A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation

Abstract

A study, comprising dissection and microscopic examination of the pectinate area with special consideration to anal glands, was performed in 29 cadavers varying from fully mature neonatal deaths to 52 yr of age. At the junction of the anal canal proper with the rectal neck, an anorectal sinus (a submucosal anal circumferential depression) was identified in 18 specimens; in 6 specimens, the anorectal sinus was replaced by a fibroepithelial band (anorectal band); in 5 specimens, the anorectal sinus was absent, and in 3 of the 5 specimens only scattered epithelial cells (epithelial debris of the anorectal sinus) were detected. The anorectal sinus may be an embryonic vestige which results from hindgut invagination by the proctodeum. Its persistence or partial obliteration would result in the formation of tubular structures which are considered by investigators as anal glands. The sinus may be completely obliterated or may leave behind a submucosal anorectal band or scattered epithelial debris. Evidence in favor of this new concept is presented. The role of the anorectal sinus, anorectal band and epithelial debris in the genesis of some idiopathic anal lesions is discussed.