Glandulaariepiteeli

Glandulaariepiteeli, or glandular epithelium, refers to epithelial tissue specialized to form glands or to line glandular structures and enable secretion. It lines the secretory portions of exocrine glands and constitutes the parenchyma of endocrine glands. Exocrine glands secrete through ducts onto surfaces or cavities, such as the skin or the gastrointestinal lumen, whereas endocrine glands release hormones into the interstitial fluid and bloodstream without a duct system.

Histologically, glandular epithelium is polarized, with an apical secretory surface and a basolateral domain connected by tight junctions. Secretory cells may be organized as simple glands (unbranched ducts) or compound glands (branched ducts) and as tubular, acinar (alveolar), or tubuloacinar units. Cells may be mucous, serous, or mixed in character. The presence of mucous cells produces viscous secretions; serous cells produce watery, enzyme-rich secretions; mixed glands contain both. Some glands contain myoepithelial cells that contract to expel secretions.

Secretory mechanisms include merocrine (exocytosis of vesicles), apocrine (partial loss of cytoplasm), and holocrine (cell rupture). Most sweat, saliva, and pancreatic secretions are merocrine; sebaceous glands are typically holocrine; mammary glands illustrate features that can involve multiple modes of secretion.

Glandular epithelium is widespread, found in the lining of the gastrointestinal and respiratory tracts, the skin, and endocrine organs. Dysfunction or neoplastic transformation of glandular epithelium underlies conditions such as glandular hyperplasia, adenomas, and adenocarcinomas.