Apocrina

Apocrine secretion is a mode of glandular secretion in which the secretory product is released together with a portion of the secretory cell’s apical cytoplasm. During the process, the apical part of the cell pinches off as a membrane-bound fragment that contains secretory material, while the remaining cell regenerates the apical surface. This contrasts with merocrine (exocytotic) secretion, where secretory granules are released without loss of cytoplasm, and holocrine secretion, in which entire cells disintegrate to liberate their contents.

Apocrine glands are found in various tissues and species. In humans, classic examples include certain sweat glands in the axillae and groin that produce a thicker, lipid-rich secretion; after bacterial action, this can contribute to body odor. The mammary gland is often discussed in relation to apocrine processes, where lipid components of milk involve apocrine-like mechanisms, though many secretory aspects of milk are merocrine. In many animals, apocrine glands serve scent or pheromone roles, including specialized scent glands in fur-bearing species.

In histology and pathology, apocrine secretion is used to describe gland types and their secretory patterns. Apocrine metaplasia refers to tissue changes in which glandular epithelium acquires apocrine characteristics, a finding observed in certain breast and other glandular tissues. Rare primary apocrine carcinomas can arise in the skin or breast and show apocrine morphology. The study of apocrine secretion continues to clarify its physiological and pathological significance across tissues.