The small intestine is part of the digestive system. It is a hollow, tube-like organ that connects to the stomach on one end and the large intestine on the other. The small intestine is the longest part of the gastrointestinalgastrointestinalReferring to or having to do with the digestive organs, particularly the stomach, small intestine and large intestine. (GI) tract, making up about three-quarters of the digestive system. It is also known as the small bowel.
The gastrointestinal tract is a tube that extends from the mouth to the anus. It includes the:
Several other organs of the digestive system help to digest food, including the liver, gallbladder and pancreas.
The small intestine is about 4.75–6 metres (15–20 feet) long and an average of 2.5 centimetres (1 inch) in diameter. It is looped and coiled and fills up much of the abdominal cavity (the space in the abdomen that contains the intestines and other organs). The small intestine has 3 parts:
The jejunum and ileum are supported by a sheet of mesentery. Mesentery is a membrane that suspends the small intestine from the back of the abdominal wall and supports blood vessels, nerves and lymph vessels that supply the small intestine. The small intestine is surrounded by the large intestine.
The inner surface of the small intestine is velvety in appearance. This is due to many finger-like projections of the mucous membrane called villi. The villi increase the surface area of the small intestine, which helps it absorb digested food.
The inside layers of the small intestine are made up of the same 4 layers that make up most of the gastrointestinal tract:
The main function of the small intestine is to break down (digest) food and absorb nutrients, such as electrolyteselectrolytesA substance in the blood and other body fluids that carries an electric charge. Electrolytes are responsible for the movement of nutrients and wastes into and out of cells to keep body fluids balanced and to allow muscles to function properly., vitamins and minerals. The small intestine is the most important absorbing organ in the gastrointestinal tract. About 90% of nutrient absorption takes place in the small intestine.
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