40 14.1 Introduction to the Digestive System

Introduction^[1]

The digestive system works continuously, whether you are eating a meal or you are between meals. Consider what happens when you eat an apple. You probably enjoy tasting the apple as you chew it, but in the hours that follow, unless something goes amiss and you get a stomachache, you don’t notice that your digestive system is working digesting the apple and absorbing its vitamins and other nutrients. By the time any waste material is excreted, the body has removed all nutrients that can be used from the apple to fuel your body.

Gastroenterology is the study of the normal function and diseases of the gastrointestinal (GI) system, also called the digestive system, including the esophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, bile ducts, and liver. The gastrointestinal tract, also called the alimentary canal (aliment = “to nourish”) or gut, is a one-way tube that is about 25 feet long. Interestingly, the length increases to about 35 feet if measured after death due to smooth muscle tone being lost.

This long, hollow tube begins at the mouth and ends at the anus. Between those two points, the canal has several unique areas, including the pharynx, esophagus, stomach, and small and large intestines to fit the functional needs of the body. Both the mouth and anus are open to the external environment, so food and wastes within the GI tract are technically considered to be outside the body. After food undergoes the processes of digestion and absorption, the nutrients from food enter the body and provide nutrients to the cells.

See Figure 14.1 for an illustration of the components of the digestive system.

Figure 14.1. Components of the Digestive System (https://openstax.org/books/anatomy-and-physiology/pages/23-1-overview-of-the-digestive-system )

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