[Relationship between the dynamics of urachal microvessels and its reduction]

Three stages of the urachus morphogenesis, its stabilization, functional activity and involution find their reflection in all morphological characteristics mentioned. The stage of ductal stabilization is characterized by its tubular structure with lack of any definite anatomical criteria to subdivide it into certain parts. In the urachus wall, five constituents of the microcirculatory bed are differentiated, two microvessel network develop for its nutrition, external and internal. The stage of functional activity coincides with the 5th month of the intrauterine life. At that stage, the tubular structure of the urachus is fully developed and the main elements of its wall are formed. The vessel of the microcirculatory bed are definitely differentiated and the vascular diameter reaches its maximum. The stage of the urachus involution from the view-point of its anatomy is characterized by a possibility to distinguish three dynamically changing parts: obliterated, obliterating and open. During this period, a gradual but quite definite change of its histostructure occurs and gradually the differentiated functioning duct becomes a rudimentary connective tissue cord. Under such reduction in the wall layers of the duct, the diameter and number of microvessels reduce downward. This process is proved morphometrically.