The dentate line is located in the area of the anal canal and is the demarcation line where different tissue types from different embryonic sources meet. The shape resembles the dentate line, in the shape of teeth arranged in a row, hence the name dentate line. The tissue above the dentate line is the mucosal epithelial tissue of the rectum, and the tissue below the dentate line is a single layer of squamous epithelial tissue, i.e., below the dentate line is skin tissue, but it is a single layer of epithelium, while the rest of the skin is a double layer of squamous epithelial tissue. Tissue above the dentate line, blood supply from the inferior mesenteric artery, dentate line below the tissue from the body circulation, belong to the two circulatory system, at the same time, there are differences in the distribution of nerves, so the dentate line in the anal canal area, the digestive tract, and even for the anorectal department, have an extremely important position. Hemorrhoids above the dentate line are called internal hemorrhoids, hemorrhoids below the dentate line are called external hemorrhoids, and the difference in the tissues above and below the dentate line is also the difference in the tissues that internal and external hemorrhoids are composed of. Therefore, the dentate line implies that there is a change in the shape of the anal canal, which belongs to the anatomical boundary.