Renal System Development

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The paired adult kidneys consist of a functional unit called the "nephron", that filters blood, excretes waste, reabsorbs water (and other compounds) and has endocrine functions. Each adult human kidney typically contains about 750,000 nephrons, though the total number can vary significantly from as few as 250,000 to as many as 2,000,000.[1][2]

In the embryo, nephron development, nephrogenesis, occurs through several stages involving classical epithelial/mesenchyme type of interactions. Nephrogenesis continues into the late fetal period (GA week 34–35) and while the fetal kidney does produce urine, not until after birth does the glomerular filtration rate (GFR) increases rapidly due to a postnatal drop in kidney vascular resistance and an increase in renal blood flow.

The urinary system is developmentally and anatomically associated with genital development, often described as the "urogenital system". (More? genital)

Renal Links: renal | Lecture - Renal | Lecture Movie | urinary bladder | Stage 13 | Stage 22 | Fetal | Renal Movies | Stage 22 Movie | renal histology | renal abnormalities | Molecular | Category:Renal
Historic Embryology - Renal  
1905 Uriniferous Tubule Development | 1907 Urogenital images | 1911 Cloaca | 1921 Urogenital Development | 1915 Renal Artery | 1917 Urogenital System | 1925 Horseshoe Kidney | 1926 Embryo 22 Somites | 1930 Mesonephros 10 to 12 weeks | 1931 Horseshoe Kidney | 1932 Renal Absence | 1939 Ureteric Bud Agenesis | 1943 Renal Position

Some Recent Findings

Human renal branching development between week 5 to 8
Human renal branching development between week 5 to 8.[3]
Cloacal septation model[4]
  • A practical guide to the stereological assessment of glomerular number, size, and cellular composition[5] "The evaluation of a range of measures in the kidneys, such as developmental stage, rate and success, injury, and disease processes, relies on obtaining information on the three-dimensional structure of the renal corpuscles, and in particular the glomerular capillary tufts. To do this in the most accurate, comprehensive, and unbiased manner depends on a knowledge of stereological methods. In this article, we provide a practical guide for researchers on how to quantitate a number of structures in the kidneys, including the estimation of total glomerular number, glomerular capillary length and filtration surface area, and the cellular composition of individual glomeruli. Guidance is also provided on how to apply these methods to kidneys at different sizes and levels of maturity."
  • Branching morphogenesis of the urinary collecting system in the human embryonic metanephros[3] "An elaborate system of ducts collects urine from all nephrons, and this structure is known as the urinary collecting system (UCS). This study focused on how the UCS is formed during human embryogenesis. Fifty human embryos between the Carnegie stage 14 and 23 were selected from the Kyoto Collection at the Congenital Anomaly Research Center of Kyoto University, Japan. Metanephroses, including the UCS, were segmented on serial digital virtual histological sections. Three-dimensional images were computationally reconstructed for morphological and quantitative analyses. A CS timeline was plotted. It consisted of the 3-D structural morphogenesis of UCS and quantification of the total amount of end-branching, average and maximum numbers of generations, deviation in the metanephros, differentiation of the urothelial epithelium in the renal pelvis, and timing of the rapid expansion of the renal pelvis. The first UCS branching generation occurred by 16. The average branching generation reached a maximum of 8.74 ± 1.60 and was already the twelfth in 23. ...Differentiation may have continued up until the tenth generation to allow for renal pelvis expansion. The branching speed was not uniform. There were significantly more branching generations in the polar- than in the interpolar regions (P < 0.05). Branching speed reflects the growth orientation required to form the metanephros. Further study will be necessary to understand the renal pelvis expansion mechanism in 23."
  • Spatiotemporal heterogeneity and patterning of developing renal blood vessels[6] "Here, we examine the developing kidney vasculature to assess its 3-dimensional structure and transcriptional heterogeneity. First, we observe that endothelial cells (ECs) grow coordinately with the kidney bud as early as E10.5, and begin to show signs of specification by E13.5 when the first arteries can be identified. We then focus on how ECs pattern and remodel with respect to the developing nephron and collecting duct epithelia. ECs circumscribe nephron progenitor populations at the distal tips of the ureteric bud (UB) tree and form stereotyped cruciform structures around each tip. Beginning at the renal vesicle (RV) stage, ECs form a continuous plexus around developing nephrons. The endothelial plexus envelops and elaborates with the maturing nephron, becoming preferentially enriched along the early distal tubule."
More recent papers  
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More? References | Discussion Page | Journal Searches | 2019 References | 2020 References

Search term: Renal Embryology | Renal Development | Nephrogenesis | Intermediate Mesoderm | Ureter Development | Urethera Development | Renal Pelvis Development | Urinary Bladder Development

