Proliferation

PROLIFERATION (from Latin proles-offspring and fero-I carry), a term introduced by Virchow to denote the formation of new cells through their multiplication by division. As a general and very broad concept, P. can relate to processes of the most varied character. Thus, cell P. lies at the basis of regenerative tissue formation (see Regeneration); P. is observed in various hyperplasias (see Hyperplasia); finally, cell P. lies at the basis of tumor tissue growth. Naturally, such proliferative processes can occur in the most diverse tissues, however the capacity of tissue elements for P. is by no means the same: the more highly differentiated the cells, the less capable they are of P.; in particular, in complex tissues, e.g., in epithelium, P. almost as a rule originates from those tissue zones which consist of less differentiated elements; such zones are called proliferation centers or growth centers. In multi-layered flat epithelium, the proliferation center corresponds to the zone of the Malpighian or germ layer, in glands- the places of transition of excretory ducts into glandular alveoli. The consequence of P. is usually the formation of new tissue (tissue production), however this is not a rule: for example, elements resulting from inflammatory P. often do not build new tissue, but merely penetrate, infiltrate the surrounding tissue.