Answer:
an organ is a collection of tissues joined in a structural unit to serve a common function.[1] In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue, and smooth muscle tissue.[2] Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.
