Talk:Urinary Bladder Development
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Cite this page: Hill, M.A. (2021, April 20) Embryology Urinary Bladder Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Urinary_Bladder_Development
Immunohistochemical expression analysis of the human fetal lower urogenital tract
Shen J, Isaacson D, Cao M, Sinclair A, Cunha GR & Baskin L. (2018). Immunohistochemical expression analysis of the human fetal lower urogenital tract. Differentiation , 103, 100-119. PMID: 30287094 DOI.
Differentiation. 2018 Sep - Oct;103:100-119. doi: 10.1016/j.diff.2018.09.004. Epub 2018 Sep 19.
Shen J1, Isaacson D1, Cao M1, Sinclair A1, Cunha GR1, Baskin L2.
Abstract We have studied the ontogeny of the developing human male and female urogenital tracts from 9 weeks (indifferent stage) to 16 weeks (advanced sex differentiation) of gestation by immunohistochemistry on mid-sagittal sections. Sixteen human fetal pelvises were serial sectioned in the sagittal plane and stained with antibodies to epithelial, muscle, nerve, proliferation and hormone receptor markers. Key findings are: (1) The corpus cavernosum in males and females extends into the glans penis and clitoris, respectively, during the ambisexual stage (9 weeks) and thus appears to be an androgen-independent event. (2) The entire human male (and female) urethra is endodermal in origin based on the presence of FOXA1, KRT 7, uroplakin, and the absence of KRT10 staining. The endoderm of the urethra interfaces with ectodermal epidermis at the site of the urethral meatus. (3) The surface epithelium of the verumontanum is endodermal in origin (FOXA1-positive) with a possible contribution of Pax2-positive epithelial cells implying additional input from the Wolffian duct epithelium. (4) Prostatic ducts arise from the endodermal (FOXA1-positive) urogenital sinus epithelium near the verumontanum. (5) Immunohistochemical staining of mid-sagittal and para-sagittal sections revealed the external anal sphincter, levator ani, bulbospongiosus muscle and the anatomic relationships between these developing skeletal muscles and organs of the male and female reproductive tracts. Future studies of normal human developmental anatomy will lay the foundation for understanding congenital anomalies of the lower urogenital tract. Copyright © 2018 International Society of Differentiation. Published by Elsevier B.V. All rights reserved. KEYWORDS: Human fetal lower urogenital tract; Immunohistochemical; Sagittal sections PMID: 30287094 DOI: 10.1016/j.diff.2018.09.004
Descent of mesonephric duct to the final position of the vas deferens in human embryo and fetus
Anat Cell Biol. 2016 Dec;49(4):231-240. doi: 10.5115/acb.2016.49.4.231. Epub 2016 Dec 31.
Jin ZW1, Abe H2, Hinata N3, Li XW1, Murakami G4, Rodríguez-Vázquez JF5.
Because the ureter arises from the mesonephric or Wolffian duct (WD), the WD opening should migrate inferiorly along the urogenital sinus or future urethra. However, this process of descent has not been evaluated morphometrically in previous studies and we know little about intermediate morphologies for the descent. In the present work, serial sagittal sections of 15 specimens at gestational age 6-12 weeks and serial horizontal sections of 20 specimens at 6-10 weeks were analyzed. Monitoring of horizontal sections showed that, until 9 weeks, a heart-, lozenge- or oval-shape of the initial urogenital sinus remained in the bladder and urethra. Thus, the future bladder and urethra could not be distinguished by the transverse section or plane. The maximum width of the urogenital sinus or bladder at 6-10 weeks was 0.8 mm, although its supero-inferior length reached 5 mm at 10 weeks. During earlier stages, however, the medial shift of the WD was rather evident. Depending on the extent of upward growth of the bladder smooth muscle, the descent of the vas deferens became evident at 10-12 weeks. Development of the urethral rhabdosphincter likely resulted in the differentiation of urogenital sinus into the urethra and bladder before formation of the bladder neck with 3-layered smooth muscles. Development of the prostate followed these morphological changes, later accelerating the further descent of the WD opening. Because of their close topographical relationships, slight anomalies or accidents of the umbilical cord at 10-12 weeks may have a significant effect on normal anatomy. KEYWORDS: Bladder; Human development; Mesonephric duct; Urogenital sinus; Vas deferens; Wolffian duct
PMID 28127497 PMCID: PMC5266102 DOI: 10.5115/acb.2016.49.4.231
Morphology of the fetal bladder during the second trimester: Comparing genders
J Pediatr Urol. 2014 Nov 11. pii: S1477-5131(14)00305-2. doi: 10.1016/j.jpurol.2014.11.006. [Epub ahead of print]
Favorito LA1, Pazos HM2, Costa SF3, Costa WS4, Sampaio FJ5.
