epitelu

Epitelu is the term used in several languages to denote the epithelium, the cellular tissue that lines surfaces and forms glands. In anatomy, epitelu covers the exterior of the body and lines internal cavities and ducts, providing protection and interfaces with the environment.

Epitelu consists of tightly packed cells arranged in continuous sheets. The layer has an apical surface facing a lumen or the outside and a basolateral surface anchored to a basement membrane. It is avascular; nutrients and gases diffuse from the underlying connective tissue to nourish the epithelial cells.

Classification of epitelu follows two main schemes: by the number of cell layers (simple, stratified, pseudostratified) and by cell shape (squamous, cuboidal, columnar, transitional). Specialized forms include ciliated pseudostratified columnar epithelium of the respiratory tract and stratified squamous epithelium of the skin and oral mucosa. Epitelu also forms glandular tissue, with glands classified as exocrine (ducted) or endocrine (ductless).

Functions of epitelu include protection, selective permeability, absorption, secretion, sensation, and filtration. Regeneration is rapid; basal cells divide to replace lost cells, a process sustained by stem cell niches and signals from the underlying connective tissue.

Clinically, changes in epitelu can indicate disease; metaplasia, dysplasia, or carcinoma arise from epithelial cells. Examples include the respiratory epithelium lining airways, the intestinal epithelium with absorptive enterocytes, and the transitional epithelium of the urinary bladder.