Urinary System Embryology

Question 1

What is the allantois?

Answer 1

An outpouching of endoderm at the hindgut that extends into the body stalk

Question 2

What does the body stalk later form?

Answer 2

Umbilical cord

Question 3

What is the cloaca?

Answer 3

Common outlet for digestive, urinary and reproduction trac

Question 4

How does the cloaca develop?

Answer 4

1. Cloaca divides to form rectum (GI tract) and anteriorly the urogenital sinus
2. Mesonephric duct drains into urogenital sinus
3. Urogenital sinus later forms the urinary bladder and its caudal ends forms the urethra

Question 5

How many sets of kidneys develop during nephrogenesis?

Answer 5

• 3
  
  • Pronephros
  • Mesonephros
  • Metanephros

Question 6

What is the pronephros formed from?

Answer 6

Pronephric duct and rudimentary pronephric tubules

Question 7

What does the pronephros drain into?

Answer 7

Cloaca

Question 8

When does the pronephros degernate by?

Answer 8

Week 5, except the pronephric duct

Question 9

What is the mesonephros formed from?

Answer 9

Intermediate mesoderm in trunk region, late week 4

Question 10

What does the mesonephric duct develop from?

Answer 10

Pronephric

Question 11

For how long does the mesonephros function as the kidney?

Answer 11

About 4 weeks

Question 12

What do the mesonephric tubules drain into?

Answer 12

Mesonephric duct

Question 13

When does the metanephros start to develop and function?

Answer 13

The metanephros starts to develop from about week 5 but starts to function around week 9

Question 14

What does the metanephros consist of?

Answer 14

• Ureteric bud that develops off the mesonephric duct
• Metanephric mesoderm (most caudal part of the intermediate mesoderm)

Question 15

What does the ureteric bud develop from?

Answer 15

Mesonephric duct

Question 16

What happens to the mesonephros?

Answer 16

• Will be incorporated into developing gonad
• (undifferentiated cells from yolk sac migrate in to form the spermatogonia/oogonia)
• Mesonephric tubules becomes the rete testis
• Mesonephric duct becomes the vas deferens
• (in females the mesonephros becomes the ovary but the tubules and mesonephric duct degenerate)

Question 17

What does the mesonephros develop into?

Answer 17

Incorporated into developing gonad

Question 18

What does the mesonephric tubules develop into?

Answer 18

• Males
  
  • Rete testis
• Females
  
  • Degenerates

Question 19

What does the mesonephric duct develop into?

Answer 19

• Males
  
  • Vas deferens
• Females
  
  • Degenerates

Question 20

What does the ureteric bud develop into?

Answer 20

• Uretic bud undergoes repeated branching at its distal end
• Stalk becomes the ureter, the expanded cranial end becomes the renal pelvis
• First 4 generations of branches become confluent to become the major calyces
• Next 4 generations from the minor calyces
• Remaining generations form the collecting tubules

Question 21

How does the nephron develop?

Answer 21

Uretic bud and metanephric mesoderm reciprocally induce each other

Question 22

What is a nephron?

Answer 22

• Nephron is the renal corpuscle + proximal tubule (PCT) + loop of Henle + distal tubule (DCT)

Question 23

What is a uriniferous tubule?

Answer 23

• Uriniferous tubule is the nephron and collecting duct

Question 24

What does a nephron develop from?

Answer 24

Metanephric mesoderm

Question 25

What does the collecting duct develop from?

Answer 25

Ureteric bud

Question 26

What does the calyces develop from?

Answer 26

Ureteric bud

Question 27

What do the renal pelvis' develop from?

Answer 27

Ureteric bud

Question 28

What does the ureter develop from?

Answer 28

Ureteric bud

Question 30

Where do the kidneys initially lie and where do they end up?

Answer 30

Kidneys initially lie on either side of bladder in the developing pelvis, then appear to ascend into the abdomen mainly due to differential growth of lower body inferiorly away from kidneys: * They come to lie in upper abdomen (T12-L3) * Hilum rotates from ventral to medial (about 90^o) * Ascend stops when they come in contact with adrenal glands Segmental breakdown and reform of vascular supply occurs during ascent

Question 31

Summarise in steps the develop of the kidneys?

Answer 31

1. Allantois and cloaca develop into urinary bladder and urethra 2. Intermediate mesoderm develops into rudimentary pronephros in neck (week 4), mesonephros in trunk region (week 5 to 9) with a duct and tubules, duct drains into cloaca 3. Ureteric buds grows out of the caudal end of the mesonephric duct 4. This branches to form the renal pelvis, calyces and collecting duct 5. Ureteric bud and the metanephric mesoderm reciprocally induce each other 6. Kidneys ascend due to differential growth of abdominopelvic structures and acquires new blood vessels 7. Rotates so that hilum faces medially

Question 32

What does the allantois develop into?

Answer 32

Urinary bladder