OBJECTIVES: The aim of the present study was to determine, by histological and stereological analysis, whether there are between-gender structural differences in the bladder in the second gestational trimester in human fetuses. MATERIAL AND METHODS: Forty bladders, which were obtained from 40 human fetuses (20 males and 20 females) ranging in age from 13 to 23 weeks post-conception (WPC), were studied. The fetuses were macroscopically well preserved, without anomalies of the urinary and genital systems; the cases with syndromes were abandoned. The bladders were dissected and embedded in paraffin, from which 5-μm thick sections were obtained and stained with: Masson's trichrome, to quantify connective and smooth muscle tissue; Weigert's resorcin fuchsin, to observe elastic fibers; picrosirius red with polarization, to observe collagen; and anti-beta III tubulin antibody, to observe the bladder nerves. The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was performed with the Image Pro and Image J programs, using a grid to determine volumetric densities (Vv). Means were statistically compared using simple linear regression and the paired t-test (P < 0.05). RESULTS: The fetuses weighed between 60 and 490 g, and had crown-rump lengths between 9.5 and 20.4 cm. No elastic system fibers were observed in any bladders. Quantitative analysis indicated no differences in the Vv of the smooth muscle cells in the male bladders (26.19-50.16%; mean = 35.66%) compared to the female ones (30.60-45.63%; mean = 38.73%) (P = 0.740) and there were also no differences in the Vv of the connective tissue in females (40.52-60.40%; mean = 50.69%) and males (38.84-70.16%; mean = 57.04%) (P = 0.0506). There were no differences observed in the distribution of the nerves and collagen between the genders. CONCLUSION: The histological analysis of the smooth muscle, collagen, nerves and connective tissue of the developing bladders revealed that there are no gender differences during weeks 13-23 of gestation. Copyright © 2014 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. KEYWORDS: Bladder; Embryology; Histology; Human fetuses; Prostate growth
Identification of potential bladder progenitor cells in the trigone
Dev Biol. 2014 Sep 1;393(1):84-92. doi: 10.1016/j.ydbio.2014.06.018. Epub 2014 Jun 30.
Sun W1, Wilhelmina Aalders T2, Oosterwijk E3.
Urothelial cells are specialized epithelial cells in the bladder that serve as a barrier toward excreted urine. The urothelium consists of superficial cells (most differentiated cells), intermediate cells, and basal cells; the latter have been considered as urothelium progenitor cells. In this study, BrdU or EdU was administrated to pregnant mice during E8-E13 for 2 consecutive days when bladder development occurs. The presence of label retaining cells was investigated in bladders from offspring. In 6 months old mice ~1% of bladder cells retained labeling. Stem cell markers as defined for other tissues (e.g., p63, CD44, CD117, trop2) co-localized or were in close vicinity to label retaining cells, but they were not uniquely limited to these cells. Remarkably, label retaining cells were distributed in all three cell layers (p63+, CK7+, and CK20+) of the urothelium and concentrated in the bladder trigone. This study demonstrates that bladder progenitor cells are present in all cell layers and reside mostly in the trigone. Understanding the geographic location of slow cycling cells provides crucial information for tissue regenerative purposes in the future. Copyright © 2014 Elsevier Inc. All rights reserved. KEYWORDS: Bladder progenitor cells; Bladder trigone; Label retaining cells
Spatio-temporal distribution of Smads and role of Smads/TGF-β/BMP-4 in the regulation of mouse bladder organogenesis
PLoS One. 2013 Apr 19;8(4):e61340. doi: 10.1371/journal.pone.0061340. Print 2013.
