The vesical sphincters and ejaculation in the ram.

Abstract

SUMMARY Cinefluorograms were obtained of the posterior urethra of the ram visualised by injection of Hypaque into the vas deferens. Three sets of observations were made: 1 At rest, the posterior urethra remains empty. Any fluid introduced via the vas deferens is promptly expelled into the bladder, and only sometimes into the distal urethra. This may be due partly to intramural tension of the urethral wall and partly to muscular action. 2 Ejaculation was induced by means of electrical stimulation via the rectum and recorded cinefluorographically. During ejaculation the contents of the vas and ampulla are expressed distally through a wide open channel with no reflux into the bladder. Between contractions, fluid remaining in the posterior urethra is expelled into the bladder. There must therefore be a mechanism for preventing reflux during ejaculation, and it is suggested that this is due to a combination of elasticity of the prostatic urethra and prostatic contraction. 3 Ejaculation was observed in one ram after separation of the bladder from the prostate. This would confirm the conclusion of (2) above, and also does not disprove the theory of passive continence or the anatomical observations of the “internal sphincter”, which suggests that this is an opening rather than a closing mechanism. The bladder and its internal sphincter play little or no part in the control of ejaculation.