Peripheral nerves controlling the closure of internal urethral orifice during ejaculation.

The peripheral nervous pathways controlling seminal emission and closure of the internal urethral orifice during ejaculation were examined experimentally using male adolescent dogs. The experimental methods were measurement of the contraction of the internal urethral orifice and measurement of the change of the posterior urethral pressure induced by selective stimulation of the nerves related to the hypogastric nerve. Further, the change of actual ejaculation caused by manual stimulation of the penis was observed after excision of the nerves. Results included the following: (1) The seminal emission and the closure of the internal urethral orifice on ejaculation were controlled by the hypogastric nerve. (2) The nerve fibers which controlled these two phenomena took different paths above the lower mesenteric plexus. (3) Seminal emission was controlled by the splanchnic nerves which originated from the lower thoracic and upper lumbar ganglia of the sympathetic trunk, and the closure of the internal urethral orifice by those which originated from the lower lumbar ganglia of the trunk.