What is a Hemorrhoid?
Anatomy of Hemorrhoids
The blood vessels that supply blood to the rectum canal descend from the rectum. The rectum is above the sphincter. This area contains a network of arteries that make the conditions perfect for hemorrhoids. This is also the reason that blood from hemorrhoids is a bright red, because it is fresh arterial blood rather than venous blood. This also is why bleeding from hemorrhoids can be very severe. The blood vessels that supply blood to the hemorrhoidal vessels pass through the tissue around the hemorrhoidal cushions.
The sphincter veins drain blood away from the canal and hemorrhoids. The veins drain in two directions; one drains upwards into the rectum, and the other downward through the skin surrounding the anus. The dentate line differentiates the transition from anoderm (anus skin) to the rectum lining.
Formation of Hemorrhoids
If the hemorrhoid forms at the top of the rectum canal, or inside the anus, it is considered an internal hemorrhoid. If it originates near the anus in the sphincter, it is considered an external hemorrhoid. Technically, the difference between an internal and external hemorrhoid is if it is above or below the dentate line.
During the formation of internal hemorrhoids, the vessels of the hemorrhoidal cushions swell along with the supporting tissues. When these bulging cushions protrude into the rectum canal, problems arise. No one knows exactly how external hemorrhoids form.