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  • state the developmental origins of the urogenital and nephrogenic ridges
  • Happens during the 4th week of development
  • intermediate mesoderm (located between the somites and lateral mesoderm) begins to proliferate
  • This forms bilateral, longitudinal urogenital ridges, which bulge into the dorsal aspect of the coelom
  • Nephrogenic ridge (cord): Formed by the lateral part of each ridge
  • which gives rise to much of the urinary system, while the medial part of the ridge becomes the genital, or gonadal ridge, responsible for the formation of parts of the male and female reproductive systems.

  • state the roles of the ureteric bud and metanephric mesoderm in kidney development

  • list the parts of the kidney tubule and duct system that are derived from the ureteric bud and metanephric vesicle

  • outline the ascent of the kidneys and the accompanying changes in blood supply

  • outline the development of the bladder and urethra from the urogenital sinus

  • outline the role of the mesonephric ducts in the formation of the trigone of the bladder

  • explain the following in terms of abnormal development of the urinary system: renal agenesis, pelvic kidney, horseshoe kidney, polycystic, ectopic kidneys, exstrophy bladder .


Renal agenesis

  • lack of a kidney
  • results from the absence of a ureteric bud, or from failure of the ureteric bud to reach the metanephric mesoderm and induce nephron formation
  • If the condition is unilateral, the remaining kidney can usually compensate by enlarging
  • Bilateral renal agenesis is a very serious condition, and many newborn infants affected with the condition die shortly after birth

Ectopic kidney

  • usually found in the pelvis and results from its failure to "ascend"
  • It usually retains its "primitive" blood supply from vessels in the pelvis

Horseshoe kidney

  • Early in development, the lower poles of the two kidneys are closely related and can fuse
  • The ascent a horseshoe kidney is restricted because the fused part becomes trapped under the origin of the inferior mesenteric artery as it leaves the aorta
  • Early division of the ureteric bud leads to partial or complete duplication of the ureter
  • This condition is rarely associated with a duplicate kidney, however

Polycystic kidneys

  • contain large numbers of small or large cysts
  • At one time it was thought that the condition arose as a result of the failure of the distal tubules and collecting tubules to unite
  • In most cases, the cysts seem to result from dilation of specific parts of the developing nephron