The external sphincter muscle of urethra (or sphincter urethrae membranaceae) surrounds the whole length of the membranous portion of the urethra

Urethra

In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...

, and is enclosed in the fasciæ of the urogenital diaphragm.

Its external fibers arise from the junction of the inferior rami

Rami

Rami or RAMI can refer to:*Rami, the plural of ramus, literally a branch, as of a plant, nerve, or blood vessel*Specifically, rami are upward portions on both sides of the mandible...

 of the pubis

Pubis (bone)

In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons 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

Raphé

Raphé can refer to:* Rafe, a diacritic ֿ a short horizontal overbar placed above certain letters to indicate that they are to be pronounced as fricatives* Raphe, scientific term...

.

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

Membranous urethra

The intermediate part of male urethra is the shortest, least dilatable, and, with the exception of the external orifice, the narrowest part of the canal....

.

External links

- "Muscles of the female urogenital diaphragm (deep perineal pouch) and structures located inferior to it."