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Conserved and Divergent Features of Human and Mouse Kidney Organogenesis[7] "Human kidney function is underpinned by approximately 1,000,000 nephrons, although the number varies substantially, and low nephron number is linked to disease. Human kidney development initiates around 4 weeks of gestation and ends around 34-37 weeks of gestation. Over this period, a reiterative inductive process establishes the nephron complement. Studies have provided insightful anatomic descriptions of human kidney development, but the limited histologic views are not readily accessible to a broad audience. In this first paper in a series providing comprehensive insight into human kidney formation, we examined human kidney development in 135 anonymously donated human kidney specimens. We documented kidney development at a macroscopic and cellular level through histologic analysis, RNA in situ hybridization, immunofluorescence studies, and transcriptional profiling, contrasting human development (4-23 weeks) with mouse development at selected stages (embryonic day E15.5 and postnatal day 2). The high-resolution histologic interactive atlas of human kidney organogenesis generated can be viewed at the GUDMAP database ( together with three-dimensional reconstructions of key components of the data herein. At the anatomic level, human and mouse kidney development differ in timing, scale, and global features such as lobe formation and progenitor niche organization. The data also highlight differences in molecular and cellular features, including the expression and cellular distribution of anchor gene markers used to identify key cell types in mouse kidney studies." mouse
  • Reciprocal Spatiotemporally Controlled apoptosis Regulates Wolffian Duct Cloaca Fusion[8] "The epithelial Wolffian duct (WD) inserts into the cloaca (primitive bladder) before metanephric kidney development, thereby establishing the initial plumbing for eventual joining of the ureters and bladder. Defects in this process cause common anomalies in the spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). However, developmental, cellular, and molecular mechanisms of WD-cloaca fusion are poorly understood. Through systematic analysis of early WD tip development in mice, we discovered that a novel process of spatiotemporally regulated apoptosis in WD and cloaca was necessary for WD-cloaca fusion."
  • zebrafish Pronephros Development[9] "The pronephros is the first kidney type to form in vertebrate embryos. The first step of pronephrogenesis in the zebrafish is the formation of the intermediate mesoderm during gastrulation, which occurs in response to secreted morphogens such as BMPs and Nodals. Patterning of the intermediate mesoderm into proximal and distal cell fates is induced by retinoic acid signaling with downstream transcription factors including wt1a, pax2a, pax8, hnf1b, sim1a, mecom, and irx3b. In the anterior intermediate mesoderm, progenitors of the glomerular blood filter migrate and fuse at the midline and recruit a blood supply. More posteriorly localized tubule progenitors undergo epithelialization and fuse with the cloaca. The Notch signaling pathway regulates the formation of multi-ciliated cells in the tubules and these cells help propel the filtrate to the cloaca. The lumenal sheer stress caused by flow down the tubule activates anterior collective migration of the proximal tubules and induces stretching and proliferation of the more distal segments. Ultimately these processes create a simple two-nephron kidney that is capable of reabsorbing and secreting solutes and expelling excess water-processes that are critical to the homeostasis of the body fluids. The zebrafish pronephric kidney provides a simple, yet powerful, model system to better understand the conserved molecular and cellular progresses that drive nephron formation, structure, and function." zebrafish
  • Histone deacetylase 1 and 2 regulate Wnt and p53 pathways in the ureteric bud epithelium[10] "Histone deacetylases (HDACs) regulate a broad range of biological processes through removal of acetyl groups from histones as well as non-histone proteins. Our previous studies showed that Hdac1 and Hdac2 are bound to promoters of key renal developmental regulators and that HDAC activity is required for embryonic kidney gene expression. However, the existence of many HDAC isoforms in embryonic kidneys raises questions concerning the possible specificity or redundancy of their functions. We report here that targeted deletion of both the Hdac1 and Hdac2 genes from the ureteric bud (UB) cell lineage of mice causes bilateral renal hypodysplasia. One copy of either Hdac1 or Hdac2 is sufficient to sustain normal renal development."
  • Bmp7 functions via a polarity mechanism to promote cloacal septation[4] "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. ...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."
  • Size and location of the kidneys during the fetal period[11] "The level of the left kidney was higher than the level of the right kidney in the fetal period. The posterior surface relations to the ribs showed certain ascendance during gestation, corresponding to vertebral levels. However, fetal kidneys do not reach the same level as adults at full term. The kidneys move farther apart from the midline of the body during the fetal period. The dimensions, weight, and volume of the kidneys increased with gestational age during the fetal period. The ratio between kidney weights and fetal body weights were determined, and we observed that the ratio decreased during the fetal period. There were no sex or laterality differences in any parameter." (See also Fetal Development)
  • Characterization of Mesonephric Development and Regeneration Using Transgenic Zebrafish.[12] "The majority of previous studies have focused on the pronephros of zebrafish, which consists of only two nephrons and is structurally simpler than the mesonephros of adult fish and the metanephros of mammals. To evaluate the zebrafish system for more complex studies of kidney development and regeneration, we investigated the development and post-injury regeneration of the mesonephros in adult zebrafish." (See also Zebrafish Development)


Renal Nephron
  • Understand the 3 main stages of kidney development.
  • Understand development of the nephron and renal papilla.
  • Brief understanding of the mechanisms of nephron development.
  • Understand the development of the cloaca, ureter and bladder.
  • Brief understanding of abnormalities of the urinary system.

Textbook References

Stage 13 kidney sections.jpg
  • The Developing Human: Clinically Oriented Embryology (8th Edition) by Keith L. Moore and T.V.N Persaud - Moore & Persaud Chapter 13 p303-346
  • Larsen’s Human Embryology by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West - Chapter 10 p261-306

Renal Movies

Renal Development

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 ‎‎Renal Overview
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 ‎‎Urogenital Septum
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 ‎‎GIT Stage 13
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 ‎‎Renal Vascular
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  • Mesoderm then intermediate mesoderm
  • Vascular Development
  • Gastrointestional
  • Cloacal development
  • Endocrine - covered in future lecture/lab

Kidney Anatomy

Adult nephron structure
  • Nephron - Functional unit of kidney
  • Humans up to 1 million
  • Filtration of waste from blood
  • Endocrine
  • Blood pressure regulation

The key structure of the adult nephron is the glomerulus (renal corpuscle), which represents the initial vascular/renal interface.

