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Cell Death

Mors cellularis

For medical students2 min readUpdated 2026-10-10

Cell death in the body occurs primarily through two mechanisms: necrosis and apoptosis. The former is the result of irreversible injury, whereas the latter is a strictly regulated process of genetic "suicide".

Main typesNecrosis ("homicide") and apoptosis ("suicide").
ApoptosisTriggered via activation of the genetic death program.
NecrosisThe end result of irreversible cell injury.
PhenoptosisIncludes apoptosis, vacuolar cell death, and terminal differentiation.

Necrosis: Accidental Cell Death

In pathology, necrosis is viewed as cellular "homicide." This state occurs due to the action of various injurious factors that lead to irreversible structural damage. Unlike programmed processes, necrosis is the final point of injury where the cell can no longer maintain vital functions.

Apoptosis: Genetic Suicide

The term apoptosis describes the process of cellular "suicide." Its key feature is that death occurs without prior lethal injury. The cell activates an internal genetic program that systematically leads to its demise. This is a physiologically vital mechanism that allows the organism to eliminate unwanted or damaged elements.

Variants of Programmed Death

In addition to classic apoptosis, programmed cell death (phenoptosis) includes:

  1. Vacuolar cell death.
  2. Terminal cell differentiation.

It is important to note that in modern classification, necrosis is categorized separately from programmed processes because it is not regulated by the cell's genetic apparatus.

Mnemonic

Necrosis is like a car crash (sudden trauma, accidental death); Apoptosis is set by an alarm clock (programmed self-destruction).

Frequently asked questions

What happens during terminal cell differentiation?

Terminal differentiation is the natural completion of a cell's life cycle, during which it permanently loses its ability to divide. This process is considered a form of programmed cell death.

Examples of postmitotic cells include:

  • Nerve cells — neurons.
  • Heart muscle cells — cardiomyocytes.
  • Syncytia — skeletal muscle fibers.
  • Epidermal cells — all layers except the basal layer (undergoing cornification/keratinization).
What factors cause irreversible cell injury in necrosis?

Irreversible cell injury in necrosis is caused by various damaging factors, including:

  • Physical factors — mechanical, thermal, vibrational, and radiation effects.
  • Chemical factors — acids, alkalis, poisons, environmental toxins (asbestos, ethanol), drugs, as well as high concentrations of glucose, salts, and oxygen.
  • Toxic factors — bacterial and other biological agents.

Chemical factors cause irreversible damage by disrupting membrane permeability, osmotic homeostasis, enzyme integrity, or cofactors. An increase in cytoplasmic Ca²⁺ activates lytic ATPases, phospholipases, and proteases, facilitating the transition from reversible changes to irreversible cell injury.

What is the main difference between necrosis and apoptosis?

Necrosis is the result of external injury ("homicide"), whereas apoptosis is the execution of an internal genetic program ("suicide").

Is necrosis a form of programmed cell death?

No, necrosis is not classified as programmed cell death; it is the consequence of irreversible injury.

What does phenoptosis include?

Phenoptosis includes apoptosis, vacuolar cell death, and terminal differentiation.

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