Just behind the anus, in the anal canal, lie two muscles that contract and expand. They constrict to retain feces and expand to allow it and gas to pass during bowel movements. These two muscles are the exterior and the interior sphincter. The anal canal is the first 2 inches of skin before the anus opening. The sphincters help keep it closed during rest and open during defecation. Prior to the anal canal is the rectum, which extends vertically from the end of the colon to the anal canal. The rectum is approximately 5 inches long and 1 1/2 inches wide.
Anal health requires cleanliness and lubrication whenever it is needed since the anus does not produce lubrication by itself. During bowel movements and wiping, do not wipe too hard as over time this will damage the blood vessels around the anus and sometimes cause blood vessel rupture, resulting in red poop or bloody toilet paper.