Here's why:

* Location: Epithelial tissue forms the outer layer of skin, lines the inside of hollow organs (like the stomach and intestines), and covers the surface of body cavities.

* Function: It acts as a barrier, protecting the underlying tissues from injury and infection. It also helps regulate the passage of substances into and out of the body.

While there are many different types of epithelial tissue, they all share these basic characteristics:

* Closely packed cells: Epithelial cells are tightly packed together, forming a continuous sheet.

* Avascular: They lack blood vessels and receive nutrients and oxygen by diffusion from the underlying connective tissue.

* Regenerative: Epithelial tissue has a high rate of cell division, allowing it to quickly repair itself after injury.