Islam SS, Mokhtari RB, Kumar S, Maalouf J, Arab S, Yeger H, Farhat WA. Source Developmental and Stem Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada.
Although Shh, TGF-β and BMP-4 regulate radial patterning of the bladder mesenchyme and smooth muscle differentiation, it is not known what transcription factors, local environmental cues or signaling cascades mediate bladder smooth muscle differentiation. We investigated the expression patterns of signaling mediated by Smad2 and Smad3 in the mouse embryonic bladder from E12.5 to E16.5 by using qRT-PCR, in situ hybridization and antibodies specifically recognizing individual Smad proteins. The role of Smad2 and Smad3 during smooth muscle formation was examined by disrupting the Smad2/3 signaling pathway using TβR1 inhibitor SB-431542 in organ culture system. qRT-PCR results showed that R-Smads, Co-Smad and I-Smads were all expressed during bladder development. RNA ISH for BMP-4 and immunostaining of TGF-β1 showed that BMP-4 and TGF-β1 were expressed in the transitional epithelium, lamina propia and muscularis mucosa. Smad1, Smad5 and Smad8 were first expressed in the bladder epithelium and continued to be expressed in the transitional epithelium, muscularis mesenchyme and lamina propia as the bladder developed. Smad2, Smad3 and Smad4 were first detected in the bladder epithelium and subsequently were expressed in the muscularis mesenchyme and lamina propia. Smad6 and Smad7 showed overlapping expression with R-Smads, which are critical for bladder development. In bladder explants (E12.5 to E16.5) culture, Smad2 and Smad3 were found localized within the nuclei, suggesting critical transcriptional regulatory effects during bladder development. E12.5 to E16.5 bladders were cultured with and without TβR1 inhibitor SB-431542 and assessed by qRT-PCR and immunofluorescence. After three days in culture in SB-431542, α-SMA, Smad2 and Smad3 expressions were significantly decreased compared with controls, however, with no significant changes in the expression of smooth muscle myosin heavy chain (SM-Myh. Based on the Smad expression patterns, we suggest that individual or combinations of Smads may be necessary during mouse bladder organogenesis and may be critical mediators for bladder smooth muscle differentiation.
Bmp7 functions via a polarity mechanism to promote cloacal septation
PLoS One. 2012;7(1):e29372. Epub 2012 Jan 13.
Xu K, Wu X, Shapiro E, Huang H, Zhang L, Hickling D, Deng Y, Lee P, Li J, Lepor H, Grishina I. Source Department of Urology, School of Medicine, New York University, New York, New York, United States of America. Abstract BACKGROUND: During normal development in human and other placental mammals, the embryonic cloacal cavity separates along the axial longitudinal plane to give rise to the urethral system, ventrally, and the rectum, dorsally. Defects in cloacal development are very common and present clinically as a rectourethral fistula in about 1 in 5,000 live human births. Yet, the cellular mechanisms of cloacal septation remain poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: We previously detected Bone morphogenetic protein 7 (Bmp7) expression in the urorectal mesenchyme (URM), and have shown that loss of Bmp7 function results in the arrest of cloacal septation. Here, we present evidence that cloacal partitioning is driven by Bmp7 signaling in the cloacal endoderm. We performed TUNEL and immunofluorescent analysis on cloacal sections from Bmp7 null and control littermate embryos. We found that loss of Bmp7 results in a dramatic decrease in the endoderm survival and a delay in differentiation. We used immunological methods to show that Bmp7 functions by activating the c-Jun N-terminal kinase (JNK) pathway. We carried out confocal and 3D imaging analysis of mitotic chromosome bundles to show that during normal septation cells in the cloacal endoderm divide predominantly in the apical-basal direction. Loss of Bmp7/JNK signaling results in randomization of mitotic angles in the cloacal endoderm. We also conducted immunohistochemical analysis of human fetal sections to show that BMP/phospho-SMAD and JNK pathways function in the human cloacal region similar as in the mouse. CONCLUSION/SIGNIFICANCE: Our results strongly indicate that Bmp7/JNK signaling regulates remodeling of the cloacal endoderm resulting in a topological separation of the urinary and digestive systems. Our study points to the importance of Bmp and JNK signaling in cloacal development and rectourethral malformations.
