Tour the Digestive System

An Organ-by-Organ Introduction to Digestion

Organs of the Digestive System

Learn about the Organs of Digestion and their Function. Photo © A.D.A.M.

The organs of the digestive system work together to digest and absorb food. Let's look at each organ and learn what it does.

What is the digestive system? Find out with this organ-by-organ introduction through pictures.

Diseases of the liver, such as hepatitis, can have major complications that affect other parts of the body. One reason is because the liver is involved in so many essential functions, like digestion. The digestive system is a collection of organs that work together to digest and absorb food. Digestion is the process the body uses to break down foods into molecules that the body can use for energy and nutrients. Let's look at the individual parts of the digestive system.

The Mouth

Photo © A.D.A.M.

Have you ever noticed how your mouth can start "watering" at the sight of your favorite food? That's because digestion begins in the mouth. The teeth grind the food and mix it with saliva to form a kind of ball, called a bolus. During the mixing, an enzyme called "salivary amylase" starts breaking down carboyhydrates. Once the food is soft and relatively flexible, the tongue pushes it to the back of the mouth and swallows it down the esophagus.

The Esophagus

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The esophagus is a flattened, muscular tube that connects the mouth to the stomach. As food is swallowed, the esophagus expands, and it takes food between one to eight seconds to pass through, depending on the food's degree of softness. One common medical problem of the esophagus is heartburn, which is a burning sensation caused by acid leaking from the stomach and irritating the lower part of the esophagus.

The Stomach

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The stomach is a "J-shaped" muscular pouch that receives food from the esophagus and sends it to the small intestine. Inside the stomach, food is churned around and mixed with enzymes and acid until it's a liquid, called chyme. The stomach is the main site for protein digestion and uses powerful enzymes, called pepsins, and hydrochloric acid to digest foods like meats, milk and cheese.

The Small Intestines

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The small intestine is about 24 feet long. It's a muscular tube that is divided into three distinct parts: duodenum, jejunum and ileum. The three parts are major sites of digestion and absorption. Absorption is a crucial part of the digestive system that brings the molecules from the digested food into the blood and, ultimately, the cells.

The Large Intestine

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The last part of the digestive tract, the large intestine is a muscular tube about 5 feet long. It's divided into the cecum, colon and rectum. Together, they tie up all the loose ends of digestion. This includes completing any nutrient absorption and processing the wastes into feces. Another important function of the large intestines is making some types of vitamin B and vitamin K.

The Pancreas

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The pancreas is a necessary organ of digestion. It assists the small intestine by secreting pancreatic juice, a liquid with enzymes and sodium bicarbonate that is able to stop the digestion process of pepsin. It also secretes insulin -- important for the processing of sugar in the blood.

The Liver

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The liver has many functions. First, it produces bile, which the small intestine uses to help digest the fats in food. It also metabolizes proteins, carbohydrates and fats; helps regulate blood sugar levels; stores glycogen for quick energy; makes fibrinogen which clots blood; makes vitamin A; and recycles worn out red blood cells to name a few. Clearly, this is one organ we can't live without.

The Gallbladder

Photo © A.D.A.M.

Tucked under the liver, the gallbladder is a storage container for bile, a yellow-green fluid that's made up of salts, cholesterol and lecithin. The small intestine uses bile to digest fats. Most people never think about their gallbladder until a problem with gallstones or gall bladder disease, such as cholecystitis, develops. Also, the gallbladder sometimes plays a part in jaundice - namely, if bile cannot leave the gallbladder, it can enter the bloodstream and lead to jaundice.

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