WHAT ARE HEMORRHOIDS?

Normal, healthy individuals are born with bunches of veins called hemorrhoidal vessels. They lie beneath the lining of the lower part of the rectum and anal canal. These vessels, along with the surrounding tissues, form the anal cushions. Anal cushions are normal anatomical structures and assure the complete closure of the anal canal when the body is relaxed.

When the hemorrhoidal vesseles contained in the anal cushions become enlarged, dilated (varicose) and tortuous, they appear as noticeable swellings in the anal canal and perianal area and are then called hemorrhoids or piles. (Piles come from the Latin word "pila", meaning "ball".)
Hemorrhoids appear in three sites in the anal canal, corresponding with the location of hemorrhoidal vessels.
 

Hemorrhoids are masses of enlarged vessels in the lower part of the rectum and anal canal.

ANATOMY OF ANAL CANAL

The anal canal extends between the anal verge below and the rectum above and is surrounded by the anal sphincter muscle. It is about four centimeters long and is divided into the upper half that has no pain nerve endings and the lower half with pain nerve endings, like the penanal skin. The rectum extends upward to join the colon and distends to hold the fecal mass.