Food digestion and nutrient absorption take place primarily in the small intestine, according to eMedicineHealth. Nutrient absorption is facilitated by villi and microvilli, fingerlike projections from the intestinal wall that serve to increase the surface area of the intestine so that nutrients can be fully absorbed.
The small intestine consists of three parts, explains the International Foundation for Functional Gastrointestinal Disorders. Those parts are the duodenum, jejunum and the ileum. Each part of the small intestine digests and absorbs specific nutrients.
Food, liquid and digestive juices, collectively known as chyme, first enter the duodenum from the stomach, states the IFFGD. A potent mixture of enzymes, bile salts and bicarbonate from the liver, pancreas and the intestinal walls themselves breaks down carbohydrates, fats and fat soluble vitamins. The bicarbonate also neutralizes the stomach acid present in the chyme.
The chyme continues to move into the second part of the small intestine, the jejunum. Approximately 90 percent of nutrient absorption occurs here, says the IFFGD. Proteins, carbohydrates, minerals and vitamins are further broken down in this section.
Finally, the chyme enters the final section of the small intestine, the ileum. This section absorbs vitamin B-12, bile salts and water before sending the remaining chyme into the large intestine for the absorption of fluid and electrolytes, according to the IFFGD.