FEATURES OF THE SOURCES OF RUDIMENTS AND THE MORPHOGENESIS OF THE STRUCTURES OF THE HUMAN ORAL CAVITY FLOOR

Objective – to determine the features of the sources and chronological sequence of therudements’appearance of the structures of the human oral cavity fl oor.Materials and methods. A series of consecutive histological sections of 18 human embryospecimens aged 4 to 6 weeks of intrauterine development were studied using a complex ofmorphological research methods.Results. In 4-week-old human embryos, an unpaired frontal hump and paired externalsymmetrical anatomical formations are determined – branchial arches: mandibular(fi rst), sublingual (second) and glossopharyngeal (third). The fourth and fi fth branchialarches are fused with the previous arches and do not reach the midline. At the beginningof the prenatal development, the processes of diff erentiation of the fi rst branchial archlead to the formation of its maxillary and mandibular processes. The latter is the sourceof the main structures of the fl oor of the oral cavity and the mandible, in particularMeckel’s cartilage. The rudiment of the tongue is fi rst observed in 4-week-old embryos.Two lateral lingual buds are visualized and somewhat lower – an unpaired median lingualbud, which are the laying of the anterior two thirds of the tongue (oral part of the tongue).The posterior third of the tongue – its pharyngeal part, develops from a single medianmesodermal protrusion covered with endoderm – the laryngopharyngeal bud. The latteroriginates from the third branchial arch and partly from the fourth branchial arch.Conclusions. 1. At the beginning of the 5th week of development, the processes ofdiff erentiation of the branchial apparatus of the embryo, in particular the fi rst branchialarch, lead to the formation of its maxillary and mandibular processes. The latter is the source of the main structures of the fl oor of the oral cavity and the mandible. 2. The sources of the human tongue are fi rst observed in 4-week-old embryos on the ventral wall of the stomodeum and are represented by the lingual buds. 3. The nervous supply of the tongue comes from the corresponding nerves associated with the branchial arches. 4. The muscles of the tongue develop from the paraxial mesoderm of the occipital somites at the end of the 4th week of development, therefore their innervation is provided by the hypoglossal nerve.