The digestive system consists of the mouth, esophagus, stomach, pancreas, gallbladder, liver, small intestine, large intestine, colon and rectum. The main function of the digestive system is to break down food into smaller molecules that the body can absorb. The digestive system is responsible for many duties in order to achieve the essential function of digestion.
Movement of Food
The food you eat goes in through the mouth and must be moved through the digestive tract to be broken down. The digestive tract is a series of hollow organs connected by tubes from the mouth to the anus, including the mouth, esophagus, stomach, small intestine, large intestine, colon and rectum. Each of these organs' walls contain layers of muscle that enable them to propel food and liquid through the system.
Production of Digestive Juices
The digestive system contains glands that produce enzymes to aid in the digestion. The salivary glands in the mouth produce saliva that begins to break the food into smaller pieces. The stomach produces stomach acid that breaks down the proteins. Once food reaches the small intestine, other digestive juices produced by the pancreas and liver allow for the breakdown of carbohydrates, fats and proteins.
Absorption of Nutrients
Not only must the digestive system break down the food, it is also responsible for absorbing the nutrients. This absorption takes place in the small intestine, which contains small fingerlike projections called villi. The presence of these villi increases the surface area, allowing more nutrients to be absorbed.
Production of Hormones
The stomach and small intestine produce hormones that control the functions of the digestive system. Gastrin initiates the production of stomach acid and is necessary for the growth of cells in the lining of the stomach, small intestine and colon. Secretin tells the pancreas to send digestive juices containing bicarbonate to the stomach, which helps to neutralize stomach acid before it enters the small intestine. Additional hormones include cholecystokinin, ghrelin and peptide YY.
Regulation of Functions
Nerves, both inside and outside the digestive system, help to regulate the functions of the system. Extrinsic nerves (those not part of the digestive system) send signals from the brain to the system to release acetylcholine, increasing digestion, and adrenaline, which slows down digestion. Intrinsic nerves found in the walls throughout the digestive tract are triggered to help regulate when food is moving through the organs.