Development of the Urinary System and Congenital Abnormalities Flashcards
What are the three sets of kidneys that develop sequentially in embryogenesis?
Pronephros, Mesonephros, and Metanephros.
Which embryonic structure gives rise to the paired kidneys and ureters?
Intermediate mesoderm (via the nephrogenic ridge/cord).
What is the primordium of the permanent kidneys called?
Metanephros.
What are the two components of the metanephros?
Ureteric bud (diverticulum of the mesonephric duct).
Metanephric blastema (nephrogenic mesoderm cap).
How does the kidney acquire its typical shape during development?
Faster growth and bifurcation of ureteric ampullae in polar regions.
What is the embryologic origin of the urinary bladder?
Endoderm (from the superior part of the anterior cloaca after partitioning by the urorectal septum).
What structure forms the trigone of the bladder?
Absorbed common excretory ducts (from mesonephric ducts).
What is the fate of the allantois after birth?
It fibroses to become the median umbilical ligament.
What causes the kidneys to ascend during development?
Elongation of the ureter and acquisition of arterial supply from higher branches of the aorta.
What congenital anomaly results from fusion of the kidneys at adjacent poles?
Horseshoe kidney (may be trapped at the inferior mesenteric artery bifurcation).
What is a pelvic kidney, and what causes it?
A kidney that fails to ascend; caused by incomplete migration during development.
What are aberrant renal arteries?
Persistent lower arterial branches that normally regress during kidney ascent.
What is the clinical significance of bladder extrophy?
Failure of mesoderm migration around the cloacal membrane, leading to defects in the abdominal wall, bladder, and epispadias.
What are the possible anomalies of the ureter?
Double/bifid ureters, ectopic openings, or imperfect bifurcation of the ureteric bud.
What are the remnants of the mesonephric tubules in males and females?
Males: Efferent ductules (functional) and vestigial structures (e.g., appendix of epididymis).
Females: Non-functional tubules like the epoophoron and paroophoron.
What is the Wolffian (mesonephric) duct, and what does it form in males?
The mesonephric duct drains the mesonephros and persists in males to form the epididymis, vas deferens, and seminal vesicles.
What induces the formation of the mesonephros after the pronephros regresses?
Factors released by the transient pronephros trigger mesonephros development.
Why do metanephric vesicles fail to form nephrons in some cases?
Failure of inductive crosstalk between the ureteric ampulla and metanephric blastema, leading to cysts.
What is the significance of the ureteric bud’s bifurcation pattern?
It determines the branching of calyces and collecting tubules, shaping the kidney’s internal architecture.
Why do fetal kidneys appear lobulated, and when does this disappear?
Lobulation reflects nephron formation patterns; it typically disappears postnatally but may persist as a normal variant.
What vascular changes occur during kidney ascent?
Lower arteries (e.g., middle sacral) regress as the kidney receives new supply from higher lateral splanchnic arteries (e.g., renal arteries).
What is a cross-fused kidney?
One kidney crosses midline during ascent and fuses with the contralateral kidney, but ureters remain on their original sides.
What is malrotation of the kidney, and is it clinically significant?
Incomplete/abnormal 90° medial rotation during ascent; usually asymptomatic but may predispose to ureteropelvic obstruction
How does the urorectal septum contribute to bladder development?
It partitions the cloaca into the anterior urogenital sinus (bladder precursor) and posterior anorectal canal.
