Kidney and urogenital Flashcards
What mesoderm does the urogenital system originate from?
Intermediate mesoderm
How many kidney systems develop in the embryo?
3
What are the names of the three primitive kidney systems rostral to caudal?
Pronephros
Mesonephros
Metanephros
How permanent are each of the primitive kidney systems?
Pronephros - transient and non-functional
Mesonephros - may function for a short time then regresses
Metanephros - forms the permanent kidney
Interactions between which two primitive structures initiates the development of the kidney?
Uretic bud and metanephric mesenchyme
What type of interaction is displayed between the uterer bud and the metanephric mesenchyme?
Reciprocal inductive interactions
What does the uretic bud induce the mesenchyme to do?
Mesenchymal to epithelia transformation
What does the mesenchyme induce the uretic bud to do?
Branching morphogenesis
Why do we need to develop kidneys?
Removing toxic nitrogenous waste while conserving water.
Ammonia alone is extremely toxic so needs lots of water to dispose of.
Urea is less toxic so allows conservation of water, but requires specialised structures and physiology to produce it and remove it.
What week does the pronephros first develop?
Early 4th week
What spinal region does the pronephros initially arise in?
Cervical
By what time have the pronephros fully regressed?
The end of the 4th week
What week does the mesonephros first develop?
The end of the 4th week
What spinal region does the mesonephros initially arise in?
Upper thoracic to upper lumbar (T1-L2/3)
How many nephron pairs form on the mesonephros in total?
30
In the mesonephros: As caudal nodes develop what happens to rostral nodes?
The degenerate
By what week have the majority of the mesonephric nodes dissapeared?
The end of the 8th week
Does any mesonephros remain in the adult female? If yes, where?
No
Does any mesonephros remain in the adult male? If yes, where?
In males few caudal tubes and mesonephric duct persist as genital duct.
When is the mesonephros functional and why does it need to be?
End of the 4th week till regression in the 8th week.
While metanephros is developing
What time does the metanephros begin to develop?
The end of the 4th week
What ‘forms’ the metanephros?
Epithelial-mesenchymal tissue interaction between ureteric bud and the adjacent metanephric mesenchyme
What is the uretic bud?
A diverticulum/outgrowth from mesonephric duct close to cloaca
What is the progression of branching morphogenesis of the uretic bud?
Bud dilates and bifurcates, forming the renal pelvis.
Branches coalesce into major calyces.
Further branches form, enlarge and merge to form the minor calyces
Collecting tubules are formed by further branching, they converge on the minor major calyx forming the renal pyramid.
How many generations of bifurcation before the branches form major calyces?
4
What generation of bifurcation forms the collecting tubules?
5-6th
What forms the renal pyramid?
Collecting tubules converging with minor calyx
What name describes the tip of each collecting duct?
Ampullae
What describes the mesenchyme directly proximal to the ampullae?
Tissue caps
What does the collecting duct induce the tissue caps to form?
Small vesicles
What do the initial small renal vesicles give rise to?
S-shaped tubules
Where does the distal end of the tubule bind?
Fuses with the collecting duct
What associates with the proximal end of the tubule?
Capillaries which grow into the pocket, form the glomerulus and Bowman’s capsule
What does the WNT1 transcription factor induce?
Branching morphogenesis
Causes tissue to respond to the induction of the uretic bud
What does WNT1 regulate production of?
GNDF (stimulates branching)
What is Wilm’s Tumour caused by?
Mutation in the WNT1 gene
What are the effects of Wilm’s Tumour?
Kidney cancer in children
In what weeks does the metanephric kidney ascend?
6th-9th
Where does the metanephric kidney move in development?
Ascends to lumbar region (L1/2)
What mainly drives kidney ascent?
Differential growth, embryo lengthens but kidneys stay in place
As the kidney ascends does its blood supply stay the same? If not, how does it change?
No, changes to higher segmental arteries
What divides the cloaca into two?
Urorectal septum
What two holes does the cloaca divide into?
Urogenital sinus and the anal canal
What does the tip of the urorectal septum become?
The perineal body
What does the bladder form from?
The allantois and urogenital sinus
What is the allantois?
Outgrowth from the hindgut
What forms the bladder?
Superior part of the urogenital sinus continuous with the allantois
What connects the bladder with the umbilicus?
Urachus
What does the urachus form in the adult?
Medial umbillical ligament
What gives rise to the urethras?
The pelvic part of the urogenital sinus
Which parts of the male urethra develop from the pelvic urogenital sinus?
Prostatic and membranous
What part of the urogenital sinus forms the penile urethra?
Phallic
What does the pelvis urogenital sinus form in females?
Membranous urethra
Why do the ureters enter the bladder separately?
Mesonephric ducts are absorbed by the bladder
What forms the mesodermal trigone?
Mesonephric ducts merging with the bladder (uretic orifices)
Initially what germ layer forms the trigone?
Mesoderm
Over time how does the trigone change?
Mesodermal lining changed with endodermal epithelium
How is the trigone distinct?
Mesoderm while rest of the bladder is endoderm
How is the trigone different in males?
More prominent as the mesonephric ducts regress less
What ‘spinal’ region does the pronephros form in?
Cervical
The trigone is formed by…
Incorporation of the distal ends of the mesonephric ducts
What does the allantois form?
The apex of the bladder and the urachus
What does uretic bud form?
Renal pelvis, calyces, collecting ducts
What forms the ureter?
Ureteric bud
