þekju

Þekju, in Icelandic anatomy and histology, refers to the epithelial tissue that lines surfaces and cavities of the body and forms coverings on organs and the skin. In clinical and educational texts it is typically simply called epithelium.

Epithelial tissue is classified by cell shape—squamous, cuboidal, and columnar—and by layering, including simple, stratified, and pseudostratified epithelia. Cells sit on the basement membrane and are joined by junctional complexes, making the tissue avascular and highly regenerative.

Functions include protection against mechanical and chemical stress, secretion by glandular epithelium, absorption and selective transport, and sensation in specialized epithelia. Cilia and microvilli modify surface interaction in the respiratory and digestive tracts.

Examples include the stratified squamous epithelium of the skin and oral mucosa; the simple columnar epithelium lining the intestines; and the pseudostratified ciliated epithelium lining much of the respiratory tract.

Developmentally, epithelia arise from all three germ layers in vertebrates and regenerate rapidly from resident stem cells in the basal layer.

Pathologies affecting þekju include metaplasia, dysplasia, and carcinomas, which originate from epithelial cells.

The term derives from Icelandic and is used in education and medicine to denote the epithelium as a fundamental tissue type.