Fig. 2. Necrosis and apoptosis: morphological features and signaling pathways.

A Hallmarks of necrosis and apoptosis are illustrated. Necrosis is an uncontrolled and pathological form of cell death, marked by cell swelling, membrane rupture, and intracellular content release, leading to inflammation and tissue damage. In contrast, apoptosis is a tightly controlled form of cell death that involves characteristic morphological features, such as cell shrinkage, chromatin condensation, membrane blebbing, nuclear fragmentation, and apoptotic body formation. B The two signaling pathways that lead to apoptosis are described. The extrinsic pathway is initiated by the binding of death ligands, such as tumor necrosis factor (TNF)-α or Fas ligand (FasL), to death receptors, which activates caspase 8. The intrinsic pathway, regulated by the Bcl-2 family, is triggered by intracellular stressors, such as DNA damage and oxidative stress, resulting in the release of cytochrome c from mitochondria and activation of caspase 9. The two pathways ultimately converge on caspase 3, which mediates the execution of apoptosis.