The digestion process The digestion process begins in the mouth. First we take a bite of food. The presccence of food in the mouth stimulates the flow of saliva from the salivary glands. Saliva moistens the food and carries dissolved food molecules to the taste buds. Saliva helps digest food because it contains enzymes that start to break it down. After the food is covered with saliva, you then begin to chew your food. Chewing breaks down food into smaller pieces and also breaks apart fiber that traps nutrients.
After the food is chewed it is formed into a ball of chewed food mixed with saliva called a bolus which is ready to be swallowed. From the mouth , the bolus moves into the pharynx. This is where swallowing occurs. During swallowing, the air passages are blocked so food goes to the stomach and not the lungs. Swallowed food then travels down the esophagus toward the stomach. In the esophagus the bolus is moved along by contractions of the smooth muscle called peristalsis. These contractions move the bolus along from the esophagus through the large intestine.
After the food travels through the esophagus, it goes to the stomach. The stomach is an expanded portion of the gastrointestinal tract that serves as a temporary storage place for food. Some digestion occurs here but very little absorption. While the bolus is in the stomach, it is mixed with highly acidic stomach secretions to form chime. After food turns into chime, it enters the small intestine. The small intestine is a narrow tube about 20 feet in length that is divided into three segments. Food enters the small intestine triggering hormonal and nervous signals that slows down the release of food into the intestine.
The small intestine is the primary site of absorption. Materials that have not been absorbed in the small intestine, then enter the large intestine. The large intestine is about 5 feet long and include the colon and rectum. Materials that are not absorbed in the colon are excreted as waste in the feces. The end of the colon is connected to the rectum where feces are stored prior to defecation. The rectum is connected to the anus which is the external opening of the digestive tract. The rectum and the anus work with the colon to prepare feces for elimination.