The digestive system

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 …

…or even a part of that wall. The liver produces yet another digestive juice--bile. The bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder into the bile ducts to reach the intestine and mix with the fat in our food. The bile acids dissolve the fat into the watery contents of the intestine; it is digested by enzymes from the pancreas and the lining of the intestine.