The Anatomical Components of Urinary Continence

Paraplegia, 1972

International Urogynecology Journal, 2019

A damaged sphincteric unit or support system, unstable urethral deformability or damaged sensory innervation are all potential causes of a dysfunctional urethral sphincter. With the current improvement in pharmacological targets and urodynamic understanding, studies have begun quantifying individual structures and their importance in closure pressure and consequently urethral continence. However, when it comes to the function of the longitudinal urethral smooth muscle layer, there is currently no consensus. The intent of this structured review is to critically examine literature regarding the female urethral anatomy and closure mechanism. We hypothesized that the longitudinal smooth muscle is a prerequisite for sufficient urethral closure and not merely involved during micturition. Overall opinions on a dysfunctional closure mechanism are controversial. Nonetheless, basic mechanics may be applied to understand simple urodynamics. With the assumption of longitudinal muscles forming a plug when contracted, this could have a substantial effect on the continence mechanism.

2014

Detailed knowledge of the anatomy of the rhabdosphincter and adjacent tissues is mandatory during urologic surgery to ensure reliable oncologic and functional outcomes. To characterize the levator ani (LA) function for the urethral sphincter, we described connective tissue morphology between the LA and urethral rhabdosphincter. The interface tissue between the LA and rhabdosphincter area in males contained abundant irregularly arrayed elastic fibers and smooth muscles. The male rhabdosphincter was positioned alongside the LA to divide the elevation force and not in-series along the axis of LA contraction. The male perineal membrane was thin but solid and extends along the inferior margin or bottom of the rhabdosphincter area. In contrast, the female rhabdosphincter, including the compressor urethrae and urethrovaginal sphincter muscles, was embedded in the elastic fiber mesh that is continuous with the thick, multilaminar perineal membrane. The inferomedial edge of the female LA was attached to the upper surface of the perineal membrane and not directly attached to the rhabdosphincter. We presented new diagrams showing the gender differences in topographical anatomy of the LA and rhabdosphincter.

International Urogynecology Journal, 2002

To reexamine the anatomy of the female urethra and related structures, three female pelves serially sectioned in sagittal, coronal or transverse planes, and four sets of transverse histological slides of female urethras, were studied. The observations were assembled, rendered as illustrations, and correlated with published works to present an overall explanation of the gross and histological anatomy of the female pelvis and perineum as related to continence. The figures accompanying the text present the anatomy in a series of views in the three anatomical planes. The anatomical relationships of the paraurethral and paravaginal tissues are examined in relation to the conflicting nomenclature applied to these structures. The figures show the spatial relationships within the pelves and perineum that explain their effective function in urinary continence.

Obstetrics & Gynecology, 1998

To describe the contribution of the posterior pelvic compartment to the urethral closure mechanism. Methods: Urethral profilometry at rest and during stress was performed in 32 continent women before and after inserting a weighted (1 kg) posterior speculum to displace the posterior vaginal wall and levator ani muscles away from the bladder neck and the urethra. Results: Insertion of the speculum decreased the pressure transmission ratios in the proximal quarter of urethra (from 81 to 76; P < < < .05) and the urethral closure pressure under stress in the proximal two urethral quarters (from 5 to ؊ ؊ ؊3 cm H 2 O in the first and from 12 to 0 cm H 2 O in the second urethral quarter; P < < < .05) in all 32 women. Before speculum insertion, 20 women had positive urethral closure pressure in the proximal urethra under stress, and 12 had negative urethral closure pressure in the proximal urethra under stress. In the 20 women with positive urethral closure pressures under stress in the proximal urethra without a speculum, the insertion of a posterior speculum decreased the pressure transmission ratios to the proximal urethral quarter (from 87 to 78; P < < < .05) and decreased the urethral closure pressures under stress in the proximal two urethral quarters (from 13 to ؊ ؊ ؊4 cm H 2 O in the first urethral quarter and from 24 to 2 cm H 2 O in the second urethral quarter; P < < < .01). In the 12 patients with negative urethral closure pressures under stress in the proximal urethra without a speculum, the profilometry values were unchanged by insertion of a speculum. Conclusion: These observations indicate that the posterior vaginal compartment may contribute to the closure mechanism of the proximal urethra in continent women. (Obstet Gynecol 1998;91:229-33.

