Anatomical features of the human fetus mandible

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Abstract

Aim – to obtain new data on the anatomy of the mandible of a human fetus aged 19–23 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 19–23 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 45.3–60.2 mm), the angular width is 23.4 ± 1.7 mm (with a range of 19.0–27.8 mm). The height of the branch at the cutting level was equal to 6.2 ± 1.4 mm (with a range of 3.6–9.0 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 19–23 weeks is formed and has fetal characteristics. During this period, no significant bilateral differences were revealed, sexual differences start to form.

About the authors

Anastasiya V. Neprokina

Orenburg State Medical University

Author for correspondence.
Email: neprokina@mail.ru
ORCID iD: 0000-0003-1117-0163
SPIN-code: 1006-0756

assistant of the Department of Human anatomy

Russian Federation, Orenburg

Elena D. Lutsay

Orenburg State Medical University

Email: elut@list.ru
ORCID iD: 0000-0002-7401-6502

PhD, Professor, Department of Human anatomy, Director of the Institute of professional education

Russian Federation, Orenburg

Marina A. Vinidictova

Orenburg Regional Clinical Hospital No.2

Email: marinabogatyrjova@rambler.ru

ultrasound doctor

Russian Federation, Orenburg

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2. Figure 1. The mandible of the fetus (female; 20 weeks). 1 – body; 2 – branch; 3 – coronoid process; 4 – condylar process; 5 – clipping; 6 – opening of the lower jaw; I – the angle of the lower jaw; II – the height of the alveolar arch; III – the height of the branch at the level of the cut; IV – the distance between the coronoid and condylar processes.

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3. Figure 2. Fragment of the mandible of the fetus (male; 19 weeks). 1 – body; 2 – branch; 3 – coronoid process; 4 – condylar process; 5 – alveoli; 6 – interalveolar septa; 7 – mandibular nerve.

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4. Figure 3. Ultrasound scan of the fetal mandible. A – Female fetus 20 weeks. B – Female fetus 19 weeks. 1 – angular width; 2 – projection length.

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5. Figure 4. Fragment of the frontal histotopogram of the fetal mandible. 1 – the wall of the dental alveoli; 2 – the rudiment of a milk tooth; 3 – laying of a permanent tooth; 4 – inferior alveolar nerve; 5 – tongue; 6 – sublingual salivary gland.

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Copyright (c) 2021 Neprokina A.V., Lutsay E.D., Vinidictova M.A.

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