male membranous urethra

The shortest, least dilatable, and, with the exception of the external orifice, the narrowest part of the male urethral canal located in the deep perineal pouch and lined by pseudostratified columnar epithelium; it extends downward and forward, with a slight anterior concavity, between the apex of the prostate and the bulb of the urethra, perforating the urogenital diaphragm below and behind the pubic symphysis; the membranous portion of the urethra is completely surrounded by the fibers of the sphincter urethrae membranaceae; on either side near its termination are the bulbourethral glands.