show discontinuities in plasma and organelle membranes, marked dilation of mitochondria, and aggregates of denatured protein.

Question 18

What are the three patterns of nuclear changes in necrotic cells?

Answer 18

The three patterns are karyolysis, pyknosis, and karyorrhexis.

Question 19

What is karyolysis?

Answer 19

Karyolysis is the fading of chromatin basophilia due to loss of DNA from enzymatic degradation.

Question 20

What is pyknosis?

Answer 20

Pyknosis is characterized by nuclear shrinkage and increased basophilia, with chromatin condensing into a dense mass.

Question 21

What is karyorrhexis?

Answer 21

Karyorrhexis is the fragmentation of the pyknotic nucleus.

Question 22

What characterizes irreversible cell injury?

Answer 22

Irreversible injury is characterized by inability to reverse mitochondrial dysfunction and profound disturbances in membrane function.

Question 23

What is coagulative necrosis?

Answer 23

Coagulative necrosis preserves the architecture of dead tissue for several days, resulting in a firm texture.

Question 24

How does liquefactive necrosis differ from coagulative necrosis?

Answer 24

Liquefactive necrosis involves digestion of dead cells, transforming tissue into a viscous liquid.

Question 25

What is pus in the context of liquefactive necrosis?

Answer 25

Pus is the necrotic material that is frequently creamy yellow due to the presence of leukocytes.

Question 26

What is fat necrosis?

Answer 26

Fat necrosis refers to focal areas of fat destruction, typically resulting from the release of activated pancreatic lipases into the pancreas and peritoneal cavity.

This occurs in acute pancreatitis, where pancreatic enzymes leak out of damaged acinar cells and liquefy fat cell membranes.

Question 27

What does liquefactive necrosis indicate?

Answer 27

Liquefactive necrosis often manifests as hypoxic death of cells within the central nervous system, leading to tissue dissolution.

It is commonly seen in brain infarcts.

Question 28

What is gangrenous necrosis?

Answer 28

Gangrenous necrosis is a term used for necrosis in a limb, usually the lower leg, that has lost blood supply and typically involves coagulative necrosis.

When bacterial infection is present, it can lead to wet gangrene due to liquefactive necrosis.

Question 29

What characterizes caseous necrosis?

Answer 29

Caseous necrosis is often found in tuberculous infections, characterized by a friable white appearance and a structureless collection of fragmented cells.

It is associated with granulomas.

Question 30

What is fibrinoid necrosis?

Answer 30

Fibrinoid necrosis is a form of vascular damage seen in immune reactions, where immune complexes and plasma proteins deposit in artery walls, resulting in a bright pink appearance in H&E stains.

It is associated with immunologically mediated vasculitis syndromes.