Endodermal origin of bladder trigone inferred from mesenchymal-epithelial interaction
J Urol. 2010 Jan;183(1):386-91.
Tanaka ST, Ishii K, Demarco RT, Pope JC 4th, Brock JW 3rd, Hayward SW.
Department of Urologic Surgery, Monroe Carell, Jr Children's Hospital at Vanderbilt, Nashville, Tennessee 37232-9820, USA. email@example.com
Abstract PURPOSE: In the classic view of bladder development the trigone originates from the mesoderm derived wolffian ducts while the remainder of the bladder originates from the endoderm derived urogenital sinus. Recent molecular developmental studies have questioned the veracity of this received wisdom, suggesting an endodermal origin for the trigone. To shed further light on this issue we observed mesenchymal-epithelial interactions between trigone epithelium and fetal urogenital sinus mesenchyma to infer the trigonal germ layer of origin.
MATERIALS AND METHODS: Mouse trigone epithelium was recombined with fetal rat urogenital sinus mesenchyma in tissue recombinant grafts that were placed beneath the renal capsule of athymic mouse hosts. Grafts were harvested at 4 weeks. Control grafts with bladder dome and ureteral epithelium were also examined. Tissues were evaluated with hematoxylin and eosin, and Hoechst dye 33258 to confirm cell species origin. Immunohistochemistry was done with androgen receptor, broad spectrum uroplakin, dorsolateral prostate secretions and seminal vesicle secretions to differentiate prostatic and seminal vesicle differentiation.
RESULTS: Grafts of mouse trigone epithelium with fetal rat urogenital sinus mesenchyma yielded epithelial tissue that stained for dorsolateral prostate secretions but not for seminal vesicle secretions. Control grafts of bladder dome epithelium yielded the expected endodermal prostate differentiation. Control grafts of ureteral epithelium yielded the expected mesodermal seminal vesicle differentiation.
CONCLUSIONS: The consistent finding of prostatic epithelium in tissue recombinants of trigone epithelium and fetal urogenital sinus mesenchyma reinforces the hypothesis that the trigone is derived from the endoderm and not from the mesoderm, as commonly accepted.
PMID: 19914648 http://www.ncbi.nlm.nih.gov/pubmed/19914648
The exstrophy-epispadias complex
Orphanet J Rare Dis. 2009 Oct 30;4:23. doi: 10.1186/1750-1172-4-23.
Ebert AK1, Reutter H, Ludwig M, Rösch WH. Author information Abstract Exstrophy-epispadias complex (EEC) represents a spectrum of genitourinary malformations ranging in severity from epispadias (E) to classical bladder exstrophy (CEB) and exstrophy of the cloaca (EC). Depending on severity, EEC may involve the urinary system, musculoskeletal system, pelvis, pelvic floor, abdominal wall, genitalia, and sometimes the spine and anus. Prevalence at birth for the whole spectrum is reported at 1/10,000, ranging from 1/30,000 for CEB to 1/200,000 for EC, with an overall greater proportion of affected males. EEC is characterized by a visible defect of the lower abdominal wall, either with an evaginated bladder plate (CEB), or with an open urethral plate in males or a cleft in females (E). In CE, two exstrophied hemibladders, as well as omphalocele, an imperforate anus and spinal defects, can be seen after birth. EEC results from mechanical disruption or enlargement of the cloacal membrane; the timing of the rupture determines the severity of the malformation. The underlying cause remains unknown: both genetic and environmental factors are likely to play a role in the etiology of EEC. Diagnosis at birth is made on the basis of the clinical presentation but EEC may be detected prenatally by ultrasound from repeated non-visualization of a normally filled fetal bladder. Counseling should be provided to parents but, due to a favorable outcome, termination of the pregnancy is no longer recommended. Management is primarily surgical, with the main aims of obtaining secure abdominal wall closure, achieving urinary continence with preservation of renal function, and, finally, adequate cosmetic and functional genital reconstruction. Several methods for bladder reconstruction with creation of an outlet resistance during the newborn period are favored worldwide. Removal of the bladder template with complete urinary diversion to a rectal reservoir can be an alternative. After reconstructive surgery of the bladder, continence rates of about 80% are expected during childhood. Additional surgery might be needed to optimize bladder storage and emptying function. In cases of final reconstruction failure, urinary diversion should be undertaken. In puberty, genital and reproductive function are important issues. Psychosocial and psychosexual outcome depend on long-term multidisciplinary care to facilitate an adequate quality of life. PMID: 19878548 PMCID: PMC2777855 DOI: 10.1186/1750-1172-4-23
The development of the bladder trigone, the center of the anti-reflux mechanism
Development. 2007 Oct;134(20):3763-9. Epub 2007 Sep 19.
