[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Urogenital system](https://durgical.com/en/embryology/#a-urogenital) › Kidney: pronephros, mesonephros, metanephros and ascent [Embryology](https://durgical.com/en/embryology/) · [Urogenital system](https://durgical.com/en/embryology/#a-urogenital) # Kidney: pronephros, mesonephros, metanephros and ascent - Process The embryo builds a kidney three times in a row; only the third one, the metanephros, becomes the permanent kidney. Updated 2026-11-01 **See it in 3D:** [Kidneys](https://durgical.com/en/anatomy/kidney/) · [Ureters](https://durgical.com/en/anatomy/ureter/) · [Renal pelvis](https://durgical.com/en/anatomy/renal-pelvis/) · [Left renal artery](https://durgical.com/en/anatomy/renal-artery/) · [Right renal artery](https://durgical.com/en/anatomy/renal-artery-abdomen/) ## Key points - Ureteric bud (from the mesonephric duct): ureter, renal pelvis, calyces and collecting ducts. - Metanephric blastema: the nephron, from glomerulus to distal convoluted tubule. - Reciprocal induction: the blastema secretes GDNF, the bud answers through RET and in turn induces nephrons; WT1 is essential. - The kidney ascends from the pelvis to the lumbar region between weeks 6 and 9 and rotates so the hilum faces medially. - From the second trimester fetal urine is the main source of amniotic fluid: no kidneys means oligohydramnios. - Accessory renal arteries are temporary branches of the ascent that failed to regress. ## What it is The kidneys arise from intermediate mesoderm in three generations that appear from head to tail: pronephros, mesonephros and metanephros. The permanent kidney comes from a dialogue between the ureteric bud and the metanephric blastema, and then ascends from the pelvis to the lumbar region. Almost every congenital kidney anomaly is a failure of that dialogue or of the ascent. ## Key facts - Week 4: cervical pronephros, rudimentary and non-functional; it disappears quickly. - Weeks 4–5: thoracolumbar mesonephros; it works briefly and leaves behind the mesonephric (Wolffian) duct. - Week 5: the metanephros begins as the ureteric bud enters the metanephric blastema. - By about weeks 10–12 the permanent kidney is making urine. - Nephron formation ends around weeks 32–36: a very preterm baby is born with fewer nephrons. ## Structure - Two tissues of different origin: the collecting system (ureteric bud) and the nephron (metanephric blastema). - The nephron includes the glomerulus, Bowman capsule, proximal tubule, loop of Henle and distal tubule. - The junction of distal tubule and collecting duct joins the two parts; if they fail to connect, cysts form. ## Step by step - Intermediate mesoderm forms the nephrogenic cord on each side of the embryo. - The pronephros appears in the cervical region and almost immediately regresses. - The mesonephros forms tubules and the mesonephric duct, which reaches the cloaca. - The ureteric bud sprouts from the mesonephric duct and enters the metanephric blastema. - The bud branches to form the ureter, pelvis, calyces and collecting ducts. - Each bud tip induces a vesicle in the blastema that becomes a nephron. - The kidney ascends from the pelvis to the lumbar region and rotates; its arteries are replaced from higher levels. ## Markers - WT1 - GDNF - RET - PAX2 - WNT9B ## Clinical notes - If the ureteric bud fails to form or to reach the blastema, the kidney is absent; bilateral agenesis gives the Potter sequence. - Fusion of the lower poles stops the ascent: horseshoe kidney. A kidney that never ascends stays pelvic. - A bud that splits early, or two buds, gives a bifid or duplicated ureter. - Persistent metanephric blastema (nephrogenic rests) is linked to Wilms tumour; WT1 lies on 11p13. - ACE inhibitors in the second and third trimesters damage the fetal kidney and cause oligohydramnios. ## Memory aid “Pro leaves, meso lends its duct, meta stays.” The bud builds the pipes that collect; the blastema builds the units that filter. ## Test yourself Think of the answer, then tap the question to see it. ## Which embryonic structure gives rise to the ureter, renal pelvis and collecting ducts? The ureteric bud, an outgrowth of the mesonephric duct that enters the metanephric blastema around week 5. ## Which part of the kidney comes from the metanephric blastema? The nephron: glomerulus, Bowman capsule, proximal tubule, loop of Henle and distal tubule. ## Why does absence of both kidneys reduce amniotic fluid? From the second trimester fetal urine is the main source of amniotic fluid; without it there is oligohydramnios. ## What explains accessory renal arteries in an adult? During its ascent the kidney is supplied by successive aortic branches at higher levels; the lower ones normally regress and, if they persist, remain as accessory arteries. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/kidney-pronephros-mesonephros-metanephros-and-ascent/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Kidneys](https://durgical.com/en/anatomy/kidney/) - [Ureters](https://durgical.com/en/anatomy/ureter/) - [Renal pelvis](https://durgical.com/en/anatomy/renal-pelvis/) - [Left renal artery](https://durgical.com/en/anatomy/renal-artery/) - [Right renal artery](https://durgical.com/en/anatomy/renal-artery-abdomen/) ## Related - [Renal agenesis and the Potter sequence](https://durgical.com/en/embryology/renal-agenesis-and-the-potter-sequence/) - [Horseshoe kidney and renal ectopia](https://durgical.com/en/embryology/horseshoe-kidney-and-renal-ectopia/) - [Duplicated ureter, UPJ obstruction and posterior urethral valves](https://durgical.com/en/embryology/duplicated-ureter-upj-obstruction-and-posterior-urethral-valves/) - [Multicystic dysplastic kidney and polycystic kidney disease](https://durgical.com/en/embryology/multicystic-dysplastic-kidney-and-polycystic-kidney-disease/) - [Bladder, urachus and urethra](https://durgical.com/en/embryology/bladder-urachus-and-urethra/) - [Genital ducts: Wolffian (mesonephric) and Müllerian (paramesonephric)](https://durgical.com/en/embryology/genital-ducts-wolffian-and-mullerian/) - [Amniotic fluid: polyhydramnios and oligohydramnios](https://durgical.com/en/embryology/amniotic-fluid-polyhydramnios-and-oligohydramnios/) - [Pulmonary hypoplasia](https://durgical.com/en/embryology/pulmonary-hypoplasia/) - [ACE inhibitors and ARBs: fetal kidney damage](https://durgical.com/en/embryology/ace-inhibitors-and-arbs-fetal-kidney-damage/) - [Germ-layer derivatives: ectoderm, mesoderm, endoderm](https://durgical.com/en/embryology/germ-layer-derivatives-ectoderm-mesoderm-endoderm/) ## Related conditions - [Wilms tumour (nephroblastoma)](https://durgical.com/en/conditions/wilms-tumour/) - [Vesicoureteral reflux](https://durgical.com/en/conditions/vesicoureteral-reflux/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Embryology, Kidney, Bladder, and Ureter - StatPearls - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK547747/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Embryology, Genitourinary - StatPearls - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK559309/) (StatPearls Publishing (NCBI Bookshelf), 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/kidney-pronephros-mesonephros-metanephros-and-ascent/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/kidney-pronephros-mesonephros-metanephros-and-ascent/