Muscles of mastication in Meckel's cartilage and human mandible development

Introduction: The mandible derives from the 1st pharyngeal arch ectomesenchyme and its development is closely connected to Meckel's cartilage, mandibular division of trigeminal nerve and muscles of mastication. Aim: The aim of this study was to investigate the relationships between these components in prenatal development. Material and methods: 30 human embryos aged from 37 days and 5 human fetuses were examined. All of them were embedded in toto in paraplast and serially sectioned in three planes. Histological sections were stained according to various methods. Results: At the stage 16 Meckel's cartilage is a very delicate structure supporting mandibular process. Near its ventral end the primordium of maleus and incus, stylohyoideus and styloglossus mascle were visible. Mylohyoideus muscle was visible on the medial side of the cartilage. At the stage 17 the primary mandibular center of ossification developed. Genioglossus muscle and geniohyoideus muscle developed too. These muscles established their temporary attachment to the Meckel's cartilage in embryos at stage 18. At that stage the trunk of mandible was observed. The intramembranous bone lied on the lateral and lower part of Meckel's cartilage. The primordium of maseter muscle develops within angle cartilage at the next stage. In the same time articular disc and tensor of soft palate muscle connection with Meckel's cartilage was observed. During the development of processus coronoideus at 21 stage pterygoideus lateralis muscle was connected with Meckel's cartilage. These connections between cartilage and muscles of mastication were observed till the 10th week of fetal development. After that the connection of all functional parts of developing and ossifying mandible was noted. The attachments of muscles of mastication moved to the mandible. Conclusions: The mandible develops independently of Meckel's cartilage. Muscles of mastication at first are connected with Meckel's cartilage and probably take a part in secondary palate development.