Hypertrophy

Definition

Increase in the size of individual cells, leading to enlargement of a tissue or organ without an increase in cell number; contrasts with hyperplasia, which involves cell proliferation. In arthropods—especially those with eutely, where the total somatic cell count is fixed at maturity—hypertrophy is the primary mechanism of post-embryonic growth and functional adaptation.

Etymology

Greek hyper- (over, above) + -trophia (nourishment, growth)

Example

In adult female mosquitoes (Culicidae), the flight muscles undergo dramatic hypertrophy during the gonotrophic cycle, with individual myofibrils enlarging to support the energy demands of host-seeking flight and blood-meal digestion; similarly, the venom glands of parasitoid wasps enlarge through cellular hypertrophy as they mature.

Synonyms

• cellular enlargement

Related Terms

• Hyperplasia
• eutely
• Atrophy
• metaplasia
• Oogenesis
• myogenesis
• ecdysteroid

Usage Notes

Distinguish carefully from hyperplasia: hypertrophy involves larger cells, hyperplasia involves more cells. In insects with complete cell-number constancy (true eutely), such as some nematodes and potentially certain insect tissues, hypertrophy is essentially the sole mode of growth; however, many insects exhibit limited hyperplasia in specific lineages. The term is sometimes used loosely for tissue enlargement without microscopic confirmation of mechanism.