Human Digestive System
Single-celled organisms can directly take in nutrients from their outside environment. Multi-cellular animals, with most of their cells removed from contact directly with the outside environment, have developed specialized structures for obtaining and breaking down their food.
The human digestive system is a complex series of organs and glands that processes food. It is a coiled, muscular tube (6-9 meters long when fully extended) extending from the mouth to the anus. Inside this tube is a lining called the mucosa.…
