The two primary physiological methods of cell death are apoptosis and senescent death (SD).
Apoptosis: Programmed Cell Death
Apoptosis is a highly regulated process of programmed cell death. It's essential for development, tissue homeostasis, and eliminating damaged cells. Apoptosis involves a cascade of molecular events leading to cell shrinkage, DNA fragmentation, and the formation of apoptotic bodies that are efficiently cleared by phagocytes. This prevents inflammation.
- Example: During development, apoptosis shapes the hands and feet by eliminating cells between the digits.
Senescent Death (SD)
Senescent death refers to the irreversible growth arrest of cells. Senescent cells remain metabolically active but lose their ability to proliferate. They can contribute to age-related diseases by secreting inflammatory molecules. While not strictly "death" in the same way as apoptosis, it represents a terminal state.
- Example: The accumulation of senescent cells in tissues contributes to aging and age-related diseases.
The provided references support these two as primary physiological modes of cell death. While other forms of cell death exist (like necrosis), they are generally considered pathological rather than part of normal physiological processes. The reference specifically mentions that "physiologically there are only two major modes of cell death, i.e. apoptosis and SD".
