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, and mixing it with digestive juices from the pancreas and bile from the liver. This process helps break down food further, allowing nutrients to be absorbed in later sections of the intestine. The duodenum is about 10 to 12 inches long and has a C-shaped structure. It is divided into four parts: the superior, descending, horizontal, and ascending portions. Proper functioning of the duodenum is essential for effective digestion and nutrient absorption.