Here's why:
* Membranes: Epithelial tissue forms the lining of all body cavities and surfaces, creating membranes that act as barriers and interfaces. For example, the skin is a type of epithelial membrane.
* Glands: Epithelial tissue also forms the functional units of glands, which are structures that secrete substances. These glands can be either exocrine (secreting onto a surface) or endocrine (secreting hormones into the bloodstream).
Epithelial tissue is characterized by:
* Closely packed cells: Cells are arranged in sheets with little or no intercellular space.
* Avascularity: Epithelial tissue lacks its own blood supply and receives nutrients from the underlying connective tissue.
* High regenerative capacity: Epithelial cells are constantly being replaced.
Therefore, epithelial tissue is crucial for the formation and function of both membranes and glands.
