Digestion From Start To Finish

Ever wonder what happens to food after it has been chewed and swallowed? How does our body use all that good stuff we put into our mouths for nourishment? Our food and drink must be changed into smaller units – molecules of nutrients – before it can be absorbed into the blood and carried to cells throughout the body for energy.

The first major muscle movement occurs when we swallow food or liquid – a voluntary process. Once swallowing has occurred, the process becomes involuntary and falls under the control of our nerves. The large, hollow organs that comprise our digestive system contain muscles that enable their walls to move. The movement of these walls – which consists of a narrowing and then a push that resembles a wave in the ocean - propels the food through the system and mixes it in the process.

The first organ our food enters is the long tube-like structure known as the esophagus, which connects the throat to the stomach below. There is a small ring-like valve that closes the passage between the two, but as food approaches this ring, the surrounding muscles relax allowing the food to pass.

The stomach is the organ most commonly associated with food and digestion because most people associate feelings of fullness with a full stomach. And the stomach has three important tasks to complete when the food arrives. The stomach first receives large volumes of swallowed food and liquid and mixes it up in the lower stomach with digestive juice. Then the stomach empties its contents slowly into the small intestine. The speed of the emptying can vary based on the makeup of the food (mainly its fat and protein content), as well as the degree of muscle action in both the stomach and the small intestine.

As the food passes through the small intestine, it is dissolved in juices from the pancreas, liver and intestine, mixed and pushed forward for further digestion. Finally, all of the digested nutrients are absorbed through the intestinal walls. The waste products of this process, including the undigested parts of the food, are then propelled into the colon, where they remain until the feces are expelled by a bowel movement. For more information on how our bodies use various components of food, click here.