The digestive system is a series of tubelike organs from the mouth to the anus. The digestive tract includes your mouth, throat, esophagus, stomach, small intestine, large intestine or colon, rectum and anus.
The nervous system plays an important part in digestion as well. Two types of nerves help control digestion. Extrinsic nerves come to the digestive organs from the brain or the spinal cord and release two chemicals: acetylcholine and adrenaline. Acetylcholine causes the muscle layer of the digestive organs to squeeze with more force and push the food and juice through the digestive tract. It also causes the stomach and pancreas to produce more juice. Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs, slowing or stopping digestion.
The intrinsic nerves are embedded in the walls of the esophagus, stomach, small intestine, and colon and are triggered to act when the walls of the hollow organs are stretched by food. They release substances that speed up or delay the movement of food and the production of juices by the digestive organs. Together the nerves, hormones, blood and organs work together to digest and absorb nutrients from all the food and liquids consumed each day in order to give the body energy.
A powerful connection lies between the digestive system and the brain. Psychological factors influence contractions of the intestine, secretion of digestive enzymes, and other functions of the digestive system. Susceptibility to infection, which leads to various digestive system disorders, is strongly influenced by the brain. In turn, the digestive system influences the brain. For example, long-standing or recurring diseases such as irritable bowel syndrome, ulcerative colitis, and other painful diseases affect emotions, behaviors, and daily functioning. This two-way association has been called the brain-gut axis.