Related Images: Nephron histology overview | glomerulus structure | vascular and renal poles


  • Bladder - Urine storage
  • Endoderm allantois


  • Intermediate mesoderm - Lies between somites and lateral plate

Intermediate Mesoderm

Stage7 intermediate-mesoderm.jpg

Week 3 - Stage 7 dorsal view
intermediate mesoderm (orange lateral strips)


Cross-section showing mesoderm regions

  • development occurs laterally symmetrical (left right)
  • intermediate mesoderm lying beside the dorsal aorta
  • initially form mesonephric tubules (epithelial)
  • these tubules connect to a common duct, mesonephric duct
  • the mesonephric duct then extends within the mesoderm, rostro-caudally
  • eventually making contact with the cloaca

Mesonephric Duct

Later in development, both the mesonephric duct and the cloaca both continue to differentiate and undergo extensive remodelling (and renaming)

Ureteric Bud

Mouse E12.5 kidney in vitro
  • arise near the cloacal connection of the mesonephric duct
  • branch from the mesonephric duct laterally into the intermediate mesoderm
  • induce the surrounding mesoderm to differentiate - metanephric blastema
    • this mesoderm will in turn signal back to differentiate the ureteric bud

Epithelial - mesenchymal interaction

Ureteric Bud forms - ureter, pelvis, calyces, collecting ducts

Metanephric Blastema

  • forms glomeruli, capsule, nephron tubules
  • this development continues through fetal period

Nephros Development

Three pairs appearing in sequence within intermediate mesoderm during development.

  1. pronephros
  2. mesonephros
  3. metanephros


  • week 4 few cells in cervical region fish
  • Human E18, Mouse E7.5pronephric duct forms first with associated nephrogenic mesenchyme
  • grows rostro caudally cervical -> cloaca
  • E22 nephrogenic mesenchyme differentiates to form pronephroi not functional in mammals degenerates rapidly


The mesonephros, historically called the Wolffian body, is the embryonic stage of renal development that is entirely lost during development of the later fetal /adult metanepros. The only developmental structure not lost is the mesonephric duct.

Human E24, Mouse E9.5 caudal to pronephros
  • forms by induction from pronephros
  • pronephric duct now becomes mesonephric duct (also called Wolffian Duct)
  • extends downwards in intermediate mesoderm towards cloaca, later urogenital sinus
Stage 13 kidney sections 2.jpg

Week 5 - Stage 13 mesonephros
(extending the length of the body)

Stage22 mesonephros.jpg

Week 8 - 22 mesonephros
(now degenerating)

Wolffian body

Historic name for the developing combined renal (mesonephros) and genital (paramesonephrotic blastema) structures. This term is no longer used in describing development.

Historic Embryology
Caspar Friedrich Wolff (1734-1794)
Theoria Generationis 1774.jpg

Caspar Friedrich Wolff (1734-1794) was a German embryologist and anatomist best known today for identifying the Wolffian duct (mesonephric duct; ductus deferens, epididymis), Wolffian body (mesonephros) and Wolffian cyst (mesonephric origin uterine broad ligament cyst) that bear his name. Thought also to be a founder of the germ layer theory. His doctorate dissertation Theoria generationis (1774) discarded the developmental theory of preformation. Later in his career, his teaching in Berlin was opposed by the professors of the Medical-Surgical College, who had guild privileges to teach medicine.


Early fetal kidney (week 10)
  • Human E35-37, Mouse E11 epithelia bud at end of mesonephric duct ureteric bud and associated metanephric mesenchyme

Ureteric Bud

  • induced by metanephric mesenchyme to differentiate
  • forms collecting tubules, renal pelvis, ureter
  • metanephric mesenchyme induced by ureteric to differentiate forms nephron


In humans, nephrogenesis only occurs before birth, though nephron maturation continues postnatally. Mean glomerular number shown to level at 36 weeks, increasing from about 15,000 at 15 weeks to 740,000 at 40 weeks. Gray1128.jpg

Adult nephron structure

Nephron histology.jpg

Nephron histology

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Nephron development has four identifiable developmental stages:

  1. Vesicle (V) stage (13-19 weeks, second trimester)
  2. S-shaped body (S) stage ( 20-24 weeks, second trimester)
  3. Capillary loop (C) stage (25-29 weeks, third trimester)
  4. Maturation (M) stage (infants aged 1-6 months, neonatal and postnatal)
  • disorganised mesenchymal cells become a highly organised epithelial tubule
  • Condensation - groups of about 100 cells condense tightly together to form a distinct mass
  • Epithelialisation - condensed cells lose their mesenchymal character and gain epithelial
  • At end of this period formed a small epithelial cyst complete with a basement membrane, cell-cell junctions and a defined cellular apico-basal polarity.
Nephron development 01.jpg

Nephron development[13]

