title: Nerves in the intersphincteric space of the human anal canal with special reference to their continuation to the enteric nerve plexus of the rectum.
abstract: In the intersphincteric space of the anal canal, nerves are thought to "change" from autonomic to somatic at the level of the squamous-columnar epithelial junction of the anal canal. To compare the nerve configuration in the intersphincteric space with the configuration in adjacent areas of the human rectum, we immunohistochemically assessed tissue samples from 12 donated cadavers, using antibodies to S100, neuronal nitric oxide synthase (nNOS), and tyrosine hydroxylase (TH). Antibody to S100 revealed a clear difference in intramuscular nerve distribution patterns between the circular and longitudinal muscle layers of the most inferior part of the rectum, with the former having a plexus-like configuration, while the latter contained short, longitudinally running nerves. Most of the intramural ganglion cells in the anal canal were restricted to above the epithelial junction, but some were located just below that level. Near or at the level of the epithelial junction, the nerves along the rectal adventitia and Auerbach's nerve plexus joined to form intersphincteric nerves, with all these nerves containing both nNOS-positive parasympathetic and TH-positive sympathetic nerve fibers. Thus, it was histologically difficult to distinguish somatic intersphincteric nerves from the autonomic Auerbach's plexus. In the intersphincteric space, the autonomic nerve elements with intrapelvic courses seemed to "borrow" a nerve pathway in the peripheral branches of the pudendal nerve. Injury to the intersphincteric nerve during surgery may result in loss of innervation in the major part of the internal anal sphincter.
authors.affiliation: Department of Urology, Hiroshima University School of Medicine, Hiroshima, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Hieda
authors.forename: Kwang Ho
authors.initials: KH
authors.lastname: Cho
authors.forename: Takashi
authors.initials: T
authors.lastname: Arakawa
authors.forename: Mineko
authors.initials: M
authors.lastname: Fujimiya
authors.forename: Gen
authors.initials: G
authors.lastname: Murakami
authors.forename: Akio
authors.initials: A
authors.lastname: Matsubara
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000294:innervation*; D002102:Cadaver; D017615:Enteric Nervous System / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D052248:Nitric Oxide Synthase Type I; D010275:Parasympathetic Nervous System / Q000033:anatomy & histology*; D012007:Rectum / Q000294:innervation*; D009418:S100 Proteins; D013564:Sympathetic Nervous System / Q000033:anatomy & histology*; D014446:Tyrosine 3-Monooxygenase
chemical_list: D009418:S100 Proteins; D052248:Nitric Oxide Synthase Type I; D014446:Tyrosine 3-Monooxygenase
keywords: anal canal; internal anal sphincter; intersphincteric space; nerves; neuronal nitric oxide synthase; tyrosine hydroxylase