Viana R1, Batourina E, Huang H, Dressler GR, Kobayashi A, Behringer RR, Shapiro E, Hensle T, Lambert S, Mendelsohn C.
The urinary tract is an outflow system that conducts urine from the kidneys to the bladder via the ureters that propel urine to the bladder via peristalsis. Once in the bladder, the ureteral valve, a mechanism that is not well understood, prevents backflow of urine to the kidney that can cause severe damage and induce end-stage renal disease. The upper and lower urinary tract compartments form independently, connecting at mid-gestation when the ureters move from their primary insertion site in the Wolffian ducts to the trigone, a muscular structure comprising the bladder floor just above the urethra. Precise connections between the ureters and the trigone are crucial for proper function of the ureteral valve mechanism; however, the developmental events underlying these connections and trigone formation are not well understood. According to established models, the trigone develops independently of the bladder, from the ureters, Wolffian ducts or a combination of both; however, these models have not been tested experimentally. Using the Cre-lox recombination system in lineage studies in mice, we find, unexpectedly, that the trigone is formed mostly from bladder smooth muscle with a more minor contribution from the ureter, and that trigone formation depends at least in part on intercalation of ureteral and bladder muscle. These studies suggest that urinary tract development occurs differently than previously thought, providing new insights into the mechanisms underlying normal and abnormal development. PMID 17881488
Is the male dog comparable to human? A histological study of the muscle systems of the lower urinary tract
Anat Histol Embryol. 2002 Aug;31(4):198-205.
Stolzenburg JU, Schwalenberg T, Do M, Dorschner W, Salomon FV, Jurina K, Neuhaus J.
Department of Urology, University of Leipzig, Stephanstr. 11, Germany. firstname.lastname@example.org Abstract Because of their superficial anatomical resemblance, the male dog seems to be suitable for studying the physiologic and pathological alterations of the bladder neck of human males. The present study was carried out to compare and contrast the muscular anatomy of the male dog lower urinary tract with that of humans. The complete lower urinary tract, including the surrounding organs (bulb of penis, prostate, rectum and musculature of the pelvic floor) were removed from adult and newborn male dogs and histologically processed using serial section technique. Based on our own histological investigations, three-dimensional (3D)-models of the anatomy of the lower urinary tract were constructed to depict the corresponding structures and the differences between the species. The results of this study confirm that the lower urinary tract of the male dog bears some anatomical resemblance (musculus detrusor vesicae, prostate, prostatic and membranous urethra) to man. As with human males, the two parts of the musculus sphincter urethrae (glaber and transversostriatus) are evident in the canine bladder neck. Nevertheless, considerable differences in formation of individual muscles should be noted. In male dogs, no separate anatomic entity can be identified as vesical or internal sphincter. The individual course of the ventral and lateral longitudinal musculature and of the circularly arranged smooth musculature of the urethra is different to that of humans. Differences in the anatomy of individual muscles of the bladder neck in the male dog and man suggest that physiological interpretations of urethral functions obtained in one species cannot be attributed without qualification to the other.
Gray's Anatomy - The Urinary Bladder
(Vesica Urinaria; Bladder)
The urinary bladder (Fig. 1135) is a musculomembranous sac which acts as a reservoir for the urine; and as its size, position, and relations vary according to the amount of fluid it contains, it is necessary to study it as it appears (a) when empty, and (b) when distended.) In both conditions the position of the bladder varies with the condition of the rectum, being pushed upward and forward when the rectum is distended.