  • a - condensed aggregate forms
  • b - renal vesicle forms
  • c - S-shaped body (red), renal progenitors are localised, at this stage podocyte-committed progenitors (red + blue) as well as tubular-committed progenitors (orange) can already be seen.
  • d - mature nephron, renal progenitors (red), podocyte-committed progenitors (red + blue), as well as tubular-committed progenitors (orange) are distributed along the nephron.
  • e - glomerulus, renal progenitors (red) are localized at the urinary pole of the Bowman capsule. Podocyte-committed progenitors (red + blue) localize along the Bowman capsule.
  • cyst invaginates twice to form a comma
  • then a S-shaped body one invagination site later becomes the glomerular cleft
  • At about this time blood vessel progenitors invade cleft to begin construction of vascular component of glomerulus
  • Tubule maturation specialised transporting segments of nephron differentiate complex of convoluted tubules is created
  1. ureteric bud (gray) extends from the mesonephric (Wolffian) duct
  2. upon contact with the metanephric mesenchyme (red), reciprocal signaling induces both bud bifurcation and condensation of the mesenchyme to generate the cap mesenchyme.
  3. blastemal mesenchyme then undergo a MET to generate the renal vesicle
  4. renal vesicle continues to form the comma-shaped and S-shaped body
  5. distal end fuses with the ureteric bud (which forms the collecting duct)
  6. proximal end joins to form the glomerulus, generating the mature nephron (dark orange).
Renal development cartoon01.jpg

Renal Development Interactions[14]

Bowmans Capsule
Bowmans Capsule forms two layers with a space between these layers.
  • Outer later - (parietal) single layer of simple squamous epithelium. Does not function in filtration.
  • Space - (Bowman's space, "urinary space", "capsular space") space filled by fluid (filtrate) passing through podocyte filtration slits
  • Inner layer - (visceral) formed by podocytes on thickened glomerular basement membrane covering glomerular capillaries.

Nephron EM01.jpg

Within the glomerulus a high magnification view of a podocyte showing the interdigitated foot processes (pedicels) that are wrapped around the exterior of glomerular capillaries.[15]

Nephron EM02.jpg

Embryonic Kidney

Embryonic stage descriptions based on Carnegie Collection embryos.[16]

Week 4

  • Carnegie stage 12 - 29 somite embryo mesonephros tubules begin at the level of somite 8 and are distinct as far caudally as somite 20, whence they extend as a continuous nephrogenic cord to t he level of somite 24. Opposite each somite there are two or more tubules. Thus they are not metameric, any more than the mesonephric duct is metameric, or the umbilical vein. The number of nephric vesicles is being increased by progressive differentiation caudally from the nephrogenic cord.[17] The mesonephric duct at first ends blindly immediately short of the cloaca, but soon becomes attached to the cloaca (i.e., to the terminal part of the hindgut) and acquires a lumen.
  • Carnegie stage 13 - Mesonephros glomeruli begin to develop, and nephric tubules become S-shaped.[18] A ureteric bud may possibly be present in some specimens[19] fig. 4), although further confirmation is needed. The mesonephric duct, which becomes separated from the surface ectoderm except in its caudal portion, is fused to the cloaca, into which it may open. A urorectal cleavage line is apparent.

Week 5

  • Carnegie stage 14 - In embryos of this stage the mesonephros is well along in its organogenesis. The steps in this process are made easier to follow by the fact that the development occurs progressively in a rostrocaudal direction. Here again is an organ in which the epithelial elements constitute its primary tissue and seem largely to determine its form. The non-epithelial mesonephric elements, though necessary complements for epithelial-mesenchymal interaction, give the appearance of being subsidiary. It has already been seen that the coelomic surface cells possess various inherent potentialities. The surface of the coelom can be mapped in definite areas in accordance with the distribution of these various kinds of surface cells. Running along each side of the median plane is a narrow strip of coelom where, by the proliferation and delamination of its surface cells, there is produced a longitudinal series of epithelial tubules that constitute the units of the mesonephros. This follows the manner in which nephric elements were formed in previous stages, and it is now about to be repeated, with certain modifications, in the development of the metanephros, which is still in the primordial state of a budding ureter with its nephrogenic capsule (fig. 14-6). One can go a step further in regard to the inherent constitution of these coelomic epithelial tubules. Not only do they become tubules, but from the beginning they show regional differentiation. The proximal end promptly blends with and opens into the mesonephric duct, and this part of the tubule persists as a collecting duct. The distal free end at the same time begins its expansion into a highly specialized part of the tubule, namely the mesonephric corpuscle. The intervening central segment of the tubule becomes the convoluted secretory portion. Embryos in this stage are especially favorable for the study of the process of formation of the mesonephric corpuscle. The proliferation of the tubular epithelium at the free end results in its maximum expansion. This occurs in such a way as to produce an indented flattened vesicle, known as a glomerular capsule. As seen in section, it has an arched floor-plate several cells thick and a thin, single-layered roof membrane. The two are continuous with each other but are very different in their potentialities. The roof membrane becomes attenuated as an impermeable membrane. The floor plate continues active proliferation and many of its cells were believed by Streeter to delaminate and apparently become angioblasts, participating in the formation of the vascular glomerulus and its supporting tissues. It is now maintained, however, that the glomerular capillaries (in the metanephros) come from adjacent vessels and never develop in situ from epithelial cells (Potter, 1965). Further details of renal development have been provided by several authors (e.g., Potter, 1972). The residual cells facing the capsular lumen in the mesonephros at stage 14 are reduced in the more advanced phases to a single layer, covering and conforming everywhere to the tabulations of the underlying capillary tufts. Angiogenesis around the secretory part of the tubule is not far advanced. Angiogenic strands connect with the caudal cardinal vein, and throughout the mesonephros there are isolated clumps of angioblasts, particularly around the capsules. These show the typical difference in complexity of the three parts of the tubule: (1) collecting duct, (2) secretory segment, and (3) glomerular capsule.
  • Carnegie stage 15 - The ureteric bud is longer, and its tip is expanded as the pelvis of the ureter (fig. 15-10). The primary urogenital sinus is distinguishable.

