External hemorrhoids are formed by the inferior rectal venous plexus, located below the dentate line, and are covered by the skin of the anal canal. The most common type is thrombosed external hemorrhoids, which form when a blood clot develops in the subcutaneous venous plexus of the anal canal. Connective tissue external hemorrhoids and inflammatory external hemorrhoids are also relatively common, both located below the dentate line, around the anal margin and inside the anal canal. Generally speaking, hemorrhoids below the dentate line are called external hemorrhoids, and those above the dentate line are called internal hemorrhoids.