The Empty Bladder
When hardened in situ, the empty bladder has the form of a flattened tetrahedron, with its vertex tilted forward. It presents a fundus, a vertex, a superior and an inferior surface. The fundus (Fig. 1152) is triangular in shape, and is directed downward and backward toward the rectum, from which it is separated by the rectovesical fascia, the vesiculæ seminales, and the terminal portions of the ductus deferentes. The vertex is directed forward toward the upper part of the symphysis pubis, and from it the middle umbilical ligament is continued upward on the back of the anterior abdominal wall to the umbilicus. The peritoneum is carried by it from the vertex of the bladder on to the abdominal wall to form the middle umbilical fold. The superior surface is triangular, bounded on either side by a lateral border which separates it from the inferior surface, and behind by a posterior border, represented by a line joining the two ureters, which intervenes between it and the fundus. The lateral borders extend from the ureters to the vertex, and from them the peritoneum is carried to the walls of the pelvis. On either side of the bladder the peritoneum shows a depression, named the paravesical fossa (Fig. 1037). The superior surface is directed upward, is covered by peritoneum, and is in relation with the sigmoid colon and some of the coils of the small intestine. When the bladder is empty and firmly contracted, this surface is convex and the lateral and posterior borders are rounded; whereas if the bladder be relaxed it is concave, and the interior of the viscus, as seen in a median sagittal section, presents the appearance of a V-shaped slit with a shorter posterior and a longer anterior limb—the apex of the V corresponding with the internal orifice of the urethra. The inferior surface is directed downward and is uncovered by peritoneum. It may be divided into a posterior or prostatic area and two infero-lateral surfaces. The prostatic area is somewhat triangular: it rests upon and is in direct continuity with the base of the prostate; and from it the urethra emerges. The infero-lateral portions of the inferior surface are directed downward and lateralward: in front, they are separated from the symphysis pubis by a mass of fatty tissue which is named the retropubic pad; behind, they are in contact with the fascia which covers the Levatores ani and Obturatores interni.
FIG. 1135– Median sagitta section of male pelvis. (See enlarged image)
When the bladder is empty it is placed entirely within the pelvis, below the level of the obliterated hypogastric arteries, and below the level of those portions of the ductus deferentes which are in contact with the lateral wall of the pelvis; after they cross the ureters the ductus deferentes come into contact with the fundus of the bladder. As the viscus fills, its fundus, being more or less fixed, is only slightly depressed; while its superior surface gradually rises into the abdominal cavity, carrying with it its peritoneal covering, and at the same time rounding off the posterior and lateral borders.
The Distended Bladder.—When the bladder is moderately full it contains about 0.5 liter and assumes an oval form; the long diameter of the oval measures about 12 cm. and is directed upward and forward. In this condition it presents a postero-superior, an antero-inferior, and two lateral surfaces, a fundus and a summit. The postero-superior surface is directed upward and backward, and is covered by peritoneum: behind, it is separated from the rectum by the rectovesical excavation, while its anterior part is in contact with the coils of the small intestine. The antero-inferior surface is devoid of peritoneum, and rests, below, against the pubic bones, above which it is in contact with the back of the anterior abdominal wall. The lower parts of the lateral surfaces are destitute of peritoneum, and are in contact with the lateral walls of the pelvis. The line of peritoneal reflection from the lateral surface is raised to the level of the obliterated hypogastric artery. The fundus undergoes little alteration in position, being only slightly lowered. It exhibits, however, a narrow triangular area, which is separated from the rectum merely by the rectovesical fascia. This area is bounded below by the prostate, above by the rectovesical fold of peritoneum, and laterally by the ductus deferentes. The ductus deferentes frequently come in contact with each other above the prostate, and under such circumstances the lower part of the triangular area is obliterated. The line of reflection of the peritoneum from the rectum to the bladder appears to undergo little or no change when the latter is distended; it is situated about 10 cm. from the anus. The summit is directed upward and forward above the point of attachment of the middle umbilical ligament, and hence the peritoneum which follows the ligament, forms a pouch of varying depth between the summit of the bladder, and the anterior abdominal wall.
