The aim of the study is to define the features of organogenesis and histogenesis of sacral vertebrae in human embryos, which predetermine the anatomical structure of the sacrum in postnatal ontogenesis. Material and methods. The authors studied human embryo serial sections at 17–23 stages from the Carnegie virtual embryological collection, total preparations and serial sections of the lumbosacral region of the fetal spine at 8–20 weeks of gestation without visible developmental anomalies. Histological sections were stained with hematoxylin and eosin; total preparations were stained with alizarin red and alcian blue. In addition, the study included 19 adult sacra from the anatomical collection of the Belarusian State Medical University. Results. It was found that consolidation of the anlages of the upper sacral vertebrae starts at the early stages of embryogenesis by the fusion of their costal-transverse processes. During the first half of intrauterine development, the arch and articular processes of the adjacent vertebrae remain separate from each other. In contrast to other segments of the spinal column, five primary centers of ossification are formed in the anlages of the upper sacral vertebrae

The aim of the study is to compare the structure of the lumbosacral transitional vertebra, which were detected by computed tomography (CT) and identified on dried human sacral, and to discuss possible pathogenetic mechanisms of this congenital malformation. The article presents 9 cases of lumbosacral transitional vertebra, including 6 cases of L5 sacralization and 3 cases of S1 lumbarization. The formation of the transitional lumbosacral vertebra is genetically determined. All types of such developmental anomaly can be detected only on CT. L5 sacralization repeats the process of fusion of the sacral vertebra into a single bone. A lack of the costotransverse bars of the first sacral vertebrae fusion results in the S1 lumbarization.