Introduction. Development of mentum and mandibular symphysis has been rarely investigated. Formation of mentum is considered to be influenced by many factors. However the structure of the anterior part of Meckel’s cartilage and its possible role in the formation of the mandibular symphysis has not been specified, similarly to the importance of the rapid connection of both halves of the mandible during the fetal development. Material and methods. The observations were carried out on serial sections made in three planes (5 µm for embryos, 7 µm for fetuses) stained according to various histological methods. 30 human embryos (37 to 56 days) and 5 fetuses (9 to 35 weeks) were examined under light microscopy. Results. Since stage 16 Meckel’s cartilages were separated in midline by mesenchyme. At stage 18 there is wide space between cartilages filled with mesenchyme and the fibres of suprahyoid muscles inserted in the inferior surface of Meckel’s cartilage were observed. At stage 22 both Meckel’s cartilages touched each other within the symphysis menti. Between the 9th and 12th week the cartilages were separated with mesenchyme penetrated by connective tissue, the shape of the symphysis was pyramidal. Between the 13th and 18th week marrow cavities and degeneration of the cartilage in the mental region was observed, symphysis was filled with fibrous tissue penetrated by blood vessels. From the 35th week calcified cartilage was still observed within the bone. Conclusions. The mandibular symphysis’ formation is a multistage process started during embryogenesis and almost completely finished before birth.

Key words: symphyseal fusion, prenatal development, chin, maxillofacial development, orthodontics.