This section of notes introduces the early development of the urinary bladder and the associated ureters and urethra. The early origins of the bladder can be seen at the superior end of the common urogenital sinus, open inferiorly to the cloaca and superiorly to the allantois. Septation of the claoca divides the anterior region to the primordial bladder component from the posterior rectal component.
Cloacal septation animation (lateral view, click to open)
Cloaca septum movie | Cloaca septum large movie
Ultrasound measurement of the bladder size can be used as a diagnostic tool for developmental abnormalities. Bladder exstrophy is a developmental abnormality associated with bladder development. Its origins appear to occur not just by abnormal bladder development, but by a congenital malformation of the ventral wall of abdomen (between umbilicus and pubic symphysis). There may also be other anomolies associated with failure of closure of abdominal wall and bladder (epispadias, pubic bone anomolies). (More? Abnormalities)
Page Links: Introduction | Some Recent Findings | Development Overview | Stage 22 Overview | Abnormalities | Fetal Bladder | Detrusor Muscle | Ureter Development | Urethra Development | Adult Bladder Anatomy | Adult Bladder Histology | Development in Other Species | Computer Activities | Glossary | References
Related Pages: Renal Abnormalities | Urogenital References | Stage 22 | Selected stage 22 Human highpower
Körner I.[Fetal bladder development. A current overview] Urologe A. 2007 Dec;46(12):1643-6. German. PMID: 17999044
"Human fetal bladder development starts in the 9th to 10th week of gestation (LMP). Smooth muscle cell formation is induced by Hedgehog proteins and their signaling in the surrounding mesenchyma of the fetal bladder cavity. Bladder wall thickness increases significantly with advancing gestation, mediated by linear growth patterns irrespective of the related sex. lt is the aim of this article to address new insights into bladder development to enhance our knowledge about normal and pathological conditions that occur when developmental processes are disturbed."
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F4: R kidney and R ureter. Inferior vena cava. L. kidney, L renal hilus and L ureter. R testis with R mesonephric duct (precursor of vas deferens). L testis. Umbilical arteries passing into umbilical cord allantois between them. |
F5: Kidneys. Ureters. Note umbilical arteries and allantois. Also note how R testis and mesonephric structures are attached to parietal peritoneum by a mesogonad. |
F6: Kidneys. Ureters. Note umbilical arteries and allantois. Also note how R testis and mesonephric structures are attached to parietal peritoneum by a mesogonad. |
F7: In F7, (dorsal to R testis and liver) note with the distinct lumen of the mesonephric duct, almost solid column of paramesonephric cells and remnants of mesonephric tubules. "mesogonad". Ureters. Bladder with submucosa and detrusor muscle. Umbilical arteries. Division of aorta. |
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G1: Ureters, Bladder. Umbilical arteries. Testis with remains of mesonephros (dorsal), mesonephric duct and paramesonephric cells. Sigmoid colon and mesocolon. |
G2: Ureters being displaced ventrally, crossing common iliac arteries. Sigmoid colon. Bladder. Mesonephric ducts (lateral) and paramesonephric ducts (smaller, medial) located dorsal to bladder. |
G3: Ureters (cut twice): descending dorsal to bladder and ascending ventrally to enter the bladder at trigone, through the submucosa). Fusion of paramesonephric ducts. Paired mesonephric ducts. Umbilical arteries looping off common iliac arteries. Pubic symphysis. Colon. |
G4: Most caudal part of loop of ureters. Urethra emerging from bladder. Mesonephric ducts. Rectocolic junction. |
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G5: Urethra (in region of future prostate gland - note crescentic shape). Rectum. Rectovesical pouch. Between G4 and G5, each mesonephric duct (vas deferens) has joined the prostatic urethra (caudal to the ureters), thereby increasing the caliber of the latter. |
G6: Penile urethra, emerging inferiorly to the glans penis. Scrotal swellings (appear before testis descends). |
G7: Penile urethra, emerging inferiorly to the glans penis. Scrotal swellings (appear before testis descends). |
Early Fetal Bladder (Week 10, female)
This excerpt shows a sagittal section in the pelvic region showing the location of the developing bladder lying on the anterior body wall. The most obvious feature is the detrusor muscle within the bladder wall.
