Atrophy

Definition

The reduction in size, mass, or functional capacity of a cell, tissue, organ, or body part after it has reached normal maturity, resulting from decreased anabolic activity, diminished trophic stimulation, disuse, nutrient deprivation, or pathological conditions. In arthropods, atrophy commonly occurs during dormancy (diapause), following autotomy, under parasitic infection, or with aging.

Etymology

From Greek atrophia, 'lack of nourishment,' from a- (without) + trophe (nourishment).

Example

In overwintering adult lady beetles (Coleoptera: Coccinellidae), flight muscles atrophy during diapause to conserve energy reserves; the muscles regenerate when spring temperatures trigger reproductive activation.

Related Terms

• hypoplasia
• apoptosis
• Autotomy
• Diapause
• castration
• degeneration
• Regeneration
• trophic

Usage Notes

Distinguished from hypoplasia (failure to reach normal size due to reduced cell number during development) and aplasia (complete failure of organ formation). In entomology, atrophy is often reversible—flight muscle atrophy in diapausing insects typically reverses upon return to favorable conditions, unlike vertebrate denervation atrophy. The term is also used for parasitic castration, where parasite infection causes gonadal atrophy in hosts such as crabs or snails.