Epithelial cells

Epithelial cells form continuous sheets (epithelia) that cover external body surfaces and line internal cavities and tubes. They are polarized, with distinct apical, lateral, and basal domains. Functions include protection (skin), absorption (intestine), secretion (glands), filtration (kidney), and sensation (taste buds). They are classified by shape (squamous, cuboidal, columnar) and layering (simple, stratified).