Lecture 1.1b - Cell injury and cell death 1

Necrosis

• Defined as the morphological changes that occur in a living organism after a cell has been dead for some time, characterized as non-programmable cell death.
• Typically seen after 12-24 hours.
• Oncosis is a type of cell death that occurs with swelling, representing the spectrum of changes that occur in injured cells prior to death.

Types of Necrosis

• Two main types: coagulative and liquefactive (colliquitive).
• Two other special types: caseous and fat necrosis.

Coagulative Necrosis

• Characterized by denaturation of proteins dominating over the release of active proteases.
• Cellular architecture is somewhat preserved, resulting in a "ghost outline" of cells.

Liquefactive Necrosis

• Characterized by complete dissolution of necrotic tissue.
• Typically occurs due to massive infiltration by neutrophils, leading to abscess formation.
• Release of reactive oxygen species and proteases is prominent.
• Enzyme degradation is substantially greater than denaturation, leading to enzymatic digestion (liquefaction) of tissues.

Caseous Necrosis

• Characterized by the presence of amorphous (structureless) debris.
• Particularly associated with infections, especially tuberculosis.
• Differs from coagulative necrosis in that it lacks a "ghost outline" of cells.

Fat Necrosis

• Results from the action of lipases released into adipose tissue.
• Free fatty acids accumulate and precipitate as calcium soaps (saponification).
• Grossly visible as pale yellow/white nodules.