Week 6

  • Carnegie stage 16 - The metanephros, which is now reniform, is still sacral in level. The ureter is elongating and, in more advanced embryos, the pelvis of the ureter divides into rostral and caudal poles. The urorectal septum, the formation of which is disputed, is well marked.
  • Carnegie stage 17 - The mesonephros shows epithelial plaques in the visceral layer of the glomerular capsule and hence can produce urine (Silverman, 1969)[20]. The pelvis of the ureter usually shows three main divisions, and calices appear. The urogenital sinus presents a pelvic part (vesico-urethral canal) and a phallic part (definitive urogenital sinus).

Week 7

  • Carnegie stage 18 - Collecting tubules develop from the calices at stages 17 and 18. They are surrounded by sharply outlined condensed primordia in the process of forming secretory tubules. Renal corpuscules are not yet present. By stage 18 the mesonephric duct and the ureter open almost independently into the vesico-urethral canal[18]: i.e., the common excretory duct is disappearing. The cloacal membrane is ready to rupture.
  • Carnegie stage 19 - Lack of orientation in metanephrogenic tissue. Beginning formation of renal vesicles.[21]

Week 8

  • Carnegie stage 20 - The external surface of the metanephros is said to be slightly lobulated. A reconstruction of the urinary system has been published by Shikinami[18] (fig. 5). S-shaped lumen in renal vesicles. Spoon-shaped capsules (Bowman’s).[21]
  • Carnegie stage 21 - Metanephros is spoon-shaped glomerular capsules are developing, no large glomeruli.[21]
  • Carnegie stage 22 - Metanephros few large glomeruli.[21]
  • Carnegie stage 23 - Short secretory tubules. Numerous large glomeruli. Long secretory tubules. High epithelium in some tubules. Increased number and convolutions of tubules.[21] Comparison between the mesonephros and the metanephros in staged embryos is lacking. In metanephros, the kidneys have ascended from a sacral level at stages 13–15 to a lumbar level at stages 17–23. At stage 23 they are generally at the level of lumbar vertebrae 1–3..

Fetal Kidney

Fetal kidney MRI 01.jpg MRI appearance of normal fetal kidney.[22] Sagittal T2- SSFSE of a fetal abdomen at GA 25 week. Adequate volume of the amniotic fluid and the developing lungs indicate good renal function.

  • two arrowheads - note the size and the signal appearance of the normal kidney.
  • white arrow - the fluid-filled urinary bladder
  • black arrow - the developing lung.

Note that the urinary bladder can occupy a considerable portion of the abdomen as a normal finding.

Links: Magnetic Resonance Imaging
Fetal nephron development[13]
Fetal nephron development 01.jpg

After nephron development has completed and concomitant with the development of the renal papilla in the newborn, the thin ascending limb of Henle’s loops is generated as an outgrowth from the S3 segment of the proximal tubule and from the distal tubule anlage of the nephron.

Endocrine Kidney

Covered also in Endocrine Development lecture

  • Renin - Increase Angiotensin-aldosterone system
  • Prostaglandins - decrease Na+ reabsorption
  • Erythropoietin - Increase Erythrocyte (rbc) production
  • 1,25 (OH)2 vitamin D - Calcium homeostasis
  • Prekallikreins - (plasma protein inactive precursor of kallikrein) Increase kinin production (altered vascular permeability)


File:Endoderm development

  • hindgut region ending at the cloacal membrane
  • divided (ventro-dorsally) by the urogenital septum
    • ventral - common urogenital sinus
    • dorsal - rectum
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 ‎‎Urogenital Septum
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Common Urogenital Sinus

  • superior end continuous with allantois
  • common urogenital sinus and mesonephric duct fuse (connect)
  • differentiates to form the bladder
  • inferior end forms urethra
    • this will be different in male and female development

Urinary Bladder

Adult bladder
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  • early origins of the bladder at the superior end of the common urogenital sinus
  • 8 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.
  • associated ureters and urethra

Dorsal view of developing bladder

  • Ultrasound measurement of the bladder size can be used as a diagnostic tool for developmental abnormalities.

Bladder Structure

Bladder histology

Can be described anatomically by its 4 layers from outside inward:

  • Serous - the superior or abdominal surfaces and the lateral" surfaces of the bladder are covered by visceral peritoneum, the serous membrane (serosa) of the abdominal cavity, consisting of mesthelium and elastic fibrous connective tissue.
  • Muscular - the detrusor muscle is the muscle of the urinary bladder wall.
  • Submucosa - connects the muscular layer with the mucous layer.
  • Mucosa - (mucus layer) a transitional epithelium layer formed into folds (rugae).

Detrusor Muscle

  • The adult detrusor muscle consists of three layers of smooth (involuntary) muscle fibres.
    • external layer - fibres arranged longitudinally
    • middle layer - fibres arranged circularly
    • internal layer - fibres arranged longitudinally

Ureter Development

  • 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.

