Digestive System Definition: What It Is and What It Does

The digestive system plays a very important role in the body, so understanding its definition and function is helpful.

The digestive system or digestive tract is a long, twisting tube that begins with the mouth and ends with the anus. Along the digestive tract are the esophagus, pharynx, stomach, large and small intestines, pancreas, liver, gallbladder, and rectum. The function of the digestive system, in the simplest terms, is to convert the food we eat into nutrients and energy.

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The entire digestive tract, from mouth to anus, can measure 30 feet in length, says LiveScience. Without a healthy digestive system, the body will never be nourished or be able to rid itself of waste.

Inner Body defines the six basic functions that occur within the digestive system as:

• Ingestion (eating)
• Secretion
• Mixing and moving
• Digestion
• Absorption
• Excretion

Digestion begins in the mouth where the teeth, tongue, and salivary glands begin the process of breaking down food. Chewing grinds food into smaller pieces that are mixed with saliva and moved down through the pharynx and into the esophagus.

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Once food is in the esophagus, a series of involuntary muscular contractions called peristalsis moves it further along until it finally reaches the stomach, a muscular sac that mixes and further pulverizes food. The stomach contains strong acids and enzymes that break food down into simple components that eventually pass into the intestines.

The small intestine is where most nutrient absorption occurs. This long tube is coiled and lined with many ridges and folds to increase its surface area for taking in nutrients. In the small intestine, food is also mixed with secretions from the liver and pancreas. By the time food passes out of the small intestine and into the large intestine, more than 90 percent of the nutrients have been extracted, says Inner Body.

Finally, whatever is left that cannot be digested passes into the large intestine. The large intestine is where this waste is further fermented and stored. According to Inner Body, the large intestine can also absorb small remaining amounts of nutrients and extract excess water from the waste which will finally leave the body through the anus.

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