Disposition of the striated urethral sphincter and its relation to the prostate in human fetuses (original) (raw)
Related papers
The development of the external urethral sphincter in humans
BJU International, 2001
Objective To assess the hypothesis that during fetal development, the external urethral sphincter changes from a concentric sphincter of undifferentiated muscle fibres to a transient ring of striated muscle which regresses caudo‐cranially in the posterior urethra during the first year of life, when the sphincter assumes its omega‐shaped configuration.Materials and methods The anatomy and development of the external urinary sphincter was assessed in human males and females during fetal life. Plastic‐embedded sections (transverse, sagittal and frontal planes; 300–700 µm) of the pelvis of 31 females and 31 males (9 weeks of gestation to newborn) were stained with azure II/methylene blue/basic fuchsin and viewed at × 4–80. The sections of interest were taken from the bladder neck to the perineum. The sections of the membranous urethra were reconstructed three‐dimensionally using a computer program.Results In both male and female an omega‐shaped external sphincter was apparent in all spe...
Bju Int, 2002
Objective To assess the hypothesis that during fetal development, the external urethral sphincter changes from a concentric sphincter of undifferentiated muscle fibres to a transient ring of striated muscle which regresses caudo-cranially in the posterior urethra during the first year of life, when the sphincter assumes its omega-shaped configuration. Materials and methods The anatomy and development of the external urinary sphincter was assessed in human males and females during fetal life. Plastic-embedded sections (transverse, sagittal and frontal planes; 300-700 mm) of the pelvis of 31 females and 31 males (9 weeks of gestation to newborn) were stained with azure II/methylene blue/basic fuchsin and viewed at r 4-80. The sections of interest were taken from the bladder neck to the perineum. The sections of the membranous urethra were reconstructed three-dimensionally using a computer program. Results In both male and female an omega-shaped external sphincter was apparent in all specimens at >10 weeks of gestation. In the early fetal period (ninth week), there was undifferentiated mesench-yme; in this period the mesenchyme was more dense in the anterior part and loose in the posterior part of the urethra. In females, there was a close connection between the urethra and the anterior wall of the vagina. Conclusion The omega-shaped configuration of the external urethral sphincter was recognisable from 10 weeks of gestation in both sexes. There was no suggestion of a change from a cylindrical to an omegashaped sphincter in the fetal period to birth. Also, a transient 'tail' posterior to the sphincter was not apparent. The rectovesical septum was well developed in neonates. There is no reason to assume that the development of the septum leads to an apoptosis of muscle cells in the posterior part of the external sphincter in males after birth. The anatomical development of the external sphincter does not explain transient outlet obstruction during fetal life. The function of the muscle may change during development because of neuronal maturation.
Anatomy & cell biology, 2012
To investigate why the development of a completely circular striated sphincter is so rare, we examined histological sections of 11 female and 11 male mid-term human fetuses. In male fetuses, the striated muscle initially extended in the frontal, rather than in the horizontal plane. However, a knee-like portion was absent in the female fetal urethra because, on the inferior side of the vaginal end, a wide groove for the future vestibule opened inferiorly. Accordingly, it was difficult for the developing striated muscle to surround the groove, even though there was not a great difference in width or thickness between the female vestibule and the male urethra. The development of a completely circular striated sphincter seems to be impossible in females because of interruption of the frontal plane by the groove-like vestibule. However, we cannot rule out the possibility that before descent of the vagina, the urethral striated muscle extends posteriorly.
European Urology, 2005
Objectives: The precise location, origin and nature of nerve fibers innervating the urethral sphincter have not been clearly established. Classical anatomical studies based on cadaver dissections have provided conflicting results concerning the location of pudendal and autonomic nerve fibers. This study was designed to identify nerve fibers innervating the urethral sphincter and to provide a three-dimensional representation of their tissue relations in the female human fetus. Materials and methods: Histology and immunohistochemistry (Masson's Trichromic, Luxol Fast Blue, Protein S 100 immunostaining and smooth fiber actin immunostaining) were performed on the external urethral sphincter of ten female fetuses with a crown-rump length of 112 to 340 mm. Three-dimensional reconstructions of the urethral structure and innervation were obtained from serial sections using Surf Driver 3.5.3 software (David Moody and Scott Lozanoff). Results: Three-dimensional reconstructions of the same sections with different stains demonstrated the precise structure of the muscle layers (smooth and striated muscle fibers) and nerve fibers (myelinated and unmyelinated) and their relations with the urethra and vaginal wall. The proximal third consisted of a circular smooth muscle sphincter, the middle third consisted of two circular layers of smooth and striated muscle fibers and the distal third consisted of a circular layer of smooth muscle fibers surrounded by an omega-shaped layer of striated muscle fibers.
