Title: 18.5: Lower Gastrointestinal Tract - Biology LibreTexts
Headings: 18.5: Lower Gastrointestinal Tract
18.5: Lower Gastrointestinal Tract
What Is It?
Organs of the Lower Gastrointestinal Tract
Small Intestine
Duodenum
Digestion of Carbohydrates in the Duodenum
Digestion of Proteins in the Duodenum
Digestion of Lipids in the Duodenum
Jejunum
Ileum
Large Intestine
Parts of the Large Intestine
Functions of the Large Intestine
Feature: My Human Body
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Content: This increases the access to the molecules by pancreatic lipase. Jejunum
The jejunum is the middle part of the small intestine, connecting the duodenum and the ileum. The jejunum is about 2.5 m (8.2 ft) long. Its main function is the absorption of the products of digestion, including sugars, amino acids, and fatty acids. Absorption occurs by simple diffusion (water and fatty acids), facilitated diffusion (the simple sugar fructose), or active transport (amino acids, small peptides, water-soluble vitamins, and most glucose). All nutrients are absorbed into the blood except for fatty acids and fat-soluble vitamins, which are absorbed into the lymph. Although most nutrients are absorbed in the jejunum, there are a few exceptions: Iron is absorbed in the duodenum. Vitamin B12 and bile salts are absorbed in the ileum. Water and lipids are absorbed throughout the small intestine, including the duodenum and ileum in addition to the jejunum.