Definition:

Apoptosis is a highly controlled and programmed cell death mechanism characterized by distinct morphological and biochemical changes.

Overview:

Apoptosis, also known as programmed cell death or cell suicide, is a crucial physiological process that maintains tissue homeostasis in multicellular organisms. It plays a critical role in embryonic development, immune response regulation, and elimination of damaged, infected, or unwanted cells. Unlike necrosis, which is a form of accidental cell death resulting from injury, apoptosis is a tightly regulated cellular process.

Morphological Changes:

The hallmark morphological changes observed during apoptosis include cellular shrinkage, membrane blebbing, nuclear condensation, chromosomal fragmentation, and formation of apoptotic bodies. These changes distinguish apoptotic cells from healthy cells and help in their recognition and removal by phagocytic cells.

Signal Transduction Pathways:

Apoptosis can be triggered by a variety of internal or external signals, which are transmitted through specific signal transduction pathways. These pathways involve a multitude of proteins, such as caspases, Bcl-2 family members, tumor suppressors, death receptors, and cytochrome c. The activation of these proteins results in a cascade of events that ultimately leads to cell dismantling and controlled degradation.

Functions and Importance:

Apoptosis plays a critical role in maintaining tissue homeostasis by eliminating excess or damaged cells. It is essential for embryogenesis, organ development, and shaping of various tissues and organs in a developing organism. Furthermore, apoptosis is crucial in several physiological processes, including immune response regulation, hormone-dependent tissue remodeling, and removal of potentially harmful cells, such as virus-infected or cancerous cells. Dysregulation of apoptosis has been implicated in various diseases, such as cancer, autoimmune disorders, and neurodegenerative disorders.