title: Fetal Tendinous Connection Between the Tensor Tympani and Tensor Veli Palatini Muscles: A Single Digastric Muscle Acting for Morphogenesis of the Cranial Base.
abstract: Some researchers contend that in adults the tensor tympani muscle (TT) connects with the tensor veli palatini muscle (TVP) by an intermediate tendon, in disagreement with the other researchers. To resolve this controversy, we examined serial sections of 50 human embryos and fetuses at 6-17 weeks of development. At 6 weeks, in the first pharyngeal arch, a mesenchymal connection was found first to divide a single anlage into the TT and TVP. At and after 7 weeks, the TT was connected continuously with the TVP by a definite tendinous tissue mediolaterally crossing the pharyngotympanic tube. At 11 weeks another fascia was visible covering the cranial and lateral sides of the tube. This "gonial fascia" had two thickened borders: the superior one corresponded to a part of the connecting tendon between the TT and TVP; the inferior one was a fibrous band ending at the os goniale near the lateral end of the TVP. In association with the gonial fascia, the fetal TT and TVP seemed to provide a functional complex. The TT-TVP complex might first help elevate the palatal shelves in association with the developing tongue. Next, the tubal passage, maintained by contraction of the muscle complex, seems to facilitate the removal of loose mesenchymal tissues from the tympanic cavity. Third, the muscle complex most likely determined the final morphology of the pterygoid process. Consequently, despite the controversial morphologies in adults, the TT and TVP seemed to make a single digastric muscle acting for the morphogenesis of the cranial base.
authors.affiliation: Department of Anatomy and Human Embryology, Faculty of Medicine, Institute of Embryology, Complutense University, Madrid, Spain.
authors.forename: José Francisco
authors.initials: JF
authors.lastname: Rodríguez-Vázquez
authors.affiliation: Division of Anatomy, Department of Human Development and Fostering, Meikai University School of Dentistry, Saitama, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Sakiyama
authors.affiliation: Department of Anatomy, Akita University School of Medicine, Akita, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
authors.affiliation: Division of Anatomy, Department of Human Development and Fostering, Meikai University School of Dentistry, Saitama, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Amano
authors.affiliation: Division of Internal Medicine, Iwamizawa Kojin-Kai Hospital, Iwamizawa, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Murakami
mesh_terms: D000328:Adult; D047108:Embryonic Development; D005333:Fetus / Q000196:embryology*; D006801:Humans; D009024:Morphogenesis; D010156:Palatal Muscles / Q000033:anatomy & histology* / Q000196:embryology / Q000502:physiology; D010160:Palate, Soft / Q000033:anatomy & histology* / Q000196:embryology / Q000502:physiology; D019291:Skull Base / Q000033:anatomy & histology* / Q000196:embryology / Q000502:physiology; D013719:Tensor Tympani / Q000033:anatomy & histology* / Q000196:embryology / Q000502:physiology
keywords: middle ear; palatal shelves; pharyngotympanic tube; tensor tympani muscle; tensor veli palatini muscle