Human intestines are divided into large and small intestines, which are connected to the small intestine at the upper end and to the anus at the lower end, while the small intestine is connected to the pylorus at the upper end to connect with the stomach and to the large intestine at the lower end. 1. Large intestine: divided into cecum, colon and rectum, the large intestine is the most important part of the digestive system, absorbing digestive matter and water conducted from the small intestine, and excreting stool residue out of the body. 2. Small intestine: divided into duodenum, jejunum and ileum, the small intestine is the longest part of the digestive tube, the adult small intestine is generally about 5 meters long, is the body’s main place of absorption of nutrients, food in the small intestine stays longer. The large intestine and small intestine are important organs of the human body, and any discomfort in either part may lead to abnormalities in digestion and absorption, so early medical attention should be sought.