[citation needed] It extends from the apex of the prostate proximally to the bulb of urethra distally.

It is surrounded by the external urethral sphincter, which is in turn envelopped by the superior fascia of the urogenital diaphragm.

[1] 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 about 2.5 cm below and behind the pubic symphysis.

[citation needed] The hinder part of the urethral bulb lies in apposition with the inferior fascia of the urogenital diaphragm, but its upper portion diverges somewhat from this fascia: the anterior wall of the membranous urethra is thus prolonged for a short distance in front of the urogenital diaphragm; it measures about 2 cm in length, while the posterior wall which is between the two fasciæ of the diaphragm is only 1.25 cm long.

[citation needed] This article incorporates text in the public domain from page 1235 of the 20th edition of Gray's Anatomy (1918)