What are the three evolutionary stages of kidney development in humans?

The human kidney develops through three stages, reflecting evolutionary history: Pronephros (cervical, nonfunctional, regresses early), Mesonephros (thoracolumbar, temporarily functional), and Metanephros (sacral, forms the permanent kidneys).

How does the collecting system of the kidney form during development?

The collecting system originates from the ureteric bud, an outgrowth from the mesonephric duct. It invades the metanephric blastema and undergoes branching to form structures like the ureter, renal pelvis, calyces, and collecting ducts.

What is the role of the intermediate mesoderm in kidney development?

The intermediate mesoderm is a longitudinal strip of intraembryonic mesoderm that forms the urogenital ridge. Its lateral part, the nephrogenic cord, gives rise to the urinary system, including the kidneys.

What are some common congenital kidney abnormalities?

Common abnormalities include renal agenesis (unilateral or bilateral), horseshoe kidney (fused lower poles), polycystic kidney (multiple cysts), and pelvic kidney (failure to ascend). These often arise from developmental disruptions.

How do the kidneys ascend and rotate during development?

The kidneys initially form in the sacral region and ascend to the T12–L3 levels due to growth of the posterior abdominal wall. They also undergo a 90° rotation, with the hilum moving from an anterior to a medial orientation.

What is the cloaca and how does it relate to kidney development?

The cloaca is the terminal part of the hindgut, divided by the urorectal septum into dorsal (primitive rectum) and ventral (primitive urogenital sinus) parts. It contributes to structures involved in urinary and reproductive system formation.

How are nephrons formed during kidney development?

Nephrons develop from the metanephric blastema through stages: cells aggregate into caps, form vesicles, and then S-shaped tubules. These differentiate into components like Bowman’s capsule, glomerulus, and renal tubules, connecting to collecting ducts.

Kidney Development – Pronephros to Metanephros

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