The duodenum is the first section of the small intestine, located just after the stomach. It plays a crucial role in digestion by receiving partially digested food, known as chyme, from the stomach. The duodenum is about 10 to 12 inches long and is where most chemical digestion occurs, aided by enzymes from the pancreas and bile from the liver. In the duodenum, the chyme is mixed with digestive juices, which help break down nutrients like carbohydrates, proteins, and fats. This process prepares the nutrients for absorption in the following sections of the small intestine, specifically the jejunum and ileum.