Title: Small Intestine: Anatomy, Function, and Treatment
Headings: The Anatomy of the Small Intestine
The Anatomy of the Small Intestine
The largest digestive organ breaks down food and absorbs nutrients
Anatomy
The Mesentery
The Lymph System and the Small Intestine
Location
Anatomical Variations
Function
Absorption of Nutrients
The Lining of the Small Intestine
The Enteric Nervous System
Associated Conditions
Treatment
Tests

Content: Break down food with digestive enzymes, making it more digestible
Absorb nutrients (including fats, carbohydrates, proteins, vitamins, and minerals) into the bloodstream
Help to maintain the balance of fluids (absorbs much of the body’s ingested water) and electrolytes (such as sodium)
Move the food along into the colon
Help fight disease-causing bacteria ingested with food by mobilizing the body's immune system cells
Each segment of the small intestine has a different function, including: The duodenum receives partially digested food (called chyme) through the pylorus (from the stomach), receives digestive enzymes from the pancreas and liver to continue to break down ingested food. In addition, iron is absorbed in the duodenum. Bicarbonate (a crucial biochemical that plays a role in the body’s buffering system) is released from the pancreas to begin to neutralize the stomach acid before the chyme reaches the jejunum. The duodenum also helps to control how well the stomach empties and the rate of bile duct juices that empty into the small intestine. In addition, there is some limited absorption of nutrients that takes place in the duodenum, such as the absorption of iron. The jejunum receives the undigested food from the duodenum and absorbs nutrients such as sugar, amino acids, and fatty acids, via finger-like projections called villi. Over 95% of the body’s carbohydrate and protein absorption takes place in the jejunum. 1 ﻿
The ileum receives the food from the jejunum and empties into the large intestine. It continues the process of absorption via the intestinal wall villi, absorbing any products of digestion that were not absorbed by the jejunum.