Özbey Hüseyin, Arlı Osman Tayyar
Department of Pediatric Surgery, Division of Pediatric Urology, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey; Department of Pediatric Surgery, Sechenov First Moscow State Medical University, Moscow, Russian Federation.
Department of Biophysics, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey.
Med Hypotheses. 2020 Feb 26;140:109642. doi: 10.1016/j.mehy.2020.109642.
A clear understanding of the normal anatomy of the glanular urethra is essential for anatomical reconstruction of the male urethra. In hypospadias surgery, tubularization of the neourethra over a catheter or stent has been the standard method for decades. However, the male urethra is not a tubular structure with uniform configuration and diameter by forming a fossa (navicularis) in the glans penis. We recently investigated the structural anatomy of the glanular urethra using magnetic resonance imaging (MRI). We have shown that the male urethra does not have a uniform tubular structure and not covered by the corpus spongiosum to the end. The glanular urethra that forms the "fossa navicularis" has a wider caliber than the proximal urethra. Its vertical elliptical shape resembles a laterally compressed slit-like passage. The fossa navicularis is covered by a thin layer of fibrous tissue ("septum glandis") which is an extension of tunica albuginea of the corpus cavernosum and the corpus spongiosum. Our hypothesis is based on the results of MRI of the glanular urethra and the basic principles of fluid dynamics. We analyzed the flow dynamics of urine on this particular component of the urethra in terms of shape and structural properties. Because of its wider caliber than the proximal urethra, the glanular urethra (fossa navicularis) should cause an increase in pressure and a decrease in velocity of the urine flow. The navicular shape of the fossa and its elliptical external opening (the meatus) should allow urine to be expelled at higher flow rates and at opposite angles at the upper and lower corners which make the wave-like shape of the urine. It can be said that the changes in the volumetric form, pressure and velocity, as well as the wave-like shape of the urine flow are caused by the "fossa navicularis" covered by the "septum glandis". We propose that the "fossa navicularis" and "septum glandis" play a role as 'flow control chamber" in controlling the flow of the urine exiting the urethra, which must be taken into account for successful functional reconstruction of hypospadias.
清楚了解阴茎头尿道的正常解剖结构对于男性尿道的解剖重建至关重要。在尿道下裂手术中，几十年来，在导管或支架上进行新尿道的管状化一直是标准方法。然而，男性尿道并非具有均匀形态和直径的管状结构，因为在阴茎头内形成了一个窝（舟状窝）。我们最近使用磁共振成像（MRI）研究了阴茎头尿道的结构解剖。我们已经表明，男性尿道没有均匀的管状结构，并且并非全程都被海绵体包绕。形成“舟状窝”的阴茎头尿道口径比近端尿道宽。其垂直椭圆形形状类似于横向压缩的裂隙样通道。舟状窝被一层薄的纤维组织（“阴茎头隔”）覆盖，该组织是海绵体白膜的延伸。我们的假设基于阴茎头尿道的MRI结果和流体动力学的基本原理。我们从形状和结构特性方面分析了尿液在尿道这一特定部分的流动动力学。由于其口径比近端尿道宽，阴茎头尿道（舟状窝）应会导致尿液压力升高和流速降低。窝的舟状形状及其椭圆形外口（尿道口）应使尿液能够以更高的流速从上下角以相反角度排出，从而形成尿液的波浪状形态。可以说，体积形态、压力和速度的变化以及尿液流动的波浪状形态是由被“阴茎头隔”覆盖的“舟状窝”引起的。我们提出，“舟状窝”和“阴茎头隔”在控制尿液从尿道排出的流动中起“流量控制腔”的作用，这在尿道下裂的成功功能重建中必须予以考虑。
