The stomach has three tasks to perform once the food or liquid has passed into it. The first task is to store all swallowed food and liquid, which requires upper stomach muscles to relax enough to accept large amounts of ingest material. The stomach’s second task is to secrete digestive juices to mix with the swallowed food and liquid by using muscle movement. The stomach’s third and final task is to empty this process mixture into the small intestine.
The type of food and liquid ingested can affect the emptying of the stomach’s contents into the small intestine. These factors are fat, protein and muscle action.
Small Intestine
Once the stomach’s contents have reached the small intestine, the food is digested and dissolved by juices from the intestine, liver and pancreas. Muscles of the small intestine contract to move the digestive process along.
Once that all nutrients have been removed from the food and absorbed by the intestinal walls, there is nothing left but waste product. This includes old cells that have left the mucosa and undigested food particles known as fiber. Muscles move the waste product into the colon where it remains for one to two days before being ejected from the body in the form of a bowel movement.
Producing Digestive Juices
The first digestive juices are produced in the mouth by the salivary glands. The saliva that is produced contains enzymes that digest starch from ingested food into minuscule molecules.
The next set of digestive glands is found in the stomach lining, which produces stomach acid and an enzyme that digests ingested protein. This is a mysterious process, as researchers have not yet determined why stomach acid doesn’t eat through the stomach lining.
Once the stomach empties its contents into the small intestine, the digestive juices of two organs combine to help the digestive process along.
The pancreas is one of these organs. It secretes juices that break down the carbohydrates, fat and protein from ingested food. Other enzymes come from the gland in the wall of the small intestine to aid in the process of digestion.
The other organ that aids digestion is the liver. It produces a digestive juice known as bile, which is stored in the gallbladder. When we eat, the gallbladder sends bile to the intestine where it mixes with ingested fat. The bile works to dissolve the fat into a watery liquid. Bile works much the same as dishwashing detergent when it dissolves grease from our dishes.
After the fat has been broken down by the bile, it is digested by enzymes from the small intestine’s lining and the pancreas.