Journal of Anatomy, 2005

The structure of the striated urethral sphincter, the so-called rhabdosphincter, remains the subject of controversy.

Anatomical Science International, 2019

The male pelvic floor is a complex structure formed by several muscles. The levator ani muscle and the perineal muscles are important components of the pelvic floor. The perineal muscles comprise the external anal sphincter, bulbospongiosus, superficial transverse perineal muscles, and ischiocavernosus. Although the connections of the muscles of the pelvic floor have been reported recently, the anatomical details of each muscle remain unclear. In this study, we examined the male pelvic floor to clarify the connection between the muscles related to function. Fifteen male pelvises were used for microscopic dissection, and three male pelvises were used for histological examination. On the lateral aspect, the perineal muscles were connected to each other. Bundles of the levator ani muscle extended to connect to the perineal muscles. In addition, the extended muscle bundle from the levator ani muscle and the perineal muscles surround the external urethral sphincter. On the medial aspect,...

Neurourology and Urodynamics, 2018

Background and Objectives: The pathophysiology of female stress urinary incontinence (SUI) is far from unraveled. Capturing all aspects of this bothersome condition in one theory remains challenging. The well-known Hammock and Integral theories, both from the early 90's, were successful in explaining a large proportion of the observations made in clinical practice. Nevertheless, some (pre)clinical observations cannot be explained by the current understanding. One of the issues concerns the pressure transmission. Is this process really a passive mechanical action, or is an additional active mechanism responsible for urethral closure? The finding that an increase in urethral pressure sometimes precedes and exceeds the increase in intravesical pressure suggests the latter. This concept has never been incorporated in one of the existing theories describing SUI. This is remarkable as a lot of evidence has been generated in recent years that proves involvement of active components. This review aims to provide an additional theory in which an active reflex closure mechanism of the urethra is incorporated. Methods: Recent as well as older publications from clinical and animal studies are included to support the hypothesis. Results: The smooth muscles of the urethra, the vascular bed, and the estrogeninfluenced urethral mucosa, combined with striated muscle tone, contribute to the intra-urethral pressure. A passive transmission of force to the urethra exists only in the abdominal proximal third of the urethra. In the distal two thirds of the urethra an active closure mechanism is present, dependent on sufficient urethral support in the proper anatomical position. This active closure mechanism is generated by reflex contraction of striated muscles of the urethra and the pelvic floor. Conclusion: Continence is a result of passive as well as active urethral closure mechanisms. The most important factor in female continence seems to be the proper functioning of an active reflex urethral closing mechanism.

Urology, 1984

Journal of Anatomy, 2015

To investigate whether the pig could be considered a suitable model to study lower urinary tract function and dysfunction, the pelvic urethra of 24 slaughtered male pigs were collected, and the associated muscles were macroscopically, histologically and histochemically analyzed. In cross-sections of the urethra, a muscular complex composed of an inner layer of smooth muscle and an outer layer of striated muscle that are not separated by fascial planes was observed. A tunica muscularis, composed of differently oriented smooth muscle bundles, is only evident in the proximal part of the pelvic urethra while, in the remaining part, it contributes to form the prostatic fibromuscular stroma. The striated urethral muscle surrounds the pelvic urethra in a horseshoe-like configuration with a dorsal longitudinal raphe, extending from the bladder neck to the central tendon of perineum. Proximally to the bladder, it is constituted of slow-twitch and fast-twitch myofibers of very small diameter, and embedded in an abundant collagen and elastic fiber net. Moving caudally it is gradually encircled and then completely substituted by larger and compact myofibers, principally presenting circular orientation and fast-twitch histochemical characteristics. So, like in humans, the cranial tract of the muscular system surrounding the pelvic urethra is principally composed of smooth musculature. The striated component cranially may have a role in blocking retrograde ejaculation, while the middle and caudal tracts may facilitate urine and semen flow, and seem especially concerned with the rapid and forceful urethral closure during active continence. Some differences in the morphology and structure between pigs and humans seem due to the different morphology of the 'secondary' sexual organs that develop from the urethral wall and to the different effect of gravity on the mechanics of the urinary system in quadruped and bipedal mammals.