Small intestine Facts for Kids

Quick facts for kids Small intestine

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.

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.

The ileum: The final section of the small intestine. It is about 3 m long, and contains villi similar to the jejunum. It absorbs mainly vitamin B12 and bile acids, as well as any other remaining nutrients. The ileum joins to the cecum of the large intestine at the ileocecal junction.

Images for kids

Micrograph of the small intestine mucosa showing the intestinal villi and crypts of Lieberkühn.
This cross section diagram shows the 4 layers of the small intestine wall.
Second stage of development of the intestinal canal and peritoneum, seen from in front (diagrammatic). The liver has been removed and the two layers of the ventral mesogastrium (lesser omentum) have been cut. The vessels are represented in black and the peritoneum in the reddish tint.
Fig 400]]
Small intestine in situ, greater omentum folded upwards.
Tissue layers (mucosa, submucosa & muscularis)