Male urethra

The male urethra, or male urethra (urethra masculina), is an unpaired organ shaped like a tube with a diameter of 0.5-0.7 cm and a length of 16-22 cm. It serves to excrete urine and eject semen. It begins with the internal opening of the urethra (ostium urethrae internum) in the wall of the bladder and ends with the external opening (ostium urethrae externum), located on the head of the penis. Topographically, the male urethra is divided into three parts: prostatic, membranous and spongy, and in terms of mobility - into fixed and mobile. The boundary between the latter is the place of attachment of the sling-like ligament of the penis to the penis.

The prostatic part (pars prostatica) of the urethra is about 3 cm long and passes downwards through the prostate gland. The lumen of the male urethra is widened in the middle section. On the back wall of the prostatic part of the urethra there is an oblong elevation - the urethral crest (crista urethralis). The most protruding part of this crest is called the seminal hillock, or seminal tubercle (colliculus seminalis), at the top of which there is a depression - the prostatic utricle (utriculus prostaticus), which is a rudiment of the final section of the paramesonephric ducts. On the sides of the prostatic utricle, the mouths of the ejaculatory ducts open. Along the circumference of the seminal hillock itself are the openings of the excretory ducts of the prostate gland.

The membranous part (pars membranacea) extends from the apex of the prostate gland to the bulb of the penis. This section is the shortest (up to 1.5 cm) and narrowest. In the place where the membranous part passes through the urogenital diaphragm, the male urethra is surrounded by concentric bundles of striated muscle fibers that form the voluntary sphincter of the urethra (m.sphincter urethrae).

The longest part of the male urethra (about 15 cm) is the spongy part (pars spongiosa). In the area of the bulb of the penis, the male urethra widens somewhat, and along the rest of its length its diameter is constant. The final section of the male urethra, located in the head of the penis, widens again, forming the navicular fossa of the urethra (fossa navicularis urethrae).

The male urethra ends at the head of the penis with an external opening that is slightly stretchable, since there is a fibrous-elastic ring in the wall of the canal. On its way, the male urethra is S-shaped and has three constrictions: in the area of the internal opening of the urethra, when passing through the urogenital diaphragm and at the external opening. Expansions of the lumen of the male urethra are found in the prostate part, the bulb of the penis and in its final section - the scaphoid fossa.

The mucous membrane of the male urethra contains a large number of glands (gll.urethrales; Littre glands), opening into the lumen of the canal. In the spongy part of the urethra there are small, blindly ending depressions - lacunae, or crypts (lacunae urethrales). Outside the mucous membrane, the wall of the male urethra consists of a submucosa and a muscular membrane, represented by longitudinal and circular layers of smooth muscle (non-striated) cells.

The urethra of a newborn boy is relatively longer (5-6 cm) than in other age periods, due to its high beginning. Until adolescence, the urethra grows slowly, then its growth accelerates.

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