Embryology of urogenital system

Question 1

What are the stages of kidney development?

Answer 1

3 overlapping phases:
- pronephros (early week 4-end week 4)
- mesonephros (late week 4-week 10)
- metanephros (early in week 5)

Question 2

How do the kidneys end up in their position in the abdomen?

Answer 2

initially the developing kidneys lie in close proximity to each other in the pelvis (S1)
due to growth of the embryo caudally and diminution of the curvature
they shift (relative ascent) to a more cranial position in the abdomen by 9th week and move apart
during the ‘ascent’ there is a 90 degree medial rotation

Question 3

Common anatomical variations and abnormalities of kidneys

Answer 3

duplex system - 2 ureters from 1 kidney site
horseshoe kidney
pelvic kidney
renal agenesis - absence of kidney
arterial variations:
- aberrant renal arteries - distal arteries from ascent persist
- more than one renal artery to each kidney
- these arteries can cross the ureter, may result in hydronephrosis

Question 4

When do the gonads develop male or female characteristics?

Answer 4

7th week

Question 5

What are the gonads called before the 7th week (before they develop male/female characteristics)?

Answer 5

indifferent gonads