The formation of the spinal canal in the human embryogenesis

In the study, 29 totally cleared and double-stained human embryos of 7-12 weeks of gestational age and 33series of histological sections of 7-70 mm CRL human embryos were used. At the 5th week of gestation, the vertebrae are presented by mesenchymal condensations around the notochord. In 7 week embryos, separate centers of chondrification are identified in the vertebral primordia. At the end of the embryonic period (8th week of development) due to the fusion of the centers of chondrification, the vertebral primordia are presented by whole cartilaginous structures having a centrum located in front of the spinal cord and two neural processes that span it from two sides. The body of the future vertebrae is located on the ventral side of the spinal cord, the anteroposterior size of which is approximately twice as large as the similar size of the cartilaginous primordium of vertebral body. The neural processes are directed dorsally and cover only 3/4 of the circumference of the spinal cord from both sides...