Digestive System 101: Journey Through Your Guts

The small intestine, despite its name, is actually the longest part of the digestive tract at about 20 feet or 6 meters.The small intestine consists of three main sections. First is the duodenum, which receives digestive enzymes from the pancreas and bile from the liver.These secretions are essential for breaking down proteins, fats, and carbohydrates into smaller molecules that can be absorbed.Next is the jejunum, which is the primary absorption site. This middle section is rich in blood vessels and absorbs most of the nutrients from your food.The final section is the ileum, which handles specialized absorption including vitamin B12 and bile salts, and connects to the large intestine.A key feature of the small intestine is its specialized surface structures. Let's zoom in to see them.The small intestine contains millions of microscopic finger-like projections called villi.Each villus is covered with even smaller projections called microvilli, creating a brush border.Together, these structures dramatically increase the surface area for absorption by up to 30 times, making the small intestine incredibly efficient.The small intestine absorbs different types of nutrients. Proteins are broken down into amino acids, carbohydrates into glucose, and fats into fatty acids.These nutrients are absorbed through the villi directly into the bloodstream, which carries them throughout the body.The small intestine is remarkably efficient, absorbing approximately 90 percent of the nutrients from your food.After nutrients are absorbed in the small intestine, the remaining material moves into the large intestine for the next stage of digestion.