Krystel Nyangoh Timoh1, David Moszkowicz2, Mazen Zaitouna3, Cedric Lebacle3, Jelena Martinovic4, Djibril Diallo3, Maud Creze3, Vincent Lavoue5, Emile Darai6, Gérard Benoit3, Thomas Bessede7. 1. Unité Mixte de Recherche 1195, University Paris Sud, Institut National de la Santé et de la Recherche médicale, Université Paris-Saclay, Le Kremlin-Bicetre, France; Department of Obstetrics and Gynecology, Hopital Universitaire de Rennes, University Rennes 1, Rennes, France. 2. Unité Mixte de Recherche 1195, University Paris Sud, Institut National de la Santé et de la Recherche médicale, Université Paris-Saclay, Le Kremlin-Bicetre, France. Electronic address: k.nyangoh@gmail.com. 3. Unité Mixte de Recherche 1195, University Paris Sud, Institut National de la Santé et de la Recherche médicale, Université Paris-Saclay, Le Kremlin-Bicetre, France. 4. Department of Fetal Pathology, Hopitaux Universitaires Paris-Sud, Assistance Publique-Hôpitaux de Paris, Clamart, France. 5. Department of Obstetrics and Gynecology, Hopital Universitaire de Rennes, University Rennes 1, Rennes, France. 6. Department of Obstetrics and Gynecology, Tenon University Hospital, Assistance Publique des Hôpitaux de Paris, Unité Mixte de Recherche-S 938, Pierre and Marie Curie University, Paris, France. 7. Unité Mixte de Recherche 1195, University Paris Sud, Institut National de la Santé et de la Recherche médicale, Université Paris-Saclay, Le Kremlin-Bicetre, France; Urology Department, Hopitaux Universitaires Paris-Sud, Assistance Publique-Hôpitaux de Paris, Le Kremlin-Bicetre, France.
Abstract
BACKGROUND: Injury to the levator ani muscle or pelvic nerves during pregnancy and vaginal delivery is responsible for pelvic floor dysfunction. OBJECTIVE: We sought to demonstrate the presence of smooth muscular cell areas within the levator ani muscle and describe their localization and innervation. STUDY DESIGN: Five female human fetuses were studied after approval from the French Biomedicine Agency. Specimens were serially sectioned and stained by Masson trichrome and immunostained for striated and smooth muscle, as well as for somatic, adrenergic, cholinergic, and nitriergic nerve fibers. Slides were digitized for 3-dimensional reconstruction. One fetus was reserved for electron microscopy. We explored the structure and innervation of the levator ani muscle. RESULTS: Smooth muscular cell beams were connected externally to the anococcygeal raphe and the levator ani muscle and with the longitudinal anal muscle sphincter. The caudalmost part of the pubovaginal muscle was found to bulge between the rectum and the vagina. This bulging was a smooth muscular interface between the levator ani muscle and the longitudinal anal muscle sphincter. The medial (visceral) part of the levator ani muscle contained smooth muscle cells, in relation to the autonomic nerve fibers of the inferior hypogastric plexus. The lateral (parietal) part of the levator ani muscle contained striated muscle cells only and was innervated by the somatic nerve fibers of levator ani and pudendal nerves. The presence of smooth muscle cells within the medial part of the levator ani muscle was confirmed under electron microscopy in 1 fetus. CONCLUSION: We characterized the muscular structure and neural control of the levator ani muscle. The muscle consists of a medial part containing smooth muscle cells under autonomic nerve influence and a lateral part containing striated muscle cells under somatic nerve control. These findings could result in new postpartum rehabilitation techniques.
BACKGROUND: Injury to the levator ani muscle or pelvic nerves during pregnancy and vaginal delivery is responsible for pelvic floor dysfunction. OBJECTIVE: We sought to demonstrate the presence of smooth muscular cell areas within the levator ani muscle and describe their localization and innervation. STUDY DESIGN: Five female human fetuses were studied after approval from the French Biomedicine Agency. Specimens were serially sectioned and stained by Masson trichrome and immunostained for striated and smooth muscle, as well as for somatic, adrenergic, cholinergic, and nitriergic nerve fibers. Slides were digitized for 3-dimensional reconstruction. One fetus was reserved for electron microscopy. We explored the structure and innervation of the levator ani muscle. RESULTS: Smooth muscular cell beams were connected externally to the anococcygeal raphe and the levator ani muscle and with the longitudinal anal muscle sphincter. The caudalmost part of the pubovaginal muscle was found to bulge between the rectum and the vagina. This bulging was a smooth muscular interface between the levator ani muscle and the longitudinal anal muscle sphincter. The medial (visceral) part of the levator ani muscle contained smooth muscle cells, in relation to the autonomic nerve fibers of the inferior hypogastric plexus. The lateral (parietal) part of the levator ani muscle contained striated muscle cells only and was innervated by the somatic nerve fibers of levator ani and pudendal nerves. The presence of smooth muscle cells within the medial part of the levator ani muscle was confirmed under electron microscopy in 1 fetus. CONCLUSION: We characterized the muscular structure and neural control of the levator ani muscle. The muscle consists of a medial part containing smooth muscle cells under autonomic nerve influence and a lateral part containing striated muscle cells under somatic nerve control. These findings could result in new postpartum rehabilitation techniques.