Estudo estrutural e ontogenético do úraco e da bexiga de fetos humanos normais e com anencefalia no segundo trimestre gestacional

Abstract

The objective of this work is to present an ontogenetic and structural study of the urachus in normal human fetuses and of the bladder in normal and anencephalic fetuses during the second gestational trimester. Fifty nine fetuses were used, 47 normal (22 male and 25 female) and 12 anencephalic (5 male and 7 female) with ages between 13 and 23 weeks post conception (WPC). Stereological and biochemical methods were used to analyse the extracellular matrix fibrous components, smooth muscle and the urachal lumen. The urachal lumen was closed at the 18th WPC in both males and females. The transitional epithelium in the urachus was clearly identified in fetuses until the 17th WPC, in which the urachal lumen was open. In fetuses aged ≥ 18 WPC, the urachal epithelium was not visualized because the urachal lumen was closed. We observed a significant increase in the Vv of connective tissue in the bladders of anencephalic fetuses and a significant decrease in the Vv of smooth muscle cells in the bladders of anencephalic fetuses when compared to normal fetuses. The biochemical analyses showed a higher concentration of total collagen in the bladders of anencephalic fetuses when compared to normal fetuses. Urachal lumen closing occurs in the 17th WPC. After the lumen closing, we notice an absence of the transitional epithelium in its interior, a decrease in the amount of smooth muscle and an increase in type I collagen, which indicates a characteristic remodeling in fibrous tissue formation. The data obtained in the present study can be used as basic knowledge related to the development of the urachus and embryonic urinary tract drainage. The structural alterations of the bladder found in this study can suggest the existence of functional alterations in the bladder of anencephalic human fetuses.