External sphincter muscle of male urethra

The external sphincter muscle of urethra (or sphincter urethrae membranaceae) surrounds the whole length of the membranous portion of the urethra, and is enclosed in the fasciæ of the urogenital diaphragm.

Its external fibers arise from the junction of the inferior rami of the pubis and ischium to the extent of 1.25 to 2 cm., and from the neighboring fasciæ.

They arch across the front of the urethra and bulbourethral glands, pass around the urethra, and behind it unite with the muscle of the opposite side, by means of a tendinous raphé.

Its innermost fibers form a continuous circular investment for the membranous urethra.