Hemorrhoids grow around the dentate line of the anus, which is a line about 3 cm from the anal opening. This line is an important dividing line around the anus, with the rectal mucosa on top and the skin of the anus covering the bottom. The upper part is innervated by the autonomic nerves and has no pain sensation, while the lower part is innervated by the pubic nerves and is more sensitive to pain. If the hemorrhoids grow above the dentate line, they are called internal hemorrhoids. The main symptoms of internal hemorrhoids are painless bleeding and prolapsed masses, which only show intermittent bleeding at the beginning and may be accompanied by prolapsed masses at a later stage. Hemorrhoids that grow below the dentate line are called external hemorrhoids. The nerves of external hemorrhoids are more sensitive, so they are mainly swollen and painful, and sometimes the swelling and pain are more intense. In addition, internal and external hemorrhoids in the same location fuse together to form a mixed hemorrhoid.