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Adult female pelvis |
Adult male pelvis |
Adult Bladder cartoon, anterior view (Image: SEER Program)
The bladder can be described anatomically by its 4 layers from outside inward:
The adult detrusor muscle consists of three layers of smooth (involuntary) muscle fibres.
The adult ureter is a thick-walled muscular tube, 25 - 30 cm in length, running from the kidney to the urinary bladder. Anatomically can be described in two parts the abdominal part (pars abdominalis) and pelvic part (pars pelvina). The ureter is composed of three layers: outer fibrous layer (tunica adventitia), muscular layer (tunica muscularis) and mucous layer (tunica mucosa). The muscular layer can also be subdivided into 3 fibre layers: an external longitudinal, a middle circular, and an internal longitudinal. |
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Adult ureter cartoon (cross section) |
It runs downward and medialward in front of the Psoas major and, entering the pelvic cavity, finally opens into the fundus of the bladder. 2 The abdominal part (pars abdominalis) lies behind the peritoneum on the medial part of the Psoas major, and is crossed obliquely by the internal spermatic vessels. It enters the pelvic cavity by crossing either the termination of the common, or the commencement of the external, iliac vessels. 3 At its origin the right ureter is usually covered by the descending part of the duodenum, and in its course downward lies to the right of the inferior vena cava, and is crossed by the right colic and ileocolic vessels, while near the superior aperture of the pelvis it passes behind the lower part of the mesentery and the terminal part of the ileum. The left ureter is crossed by the left colic vessels, and near the superior aperture of the pelvis passes behind the sigmoid colon and its mesentery. 4 The pelvic part (pars pelvina) r
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Urinary bladder wall |
Transitional epithelium ureter |
A key feature of the bladder lining is the specialized transitional epithelium, which is stretched with bladder filling. Some textbooks describe transitional epithelium as a specialised stratified epithelium while others group it with pseudostratified epithelia.
Abnormalites can occur in ureter and bladder development directly, or indirectly associated with either kidney or abdominal wall development, ultrasound can identify the fetal bladder from bout 10 weeks of gestation. See also Urogenital Abnormalities and Genital Abnormalities notes.
Bladder megacystis (ultrasound image source)
Absent or Small Bladder
Bladder Exstrophy - (exstrophy of the bladder) A congenital malformation with bladder open to ventral wall of abdomen (between umbilicus and pubic symphysis) and may have other anomolies associated with failure of closure of abdominal wall and bladder (epispadias, pubic bone anomolies). Incidence of 1 per 30,000 to 50,000 live births. The theory is that the cloacal membrane can persist or overgrow in the lower anterior abdomen, preventing the normal ingrowth of mesoderm. This leads to divergence of the lower abdominal muscular structures and also the genital ridges to fuse caudal to the cloacal membrane.
Megacystis -
Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is an autosomal recessive disorder, rare, usually lethal and the most severe form of functional intestinal obstruction in the newborn. (More? OMIM - MMIHS)
Duplex Ureter -
Urethral Obstruction -
Hypospadias - the most common male penis abnormality (1 in 300) from a failure of male urogenital folds to fuse in various regions and resulting in a proximally displaced urethral meatus. An unknown cause, suggested to involve familial inheritance, low birth weight, assisted reproductive technology, advanced maternal age, paternal subfertility and endocrine-disrupting chemicals. Infants with hypospadias should not undergo circumcision.(More? Genital Abnormalities - Hypospadia).
