Apoptosis

[Robbins 9th 52]

Explanation :
The removal of supernumerary cells (in excess of the required number) during development. 
• Involution of hormone-dependent tissues on hormone withdrawal, such as endometrial cell breakdown during the menstrual cycle, ovarian follicular atresia in menopause, and regression of the lactating breast after weaning.
• Cell turnover in proliferating cell populations, such as immature lymphocytes in the bone marrow and thymus, B lymphocytes in germinal centers that fail to express useful antigen receptors and epithelial cells in intestinal crypts, to maintain a constant cell number (homeostasis).
• Elimination of potentially harmful self-reactive lymphocytes to prevent immune reactions against one’s own tissues.
• Death of host cells that have served their useful purpose, such as neutrophils in an acute inflammatory response, and lymphocytes at the end of an immune response.

Apoptosis is Programmed cell death

Most characteristic feature of apoptosis is chromatin condensation

Explanation :
Morphology of apoptotic cell -
Cell shrinkage
Chromatin condensation
Formation of cytoplasmic blebs and apoptotic body
Phagocytosis