Penile mechanisms and the role of the striated penile muscles in penile reflexes.

Gross and subgross anatomical observations of the penis pointed to a mechanical arrangement whereby contraction of the bulbocavernosus (BC) muscles would enhance erections of the glans penis and contraction of the ischiocavernosus (IC) muscles would enhance or produce penis flips. These functions for the muscles were confirmed by electromyographic recordings taken during tests of penile erections and flips in spinal male rats. Surgical removal of the BC muscles did not reduce the total number of erections during penile reflex tests, but did eliminate the flared-cut type of erections. Surgical removal of the IC muscles reduced the occurrence of penile flips and virtually eliminated the long or extended flips. It is hypothesized that contractions of the BC and IC muscles, in producing penile cups and long flips, play a role in dislodgement of previously deposited seminal plugs and deposition of new plugs during mating. Contraction of the BC muscles, in forcefully emptying contents of the urethral diverticulum, would appear to play a role in the ejaculatory process by which the sperm-dense fraction of semen is first delivered to the vagina followed by delivery of a rapidly coagulating seminal plug.