Male urethra

Male urethra masculina, urethra masculina, has an average length of 20-23 cm, is divided into three parts: the prostate, pars prostatica, membranous, pars membranacea, and spongy, pars spongiosa. It starts from the bladder with the inner opening of the urethra, ostium urethrae internum, and ends with the external opening of the urethra, the ostium urethrae externum, located on the top of the glans penis.

The urethra in its turn makes an S-shaped bend. The protuberance, going from top to bottom, forms an arc with a webbed part and the beginning of the spongy part, convex posteriorly, enveloping the pubic symphysis from below. The initial part of the spongy part, passing through the ligamentous portion of the penis, forms with the hanging portion a second knee, convex toward the anterior.

The division of the urethra into these three parts is determined by the peculiarities of the formations that surround it. In addition, in its turn, the male urethra has narrowing and widening, the knowledge of which is of great importance for the clinic.

The prostate part , pars prostatica, pervades the prostate gland from above, behind down and forward. It has a length of 3-4 cm and begins with a narrow part from the inner opening of the urethra (the first narrowed canal site). In the middle of its extension, the urethra is dilated (first expansion). On the posterior part of the prostate, starting from the uvula of the bladder, uvula vesicae urinariae, which is a longitudinal cushion on the surface of the urinary bladder, there is a middle fold - the crest of the urethra, the crista urethralis. The comb in the middle of its extension passes into a longitudinally located seed hillock, colliculus seminalis; Distally, this fold reaches the membranous part. On the top of the seed hill there is a longitudinally located pocket - the prostate, utriculus prostaticus. On each side of the crest of the urethra are the mouths of the ejaculatory ducts. On both sides of the seed hill, between it and the wall of the urethra, the mucous membrane of the urethra forms folds; In the groove that is confined to them - the prosthetic sinus, sinus prostaticus, the mouth of the prostatic duct opens, the ductuli prostatici; Part of the grooves is sometimes opened on the seed mound itself.

The membranous part, pars membranasea, is the shortest part of the urethra, its length is 1.5-2.0 cm. It is tightly fixed in the urogenital diaphragm through which it passes. The proximal part of this part of the canal is the narrowest along the entire canal (the second bottleneck); The distal section, which passes into the spongy part, becomes wider.

The inner opening of the urethra and the proximal part of the prostate part are covered by circulating smooth muscle fibers, which are a continuation of the muscles of the bladder triangle and are weaved into the muscle substance of the prostate gland. The membranous part of the canal and the distal part of the prostatic part encompass the striated muscular fibers of the urethral sfunction, m. Sphincter urethrae. These fibers are part of the deep perineal transverse muscle, therefore the membranous part is fixed in the exit from the pelvis and its mobility is negligible. A part of the muscular fibers of the urogenital diaphragm passes to the prostate and rumen parts, as a result of which the membranous part becomes even less mobile.

The spongy part, pars spongiosa, is the longest part of the urethra, its length is 17-20 cm. It begins with the widest section (the second extension) embedded in the bulb of the penis and reaches the apex of the head of the spongy body of the external opening of the urethra representing the third The channel bottleneck. The mouth of bulbourethral glands opens into the posterior (lower) wall of the bulbous part.

Proximal to the external opening of the urethra is a widening in the sagittal direction - the scaphoid fossa of the urethra (urethra), fossa navicularis urethrae, which is the third extension along the canal. The mucous membrane of the upper wall forms here a transversely located flap of the scaphoid fossa, valvula fossae navicularis, separating the open pocket from the front. On the upper wall of the spongy part there are two rows of transverse folds, bounding small (0.5 mm), open lacunae of the urethra (urethra), lacunae urethrales opening the simple tubular glands of the urethra, glandulae urethrales. A number of glands opens on the surface of the mucosa by the para-urethral ducts (channels), ductus (canales) parauretrales. Throughout the urethra there are longitudinal folds, which determine its extensibility.
The lumen of the urethra at the level of the prostate and membranous parts is represented by a semilunar, convex upward, which is due to the presence of a crest and a seed hillock. In the proximal part of the spongy part, the lumen has the appearance of a vertical slit, in the distal-transverse slit and in the region of the head-an S-shaped gap.

The membrane of the urethra consists of elastic fibers.
The pronounced muscular layer is present only in the prostate and membranous parts. In the spongy part, the mucosa is directly fused to the spongy body, and the smooth muscle fibers belong to the latter.

The mucous membrane of the urethra in the prostate is covered with a transitional epithelium, and the rest is covered by a prismatic multi-row and in the region of the scaphoid fossa by multilayered flat epithelium.

Innervation: nn. Perineales (afferent), plexus hypogastricus inferior (efferent sympathetic).

Blood supply: the prostate part is aa. Pudendae interna, as well as a. Rectalis media and a. Vesicalis inferior, membranous part - a. Rectalis inferior and a. Perinealis, spongy part - a. Bulbi penis and a. Urethralis, small branches from a. Dorsalis penis and a. Profunda penis. Venous blood flows through the veins of the penis in the plexus venosus vesicalis. Lymphatic vessels carry lymph in nodi lymphatici inguinales and iliaci interni.