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Genitourinary and trunk
Published in Tor Wo Chiu, Stone’s Plastic Surgery Facts, 2018
During the 6th to 11th weeks, the genital tubercle elongates to form the phallus under the influence of androgens. As the phallus develops, it pulls the urethral folds forwards to form the lateral walls of the urethral groove, which extends only up to the distal part of the phallus – here the epithelial lining is of endodermal origin and is known as the urethral plate (glanular urethra).
Embryology
Published in Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George, The Scientific Basis of Urology, 2010
Prior to the compartmentalization of the cloaca to form the urogenital and anorectal canals between the sixth and seventh weeks, the primitive perineum consists of little more than the cloacal membrane and genital tubercle. Separation of the cloaca into the urogenital canal and anorectal canal is accompanied by subdivision of the cloacal membrane into the urogenital membrane anteriorly and the anal membrane posteriorly. Urogenital folds surround the urogenital membrane, flanked by the labioscrotal folds. From the seventh week onward, the urogenital sinus advances onto the perineum anteriorly and onto the penis as the urethral groove. Ingrowth of the urethral groove creates a solid urethral plate, which subsequently canalizes to form the definitive urethra. Differentiation of the male external genitalia is dependent, first, on the enzymatic conversion of testosterone to dihydrotestosterone and also requires the presence of the appropriate receptors in the target tissues. During the 12th to 14th week, the external genitalia begin to adopt a distinctively male configuration in response to androgenic stimulation (17). Closure of the urethra is complete by around 15 weeks, the terminal portion being formed by ingrowth of ectoderm from the tip of the glans.
Bladder exstrophy: Considerations and management of the newborn patient
Published in Prem Puri, Newborn Surgery, 2017
Peter P. Stuhldreher, John P. Gearhart
The various steps in primary bladder closure are illustrated in Figure 80.5. A strip of mucosa 2 cm wide, extending from the distal trigone to below the verumontanum in the male and to the vaginal orifice in the female, is outlined for prostatic and posterior urethral reconstruction in the male and adequate urethral closure in the female. The male urethral groove length is typically adequate, and no transverse incision of the urethral plate needs to be performed for urethral lengthening. The diagrams in Figure 80.5a–c show marking of the incision with a marking pen from just above the umbilicus down around the junction of bladder and the paraexstrophy skin to the level of the urethral plate. The approximate plane is entered just above the umbilicus, and a plane is established between the rectus fascia and the bladder (Figure 80.5c,d). The umbilical vessels are doubly ligated and incised, allowing them to fall into the pelvis. The peritoneum is taken off the dome of the bladder at this point so that the bladder can be placed deeply into the pelvis at the time of closure. Radical dissection of the peritoneal reflection from the bladder should not be done, as the vasculature to the exstrophied bladder often will occupy this space and can be inadvertently compromised. The plane is continued caudally between the bladder and the rectus fascia until the urogenital diaphragm fibers are encountered bilaterally. The pubis will be encountered at this juncture, and use of a double-pronged skin hook into the bone will accentuate the urogenital diaphragm fibers and help the surgeon radically incise these fibers between the bladder neck, posterior urethra, and pubic bone. Gentle traction on the glans of the penis at this point will show the insertion of the corporal body in the lateral inferior aspect of the pubis. These urogenital fibers are taken down sharply with electrocautery to the pelvic floor in their entirety. If this maneuver is not performed adequately, the posterior urethra and bladder will not be placed deeply into the pelvis and will compromise closure. As well, when the pubic bones are brought together, the posterior vesicourethral unit will be brought anteriorly in an unsatisfactory position for later reconstruction.
c-Fos is upregulated in the genital tubercle of DEHP-induced hypospadiac rats and the prepuce of patients with hypospadias
Published in Systems Biology in Reproductive Medicine, 2021
Han Xiang, Shao Wang, Xiaoyan Kong, Yihang Yu, Lianju shen, Chunlan Long, Xing Liu, Guang-Hui Wei
DEHP, an endocrine disruptor, has attracted attention regarding the onset of hypospadias. In this study, DEHP was used to generate the hypospadiac rodent model. The statistical information of fetal pups, of which the body weight and anogenital distance were measured completely, is shown in the Table 1. The incidence of hypospadias was significantly higher among DEHP-treated male fetuses (42%) than among control fetuses (Table 1). In addition, the anogenital distance (AGD) and anogenital index (AGI) were significantly lower in the DEHP group than in the control group (Table 1), which were consistent with prior work that showed reduced AGD in male infants were associated with increasing urinary concentrations of DEHP metabolites in prenatal maternity (Swan et al. 2015). Other workers have shown that AGD could be a stable anatomical landmark, which reflected the action of androgen in utero(Kita et al. 2016; Dorman et al. 2018). Genital tubercles (GTs) can be observed under scanning electron microscopy (SEM) to monitor the development of external genitalia. In the control group, the penile shaft and glans penis were divided by the coronary sulcus and clearly differentiated. The midline urethral groove was obvious, and the lateral preputial fold completely covered the corpus cavernosum (Figure 1A & C). However, in the DEHP group, the skin folds did not merge completely in the middle, indicating disordered penile foreskin development (Figure 1B & D). Examination of serial histological sections of GTs revealed DEHP-induced hypospadias, characterized by delayed preputial development and abnormalities in urethral seam closure (Figure 2). In the DEHP group, the urethral plate remained from proximal to distal (Figure 2B). However, in the control group, the tubular urethra formed in the proximal region (Figure 2A). These morphological observations verified that DEHP can induce hypospadias in rats with disordered preputial development and delayed urethral plate tubularization.