The male urethra is a conduit spread over the genital & urinary systems. This musculomembranous canal is running from the bladder to the end of the penis and carries the sperm but also drains the urine from the bladder outwards. A circular muscle, the sphincter, located at its initial portion, control the urination. The urethra is much longer in men VS women (15-20 cm VS 3-4 cm).
The urethra is described based on its three aspects: its embryological aspect (localization of urethra’s portions), its anatomic appearance (nature of surrounding elements) and its functional aspect (degree of mobility).
Embryological and anatomical Appearance: localization of the urethra’s portions
The male urethra can be divided into the posterior and anterior portions
1.The posterior urethra
It includes the pre-prostatic urethra, the prostatic urethra and the membranous urethra.
The pre-prostatic urethra (also called intra-mural)
This uppermost segment is located in the bladder neck and surrounded by the smooth sphincter.
The prostatic urethra (intra pelvic)
This segment begins at the bladder neck and goes through the prostate over 2 to 3 cm, keeping an almost vertical direction. Next, it joins the genital tracts and the pelvic floor (covered by the urogenital diaphragm). This portion of the urethra can be compressed in case of prostatic disease . This is the exact area where the ejaculatory ducts take form, nearby the “verumontanum”, a landmark used in classification of several urethral developmental disorders. The posterior surface of the urethra is punctuated by the prostate glands orifices.
The membranous urethra
It is a short portion of 1 to 2 cm going through the pelvic floor obliquely forwards and downwards. It is surrounded by the external sphincter (ring consisting of striated muscle fibers).
Located in the corpus spongiosum (spongy tissues within the penis), the anterior urethra is the urethra’s lowermost and longest section. It consists of the urethra perineum, the penile urethra and ends with the urethral meatus.
The urethra perineal
It extends up to the root of the penis through an oblique path. It includes the bulbar urethra located in the perineum area. It is a wide and angled zone setting the junction between the membranous urethra and the penile urethra. It hosts the excretory ducts of Cowper’s glands producing the lubricator fluid emitted prior the ejaculation.
The penile urethra
This portion of 10 to 12 cm long and a few mm in diameter goes throughout the penis and is formed by the spongy urethra ensuring the erectile function. It receives the secretions produced by the glands of Littre, guaranteeing a proper lubrication of the urethra.
The urethral meatus
It consists of the opening of the urethra at the penis extremity. This area is the least expandable part of the urethra canal and, in general, the narrower (less than 1 cm wide).
The anterior urethra is closely connected to the erectile structures: its path goes through the corpora cavernosa gutter and is surrounded by the spongy body.
Functional aspect: mobile and fixed portions of the urethra
Functionally, the urethra consists of a fixed portion and a mobile portion.
– The fixed portion comprises the posterior urethra and urethra perineal (part of the anterior urethra). Its fixity is ensured by the prostate, the pelvic floor and the suspensory ligament of the penis whose elastic structure clears the angle between fixed and moving parts of the organ.
– The mobile part comprises the penile urethra
When the penis is not erected, the urethra looks alike a reverse-S path.
Some bibliographic elements
Medical Anatomy (4th edition, Moore and Dalley, Ed. By boeck)
http://www.fichier-pdf.fr/2012/09/01/appareil-u/ (download the pdf file located at the bottom of the page)