Development of the smooth muscle of the ureter and vesical trigone: histological investigation in human fetus.

The development of the muscular tissue of the ureter, ureterovesical junction and vesical trigone in the human fetus has been investigated using serial histological sections. The muscular tissue firstly appears in the lumbar tract of the ureter and the further smooth muscle development occurs in a cranio-caudal direction. The muscular tissue in the intravesical portion of the ureter is present only in fetuses between 22 and 24 weeks. The development of the muscular tissue of the trigone is dependent upon the development of smooth muscle of this tract.