Necrosis: forced death
In pathomorphology, necrosis is viewed as cell "murder". This condition occurs as a result of various damaging factors that lead to irreversible structural alterations. Unlike programmed processes, necrosis is the final point of injury where the cell is no longer able to maintain its viability.
Apoptosis: genetic suicide
The term apoptosis describes the process of cell "suicide". Its key feature is that death occurs without the prior development of lethal injuries. The cell activates an internal genetic program that systematically leads to its demise. This is a physiologically significant mechanism that allows the body to rid itself of unnecessary or damaged elements.
Variants of programmed cell death
In addition to classical apoptosis, the category of programmed cell death (phenoptosis) includes:
- Vacuolar cell death.
- Terminal cell differentiation.
It is important to note that in modern classification, necrosis is separated from the group of programmed processes, as it is not controlled by the cell's genetic apparatus.
Briefly: answers to topical questions
What happens during terminal cell differentiation?
Terminal differentiation is the natural completion of the cell life cycle, during which it permanently loses its ability to divide. This process is considered a variant of programmed cell death.
Examples of postmitotic cells:
- Nerve cells — neurons.
- Heart muscle cells — cardiomyocytes.
- Symplasts — skeletal muscle fibers.
- Epidermal cells — all layers except the basal layer (undergoing cornification).
What factors cause irreversible cell damage in necrosis?
Irreversible cell injury in necrosis is caused by various damaging factors. These include:
- Physical factors — mechanical, thermal, vibrational, and radiation effects.
- Chemical factors — acids, alkalis, poisons, toxic environmental agents (asbestos, ethanol), medications, as well as high concentrations of glucose, salts, and oxygen.
- Toxic factors — agents of bacterial and other origin.
Chemical factors cause irreversible damage by disrupting membrane permeability, osmotic homeostasis, and the integrity of enzymes or cofactors. An increased concentration of Ca²⁺ in the cytoplasm activates lytic ATPases, phospholipases, and proteases, which promotes the transition from reversible changes to irreversible cell injury.
Necrosis is "Ne-cross" (did not cross the line of life, died from trauma), Apoptosis is "A-po-program" (turned on its internal timer).
Class and exam questions
What is the main difference between necrosis and apoptosis?
Necrosis is the result of external injury ("murder"), while apoptosis is the execution of an internal genetic program ("suicide").
Is necrosis a form of programmed cell death?
No, necrosis does not belong to programmed cell death; it is the consequence of irreversible injury.
What does the concept of phenoptosis include?
Phenoptosis includes apoptosis, vacuolar cell death, and terminal differentiation.
What else to study on this topic
- Morphological signs of necrosis in ischemic injury.
- The role of the inflammatory response in the development of necrotic processes.
- Mechanisms of osmotic cell lysis.
- Comparative characteristics of coagulative and liquefactive necrosis.
- The biological significance of terminal differentiation.
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