The development of the external urethral sphincter in humans

Abstract

The omega-shaped configuration of the external urethral sphincter was recognisable from 10 weeks of gestation in both sexes. There was no suggestion of a change from a cylindrical to an omega-shaped sphincter in the fetal period to birth. Also, a transient 'tail' posterior to the sphincter was not apparent. The rectovesical septum was well developed in neonates. There is no reason to assume that the development of the septum leads to an apoptosis of muscle cells in the posterior part of the external sphincter in males after birth. The anatomical development of the external sphincter does not explain transient outlet obstruction during fetal life. The function of the muscle may change during development because of neuronal maturation.