The anal part, from horizontal to vertical position, is inevitably subjected to frequent impacts of gravity and strong vertical pressure (intra-abdominal pressure), and the intestinal outlet must have a corresponding anti-pressure device in order to stop the overflow of contents and maintain anal self-control. It is under these conditions that the submucosa of the human anal canal gradually developed from adaptive thickening to the cushion-like structure of hemorrhoids, which assist the sphincter muscle to form a strong gate for stool control. Thus, hemorrhoids are a product of human evolution and are a normal anatomical structure of the body. The human anal canal is essentially a tube formed by the overlapping of two muscle tubes, the outer pelvic floor transverse muscle and the inner visceral smooth muscle. However, it is difficult to effectively maintain anal self-control by relying solely on the sphincter’s own contraction, because the circular sphincter is limited in length and does not have a strong binding force on the anal canal when contracted. In order to achieve airtight and satisfactory control of gas and liquid spillage, the anal canal must also have another important condition, namely a thick and soft anal pad. The epithelium of the anal cushion is extremely rich in sensory nerve endings, and the lining of the anal canal has receptors, such as pain, touch, cold, pressure or tension, friction, and many unnamed receptors. The density of nerve endings in different areas of the anal canal is inconsistent, and the 2.5-1.5 mm plane above the dentate line has different demarcation lines for touch, pain, heat, and cold sensations. These receptors have fine discriminatory sensations that contribute to anal self-control. The rectal mucosa is rich in nerve plexuses as well as ganglion cells. Their nerve distribution form is different from that of the skin, and these nerves are important sensory devices in the anal reflex and have fine discrimination of the nature of the rectal contents. The ATZ epithelium (rectal anal canal migrating epithelium) in the anal cushion area is a highly specialized zone of sensory nerve terminal tissue that is very sensitive and is the trigger zone for evoking defecation . When the stool reaches the anal canal from the rectum, the ATZ is stimulated and reaches the brain through the sensory nerves to produce the urge to defecate. It can be seen that the self-control function of the anal pad is its most important function.