The duodenum is the first and shortest segment of the small intestine. It is also here that the pancreas connects to the intestine, releasing pancreatic enzymes for digestion and bicarbonate to neutralize acid from the stomach. Two important minerals are primarily absorbed in the duodenum, iron and calcium. The mid section of the small intestine is the longest, called the jejunum. Here bile made in the liver and stored in the gallbladder is released, an important step for later fat absorption.
Digestive enzymes continue to breakdown larger food molecules in preparation for absorption.
Carbohydrate, now converted to sugars, and most of the water soluble vitamins are primarily absorbed in the jejunum. The last small intestine segment is called the ileum. The ileum is the primary site for fat, fat soluble vitamins, protein, and cholesterol absorption, as well as vitamin B12. Concluding this phase of digestion, the remaining food residue, fluids and digestive products are passed into the large intestine or colon. The large intestine, or colorectal section, is larger in diameter than the small intestine and is responsible for absorbing most of the water, sodium and potassium.