title: The internal anal sphincter can not close the anal canal completely.
abstract: We determined the maximum closing capability of the internal anal sphincter muscle ring in vitro and in vivo. The internal sphincter, 4 to 6 mm thick, cannot close the anal canal hermetically, not even during maximal contraction. The blood-filled anal cushions have to fill up an intrasphincteric gap of at least 7 to 8 mm in diameter.
authors.affiliation: Department of Abdominal Surgery, University Clinics Gasthuisberg, Catholic University of Leuven, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Lestar
authors.forename: F
authors.initials: F
authors.lastname: Penninckx
authors.forename: H
authors.initials: H
authors.lastname: Rigauts
authors.forename: R
authors.initials: R
authors.lastname: Kerremans
mesh_terms: D001003:Anal Canal / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D011312:Pressure