FIG. 1136– Male pelvic organs seen from right side. Bladder and rectum distended; relations of peritoneum to the bladder and rectum shown in blue. The arrow points to the rectovesical pouch. (See enlarged image)
The Bladder in the Child
(Figs. 1137, 1138).—In the newborn child the internal urethral orifice is at the level of the upper border of the symphysis pubis; the bladder therefore lies relatively at a much higher level in the infant than in the adult. Its anterior surface “is in contact with about the lower two-thirds of that part of the abdominal wall which lies between the symphysis pubis and the umbilicus” (Symington 177). Its fundus is clothed with peritoneum as far as the level of the internal orifice of the urethra. Although the bladder of the infant is usually described as an abdominal organ, Symington has pointed out that only about one-half of it lies above the plane of the superior aperture of the pelvis. Disse maintains that the internal urethral orifice sinks rapidly during the first years, and then more slowly until the ninth year, after which it remains sta when it again slowly descends and reaches its adult position.
FIG. 1137– Sagittal section through the pelvis of a newly born male child. (See enlarged image)
FIG. 1138– Sagittal section through the pelvis of a newly born female child. (See enlarged image)
The Female Bladder (Fig. 1139).—In the female, the bladder is in relation behind with the uterus and the upper part of the vagina. It is separated from the anterior surface of the body of the uterus by the vesicouterine excavation, but below the level of this excavation it is connected to the front of the cervix uteri and the upper part of the anterior wall of the vagina by areolar tissue. When the bladder is empty the uterus rests upon its superior surface. The female bladder is said by some to be more capacious than that of the male, but probably the opposite is the case.
FIG. 1139– Median sagittal section of female pelvis. (See enlarged image)
The bladder is connected to the pelvic wall by the fascia endopelvina. In front this fascial attachment is strengthened by a few muscular fibers, the Pubovesicales, which extend from the back of the pubic bones to the front of the bladder; behind, other muscular fibers run from the fundus of the bladder to the sides of the rectum, in the sacrogenital folds, and constitute the Rectovesicales.
The vertex of the bladder is joined to the umbilicus by the remains of the urachus which forms the middle umbilical ligament, a fibromuscular cord, broad at its attachment to the bladder but narrowing as it ascends.
From the superior surface of the bladder the peritoneum is carried off in a series of folds which are sometimes termed the false ligaments of the bladder. Anteriorly there are three folds: the middle umbilical fold on the middle umbilical ligament, and two lateral umbilical folds on the obliterated hypogastric arteries. The reflections of the peritoneum on to the side walls of the pelvis form the lateral false ligaments, while the sacrogenital folds constitute posterior false ligaments.
Interior of the Bladder
(Fig. 1140).—The mucous membrane lining the bladder is, over the greater part of the viscus, loosely attached to the muscular coat, and appears wrinkled or folded when the bladder is contracted: in the distended condition of the bladder the folds are effaced. Over a small triangular area, termed the trigonum vesicæ, immediately above and behind the internal orifice of the urethra, the mucous membrane is firmly bound to the muscular coat, and is always smooth. The anterior angle of the trigonum vesicæ is formed by the internal orifice of the urethra: its postero-lateral angles by the orifices of the ureters. Stretching behind the latter openings is a slightly curved ridge, the torus uretericus, forming the base of the trigone and produced by an underlying bundle of non-striped muscular fibers. The lateral parts of this ridge extend beyond the openings of the ureters, and are named the plicæ uretericæ; they are produced by the terminal portions of the ureters as they traverse obliquely the bladder wall. When the bladder is illuminated the torus uretericus appears as a pale band and forms an important guide during the operation of introducing a catheter into the ureter.
FIG. 1140– The interior of bladder. (See enlarged image)
The orifices of the ureters are placed at the postero-lateral angles of the trigonum vesicæ, and are usually slit-like in form. In the contracted bladder they are about 2.5 cm. apart and about the same distance from the internal urethral orifice; in the distended viscus these measurements may be increased to about 5 cm.
The internal urethral orifice is placed at the apex of the trigonum vesicæ, in the most dependent part of the bladder, and is usually somewhat crescentic in form; the mucous membrane immediately behind it presents a slight elevation, the uvula vesicæ, caused by the middle lobe of the prostate.
