Question

Briefly describe the common Manifestation of cell injury and cell death..

Answer 1

• Cell injury or cell damage may be caused due to physical, chemical or biological factors. Physical factors include  heat or radiation damage, and other factors include nutrient disruption, defective ATP production etc. Cell injury can occur (mostly) in two ways: damage to DNA and damage to membrane. Furthermore, cell damage maybe sub-lethal (reversible) or lethal (irreversible). Sub-lethal damage can occur in the form of cell swelling, due to cellular hypoxia, which may cause injury in the form of distortion of microvilli, mitochondrial changes, loosening of intercellular attachments and dilation of the endoplasmic reticulum. Another form of sub-lethal damage include fatty changes, impairing fat metabolism. Lethal damage occurs in the form of necrosis (swelling of cytoplasm, irreversible damage to the plasma membrane, and breakdown of organelles) and apoptosis. Reversible damages can be repaired with the help of regeneration, or by replacement of cells.
• Cell death is a way by which an organism gets rid of old, diseased or infected cells. Cell death can be of many types, such as: Type I and II Programmed cell death (or PCD), Necrosis, and Mitotic catastrophe. PCD is the regulated form of cell death that occurs in the form of apoptosis (Type I) and autophagy (Type II). Apoptosis kills by morphological cell changes (like cell shrinkage, nuclear fragmentation, chromatin condensation, etc) which causes death. Autophagy occurs in the cytoplasm to get rid of abnormal protein aggregates, and damaged organelles. This happens by autophagosomic-lysosomal degradation. Necrosis refers to cell death that is caused by external factors like  trauma or infection. Furthermore, mitotic catastrophe is cell death caused by premature entry of cells into mitosis.