The Origin of the Variations of the Hyoid Apparatus in Human.
Currently, theories based on acquired calcification of the stylohyoid ligament are believed to be a pathogenesis of syndromes associated with the hyoid apparatus (HA) and its variations. We studied the development of the HA from Reichert´s cartilage using serial sections of 25 human embryos and 45 fetuses. We ensured a fact that, at the initial stage, the HA appeared as two independent cartilage segments, that is, the cranial or styloid segment and the caudal or hyoid segment of Reichert's cartilage, those are connected by a mesenchymal structure. However, between 8 and 10 weeks of development, the mesenchymal connection was lost. We hypothesize that this disconnection is likely to be one of the major factors to make a descent of the hyoid bone in evolution. The stylohyoid ligament was not observed. The variations of the HA, should be considered variations of the development of Reicherts cartilage. If these variations are maintained in the adult, are likely to explain a major symptom associated with Eagle's syndrome.
Departament of Anatomy and Human Embryology, Institute of Embryology, Faculty of Medicine, Complutense University, Madrid, Spain.
José Francisco
JF
Rodríguez-Vázquez
Departament of Anatomy and Human Embryology, Institute of Embryology, Faculty of Medicine, Complutense University, Madrid, Spain.
Samuel
S
Verdugo-López
Department of Anatomy, Akita University School of Medicine, Akita, Japan.
Hiroshi
H
Abe
Division of Internal Medicine, Iwamizawa Kojin-Kai Hospital, Iwamizawa, Japan.
Gen
G
Murakami
D001846:Bone Development; D002356:Cartilage / Q000002:abnormalities / Q000196:embryology*; D005865:Gestational Age; D006801:Humans; D006928:Hyoid Bone / Q000002:abnormalities / Q000196:embryology*; D009024:Morphogenesis; D009999:Ossification, Heterotopic / Q000196:embryology; D013194:Staining and Labeling / Q000379:methods; D013701:Temporal Bone / Q000002:abnormalities / Q000196:embryology
Reichert's cartilage; eagle's syndrome; hyoid apparatus; hyoid bone; styloid process