Necrosis

Definition

Unregulated, pathological death of cells or tissues in a living organism caused by external injury, infection, toxins, ischemia, or trauma, characterized by cell swelling, membrane rupture, and inflammatory response. Unlike apoptosis, necrosis is passive, disorderly, and typically harmful to the organism, often spreading to adjacent cells and eliciting immune responses. In arthropod contexts, necrosis commonly results from venom components (e.g., cytotoxic peptides in spider or scorpion envenomation), bacterial toxins, viral infections, or physical trauma.

Etymology

From Greek nekrosis 'state of death,' from nekroun 'to make dead,' from nekros 'dead body'; coined in pathology by Rudolf Virchow in the mid-19th century.

Example

The brown recluse spider (Loxosceles reclusa) injects sphingomyelinase D, a venom enzyme that triggers dermonecrosis—localized necrosis of skin and subcutaneous tissue—producing a characteristic sunken, ulcerated lesion with a central eschar surrounded by erythema.

Synonyms

• tissue death
• cell death (pathological)
• mortification (archaic)

Related Terms

• apoptosis
• gangrene
• autolysis
• cytotoxicity
• dermonecrosis
• myonecrosis
• venom
• envenomation
• septicemia
• Pathogen

Usage Notes

Distinguish carefully from apoptosis: necrosis is always pathological and externally triggered, whereas apoptosis is programmed, regulated, and often beneficial (e.g., metamorphic tissue remodeling in insects). In entomology and arachnology, 'necrosis' frequently appears in compound forms describing tissue-specific damage: dermonecrosis (skin), myonecrosis (muscle), and osteonecrosis (bone). The term implies visible tissue destruction; use 'cell death' for microscopic or ambiguous contexts. Some parasitoid infections and entomopathogenic fungi also induce host tissue necrosis during colonization.