Let's begin with the epithelial tissue. Now, the epithelial tissue consists of individual cells that basically serve to cover the outside portion of the body as well as the internal cavities such as the stomach, the small and large intestine as well as the kidneys. Now, these cells, the epithelial cells of the epithelial tissue are not only involved in protecting our body from outside harmful sources such as bacteria, viruses or UV radiation these cells are also responsible for absorption as well as secretion. For example, the epithelial cells found on our skin are responsible for protecting us from UV radiation. The epithelial cells found in our stomach, on the lining of our stomach are basically responsible for secreting hydrochloric acid which gives our stomach its high acidity. And finally, the epithelial cells found in our intestines are responsible for absorbing the nutrients that we ingest into our body.