Your body turns the food you eat into nourishment through the process of digestion. The digestive system includes a digestive tract and other organs that help your body break down and absorb food into the blood. Your body uses the nutrients to build and nourish cells and to provide your body with energy.
Movement Through System
Your digestive tract includes large, hollow organs with a layer of muscle that allows their walls to move. The digestive tract of an adult is approximately 30 feet long. When organ walls move, food and liquid is mixed within each organ and propelled through the system. When you swallow food, your nerves push it into the esophagus. To prevent you from choking, a flap of tissue closes automatically over your windpipe. A sphincter opens in the esophagus, allowing the food to pass into the stomach. The stomach mixes the food, liquid and digestive juice and then empties it into the small intestine. The food dissolves into the juices from the pancreas, liver and intestine. The intestinal walls absorb the nutrients, which are transported throughout the body. Undigested parts of the food and older cells are pushed into the colon until they are expelled.
Digestive Juice Production
Your body has digestive glands that help break down food. The salivary glands in your mouth contain the first enzymes with which your food comes into contact. The glands contain an enzyme that digests food starch into smaller pieces. The stomach lining produces a stomach acid and an enzyme that digests the protein in your food. The pancreas releases additional juices containing enzymes that break down carbohydrates, fats and proteins. Enzymes from glands in the intestinal walls also aid in the digestive process. The liver produces another digestive juice, called "bile," that dissolves fat. Once the fat is dissolved, enzymes from the pancreas and intestinal lining digest the fat.
Nutrient Absorption and Transportation
The small intestine absorbs more of the digested food molecules, along with water and minerals. The small intestine have mucosa that are covered with small finger-like projections called "villi," which are covered in even smaller projections called "microvilli." Your body absorbs the nutrients through a vast surface area created by these structures. Absorbed materials cross the mucosa into the blood with the assistance of specialized cells. They are then carried off in the bloodstream.
Control of Digestive Process
Hormones and nerves regulate the digestive process. Hormones from the stomach and small intestine mucosa are released into the blood of the digestive tract. They travel to the heart, through the arteries, and back to the digestive system to stimulate digestive juices and organ movement. Outside nerves travel from the brain or spinal cord to the digestive organs. They release a chemical that causes the muscle layer of the digestive organs to push juice and food through the digestive tract and the stomach and pancreas to produce more digestive juice. They release another chemical that relaxes the stomach and intestine muscle and decreases blood flow to the organs to slow or stop digestion. Inside nerves are nerves embedded in the walls of the esophagus, stomach, small intestine and colon. When food stretches the walls of the organs, the inside nerves are triggered to act. They release substances that speed or delay food movement and juice production.
