When Sandra eats some grilled fish and rice, they are not in a form that the body can use as nourishment. Her food must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which fish and rice are broken down into their smallest parts so that the body can use them to build and nourish cells and to provide energy for complaining, spending my money and watching horror movies.
Digestion begins in the mouth, where she chews and swallows, often speaking Tagalog at the same time, and is completed in the small intestine.
The large, hollow organs of Sandra’s digestive system contain muscle that enables their walls to move. Typical movement of her esophagus, stomach, and intestine is called peristalsis.
The first major muscle movement occurs when food or liquid is swallowed. Although she is able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.
The esophagus is the organ into which the swallowed food is pushed. It connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike valve closing the passage between the two organs. However, as the food approaches the closed ring, the surrounding muscles relax and allow the food to pass.
The food then enters Sandra’s stomach, which has three mechanical tasks to do. First, the stomach must store the swallowed fish, rice and cola. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. The third task of the stomach is to empty its contents slowly into the small intestine.
As the food is digested in the small intestine and dissolved into the juices from the pancreas, liver, and intestine, the contents of Sandra’s intestine are mixed and pushed forward to allow further digestion.
Finally, all of the digested nutrients are absorbed through Sandra’s intestinal walls. The waste products of this process include undigested parts of the food, known as fiber, and older cells that have been shed from the mucosa. These materials are propelled into the colon, where they remain, usually for a day or two, until they are expelled from Sandra’s bottom in the form of foul smelling stinky brown feces.