epitheliala

Epitheliala is a term used in some languages to denote epithelial tissue, the cellular layer that lines body surfaces, cavities, and glands. In English, the corresponding term is epithelium or epithelial tissue. Epithelial tissue forms a continuous sheet that serves as a barrier and interface between internal and external environments, and it also participates in secretion, absorption, and sensation.

Epithelia are classified by two main criteria: the number of cell layers and the shape of the cells at the apical surface. Simple epithelia have a single cell layer, while stratified epithelia consist of multiple layers. Pseudostratified epithelia appear multi-layered but are actually a single layer of cells with nuclei at different heights. Cell shapes include squamous (flat), cuboidal, and columnar; transitional epithelium can stretch, as in the urinary bladder.

Key functions include protection (skin, oral mucosa), selective permeability and absorption (intestinal lining, kidney tubules), secretion (glandular epithelia such as glands and ducts), and sensation (epithelial receptors in skin and organs). Epithelial tissues often possess specialized features such as microvilli to increase surface area and cilia to move substances across surfaces, along with junctional complexes that create a barrier and coordinate transport.

Epithelia arise from ectoderm, endoderm, or mesoderm during development and typically exhibit high regenerative capacity, with stem cells in the basal layer replenishing cells. Clinically, epithelial dysplasia and carcinomas are common concerns, reflecting the tissue’s rapid turnover and exposure to the external environment. Representative examples include stratified squamous epithelium of the skin, simple columnar epithelium of the gut, and pseudostratified ciliated epithelium of the respiratory tract.