Trigone Development

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Urethra Development

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.[23] A recent study of male penile urethra describes a theory of a "two-step process of urethral plate canalization and urethral fold fusion to form the human penile urethra. Canalization ("opening zipper") opens the solid urethral plate into a groove, and fusion ("closing zipper")."[24][25]

Kidney Ascent

early fetal kidney
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 ‎‎Renal Vascular
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  • Pro-, Meso-, Meta- Early development descending
  • Metanephros - initially pelvic, beside aorta
  • Growth and straightening of body - Kidneys in abdomen and displace laterally

Renal Arteries

  • Arise with ascent and inferior branches lost
  • Sequential, 25% population have 2 or more renal arteries
  • branch of abdominal aorta, divides into 4-5 branches
    • each gives off small branches to suprarenal glands, ureter, surrounding cellular tissue and muscles

Note: Frequently a second renal artery (inferior renal) from abdominal aorta at a lower level, supplies lower portion of kidney


Australian renal abnormalities

There are many different forms of renal development abnormalities associated with kidney, ureters, bladder and urethra. There are many genetic disorders associated with failure or abnormal renal development. Prenatal diagnosis of obstructive and renal agenesis/dysgenesis disorders are also important for early reproductive decisions by the parents. For example, with bilateral renal agenesis, failure of both kidneys to development, is not compatible with fetal/neonatal survival. Because of their close developmental association, often described as the urogenital system, there can be an associated genital abnormalities.

More detailed information is available on the links below.

Links: Renal Abnormalities | Genital Abnormalities

Horseshoe Kidney

Horseshoe kidney
  • fusion of the lower poles of the kidney.
  • During migration from the sacral region the two metanephric blastemas can come into contact, mainly at the lower pole.
  • The ureters pass in front of the zone of fusion of the kidneys.
  • The kidneys and ureters usually function adequately but there is an increased incidence of upper urinary tract obstruction or infection.
  • Some horseshoe variations have been described as having associated ureter abnormalities including duplications.

Urorectal Septum Malformation

  • thought to be a deficiency in caudal mesoderm which in turn leads to the malformation of the urorectal septum and other structures in the pelvic region.
  • Recent research has also identified the potential presence of a persistent urachus prior to septation of the cloaca (common urogenital sinus).


  • absent or small bladder - associated with renal agenesis.

Bladder Exstrophy

  • developmental abnormality associated with bladder development.
  • 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).

Ureter and Urethra

  • Ureter - Duplex Ureter
  • Urethra- Urethral Obstruction and Hypospadias

Polycystic Kidney Disease

Multicystic kidney
  • diffuse cystic malformation of both kidneys
  • cystic malformations of liver and lung often associated, Often familial disposition
  • Two types
    • Infantile (inconsistent with prolonged survival)
    • Adult (less severe and allows survival)
  • Autosomal dominant PKD disease - recently identified at mutations in 2 different human genes encoding membrane proteins (possibly channels)

Wilms' Tumor

  • (nephroblastoma) Named after Max Wilms, a German doctor who wrote first medical articles 1899
  • most common type of kidney cancer children
  • WT1 gene - encodes a zinc finger protein
  • Both constitutional and somatic mutations disrupting the DNA-binding domain of WT1 result in a potentially dominant-negative phenotype
  • some blastema cells (mass of undifferentiated cells) persist to form a ‘nephrogenic rest’
  • Most rests become dormant or regress but others proliferate to form hyperplastic rests
  • any type of rest can then undergo a genetic or epigenetic change to become a neoplastic rest
  • can proliferate further to produce a benign lesion (adenomatous rest) or a malignant Wilms’ tumour

Prune Belly Syndrome

  • lower urinary tract obstruction
  • mainly male
  • fetal urinary system ruptures leading to collapse and "prune belly" appearance.

Renal Cysts

The Bosniak classification system (Category I - IV) was designed to separate identified cystic renal masses by analysis of computed tomography (CT) features into surgical and nonsurgical categories.[26] Named after Morton Bosniak, Yale University School of Medicine, the developer of this classification system.


Abbreviation Growth Factor Renal Development Expression Location
BMP4 Bone Morphogenetic Protein 4 prevents ectopic ureteric bud outgrowth and extra ureteric bud divisions mesenchymal cells surrounding mesonephric duct and stromal mesenchyme surrounding steric bud stalks
BMP7 Bone Morphogenetic Protein 7 survival of metanephric mesenchyme metanephric mesenchyme
Fgf8 Fibroblast Growth Factor 8 transition of the induced cap mesenchyme into RVs cap mesenchyme
GDNF Glial-cell derived neurotrophic factor induces steric bud outgrowth from mesonephric duct, interacts with Ret metanephric mesenchyme
VEGF Vascular endothelial growth factor promotes endothelial cell proliferation, differentiation s-shaped body
Wnt4 Wingless-Type MMTV Integration Site Family, Member 4 mesenchymal-to-epithelial transition cap metanephric mesenchyme, pre-tubular aggregate, nephron progenitors
Wnt5a Wingless-Type MMTV Integration Site Family, Member 5a nephrogenesis induction, ectopic bud formation steric bud, metanephric mesenchyme
Wnt9b Wingless-type MMTV integration site family, Member 9B renewal and differentiation of nephron progenitors and normal ureteric bud branching, mesenchymal-to-epithelial transition steric bud stalk epithelial cells
  • Foxd1 - (Brain Factor-2) transcription factor that is a renal stroma specific gene.
Links: Renal System - Molecular | OMIM Foxd1


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Lumbers ER, Kandasamy Y, Delforce SJ, Boyce AC, Gibson KJ & Pringle KG. (2020). Programming of Renal Development and Chronic Disease in Adult Life. Front Physiol , 11, 757. PMID: 32765290 DOI.


