Urogenitodynamics of the male bladder neck. 2. During voiding

The dynamic activity of the male bladder neck during voiding was studied by electromyography in dogs and rabbits. On vesical filling, increased electrical activity in the form of high voltage biphasic potentials was recorded from the anterolateral segment of the bladder neck. With the onset of voiding these high voltage potentials disappeared completely and only a low voltage base line activity was recorded. This indicates muscular relaxation of the anterolateral bladder neck. Concurrently, the posterior segment of the bladder neck showed insignificant electromyographic changes. We conclude that opening of the vesical outlet during voiding is achieved by the muscular relaxation of its anterolateral segment. The dynamic activity of the bladder neck is reciprocally coordinated with the detrusor muscle to produce continence and voiding of urine.