Anatomical features of the human fetus mandible

Abstract

Aim to obtain new data on the anatomy of the mandible of a human fetus aged 1923 weeks.
 Material and methods. The object of the study was 40 mandibles of human fetuses of both sexes aged from 19 to 23 weeks. The morphological method (macromicroscopic preparation; the method of saw cuts according to N.I. Pirogov; production of serial histotopograms) and the method of ultrasound scanning by the device VOLUSONS 10, RAB 6 RS sensor in 2D mode and in the "Skeleton" program (3D mode) were used.
 Results. In fetuses aged 1923 weeks the mandible represents a paired bone connected in the center by a symphysis. According to the shape of the body, it is possible to select wide and short, long and narrow mandibles in a ratio of 2 to 1, respectively 67% and 33%. The length of the alveolar arch is 52.4 5.6 mm (with a range of 45.360.2 mm), the angular width is 23.4 1.7 mm (with a range of 19.027.8 mm). The height of the branch at the cutting level was equal to 6.2 1.4 mm (with a range of 3.69.0 mm). On the anterior surface of the body, one chin opening is determined on both sides, at an average distance of 16.4 mm from the angle of the mandible and at a height of 2.2 mm. On the inner surface of the branch, the opening of the mandible is determined, located at a distance of 3.6 1.1 mm from the angle, 3.2 0.9 mm from the anterior edge of the branch, 4.1 1.2 mm from the posterior edge of the branch. In the second trimester of pregnancy, dental alveoli are determined in the mandibular dental arch of the fetus. Significant sex differences were found for the angle of the mandible (p 0.05). In girls, the angle was 141.1 10.1, in boys 129.5 9.4.
 Conclusion. The mandible of the fetus at the age of 1923 weeks is formed and has fetal characteristics. During this period, no significant bilateral differences were revealed, sexual differences start to form.