The anal canal has a lining that has three layers of spongy tissue that act like an extra barrier to keep the anus closed until one reaches the toilet. The lining of the intestines is very slimy to make it easier for fecal matter to pass, but the spongy tissue seal stops the leakage of the slime or the mucus. These pads have their own network of very little blood vessels.

Many people think that anal hemorrhoids or piles are similar to the varicose veins that could often be seen on the legs, but these are two separate things. If one of the soft pads has become displaced and slips downwards because the tissues around are not able to keep it in place, it is already a sign of hemorrhoid forming. The tiny blood vessels inside the cushion are filled with blood and cause the cushion to swell.  When a person strains while moving his or her bowels, the hemorrhoid could be pushed downward further down the canal and even outside. Hemorrhoids that appear outside are called prolapsed hemorrhoids.