lholocrine

Holocrine secretion is a mode of exocrine gland function in which secretory cells accumulate product until they disintegrate, releasing their contents into the duct or onto a surface. In contrast to merocrine secretion, where products are released by exocytosis without cell loss, and to apocrine secretion, where a portion of the cell apex is shed, holocrine secretion involves the deliberate destruction of the secretory cell. The secretory product is often mixed with cellular debris and lipids, and the gland is renewed by mitotic division of basal progenitor cells that replace the shed cells.

Classic examples are sebaceous glands of the skin, which secrete sebum, a lipid-rich substance that conditions and lubricates hair and skin. Meibomian glands in the eyelids are another example, producing lipid secretions that contribute to the tear film. Holocrine glands are typically simple branching acini or tubuloalveolar structures, and their activity is tied to the differentiation gradient of their secretory cells.

The term holocrine is standard in anatomy and physiology texts; occasional misspellings such as 'lholocrine' appear in non-authoritative sources but do not reflect a distinct process. Understanding holocrine secretion helps explain how certain gland products are delivered in a lipid-dense, cell-derived form, and why gland turnover involves continual replacement through basal cell proliferation.