The large intestine is the last section of the digestive tract and includes the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. It passes through the anal canal and opens in the anus. After the food is digested and absorbed through the small intestine, the undigested and absorbed food residue, along with the unabsorbed digestive juices in the small intestine in the form of chyme, 800~1500mL per day, is discharged into the large intestine. The rectum and anal canal have no digestive effect, but can control the excretion of feces. The chyme entering the cecum and ascending colon is rubbed by the non-pushing stirring motion, in which water and electrolytes are absorbed, so that the contents of the colon gradually become sticky and dry, and are slowly pushed to the rectum by the propulsive motion of the colon. If you do not have good bowel habits, such as busy work, travel to catch up, children play, etc., you can not finish the day’s feces, feces stay in the rectum for a long time, the rectum will absorb its water hard, so the next day there will be the phenomenon of hard fecal head, hard fecal head is not constipation, but often due to hard fecal head will be anal canal skin cracking, bleeding, pain, the formation of anal fissure, long-term hard fecal head stimulation of the anus, will appear anorectal disease Therefore, attention should be drawn to it!