The anatomy of urethra
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The male and female urethra is assimilable to a fibromuscular tube that conducts urine from the bladder to the exterior of the body.
In man, the urethra extends from the bladder neck to the tip of the penis and measure approximately 22cm. The male urethra can be divided anatomically into four parts (proximal to distal):
i) The prostatic urethra – it begins as the continuation of the bladder neck and passes through the prostate. It receives the ejaculatory ducts (containing spermatozoa from the testes and seminal fluid from the seminal vesicle glands) and the prostatic ducts (containing alkaline fluid).
ii) The membranous urethra – a short segment that passes through the pelvic floor and it is surrounded by the external urethral sphincter. It is the narrowest and least dilatable portion of the urethra. A reduction in the caliber of the membranous urethra is called stenosis instead of stricture due to the absence of sponge tissue surrounding this segment.
iii) The bulbar urethra – the segment of urethra passing through the perineum and the scrotum surrounded by the bulb and corpus spongiosum of the penis. It receives the bulbourethral glands proximally.
iiii) The pendulous urethra – the portion of urethra that courses along the undersurface of the penis. It is surrounded by corpus spongiosum and it ends at the external meatus at the tip of the penis. The last portion of this segment of urethra, just under the glans and before the meatus, is called fossa navicularis.
Another simplified classification grouped the four segments of male urethra in two comprehensive groups: the posterior urethra (prostatic and membranous) and the anterior urethra (bulbar and pendulous)
The female urethra is much shorter than the male urethra measuring approximately 4cm. It starts at the bladder neck, and passes inferiorly through the muscular pelvic floor. The urethra opens directly onto the perineum, in an area between the labia minora, known as the vestibule. Within the vestibule, the urethral orifice is located anteriorly to the vaginal opening, and 2-3cm posterior to the clitoris.
Male urethra
Female urethra
