From what embryological layer is the urogenital system derived?
Intermediate Plate Mesoderm
What embryonic layer forms the peritoneum?
The lateral plate mesoderm
splanchnic layer = visceral
Somatic layer = Parietal
What is the allantois?
An outpouching of endoderm at the hindgut that extends into the body stalk (body stalk eventually becomes umbilical cord)
It connects to the cloaca
What is the cloaca?
Caudal end of endoderm
It is divided into the urogenital sinus and rectum by a growth of mesoderm (Urorectal Sectum)
Quick summary of kidney development?
- Pronephros in early week 4
- Mesonephros by week 5
- Metanephros take over in week 9
Where in the embryo does the pronephros form?
What makes up the pronephros and what happens to it?
- Pronephric duct (drains into cloaca)
- Rudimentary Pronephric tubules
The tubules degenerate by week 5 but the duct remains
Where in the body does the mesonephros form?
Trunk region late in week 4/early week 5
What makes up the mesonephros?
The mesonephric duct, develops from the pronephric duct and still drains into the cloaca
Mesonephric tubules (Drain into the duct)
What happens to mesonephros after the metanephros takes over?
Mesonephric tubules -> Rete Testis
Mesonephric Duct -> Vas Deferens
In women they mostly degenerate and the remainder becomes ovaries.
Undifferentiated cells from the yolk sac migrate in and undergo spermatogonia & Oogonia
When/where does the metanephros develop?
Starts at week 5 and takes over functioning at week 9
Develops down on either side of the bladder
How does the metanephros develop?
Ureteric bud grows out from mesonephric duct into surrounding metanephric mesoderm and continually branches to form the collecting system
The stalk of the bud becomes the ureter and the expanded cranial end the renal pelvis
The metanephric mesoderm becomes the kidney
What do the branches of the ureteric bud become?
1st 4 generations of branches –> Major Calyces
2nd 4 generations of branches –> Minor calyces
Remaining gens become collecting tubules
What induces metanephros formation?
The ureteric bud and metanephric mesoderm Reciprocally Induce eachother
When do nephrons develop?
Continuously to about week 32
How do nephrons form?
Mesoderm converts to epithelium. Forming metanephric vesicles
Vesicles form metanephric tubules
Tubule & Collecting duct merge
Glomerulus forms and invaginates the tubule
Uriniferous tubule lenghtens
The renal corpuscle, loop of henle and proximal/distal collecting ducts
Define uriniferous tubule?
The nephron and the collecting duct
What structures develop from the ureteric bud?
How do the kidneys ascend from thier position by the bladder to their adult position?
Growth of lower body inferiorly away from them . not actual ascent
What happens to the kidney orientation?
They rotate 90*.
The hilum going from ventral to medial
How does the kidney vasculature develop?
Its forms and regresses segmentally as the kidney ascends
Heres some congenital abnormalities?
- Congenital Polycydstic Kidney Disease
- Aberrant Renal Arts
- Lobulated Kidney
- Transposition of kidney
- Horseshoe kidney
- Pancake kidney
What are aberrant renal arts?
Renal arteries enter the kidney not at the hilum
What is a lobulated kidney?
Not a nice smooth shape, instead lots of sticking out lobes
What is transposition of the kidney?
The kidney is on the wrong side, either:
- Below the other one
- Next to the other one
- Swapped sides with the other one
What is a horsheshoe and pancake kidney?
Horseshoe kidney - Fusion of the two kidneys at inf or sup pole
Pancake kidney - fuses at both poles forming a pancake of kidney across the whole abdomen