Anatomy and Embryology of the Anus.

The anus is a complex structure formed from the hindgut. The anus can be further divided into the anal canal, the anal verge, and the anal margin. The anoderm is surrounded by the internal and external anal sphincters which are the distal continuation of pelvic floor muscles and the muscularis propria of the rectum. The anal canal is divided by the dentate or pectinate line with varying endothelium, bloody supply, and innervation based on location. The practicing colorectal surgeon needs to have a strong foundation in anorectal anatomy as it is integral to understanding the pathophysiology and treatment.