Explanation:
Epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue, and nervous tissue. It covers the surfaces of organs, lines body cavities, and forms glands. Epithelial tissue always has an exposed outer surface and an inner surface anchored to connective tissue by a thin, non-cellular structure called the basement membrane.

Epithelial Tissue:
Epithelial tissue is made up of tightly packed cells that form continuous sheets or layers. It covers the external surfaces of the body and lines the internal organs and cavities. Epithelial tissue has several important functions, including protection, secretion, absorption, and transportation of substances.

Exposed Outer Surface:
The exposed outer surface of epithelial tissue refers to the surface that is in direct contact with the external environment. For example, the outer surface of the skin is exposed to the external environment. This exposed surface provides protection against mechanical injury, pathogens, and UV radiation.

Anchored Inner Surface:
The anchored inner surface of epithelial tissue refers to the surface that is in contact with underlying connective tissue. This surface is anchored to connective tissue by a thin, non-cellular structure called the basement membrane. The basement membrane is a specialized extracellular matrix that provides support and anchoring for the epithelial cells.

Basement Membrane:
The basement membrane is a thin, non-cellular structure that separates the epithelial tissue from underlying connective tissue. It is composed of two layers: the basal lamina and the reticular lamina. The basal lamina is secreted by the epithelial cells, while the reticular lamina is secreted by the underlying connective tissue. Together, these two layers form the basement membrane.

The basement membrane provides structural support to the epithelial tissue, helps to regulate the exchange of substances between the epithelial cells and the underlying connective tissue, and serves as a boundary between the epithelial tissue and the connective tissue.

In conclusion, epithelial tissue always has an exposed outer surface and an inner surface anchored to connective tissue by a thin, non-cellular structure called the basement membrane. The basement membrane provides support and anchoring for the epithelial cells and helps to regulate the exchange of substances between the epithelial tissue and the underlying connective tissue.

Epithelial Tissue: They are formed by cells which cover the external parts of the body organs and line the organ surfaces such as the surface of the skin, the reproductive tract, the airways, and the inner lining of the digestive tract. Functions of Epithelial Tissue