Title: Gastrointestinal tract - Wikipedia
Headings: Gastrointestinal tract
Gastrointestinal tract
Contents
Human gastrointestinal tract
Structure
Upper gastrointestinal tract
Lower gastrointestinal tract
Small intestine
Large intestine
Development
Histology
Mucosa
Submucosa
Muscular layer
Adventitia and serosa
Gene and protein expression
Time taken
Immune function
Immune barrier
Immune system homeostasis
Intestinal microbiota
Detoxification and drug metabolism
Clinical significance
Diseases
Symptoms
Treatment
Imaging
Other related diseases
Uses of animal guts
Other animals
See also
References
External links

Content: The combination of the circular folds, the villi, and the microvilli increases the absorptive area of the mucosa about 600-fold, making a total area of about 250 m 2 (2,700 sq ft) for the entire small intestine. Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream. There are three major divisions: Duodenum: A short structure (about 20–25 cm long) which receives chyme from the stomach, together with pancreatic juice containing digestive enzymes and bile from the gall bladder. 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 the chyme. Jejunum: This is the midsection of the small intestine, connecting the duodenum to the ileum.