Embryology of the Renal System Flashcards
What are the 3 germ layers of the embryo?
Ectoderm
Mesoderm
Endoderm
What of the 3 germ layers does the kidneys form from?
Mesoderm
What are the 3 parts of the mesoderm?
Paraxial
Intermediate
Lateral
What part of the mesoderm does the kidneys form from?
Intermediate mesoderm
What does the dorsal aorta form?
Descending aorta
What are the 3 stages of kidney development in the embryo?
Pronephros
Mesonephros
Metanephros
At what end of the embryo does the intermediate mesoderm begin to segment?
What does this form?
When about does this occur?
Cranial end
Pronephri
Day 22
Are pronephri functional?
No
What do the pronephri become?
Mesonephros
Where does the filtrate from mesonephros drain to?
Mesonephric duct which is forming alongside the mesonephri
Are mesonephri functional?
Yes
How many mesoneprhic tubules are originally formed?
How many are left once these have regressed?
What happens to the remaining mesonephric tubules?
40
20
Function as excretory units between weeks 6-10 and then regress
When do the mesonephric tubules begin to regress?
End of week 5
What vertebral levels are the remaining mesonephric tubules left at?
L1-L3
What develops at approximately week 5?
Metanephros
When does the metanephros begin to function?
Weeks 9-11 (mesonephros stops functioning at about week 10)
What does the metanephros develop into?
The permanent kidney
What does the metanephros develop from?
Ureteric bud (collecting system) Metanephric blastema (filtering system)
What does the ureteric buds sprout from?
The mesonephric ducts
At what day does the ureteric buds sprout from the distal mesonephric ducts?
Day 28
At what day does the ureteric buds penetrate a portion of the metanephric mesenchyme?
Day 32
What does the metanephric mesenchyme become once the ureteric bud connects to it?
Metanephric blastema
What is the outcome of failure of the metanephric mesenchyme and ureteric bud to connect (either due to failure of ureteric bud to grow fully or failure of it to grow at all)?
Kidney agenesis (bilateral kidney agenesis is incompatible with life)
What part of the adult kidney does the ureteric bud form?
the collecting system e.g. ureter, renal pelvis, major/ minor calyces, 1-3 million collecting ducts
How does major calyxs form?
Metanephric mesenchyme signals to the ureteric bud to start diving (get approximately 4 generations of bifurcation)
Intussusception then occurs leading to the major calyx
This repeated to form the minor calyxs, etc.
What part of the metanephros forms the nephron?
Metanephric blastema
How does the nephrons of the kidney form?
Branches of the ureteric buds release signals causing metanephric tissue to form nephric vesicles
These elongate and eventually join with the ureteric bud = collecting tube with nephron attached (also seek out capillaries and expand around them = Bowman’s capsule)
What forms the collecting ducts?
Ureteric bud
Where in the body is the kidney formed?
What happens to them once they have formed?
Very low down in the pelvis
Migrate up
How do the renal arteries develop?
Start very low down on the aorta and then as the kidneys migrate up, new vessels form and old ones regress (if they don’t regress, accessory renal artery is formed)
Are the adrenal glands related to the kidney developmentally/
No
At what week of development are the kidneys lying in the correct position?
Week 9
What developmental anomaly occurs when the inferior poles of metanephroi meet and fuse before ascent?
Horseshoe kidney
Why is a horseshoe kidney located lower down in the pelvis?
It is trapped beneath inferior mesenteric artery which projects from the anterior rota
What germ layer does the bladder form from?
Endoderm
What does the bladder form from?
The primitive urogenital sinus which forms from the cloaca (hindgut endoderm
What are the 2 structures that the cloaca (hindgut endoderm) forms?
Rectum
Primitve urogenital sinus
What structures does the primitive urogenital sinus form? (3)
Bladder
Pelvic urethra
Definitive urogenital sinus
Where does the cloaca pass into in development?
Umbilical cord
Out of the ureteric bud and the mesonephric duct, what initially communicates with the bladder?
Mesonephric duct
What does the mesonephric contribute to in males?
Reproductive tract
What tissue forms the trigone in the bladder?
Tissue of the mesonephric duct where it comes together (non-contractile unlike the rest of the bladder)
Name for when the communication between the bladder and anterior abdominal wall is retained?
Urachal fistula
What is formed when there is a persistent portion of urachus between the umbilicus and bladder?
Urachal cyst
What forms when there is a non-communicating dilation of the arches at the umbilical end?
Urachal sinus
