Renal Embryology Flashcards
3 embryonic germ cell layers
ectoderm
mesoderm
endoderm
Mesenchyme
Loosely organized embryonic connective tissue (primarily derived from mesoderm, but sometimes also from other layers)
The urogenitl system develops from…, specifically
intermediate mesoderm
specifically mesenchymal cells
During lateral (transverse) folding, the intermediate mesenchyme is pulled ventrally forming…
two urogenital ridges (on the dorsal body wall)
Each urogenital risge gives rise to…
nephrogenic cord and ridge, which form the urinary system
3 sets of successive kidneys form from the nephrogenic cord in the craniocaudal axis, called…
pronephros
mesonephros
metanephros
From the pronephros to the cloaca (causal end of gut tube), what will form?
Longitudinal nephric ducts
Pronephros are rudimentary, transient structures that develop bilaterally at…
the 5th-7th cervical segments
Two components of pronephros
- several paired clusters of cells (in lower cervical segments)
- pronephric ducts (paired tubular structures that extend caudally to the cloaca)
What happens to the cranial parts of pronephric ducts?
They degrade (cuadal parts persist)
Caudal pronephric ducts transition into…
mesonephric duct
Caudal growth of pronephric/mesonephric ducts induces formation of…
mesonephric buds
Mesonephric tubules within the mesonephric buds connect with…
mesonephric duct
What are mesonephroi?
They function as interim kidneys in humans for ~4 weeks before the definitive kidneys (i.e. metanephroi) develop
What do we call the “definitive” kidneys?
metanephroi
Renal corpuscles form from…
mesonephric tubules
Glomerular (Bowman’s) capsule forms at the…
medial end of the mesonephric tubule
Glomerulus forms from…
the developing aorta
Mesonephric ducts do not degenerate in everyone. Who keeps their mesonephric ducts?
Mesonephric ducts degenerate in females, but persist in males!
What are the primordia of permanent, definitive kidneys?
Metanephroi
Metanephroi begin developing around… and begin functioning around…
Metanephroi begin developing around week 5 and begin functioning around week 9
Two functional components of metanephroi
- Collecting portion: ureteric bud
- Excretory portion: metanephrogenic blastema
What is the ureteric bud?
Outgrowth from mesonephric duct near caudal end (sacral region)
What is the metanephrogenic blastema?
The ureteric bud stalk will become…
the ureter
Generations of repetitive branching in the ureteric bud forms different components of mature kidneys.
First 4 generations: major calyces
Second 4 generations: minor calyces
11 additional generations: system of collecting ducts
What is reciprocal induction?
Interactions between ureteric bud and metanephrogenic blastema, each one inciting the other to grow. They signal to each other reciprocally.
What is WT1
Transcription factor expressed in metanephrogenic blastema. Involved in the induction of ureteric bud growth
What is GDNF?
Glial-derived neurotropic factor (GDNF) is a signalling molecule. Expressed in metanephrogenic blastema. Regulated by Pax2.
Uriniferous tubules form fro two embryologically different components:
nephron: metanephrogenic blastema
collecting tubules/duct: ureteric bud
Describe the formation of the mesenchymal cap (3 steps)
What is Potter syndrome?
Bilateral kidney agenesis. Can be caused by RET gene mutation.
What are the consequences of Potter syndrome?
Absence of kidneys leads to decreased urine production and therefore oligohydraminos (low amniotic fluid levels).
This leads to…?
What is polycystic kidney disease?
Autosomal dominant polycystic kidney disease is one of the most common hereditary diseases linked to mutations in POLYCYSTIN genes (PKD1 & PKD2)
What is another name for nephroblastmas?
Wilm’s tumours
What are nephroblastomas/Wilm’s tumours?
?
How do developed kidneys move from the pelvis, where they developed, to the ?
The relative ascent of the kidneys is attributed to the growth of the caudal end of the embryo.
While kidneys “ascend”, what else happens?
- The kidneys rotate by 90deg so that the hilum faces medially in mature individuals.
- Origins of renal blood changes & previos branches degrade…?
What are horseshoe kidneys?
Atypical rotation and ascension of the kidneys associated with renal pole fusion (usually inferior poles).
What is the nae of a rare variant of horseshoe kidneys?
Sigmoid kidney (inferior pole of one kidney fuses with the superior pole of the other).
What are the symptoms of horseshoes kidneys?
Typically asymptomatic
Horseshoe kidneys are prone tocomplications because of poor drainage. Examples include…
hydronephrosis
??
What are the 2 main types of urinary tract duplication?
- Incomplete division: divided kidney with a bifid ureter
- Complete division: double kidney with a bifid ureter
Urinary tract duplications result from…
abnormal divisions of the ureteric bud
What is an example of ectopic kidney?
Pelvic kidney
What is an ectopic kidney?
???
What is the cloaca?
It is a common outlet at the caudal end of the developing embryo
What are the 3 parts of the urogenital sinus?
- Vesical part
- Pelvic part
- Phallic part
Partitioning (septation) of the cloaca involves the formation of…
the urorectal septum
Name 2 types of urachal anomalies
Urachal cysts
Urachal fistula
what is the urachus?
Briefly describe the formation of ureters.
What forms the trigone of the bladder?
The expanded flattened regions of mesonephric ducts
Our bladder (inside) comes from 2 different germ layers…
endoderm
mesoderm
Suprarenal (adrenal) glands arise from 2 components:
- mesodermal mesenchyme
- neural crest cells (ectoderm)
The cortex of adrenal glands forms from…
mesodermal mesenchyme
The medulla of the adrenal glands forms from…
neural crest cells (ectoderm)
The cortex begins as an aggregation of mesenchymal cells.
Two waves of these cells “delaminate” from the coelomic epithelium, forming…
The mesenchymal cells delaminate to form the fetal cortex (mostly regresses), followed by the adult cortex.
The medulla of the adrenal glands is formed by migrating…
neural crest cells
Neural crest cells that form the medulla of the adrenal glands differentiate into…
chromaffin cells
