Membranous urethra

Membranous urethra
The male urethra laid open on its anterior (upper) surface. (Membranous part labeled at upper right.)
Latin	pars intermedia urethrae masculinae, pars membranacea urethrae masculinae
Gray's	subject #256 1235

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

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.

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.

The membranous portion of the urethra is completely surrounded by the fibers of the Sphincter urethrae membranaceae.

In front of it the deep dorsal vein of the penis enters the pelvis between the transverse ligament of the pelvis and the arcuate pubic ligament; on either side near its termination are the bulbourethral glands.

Additional images

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  Structure of the penis

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  Vertical section of bladder, penis, and urethra.

External links

• intermediate+part+of+male+urethra at eMedicine Dictionary
• SUNY Labs 43:08-0102 - "The Female Pelvis: The Urethra"
• SUNY Labs 44:06-0103 - "The Male Pelvis: The Urethra"
• MedEd at Loyola Grossanatomy/dissector/practical/pelvis/pelvis11.html

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.