Membranous urethra

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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
Dorlands/Elsevier p_07/12616970

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.

Structure of the penis

Vertical section of bladder, penis, and urethra.

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

v • d • e
Male reproductive system
Scrotum layers (skin, Dartos, External spermatic fascia, Cremaster/Cremasteric fascia, Internal spermatic fascia) • Perineal raphe • Spermatic cord
Testes layers (Tunica vaginalis, Tunica albuginea) • Appendix • Mediastinum • Lobules • Septa • Leydig cell • Sertoli cell • Blood-testis barrier
Spermatogenesis Spermatogonium • Spermatocytogenesis • Spermatocyte • Spermatidogenesis • Spermatid • Spermiogenesis • Spermatozoon
seminal tract Seminiferous tubules (Tubuli seminiferi recti, Rete testis, Efferent ducts) • Epididymis  (Appendix) • Vas deferens (Ampulla) • Ejaculatory duct
urinary tract Internal urethral orifice • Urethra (Prostatic, Intermediate, Spongy, Navicular fossa) • External urethral orifice
accessory glands Seminal vesicles  (Excretory duct of seminal gland) • Prostate  (Urethral crest/Seminal colliculus/Prostatic utricle/Ejaculatory duct, Prostatic sinus/Prostatic ducts) • Bulbourethral glands
Penis root (Crus, Bulb, Fundiform ligament, Suspensory ligament) • body (Corpus cavernosum, Corpus spongiosum) • glans (Foreskin, Frenulum, Corona) • fascia (superficial/subcutaneous, deep/Buck's) • Tunica albuginea - Septum of the penis


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