DurgicalDurgical
EN
Open the app

Embryology · Urogenital system

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 · Ureters · Renal pelvis · Left renal artery · Right renal artery

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

  1. Intermediate mesoderm forms the nephrogenic cord on each side of the embryo.
  2. The pronephros appears in the cervical region and almost immediately regresses.
  3. The mesonephros forms tubules and the mesonephric duct, which reaches the cloaca.
  4. The ureteric bud sprouts from the mesonephric duct and enters the metanephric blastema.
  5. The bud branches to form the ureter, pelvis, calyces and collecting ducts.
  6. Each bud tip induces a vesicle in the blastema that becomes a nephron.
  7. 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.

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)

See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of 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 (StatPearls Publishing (NCBI Bookshelf), 2023); Embryology, Genitourinary - StatPearls - NCBI Bookshelf (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.