Cellular Injury V: Apoptosis and Autophagy

Cells respond to damage and stress through tightly regulated processes that promote survival or initiate self-destruction.

Apoptosis is a form of regulated cell death that eliminates aged or injured cells to maintain tissue balance.

During apoptosis, cells shrink, chromatin condenses and fragments, and the cell breaks apart into apoptotic bodies.

Phagocytes then engulf these bodies without triggering inflammation.

Apoptosis is crucial during embryogenesis to remove excess cells, during hormone withdrawal to eliminate hormone-dependent cells, during immune regulation to delete self-reactive immune cells, and during viral infections to destroy infected cells.

In contrast, autophagy is an intracellular recycling process that maintains cellular quality at baseline and is upregulated during stress to promote survival.

The process begins with forming a phagophore, which develops into an autophagosome that later fuses with a lysosome.

Autophagy helps sustain metabolism during starvation, clears damaged organelles, and supports overall cellular quality control.