FUNCTIONS AND TYPES OF EPITHELIAL TISSUE
Main functions of epithelial tissue:
- epithelial cells line the surface of many organs and of the whole body protecting them from mechanical forces and frm drying
- epithelia act as barriers separating compartments in the body
- forming glands that secrete molecules
- gathering small molecules and use them to synthesize larger molecules (macromolecules) that will be transported out of the cell moved out of the cell.
- to transform molecules by adding, removing or replacing their components and secreting them.
- in some cases (such as when sweat is produced by sweat glands) most of the secretion is simply transported by the cells and no or almost no sytnthesis is involved.
- transport of molecules, particles and ions between the lumen of a cavity and the connective tissue, for example by cells lining blood and lymph vessels and by cells of the digestive tract and renal tubules.
Secretion consists fundamentally of
CLASSIFICATION OF THE EPITHELIAL TISSUEL
According to its location in the body, the arrangement of its cells and its functions, the epithelial tissue is classified into two main types:
LINING EPITHELIAL TISSUE
SECRETORY OR GLANDULAR EPITHELIAL TISSUE
This classification is, however, imperfect, as there are many lining epithelia in which some or all cells are also secretory.