Cells of the body have to have energy to do their work. To get that energy, food has to be broken down into nutrient particles small enough to pass through the membrane of the cell wall. The purpose of the digestive system is to break down food eaten into a form small enough that can be used by cells.
The digestive system proper starts with the mouth and ends at the anus. As food enters the mouth, it is first broken down through chewing and the digestive process starts with chewed food mixing with saliva. Once swallowed, the food in pushed down the esophagus through muscle action to a ring-like muscle at the top of the stomach called the esophageal sphincter. When it sense food, the muscle relaxes allowing food to enter the stomach.
Once in the stomach, food is mixed with digestive juices produced in the stomach to continue the digestive process and here the food is stored until there is room for it in the small intestine. Once in the small intestine, digestive juices there and from two organs not directly in the digestive system proper – the liver, pancreas – further break down the food until is finally ready to move into the large intestine.Once here, the food mixture is pushed through the large intestine with nutrients from the digested food being absorbed through the intestinal wall. From here nutrients enter the bloodstream where they are carried to cells in all parts of the body. The nutrients are absorbed through the cell membrane and converted to usable energy through the mitochondrial process inside each cell.
Whatever food cannot be used by the body, such as fiber and undigested parts of food, is moved further down the large intestine to the rectum where it is stored until the next bowel movement where it moves out through the anus.Not all food moves through the stomach at the same rate. Carbohydrates are broken down quickly and move through fast, thus they provide the quickest form of energy.
Of the carbohydrates, simple ones, such as sugar, breaks down the fastest. Complex ones, like fresh fruits, vegetables and whole grains break down slower, and provide a more even flow of nutrients over a longer period of time, thus keeping you fuller longer. Fats and protein take the longest to break down thus they move through the slowest. Because of this, they keep you feeling fuller the longest of all foods.The digestive system is just one of the amazing processes of the human body. Digestive juices and intestinal muscle action gets the food from our mouths, to a state where it can be used by cells for energy, and discards the waste.