  • The Developing Human: Clinically Oriented Embryology (8th Edition) by Keith L. Moore and T.V.N Persaud - Moore & Persaud Chapter 13 p303-346
  • Larsen’s Human Embryology by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West - Chapter 10 p261-306
  • Before We Are Born (5th ed.) Moore and Persaud Chapter14 p289-326
  • Essentials of Human Embryology, Larson Chapter 10 p173-205
  • Human Embryology, Fitzgerald and Fitzgerald Chapter 21-22 p134-152

Online Textbooks

Search Bookshelf intermediate mesoderm | kidney development | renal development | ureteric bud | nephron development | bladder development


Scott RP & Quaggin SE. (2015). Review series: The cell biology of renal filtration. J. Cell Biol. , 209, 199-210. PMID: 25918223 DOI.

Hohenstein P, Pritchard-Jones K & Charlton J. (2015). The yin and yang of kidney development and Wilms' tumors. Genes Dev. , 29, 467-82. PMID: 25737276 DOI.

Herzlinger D & Hurtado R. (2014). Patterning the renal vascular bed. Semin. Cell Dev. Biol. , 36, 50-6. PMID: 25128732 DOI.

Upadhyay KK & Silverstein DM. (2014). Renal development: a complex process dependent on inductive interaction. Curr Pediatr Rev , 10, 107-14. PMID: 25088264

Blake J & Rosenblum ND. (2014). Renal branching morphogenesis: morphogenetic and signaling mechanisms. Semin. Cell Dev. Biol. , 36, 2-12. PMID: 25080023 DOI.

Jacob M. Yusuf F. and Jacob HJ. Development, Differentiation and Derivatives of the Wolffian and Müllerian Ducts. (2012) The Human Embryo, Dr. Shigehito Yamada (Ed.), ISBN: 978-953-51-0124-6, InTech, Available from:

Little M, Georgas K, Pennisi D & Wilkinson L. (2010). Kidney development: two tales of tubulogenesis. Curr. Top. Dev. Biol. , 90, 193-229. PMID: 20691850 DOI.

Dressler GR. (2009). Advances in early kidney specification, development and patterning. Development , 136, 3863-74. PMID: 19906853 DOI.

Michos O. (2009). Kidney development: from ureteric bud formation to branching morphogenesis. Curr. Opin. Genet. Dev. , 19, 484-90. PMID: 19828308 DOI.

Reidy KJ & Rosenblum ND. (2009). Cell and molecular biology of kidney development. Semin. Nephrol. , 29, 321-37. PMID: 19615554 DOI.

Quaggin SE & Kreidberg JA. (2008). Development of the renal glomerulus: good neighbors and good fences. Development , 135, 609-20. PMID: 18184729 DOI.

Brenner-Anantharam A, Cebrian C, Guillaume R, Hurtado R, Sun TT & Herzlinger D. (2007). Tailbud-derived mesenchyme promotes urinary tract segmentation via BMP4 signaling. Development , 134, 1967-75. PMID: 17442697 DOI.

Costantini F. (2006). Renal branching morphogenesis: concepts, questions, and recent advances. Differentiation , 74, 402-21. PMID: 16916378 DOI.

Forefronts Symposium on Nephrogenetics: from development to physiology March 8-11, 2007 Danvers, MA A meeting to synthesize an integrated view of the normal development and function of the kidney from the genetic standpoint.


Sutherland MR, Vojisavljevic D & Black MJ. (2020). A practical guide to the stereological assessment of glomerular number, size, and cellular composition. Anat Rec (Hoboken) , , . PMID: 31960613 DOI.

Desgrange A, Heliot C, Skovorodkin I, Akram SU, Heikkilä J, Ronkainen VP, Miinalainen I, Vainio SJ & Cereghini S. (2017). HNF1B controls epithelial organization and cell polarity during ureteric bud branching and collecting duct morphogenesis. Development , 144, 4704-4719. PMID: 29158444 DOI.

Hinata N, Suzuki R, Ishizawa A, Miyake H, Rodriguez-Vazquez JF, Murakami G & Fujisawa M. (2015). Fetal development of the mesonephric artery in humans with reference to replacement by the adrenal and renal arteries. Ann. Anat. , 202, 8-17. PMID: 26335195 DOI.

Grinstein M, Yelin R, Herzlinger D & Schultheiss TM. (2013). Generation of the podocyte and tubular components of an amniote kidney: timing of specification and a role for Wnt signaling. Development , 140, 4565-73. PMID: 24154527 DOI.

Rhodin MM, Anderson BJ, Peters AM, Coulthard MG, Wilkins B, Cole M, Chatelut E, Grubb A, Veal GJ, Keir MJ & Holford NH. (2009). Human renal function maturation: a quantitative description using weight and postmenstrual age. Pediatr. Nephrol. , 24, 67-76. PMID: 18846389 DOI.

Search PubMed

Search Pubmed: Renal System Development | Renal Development | intermediate mesoderm | kidney development | renal development | ureteric bud | nephron development | bladder development

Additional Images


Historic Disclaimer - information about historic embryology pages 
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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)


Open table below to see list of renal terms.