UNSW Embryology: 2008 Science ANAT2341 - Embryology Lecture - Kidney Development |
Kidney Notes Pages: Abnormalities | References | Stage13/14 | Stage 22 | Selected Human highpower | Genital | Genital Abnormalities | Urogenital Text only page | WWW Links | Molecular | References
Human Embryology Movies: Cloaca septum movie | Cloaca septum large movie | Cervical Nephrotomes, Mesonephros and Metanephros (553Kb) | Development of the Renal Collecting System (298Kb) | Movies
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Rat
Baskin LS, Hayward SW, Young PF, Cunha GR. Ontogeny of the rat bladder: smooth muscle and epithelial differentiation. Acta Anat (Basel). 1996;155(3):163-71. PMID: 8870784
"The sequential expression of smooth muscle and epithelial markers in the rat bladder has been defined. Smooth muscle differentiation, based on cell morphology and immunohistochemical localization of smooth muscle alpha-actin, myosin, vinculin, desmin, vimentin and laminin, begins at 16 days of gestation (birth = 22 days) in the rat bladder. Smooth muscle cell differentiation begins in the periphery of the bladder mesenchyme immediately subadjacent to the serosa and continues toward the urothelium. The cytokeratins 5, 7, 8, 14, 18, and 19 are expressed in the bladder epithelium as a function of developmental age with cytokeratin 7, 8, 18, and 19 being coexpressed at 15 days' gestation followed by cytokeratin 5 at 17 days' gestation and cytokeratin 14 in the newborn bladder."
(More? Rat Development)
Reviews
Search PubMed Apr 2009 "bladder development" 4766 reference articles of which 827 were reviews.
Search PubMed Now: urinary bladder development | embryonic bladder development | fetal bladder development | bladder exstrophy | developmental bladder abnormalities |
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bladder exstrophy - (exstrophy of the bladder) A congenital malformation with bladder open to ventral wall of abdomen (between umbilicus and pubic symphysis) and may have other anomolies associated with failure of closure of abdominal wall and bladder (epispadias, pubic bone anomolies).
blastema - Term used to describe a mass of undifferentiated cells. (More? Wilm's tumour)
diabetes insipidus - The disorder is related to the hormone antidiuretic hormone (ADH, also called vasopressin) its synthesis, secretion, receptors and signaling pathway. In diabetes insipidus there is an excretion of large amounts (up to 30 litres/day) of a watery urine and an unremitting thirst (More? Kidney Abnormalities - Diabetes Insipidus)
gastroschisis - an abdominal wall defect where the anterior abdomen does not close properly and the intestines protrude outside the fetus. (see also omphalocele)
hydronephrosis - (congenital hydronephrosis, Greek, hydro = water) A kidney abnormality due to partial or complete obstruction at the pelvi-ureteric junction. This leads to a grossly dilated renal pelvis causing extensive renal damage before birth.
hyperplastic rests - In kidney development, embryonic blastema cells can persist and proliferate to form a pool of cells, which under either genetic or epigenetic influence can then change to become a neoplastic rest. Normally the majority of nephrogenic rests either regress or become dormant.
mesonephros - The second temporary stage of kidney development (pro-, meso-, meta-). The intermediate mesonephros develops and disappears with the exception of its duct, the mesonephric duct, which will form the male reproductive duct system. In males, the mesonephric tubules go on to form the ducts of the testis. In females, these degenerate. A few mesonephric tubules remain as efferent ductules in the male and vestigial remnants in the female.
mesonephric duct - (= Wollfian duct) An early developing urogenital duct running the length of the embryo that will differentiate and form the male reproductive duct system. In females this duct degenerates (some remnants may remain associated in broad ligament).
metanephros - The adult kidney, third stage of mammalian kidney (pro-, meso-, meta-) development within the intermediate mesoderm.
metanephric cap - In kidney development, the intermediate mesoderm which surrounds the ureteric bud and will develop into nephrons.
