Full Urogenital Diaphragm Description
[Continued from above] . . . the base of the penis; (3) the ischiocavernosus muscle, a tendinous structure that extends down to the margin of the pubic arch and assists the function of the bulbospongiosus muscles; and (4) the sphincter urethrae are muscles that arch around the urethra and unite with those on the other side. Together they act as a sphincter that closes the urethra by compression and opens it by relaxation to control the flow of urine.