Renal Terms  
  • bladder exstrophy - 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)
  • Bowman's capsule - (capsula glomeruli, glomerular capsule) Surrounds the glomerulus within the nephron with a vascular and urinary pole and is the beginning of the tubular component. Named in 1842 after Sir William Bowman (1816 – 1892) an English surgeon and anatomist.
  • Brenner hypothesis - a clinical hypothesis that states, individuals with a congenital reduction in nephron number have a much greater likelihood of developing adult hypertension and subsequent renal failure. Developed in the 1980's by Barry Brenner at the Brigham and Women's Hospital, this also fits with the DOHAD hypothesis. (More? PubMed 3063284 | Barry Brenner)
  • capillary loop - (C stage) The third stage in nephron development between 25-29 weeks. (stage sequence: V - S - C - M)
  • 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.
  • fenestrated capillary - Specialised capillaries containing circular pores (fenestrae) that penetrate the endothelium, may be closed by a thin diaphragm.
  • glomerulus - The capillary network (tuft) within Bowman's capsule of the nephron enters at the vascular pole (afferent and efferent arteriole).
  • 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.
  • juxtaglomerular cells - Cells located at the vascular pole that secrete renin and form a part of the juxtaglomerular complex.
  • loop of Henle - Nephron region spanning from the proximal convoluted tubule to the distal convoluted tubule. Named after Named after Friedrich Gustav Jakob Henle (1809–1885) a German anatomist.
  • macula densa - Columnar cell cluster appearing as a dense row of cell nuclei where the straight portion of the distal tubule contacts the glomerulus. Region also in close contact with the efferent and afferent arterioles of the glomerulus and involved in sodium chloride regulation. (More? image)
  • maturation stage - (M stage) The forth stage in nephron development in infants aged 1-6 months. (stage sequence: V - S - C - M)
  • mesangial cells - Cells in the nephron glomerulus that form the connective tissue giving structural support to podocytes and vessels.
  • 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 - (metanephric blastema) The intermediate mesoderm which surrounds the ureteric bud and will contribute most of the adult nephron.
  • 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.
  • nephrin - protein of the slit diaphragm of renal filtration barrier, located at the cell surface in the area between two podocytes. NPHS1 gene location 19q13.12, mutations in this gene are associated with Congenital Nephrotic Syndrome (Nephrotic syndrome). (More? renal abnormalities)
  • nephrogenic rest - 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)
  • nephron - (Greek, nephros = kidney) The functional unit of the adult kidney.
  • nephros - (Greek, nephros = kidney) Term used to describe features associated with the kidney. (pronephros, mesonephros, metanephros, nephric, nephron, nephroblastoma).
  • Nephrotic syndrome - (CNS, Nephrotic syndrome) rare kidney disorder characterized by heavy proteinuria, hypoproteinemia, and edema starting soon after birth. Most cases are caused by genetic abnormalities in the components of the glomerular filtration barrier, especially nephrin and podocin. (More? renal abnormalities)
  • parietal layer - Cells of the outer of Bowman's capsule that form a simple squamous epithelium. The inner layer is the visceral layer.
  • podocin - protein of the slit diaphragm of renal filtration barrier, located at the cell surface in the area between two podocytes. NPHS2 gene location 1q25.2, mutations in this gene are associated with Congenital Nephrotic Syndrome (Nephrotic syndrome). (More? renal abnormalities)
  • podocyte - (visceral epithelial cell) kidney glomerulus cell forming the main component of the glomerular filtration barrier. (glomerular podocyte) Kidney epithelial cell type in the nephron (kidney functional unit) located in the glomerulus. Podocytes form the visceral layer of Bowman's capsule and are at the filtration barrier between capillary blood and the nephron tubular system and function to ultrafiltrate blood, and support glomerular capillary pressures. The differentiation of podocytes involves the formation of cellular foot processes and then the slit membrane. (More? image)
  • podocyte specific proteins - podocalyxin, glomerular epithelial protein-1, podocin, nephrin, synaptopodin, and alpha-actinin-4), podocyte synthesized proteins (vascular endothelial growth factor and novH), transcription factors (WT1 and PAX2).
  • 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).
  • proximal tubule - Portion of the nephron duct between Bowman's capsule to the loop of Henle, divided into the proximal convoluted tubule (PCT) and the proximal straight tubule (PST).
  • renal - (Latin, renes = kidney) Term used in relation to the kidney and associated structures (renal pelvis, renal artery)
  • S-shaped body - (S stage) The second stage in nephron development between 20-24 weeks. (stage sequence: V - S - C - M)
  • transitional epithelium - (urothelium) Histological term to describe the epithelium lining the ureters and urinary bladder. (More? image)
  • trigone - refers to the urinary bladder triangular region formed by the two ureters and the urethra.
  • ureter - The two ureters are hollow tubes that link the kidney and the bladder and carry urine. They develop from the ureteric bud and are lined by a transitional epithelium with an outer muscular wall.
  • 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).
  • vascular pole - The side of nephron Bowman's capsule where the afferent arteriole and efferent arteriole enter the glomerulus. image
  • visceral layer - Cells (podocytes) of the inner of Bowman's capsule that form extremely complex shapes. Cytoplasm form a fenestrated epithelium around the fenestrated capillaries of the glomerulus. The outer layer is the parietal layer.
  • vesicle stage - (V stage) The first stage in nephron development between 13-19 weeks. (stage sequence: V - S - C - M)
  • urinary - Term used to describe all components of the kidney system including the bladder, ureters and urethra.
  • urinary pole - The side of nephron Bowman's capsule where the proximal convoluted tubule starts. image
  • 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? 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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