Anal Canal - Definition
The anal canal is the last section of the large intestine, through which stools pass before going out of the body at the time of defecation.
Anal Canal - Location
It is situated between the rectum and the anus, beneath the pelvic diaphragm level. It can be found in the anal triangle of the perineum, between the right and left ischioanal fossa.
Anal Canal - Anatomy
The canal is around 1.5 inches long and narrower than the rectum to which it is attached. The sphincter (controlling bowel movements) encircles the canal and regulates its opening and closure.
This canal is divided into three major parts - (a) Zona columnaris which makes up the upper half of the canal and is lined with the tissue present in the small intestine, large intestine and the stomach; (b) Zona hemorrhagica and (c) Zona cutanea which together account for the lower half of the anal canal. The lower parts are comprised of tissues which are different from those lining the zona columnaris. These include the tissue that can usually be seen in the lips and other exposed skin regions.
Anal Canal - Function
This digestive structure helps lubricate fecal matter and transfer them as they pass out of the body through the rectum. The canal also helps regulate passage of stools as well as maintain continence (voluntary control over laxation).
Anal Canal - Problems
The canal of the anus can be affected by the following problems:
A common problem affecting the anal canal, hemorrhoids are swollen veins that remain within the canal but pop out during laxation. These inflamed veins can prolapse into the anus or fall out in some people. Sufferers commonly experience itching and discomfort; bleeding is not unusual in acute cases. Even minor hemorrhoids can lead to much discomfort due to the presence of stools within the canal. Small hemorrhoids usually resolve with lifestyle modifications while acute ones require medicines or surgery for cure.
Any type of infection can lead to the development of these abnormal tracts or passages develop in the skin.
These are infected protuberances which can easily result from a fistula.
These small ruptures or tears in the anal canal often result in much pain, which generally worsen due to the expansion and contraction of the anal sphincter.
Cancers of the anala canal occur only rarely, and are less common than cases of colon cancer, but are found to be much more life-threatening and cause approximately 600 deaths every year in the United States. As the canal is easily accessible from the outside, abnormalities in the area can be spotted readily and treated (usually through surgery).
Anal Canal - Pictures
The following images would provide you with useful information about the physical appearance of the anal canal.
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