Necrosis: Cellular Changes, Types, and Clinical Markers in Pathology

In necrosis, what happens to cellular membranes?

They fall apart.

What is the local host reaction that accompanies necrosis?

Inflammation.

What is the purpose of the inflammatory reaction induced by necrosis?

To eliminate debris and start the subsequent repair process.

What are the two sources of enzymes responsible for the digestion of dead cells in necrosis?

Recruited leukocytes and the disrupted lysosomes of the dying cells themselves.

According to the provided text, necrosis is considered the major pathway of cell death in what common types of injuries?

Ischemia, exposure to toxins, various infections, and trauma.

According to the provided table, how does cell size change in necrosis versus apoptosis?

In necrosis, the cell size is enlarged (swelling), whereas in apoptosis it is reduced (shrinkage).

Describe the sequence of nuclear changes that can occur in necrosis.

Pyknosis (shrinkage) → karyorrhexis (fragmentation) → karyolysis (fading).

How does the state of the plasma membrane differ between necrosis and apoptosis?

In necrosis, the plasma membrane is disrupted, while in apoptosis it remains intact but with an altered structure.

What happens to the cellular contents during necrosis?

They undergo enzymatic digestion and may leak out of the cell.

What is the key difference regarding adjacent inflammation between necrosis and apoptosis?

Inflammation is frequently present in necrosis but absent in apoptosis.

Necrosis is invariably associated with what type of role, physiologic or pathologic?

It is invariably pathologic, representing the culmination of irreversible cell injury.

The increased eosinophilia in necrotic cells is attributable to what two factors?

Increased binding of eosin to denatured cytoplasmic proteins and the loss of basophilic RNA.

Why might a necrotic cell have a glassy, homogeneous appearance?

This is mostly due to the loss of glycogen particles.

What causes the cytoplasm of a necrotic cell to appear vacuolated and 'moth-eaten'?

Enzymes have digested the cytoplasmic organelles.

What is the term for the nuclear change in necrosis characterized by nuclear shrinkage and increased basophilia?

Pyknosis.

What is the term for the fragmentation of a pyknotic nucleus during necrosis?

Karyorrhexis.

The nuclear change in which basophilia fades due to the digestion of DNA by DNase is known as _____.

karyolysis

What might replace dead cells, which are then either phagocytosed or degraded into fatty acids?

Myelin figures.

When fatty acids from degraded necrotic cells bind with calcium salts, what process can ultimately occur?

The dead cells may become calcified (dystrophic calcification).

What is the key feature of coagulative necrosis regarding tissue structure?

The underlying tissue architecture is preserved for at least several days.

What texture do tissues affected by coagulative necrosis typically take on?

A firm texture.

What is the presumed reason that eosinophilic, anucleate cells persist for days in coagulative necrosis?

The injury denatures not only structural proteins but also enzymes, which limits proteolysis.

Coagulative necrosis is characteristic of infarcts in all solid organs except for which one?

The brain.

What type of necrosis is typically seen at sites of bacterial or fungal infections?

Liquefactive necrosis.

Why does liquefactive necrosis occur in microbial infections?

Microbes stimulate the accumulation of inflammatory cells, and the enzymes of these leukocytes digest ("liquefy") the tissue.

What type of necrosis does hypoxic death of cells within the central nervous system often cause?

Liquefactive necrosis.

In liquefactive necrosis, the dead cells are completely digested, transforming the tissue into what substance?

A viscous liquid.

When liquefactive necrosis is initiated by acute inflammation in a bacterial infection, the material is creamy yellow and is called _____.

pus

What is a localized collection of pus called?

An abscess.

What is the clinical term for necrosis of a limb that has lost its blood supply?

Gangrenous necrosis.

When bacterial infection is superimposed on gangrenous necrosis, what is the resulting condition called?

Wet gangrene.

What is the most common cause associated with caseous necrosis?

Foci of tuberculous infection.

What does the term 'caseous' mean in caseous necrosis?

It means "cheese-like," referring to the friable yellow-white appearance of the necrotic area.

How does the microscopic appearance of caseous necrosis differ from coagulative necrosis regarding tissue architecture?

Unlike coagulative necrosis, the tissue architecture in caseous necrosis is obliterated and cellular outlines cannot be discerned.

A necrotic focus with an amorphous granular pink appearance on an H&E stain, where cellular outlines are lost, is characteristic of what type of necrosis?

Caseous necrosis.

What type of inflammatory lesion, characterized by a collection of macrophages, often surrounds an area of caseous necrosis?

A granuloma.

What are two common causes of fat necrosis?

Abdominal trauma or acute pancreatitis.

In acute pancreatitis, what is the mechanism that leads to fat necrosis?

Enzymes leak out of damaged pancreatic cells and digest peritoneal fat cells.

In fat necrosis, released fatty acids combine with calcium to produce what grossly identifiable lesions?

Chalky white lesions.

On histologic examination, what are the characteristic features of fat necrosis?

Shadowy outlines of necrotic fat cells surrounded by granular basophilic calcium deposits and an inflammatory reaction.

In what two general conditions is fibrinoid necrosis typically seen?

Immune reactions with antigen-antibody complexes in vessel walls, and severe hypertension.

What causes the bright pink, amorphous "fibrinoid" appearance in fibrinoid necrosis?

Deposited immune complexes and plasma proteins that have leaked into the walls of injured vessels.

How can tissue-specific necrosis be detected clinically using blood samples?

By measuring the levels of intracellular proteins that have leaked through damaged cell membranes.

The presence of the contractile protein troponin in the blood is a marker for necrosis in which tissue?

Cardiac muscle.

The presence of transaminases in the blood serves as a marker for necrosis in which organ's cells?

Hepatocytes (liver cells).

According to FIG. 1.5, what is the temporal relationship between cell death and the appearance of morphologic changes?

Cell death typically precedes ultrastructural, light microscopic, and grossly visible morphologic changes.

Basophilia in H&E staining is due to the binding of which blue dye to which cellular component?

The dye hematoxylin binds to ribonucleic acid (RNA) in the cytoplasm.

What electron microscopy finding is characterized by marked dilation of mitochondria with large amorphous densities?

This is a characteristic finding in necrotic cells.