The Macromicroscopic Anatomy and Microtopography of the Lower Jaw in Fetuses of 14–18 Weeks

In the article the features of anatomical structure and microtopography of the lower jaw of fetus at the age of 14–18 weeks were discussed. The relevance of the research is due to the prevalence of congenital pathology of the maxillofacial region, the possibilities of its early prenatal diagnosis and correction in connection with the development of fetal surgery.
The aim of the research is to get new data of the macromicroscopic anatomy and microtopography of the lower jaw in fetuses of 14–18 weeks.
Material and methods. The object of the research was the lower jaw of 40 male and female fetuses at the age of 14–18 weeks. The research was carried out using morphological methods and the method of ultrasound scanning. The qualitative and quantitative characteristics of the lower jaw were studied.
Results. The lower jaw of the fetus at the age of 14–18 weeks is already formed and has basic anatomical structures. The body, angle, ramus, condylar and coronoid processes, teeth anlages, which can be described on morphological preparations and studied using the method of ultrasound scanning, are defined in the lower jaw. In front of the lower jaw, soft tissues are located, their thickness varies from 2.1 to 3.9 mm. Behind the lower jaw, there is a slit space with a width of 0.3 to 1.5 mm, behind it the tongue and the oral part of the pharynx are situated. The latter has an irregular shape. In a fetus of 14-18 weeks, major salivary glands (parotid, sublingual and submandibular) are already formed and determined on different cuts. The length of the alveolar arch is 29.1±6.2 mm, the width of the lower jaw is 19.5±4.2 mm. At this time, the lower jaw can be presented by two anlages and a symphysis located along the median line. The symphysis on horizontal cut has a fusiform shape, it narrows to the outer and inner surfaces of the lower jaw. In the narrow part, its size varies from 0.1 to 0.4 mm, the extension in the central part is from 0.5 to 0.9 mm. In the lower jaw, the anlages of decidual teeth of an irregular shape are determined. The size of anlages varies from 1.3 to 2.3 mm, depending on the type of tooth. On some cuts under the anlage of primary tooth, it is possible to determine the anlage of permanent one. The significant bilateral and sex differences of human fetuses at the age of 14–18 weeks of intrauterine development were not revealed.
Conclusion. The lower jaw of fetuses at the age of 14–18 weeks has all elements of the anatomical structure, with certain fetal features (incomplete accretion of the mandibular processes, anlages of decidual and permanent teeth, microtopographic relationships with adjacent anatomical structures). At this stage of development, there are no significant bilateral and sex differences. The use of various methodological approaches to the research of the qualitative and quantitative anatomy of the lower jaw makes it possible to detail and supplement the substantiation of approaches for fetal surgery.

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