Urinary System Embryology Flashcards
What is the allantois?
An outpouching of endoderm at the hindgut that extends into the body stalk
What does the body stalk later form?
Umbilical cord
What is the cloaca?
Common outlet for digestive, urinary and reproduction trac
How does the cloaca develop?
- Cloaca divides to form rectum (GI tract) and anteriorly the urogenital sinus
- Mesonephric duct drains into urogenital sinus
- Urogenital sinus later forms the urinary bladder and its caudal ends forms the urethra
How many sets of kidneys develop during nephrogenesis?
- 3
- Pronephros
- Mesonephros
- Metanephros
What is the pronephros formed from?
Pronephric duct and rudimentary pronephric tubules
What does the pronephros drain into?
Cloaca
When does the pronephros degernate by?
Week 5, except the pronephric duct
What is the mesonephros formed from?
Intermediate mesoderm in trunk region, late week 4
What does the mesonephric duct develop from?
Pronephric
For how long does the mesonephros function as the kidney?
About 4 weeks
What do the mesonephric tubules drain into?
Mesonephric duct
When does the metanephros start to develop and function?
The metanephros starts to develop from about week 5 but starts to function around week 9
What does the metanephros consist of?
- Ureteric bud that develops off the mesonephric duct
- Metanephric mesoderm (most caudal part of the intermediate mesoderm)
What does the ureteric bud develop from?
Mesonephric duct
What happens to the mesonephros?
- 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)
What does the mesonephros develop into?
Incorporated into developing gonad
What does the mesonephric tubules develop into?
- Males
- Rete testis
- Females
- Degenerates
What does the mesonephric duct develop into?
- Males
- Vas deferens
- Females
- Degenerates
What does the ureteric bud develop into?
- 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
How does the nephron develop?
Uretic bud and metanephric mesoderm reciprocally induce each other
What is a nephron?
- Nephron is the renal corpuscle + proximal tubule (PCT) + loop of Henle + distal tubule (DCT)
What is a uriniferous tubule?
- Uriniferous tubule is the nephron and collecting duct
What does a nephron develop from?
Metanephric mesoderm
What does the collecting duct develop from?
Ureteric bud
What does the calyces develop from?
Ureteric bud
What do the renal pelvis’ develop from?
Ureteric bud
What does the ureter develop from?
Ureteric bud
Where do the kidneys initially lie and where do they end up?
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 90o)
- Ascend stops when they come in contact with adrenal glands
Segmental breakdown and reform of vascular supply occurs during ascent
Summarise in steps the develop of the kidneys?
- Allantois and cloaca develop into urinary bladder and urethra
- 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
- Ureteric buds grows out of the caudal end of the mesonephric duct
- This branches to form the renal pelvis, calyces and collecting duct
- Ureteric bud and the metanephric mesoderm reciprocally induce each other
- Kidneys ascend due to differential growth of abdominopelvic structures and acquires new blood vessels
- Rotates so that hilum faces medially
What does the allantois develop into?
Urinary bladder
