Digestive System Overview

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All organs, tissue, and cells of the human body need nutrients to live and grow. Providing nutrients to the body is the function of the digestive system. The digestive system is a series of tubes and organs connecting from the mouth at one end, to the anus at the other end. The main parts of the digestive system are the mouth, esophagus, stomach, small intestine, large intestine or colon, rectum, and anus. The digestive system is responsible for breaking down food, absorbing the nutrients, and removing the waste. Read on to learn more about the digestive system, and its role in your body.

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Digestive System Overview

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Digestive System
The Human Digestive System

The function of the digestive system can be broken down into six major actions:

  • Move food and liquids along the digestive tract
  • Lubricate the food to ease movement along the digestive tract
  • Mechanically breakdown carbohydrates, fats, and proteins
  • Chemically breakdown carbohydrates, fats, and proteins
  • Reabsorb nutrients and water
  • Eliminate waste products

Digestion begins in the mouth where chewing and saliva compact the food into a small bolus, and begin the breakdown of nutrients. The food is swallowed in the throat, and then muscular waves called peristalsis move the food through the esophagus, and into the stomach.

In the stomach, muscle contractions mix the food with digestive enzymes and gastric acid to further breakdown the food into chyme. After about two to four hours, the chyme then moves into the small intestine. The rate of stomach emptying into the small intestine is controlled by hormones.

Most food digestion occurs in the duodenum, the first section of the small intestine. In the duodenum, digestive enzymes from the pancreas and bile from the gallbladder are mixed with the food. The pancreatic enzymes breakdown fats, proteins, and carbohydrates. The bile helps with the digestion and absorption of fats.

Peristaltic waves continue to push the chyme along the small intestine. The middle section of the small intestine, the jejunum, absorbs most of the nutrients from the chyme. Nutrients pass into the capillaries and lymphatic vessels in the wall of the intestine. Nutrients such as glucose and amino acids are absorbed into capillaries, while fats are absorbed into the lymph vessels. Nutrients from the digestive system help build and repair tissues, provide heat and energy, and regulate body processes.

The remaining waste then moves on into the large intestine. In the large intestine, water and salts are removed from the waste before being passed along to the rectum and anus, where the waste is expelled from the body.

Two types of nerves help control the action of the digestive system. Extrinsic nerves controlled by the brain cause muscle contractions that push food along the digestive tract. They also cause the stomach and pancreas to produce more digestive juice. Intrinsic nerves within the walls of the esophagus, stomach, small intestine, and large intestine react when their walls are stretched by food. They cause the release of substances that speed up or slow down the movement of food, and the production of juices, by the digestive organs.


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