الفهرس 
Title: MR Imaging of Anal Sphincter Complex normal anatomical variants: Age- and Sex-related
ContentsOnly 14 pages are availabe for public view
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Abstract
The anatomy of the anal canal is more controversial than that of rectum, The anal canal begins at the level of attachment of the levator ani muscle to the rectum. The inner circular layer of the muscularis propria of the rectum extends into the anal canal and becomes the internal anal sphincter, while the longitudinal component of the muscularis propria becomes the longitudinal layer of the anal canal. Around these two muscular layers, the external anal sphincter, the puborectalis muscle, and the levator ani muscle can be found.Unclarity about the relationship among these three muscles has been the major source of controversy Treatment of patients with anal and low-lying rectal (anorectal) cancers requires achieving the incompatible goals. For oncologic outcomes, wider resection is needed to get safer margin. For functional outcomes, anal canal preservation is required to maintain bowel function. Recently, sphincter-saving surgery has been more frequently applied than abdominoperineal resection for the treatment of rectal cancer.To save the sphincter, understanding the anatomy of anal sphincter complex is essential. This anatomy includes anorectal sphincter muscle, pelvic nerve plexus, and perirectal vessels. In addition, Colorectal surgeons should be familiar with tumor spreading of anorectal cancer and surgical technique for sphincter saving