(Fig. 1141).—The bladder is composed of the four coats: serous, muscular, submucous, and mucous coats. The serous coat (tunica serosa) is a partial one, and is derived from the peritoneum. It invests the superior surface and the upper parts of the lateral surfaces, and is reflected from these on to the abdominal and pelvic walls.
The muscular coat (tunica muscularis) consists of three layers of unstriped muscular fibers: an external layer, composed of fibers having for the most part a longitudinal arrangement; a middle layer, in which the fibers are arranged, more or less, in a circular manner; and an internal layer, in which the fibers have a general longitudinal arrangement.
The fibers of the external layer arise from the posterior surface of the body of the pubis in both sexes (musculi pubovesicales), and in the male from the adjacent part of the prostate and its capsule. They pass, in a more or less longitudinal manner, up the inferior surface of the bladder, over its vertex, and then descend along its fundus to become attached to the prostate in the male, and to the front of the vagina in the female. At the sides of the bladder the fibers are arranged obliquely and intersect one another. This layer has been named the Detrusor urinæ muscle. 16
The fibers of the middle circular layer are very thinly and irregularly scattered on the body of the organ, and, although to some extent placed transversely to the long axis of the bladder, are for the most part arranged obliquely. Toward the lower part of the bladder, around the internal urethral orifice, they are disposed in a thick circular layer, forming the Sphincter vesicæ, which is continuous with the muscular fibers of the prostate.
The internal longitudinal layer is thin, and its fasciculi have a reticular arrangement, but with a tendency to assume for the most part a longitudinal direction. Two bands of oblique fibers, originating behind the orifices of the ureters, converge to the back part of the prostate, and are inserted by means of a fibrous process, into the middle lobe of that organ. They are the muscles of the ureters, described by Sir C. Bell, who supposed that during the contraction of the bladder they serve to retain the oblique direction of the ureters, and so prevent the reflux of the urine into them.
The submucous coat (tela submucosa) consists of a layer of areolar tissue, connecting together the muscular and mucous coats, and intimately united to the latter.
FIG. 1141– Vertical section of bladder wall. (See enlarged image)
The mucous coat (tunica mucosa) is thin, smooth, and of a pale rose color. It is continuous above through the ureters with the lining membrane of the renal tubules, and below with that of the urethra. The loose texture of the submucous layer allows the mucous coat to be thrown into folds or rugæ when the bladder is empty. Over the trigonum vesicæ the mucous membrane is closely attached to the muscular coat, and is not thrown into folds, but is smooth and flat. The epithelium covering it is of the transitional variety, consisting of a superficial layer of polyhedral flattened cells, each with one, two, or three nuclei; beneath these is a stratum of large club-shaped cells, with their narrow extremities directed downward and wedged in between smaller spindle-shaped cells, containing oval nuclei (Fig. 1141). The epithelium varies according as the bladder is distended or contracted. In the former condition the superficial cells are flattened and those of the other layers are shortened; in the latter they present the appearance described above. There are no true glands in the mucous membrane of the bladder, though certain mucous follicles which exist, especially near the neck of the bladder, have been regarded as such.
Vessels and Nerves
The arteries supplying the bladder are the superior, middle, and inferior vesical, derived from the anterior trunk of the hypogastric. The obturator and inferior gluteal arteries also supply small visceral branches to the bladder, and in the female additional branches are derived from the uterine and vaginal arteries.
The veins form a complicated plexus on the inferior surface, and fundus near the prostate, and end in the hypogastric veins.
The lymphatics are described on page 712.
The nerves of the bladder are (1) fine medullated fibers from the third and fourth sacral nerves, and (2) non-medullated fibers from the hypogastric plexus. They are connected with ganglia in the outer and submucous coats and are finally distributed, all as non-medullated fibers, to the muscular layer and epithelial lining of the viscus.
A defect of development, in which the bladder is implicated, is known under the name of extroversion of the bladder. In this condition the lower part of the abdominal wall and the anterior wall of the bladder are wanting, so that the fundus of the bladder presents on the abdominal surface, and is pushed forward by the pressure of the viscera within the abdomen, forming a red vascular tumor on which the openings of the ureters are visible. The penis, except the glans, is rudimentary and is cleft on its dorsal surface, exposing the floor of the urethra, a condition known as epispadias. The pelvic bones are also arrested in development.
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