The epithelium found in the lining layer of stomach and intestine is columnar epithelium.

Explanation:
The epithelium is a type of tissue that covers the surfaces of organs, lines the cavities of the body, and forms glands. It consists of closely packed cells that are arranged in one or more layers. The lining of the stomach and intestine is composed of columnar epithelium.

Columnar epithelium:
Columnar epithelium is a type of epithelial tissue in which the cells are tall and narrow, resembling columns. These cells have elongated nuclei located near the base of the cells. Columnar epithelium is found in various parts of the body, including the lining of the stomach and intestine.

Functions of columnar epithelium in the stomach and intestine:
1. Absorption: The columnar epithelium lining the small intestine contains microvilli, which are tiny finger-like projections that increase the surface area for absorption of nutrients. These cells also have numerous mitochondria to support the energy requirement for absorption.

2. Secretion: The columnar epithelium in the stomach and intestine secretes various substances necessary for digestion and absorption. For example, the gastric glands in the stomach secrete gastric juice, while the intestinal glands in the small intestine secrete digestive enzymes and mucus.

3. Protection: The columnar epithelium provides a protective barrier against harmful substances present in the stomach and intestine. It prevents the entry of harmful bacteria and toxins into the bloodstream.

4. Movement: In the intestines, the columnar epithelium contains specialized cells called goblet cells, which secrete mucus. This mucus helps in the movement of food along the digestive tract and facilitates smooth passage through the intestines.

In conclusion, the lining layer of the stomach and intestine is composed of columnar epithelium, which performs various functions such as absorption, secretion, protection, and movement.