Kidney Embryology

Question 1

What ducts does the kidney develop from?

Answer 1

Mesonephric

Question 2

What are the embryo ducts?

Answer 2

Mesonephric/Wolffian duct (males)

Paramesonephric/Mullerian duct (females)

Question 3

What do the embryo ducts form?

Answer 3

Mesonephric/Wolffian = epididymis, vas deferens, seminal vesicles
Paramesonephric/Mullerian = uterine tubes, uterus, cervix, upper 1/3 of vagina

Question 4

What are the main embryo structures in regards to kidney development?

Answer 4

Ducts - Wolffian/mesonephric and Mullerian/paramesonephric
Immature gonads
Mesenchyme

Question 5

How do the embryo ducts develop differently for males and females?

Answer 5

• Males: Mullerian/paramesonephric degenerates and mesonephric/Wolffian becomes male reproductive duct (lower part from the ureteric bud)
• Females: Wolffian/mesonephric degenerates apart form the lower part forming the ureteric bud and the Mullerian/paramesonephric forms the oviduct

Question 6

What are the different embryological parts of the kidney?

Answer 6

Pronephric
Mesonephric
Metanephric (functional)

Question 7

What is the most important embryological kidney part?

Answer 7

Metanephric

• forms the adult kidney
• functional
• formed from mesonephric duct

Question 8

What are the parts of the metanephric kidney part?

Answer 8

Ureteric bud

Metanephric bud

Question 9

What does the ureteric bud form?

Answer 9

Minor calyces
Major calyces
Renal Pelvis
Ureter

Question 10

What does the metanephric bud form?

Answer 10

LOH
DCT
PCT
Glomerulus and glomerular capillaries
Bowman's capsule

Question 11

What is the fate of the ureteric bud?

Answer 11

Comes into contact with the mesenchyme on the lateral side of the embryo and bifurcates into major calyces.
Major calyces divide into minor calyces which divide into collecting tubules
These structures are surrounded by the mesenchymal mass

Question 12

How does the kidney ascend from the pelvic region?

Answer 12

Metanephros originates in the sacral region at S1 and ascends to the lumbar region at T12 as the embryo unfolds
Renal arteries degenerate in the sacral region and new ones from at the end of ascent in the lumbar region

Question 13

What is the fate of the metanephric bud?

Answer 13

Fuses with the collecting duct and forms other structures (DCT, LOH, PCT, glomerulus/Bowman’s capsule/glomerular capillaries)

Question 14

What is the function of the kidney at the end of the 1st trimester?

Answer 14

Generates amniotic fluid

Placenta responsible for excreting waste products

Question 15

How is the amniotic fluid recycled?

Answer 15

Kidney produces amniotic fluid, fetus swallows it, kidney excretes it into amniotic fluid again

Question 16

What are the main congenital pathologies of the kidney?

Answer 16

• polycystic kidney
• kidney agenesis
• bifid ureter
• ectopic pelvic kidney
• horseshoe kidney

Question 17

What are the features of kidney agenesis?

Answer 17

Ureteric bud does not form and so the mesenchyme doesn’t receive any signals to form the kidney
Unilateral -> common, asymptomatic
Bilateral -> rare, don’t survive after birth, oligohydramnios, birth defects (club foot and lung defects)

Question 18

What are the features of bifid ureter?

Answer 18

Ureter splits into 2 forming a duplicate kidney or duplicate ureter
Common and doesn’t affect kidney function

Question 19

What are the features of ectopic pelvic kidney?

Answer 19

1 kidney stays in pelvic region and does not ascend
Both kidneys stay in pelvic region and fuse forming a pancake kidney
Still functional

Question 20

What are the features of a horseshoe kidney?

Answer 20

Kidneys fuse in the pelvic region and try to ascend however get stopped by the IMA and so ascend around it forming a U shape
Common and functional

Question 21

What are the features of polycystic kidneys?

Answer 21

Fluid filled cysts develop
Kidneys can fail
Cysts originate as dilations on the tubule -> enlarge and lose nephron contact -> become secretory in the epithelium increasing fluid secretions -> increased proliferation of cysts in the epithelium

Question 22

What are the causes of polycystic kidneys?

Answer 22

Autosomal Dominant = polycystin mutation, either PKD-1 which is more common or PKD2

Autosomal Recessive = fibrocystic mutations

Question 23

What is polycystin?

Answer 23

In the primary cilia for cell adhesion, calcium transport and cell cycle functions