epiteelin

Epiteelin refers to epithelial tissue, the cellular sheets that line surfaces and cavities of the body. In English the term is epithelium. Epiteelin is composed of tightly connected cells with minimal extracellular matrix and typically rests on a basement membrane. Embryologically, epithelia can derive from ectoderm, endoderm, or mesoderm and are highly specialized to perform protective, absorptive, secretory, and sensory roles.

Structure and classification: Epithelia are organized into simple epithelia, with a single cell layer, and stratified epithelia, with multiple layers. Cell shapes include squamous (flat), cuboidal (cube-like), and columnar (tall). Some epithelia have surface modifications such as microvilli to increase absorption or cilia to move fluids. Glandular epithelia form exocrine and endocrine glands. The basal surface rests on the basement membrane, and epithelia are typically avascular, receiving nutrients by diffusion from underlying connective tissue.

Functions: Epiteelin provides protection against mechanical and chemical injury, regulates permeability and exchange, participates in secretion and sensation, and forms interfaces with the environment, such as skin, airways, and the intestinal lining. In some organs, specialized epithelia contribute to gas exchange (lung alveoli) or filtration (kidney tubules).

Clinical and research notes: Epithelial tissues can give rise to carcinomas, reflect metaplasia or dysplasia in response to injury, and are central to wound healing and regeneration. The study of epithelia informs fields from anatomy and physiology to oncology and tissue engineering.