Original Paper Cells Tissues Organs 2001;169:152–157 Three-Dimensional Reconstruction of the Anal Striated Musculature in a Human Fetus R. Fröber a U. Krebs a A. Haas c M.S. Fischer c F. Schier b W. Linss a a Institute of Anatomy I, b Department of Pediatric Surgery, and c Institute of Systematic Zoology and Evolutionary Biology, Friedrich Schiller University, Jena, Germany Accepted after revision: November 14, 2000 Dr. med. Rosemarie Fröber Department of Anatomy I, Friedrich Schiller University Jena D–07740 Jena (Germany) Tel. +49 3641 9 38520, Fax +49 3641 9 38512 E-Mail rfro@mti-n.uni-jena.de ABC Fax + 41 61 306 12 34 E-Mail karger@karger.ch www.karger.com © 2001 S. Karger AG, Basel 1422–6405/01/1692–0152$17.50/0 Accessible online at: www.karger.com/journals/cto Key Words Fetal anorectum W Apparatus of continence W Levator ani W External anal sphincter W Puborectalis muscle W Rat Abstract Conflicting opinions in the recent literature indicate that the morphological organization and function of the ano- rectal continence organ has, up to now, not been clearly understood. But a clear imagination of the spatial ar- rangements of this compound muscle system is of clini- cal relevance for the pediatric surgeon performing recon- structive surgery. We analyzed 18-Ìm sections of the pel- vic region of 4 human fetuses in order to describe the individual components of this muscle complex. A series of 630 Azan-stained sections was the base for the com- puter-assisted 3D reconstruction of the levator ani and the external sphincter complex in a male human fetus (14th week p.c.). In this context, special attention was paid to the intermediate muscle layer of the puborectalis which develops ventrally from the funnel-shaped levator ani and joins the tripartite ring system of the sphincter muscle dorsally. Our findings lead to a clear imagination of the spatial arrangement of this intermediate layer and characterize the anorectal muscle complex as an inte- grated ensemble in which the puborectalis holds a key position. Copyright © 2001 S. Karger AG, Basel Introduction The anatomy of the anorectal continence organ has caused a lot of controversy in the past. The function of the muscular components is as much debated as their struc- ture. Furthermore, the spatial relationship between the external anal sphincter and the levator ani is unclear in Abbreviations used in this paper 3D three-dimensional C coccygis Eas external anal sphincter Sc subcutaneous part Sf superficial part D deep part I integument Ilc iliococcygeus Isc ischiococcygeus P pubis Pc pubococcygeus Pr puborectalis R rectum Rc rectococcygeus S sacrum U urethra