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Small intestine facts for kids

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Small intestine
Blausen 0817 SmallIntestine Anatomy.png
Diagram showing the small intestine and surrounding structures
Latin Intestinum tenue
System Digestive system
Artery Superior mesenteric artery
Vein Hepatic portal vein
Nerve Celiac ganglia, vagus
Lymph Intestinal lymph trunk

The small intestine is between the stomach and the large intestine. In humans over 5 years old, a small intestine may be five to six meters long. It is where most of the digestion and absorption happens.

The small intestine has three regions – the duodenum, jejunum, and ileum.

  • The duodenum receives bile and juice from the pancreas. It is where most digestion takes place. Secretions neutralise the stomach acidity, and enzymes digest the food.
  • The jejenum: the products of digestion (sugars, amino acids, and fatty acids) are absorbed into the bloodstream here.
  • The ileum: absorbs vitamin B12 and bile salts and any products of digestion which were not absorbed by the jejunum.

Structure

The small intestine is divided into three structural parts.

  • The duodenum is a short structure ranging from 20 cm (7.9 inches) to 25 cm (9.8 inches) in length, and shaped like a "C". It surrounds the head of the pancreas. It receives gastric chyme from the stomach, together with digestive juices from the pancreas (digestive enzymes) and the liver (bile). The digestive enzymes break down proteins and bile emulsifies fats into micelles. The duodenum contains Brunner's glands, which produce a mucus-rich alkaline secretion containing bicarbonate. These secretions, in combination with bicarbonate from the pancreas, neutralize the stomach acids contained in gastric chyme.
  • The jejunum is the midsection of the small intestine, connecting the duodenum to the ileum. It is about 2.5 m long, and contains the plicae circulares, and villi that increase its surface area. Products of digestion (sugars, amino acids, and fatty acids) are absorbed into the bloodstream here. The suspensory muscle of duodenum marks the division between the duodenum and the jejunum.

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