Diagram of the rectum and anus.
U.S. Government National Institutes of Health
<a rel="nofollow" class="external free" href="http://digestive.niddk.nih.gov/ddiseases/pubs/fecalincontinence/images/anorectum.gif">http://digestive.niddk.nih.gov/ddiseases/pubs/fecalincontinence/images/anorectum.gif</a>