STRUCTURE ORGANIZATION OF THE AREA OF ORIFICES OF CAVA VEINS IN THE HUMAN EMBRYOGENESIS
The of development of the area of orifices of cava veins have been investigated on serial cuts taken from 133 human embryos at the age of 4-8 weeks of intra-uterine development. It is has been established, that the right common cardinal vein (RCCV), left common cardinal vein (LCCV) and inferior vena cava initially open in a sinus venosus of the heart. Their orifices locate very close from each other. In process of growth of the heart the orifices of these veins gradually remove from each other that testify to gradual embedding the wall of a sinus in the wall of the right auricle and the above mentioned veins are open in the cavity of the right auricle. RCCV and the right horn of a sinus form superior vena cava, and LCCV (it’s distal portion) and the left horn - a coronal sine of heart. At the entry of a primary auricle there is the venous valve consisting of the right and left shutters. It prevents from a retrograde blood flow in a sinus venosus and afferent vessels. In due course the left shutter is reduced. The valve of the inferior vena cava (Eustahii) and the valve of the sinus coronarii (Thebesii) are formed from the right one. Also it is revealed, that in embryogenesis the layings of the future myocardial constrictors of cava veins are formed.