Its external fibers arise from the junction of the inferior pubic ramus and ischium to the extent of 1.25 to 2 cm., and from the neighboring fascia.

The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system.

[1][2] Voiding urine begins with voluntary relaxation of the external urethral sphincter.

This is facilitated by inhibition of the somatic neurons in Onuf's nucleus via signals arising in the pontine micturition center and traveling through the descending reticulospinal tracts.

[3] This article incorporates text in the public domain from page 429 of the 20th edition of Gray's Anatomy (1918)