Smooth and Striated Muscle Development in the Intrinsic Urethral Sphincter
The Journal of Urology, 1997
Purpose: The intrinsic urethral sphincter is composed of adjacent striated a n d smooth muscle. W e studied the sequential expression of smooth a n d striated muscle proteins to gain insight into the ontogeny of intrinsic sphincter development. Materials and Methods: The intrinsic urethral sphincters of timed Fischer 344 rat embryos at 14, 16 a n d 18 days of gestation, neonates on postnatal day 1 a n d a d u l t animals were examined. Serial sections of the urethra a n d adjacent levator ani muscles were studied histologically with hematoxylin a n d eosin, anti-a-smooth muscle actin, anti-a-sarcomeric actin a n d antistriated muscle myosin heavy chain antibodies. Results: The intrinsic urethral sphincter w a s identified within the periurethral mesenchyma as early as day 14 of gestation. Although striated myotubules were identified within the urethra b y hematoxylin a n d eosin staining starting on postnatal day 1, striated muscle myosin heavy chain protein w a s absent in the embryonic a n d neonatal development of the sphincter, a n d it was expressed only in the mature myotubule of adults. a-Smooth muscle actin was expressed throughout the urethral sphincter of embryonic a n d neonatal animals. In adults a-smooth muscle actin w a s confined to the smooth muscle component of the urethra. Co-expression of a-smooth and a-sarcomeric muscle actin by the striated sphincter myotubule w a s noted only in neonates. Conclusions: Development of the intrinsic urethral sphincter is characterized by sequential expression of well characterized muscle marker proteins. The co-expression of smooth a n d striated muscle markers by developing sphincter myotubule suggests the possibility that transdifferentiation of smooth t o striated muscle occurs in the developing genitourinary tract.
Embryology of the distal urethra and external genitals
Seminars in pediatric surgery, 2011
Faulty ventral openings of the urethra constitute a broad spectrum of malformations that are subsumed under the term "hypospadia." The normal development of the urethra and the genitals critically depends on the following events: (a) formation of the external genitalia, (b) fate of the cloacal membrane, and (c) formation of the distal urethra. The purpose of this study was to demonstrate these events using microsurgical techniques and scanning electron microscopy in staged rat embryos.
British Journal of Plastic Surgery, 2004
It is generally agreed that the urethral plate disintegrates, resulting in the urethral groove. This is subsequently transformed into the urethra by fusion of the urethral folds, which flank its sides. Recently, the existence of such a groove and folds has been denied and this challenge to the long accepted existence of such folds is significant since hypospadias is considered to result from failure of their fusion. The present studies indicate that mesodermal fold formation and its subsequent subepithelial fusion across the midline plays an essential role in urethral tube formation. Disruption of this process readily explains common congenital abnormalities of the urethra.
Urology, 2002
Objectives. To demonstrate that the bladder plate and bladder neck in classic bladder exstrophy are laying on smooth muscle fibers that extend laterally to the pubic bones. Methods. We compared a male fetus of 28 weeks' gestational age with classic bladder exstrophy with a normal fetus of the same age. The specimens were divided into two parts by a midsagittal section, from the bladder neck to the membranous urethra. Thin transverse slices were also obtained on one part, and longitudinal slices on the other part. Results. The smooth musculature of the bladder is normally differentiated cytologically and extends laterally to the bony structures of the pelvis. The musculature of the bladder neck and urethra are normally present compared with the control. Conclusions. The results of this study demonstrate the musculoskeletal organization of the urogenital system in classic bladder exstrophy. They also indicate that these structures should be clearly individualized and repaired in the reconstruction of classic bladder exstrophy. UROLOGY 60: 142-146, 2002. © 2002,