Multicystic Kidney - There is no functional kidney tissue present in the kidney and it is replaced by a multilocular cyst. This is non-familial and is produced by atresia of a ureter and is always unilateral.
neoplastic rest - In kidney development, a neoplastic rest can develop under either genetic or epigenetic influence from a hyperplastic rest, originating from an embryonic blastema cell. Normally the majority of nephrogenic rests either regress or become dormant.
nephrogenic rest - A kidney term used to describe the embryonic blastema cells which persist and under either genetic or epigenetic can change to become a neoplastic rest. These neoplastic rests can develop postnatally as a benign form (adenomatous rest) or a malignant Wilm's tumour form. The rests are further characterised by the time of generation leading to different anatomical kidney locations: early intralobar nephrogenic rests (within the renal lobe) and late pelilobar nephrogenic rests (periphery of the renal lobe) (More? Wilm's tumour | Urogenital Abnormalities)
nephron - (Greek, nephros = kidney) The functional unit of the kidney.
nephros - (Greek, nephros = kidney) Term used to describe features associated with the kidney. (pronephros, mesonephros, metanephros, nephric, nephron, nephroblastoma)
omphalocele an abdominal wall defect where abdominal organs (stomach, liver, intestine) are contained in a thin membranous sac outside of the abdomen.
Omphalocele-exstrophy-imperforate anus-spinal defects (OEIS) complex abnormality characterized by a combination of omphalocele, exstrophy of the bladder, an imperforate anus, and spinal defects.
pronephros - (Greek, pro = before) The first temporary stage of kidney development (pro-, meso-, meta-). This forms the kidney of primitive fish and lower vertebrates. Kidney development occurs within the intermediate mesoderm interacting with endoderm. In humans, this very rudimentary kidney forms very early at the level of the neck. It is rapidly replaced by the mesonephros, intermediate stage kidney, differentiating in mesoderm beneath.
proteinuria - The abnormal presence of protein in the urine and an indicator of diesease including diabetic kidney disease (DKD, diabetic nephropathy).
renal - (Latin, renes = kidney) Term used in relation to the kidney and associated structures (renal pelvis, renal artery)
ureter - The two ureters are hollow tubes that link and carries urine from kidney to the bladder. The tubes have a muscular wall lined with transitional epithelium.
urethra - The single muscular tube that links and carries urine from the bladder to the exterior. In humans, the urethral length differs between the sexes (male longer, female shorter).
urinary - Term used to describe all components of the kidney system including the bladder, ureters and urethra.
urine - Term used to describe the liquid waste produced by the kidney, stored in the bladder and excreted from teh body through the urethra.
urorectal septum - (URS) The structure which develops to separate the cloaca (common urogenital sinus) into an anterior urinary part and a posterior rectal part.
Wilms' tumour - A form of kidney/renal cancer (nephroblastoma) named after Dr Max Wilms who first described the tumor. This childhood kidney cancer is caused by the inactivation of a tumour suppressor gene (BRCA2) or Wilms tumor-1 gene (Wt1) and is one of the most common solid tumors of childhood, occurring in 1 in 10,000 children and accounting for 8% of childhood cancers. Wt1 also required at early stages of gonadal development. (More? Kidney Abnormal Development | OMIM - Wilm's tumour | Dr Max Wilms)
Wilms' tumor 1-associating protein - (WTAP) protein expressed in extraembryonic tissues and required for the formation of embryonic mesoderm and endoderm.
Wolffian duct - (= mesonephric duct, preferred terminology), runs from the mesonephros to cloaca, differentiates to form the male vas deferens and in the female regresses. Named after Caspar Friedrich Wolff (1733-1794), a German scientist and early embryology researcher and is said to have established the doctrine of germ layers. (More? Caspar Friedrich Wolff)
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These notes cover development of the urinary bladder.
The bladder is connected internally to the developing kidney by two ureters and connected externally by the urethra. The course and length of this external connection will differ between male and female development.
Genital development has quite different origins and developmental features, but are closely physically associated. A new more specific section of notes has been developed covering male and female gonad and genital development.
Please email Dr Mark Hill if you wish to make a comment about this current project.
