Week 2 - Embryology Flashcards
What are the 3 systems which develop sequentially?
- Pronephros
- Mesonephros
- Metanephros
Where does the pronephros originally appear?
In the cervical (neck) region
Is the pronephros functional? Explain
No - no nephrotome
What does the pronephric duct extend between?
From the cervical region down to the cloaca
What does the mesonephros arise from?
The urogenital ridge
What is the urogenital ridge?
An area of intermediate mesoderm which gives rise to the gonads as well as the kidney
Is the mesonephros functional? Explain
Yes, but no way of conserving water
What two components create the embryonic kidney?
The mesonephric tubules and the mesonephric duct
What arises from the mesonephric ducts?
The ureteric buds
What develops from the ureteric buds?
The collecting system of the kidney, and the ureters
What stimulates development of the metanephros, or definitive kidney?
The ureteric bud interacts with the metanephric blastema
In what planes does the kidney migrate to reach is final destination?
- Cranio-caudal shift from L4 to T12 ish - pelvis to abdomen
- Laterally to meet up with adrenals
- 90* rotation so renal pelvis faces midline
What causes renal agenesis?
Failure of the ureteric bud to interact with the metanephric blastema
Why might someone have an ectopic ureter?
Splitting of the ureteric bud
What is the difference between multicystic kidney disease and polycystic kidney disease?
Multicystic - acquired, generally not very serious
Polycystic - genetic, poor prognosis
What does the bladder develop from?
The hindgut
What is the cloaca?
The dilated section at the caudal end of the hindgut
What is the difference between the allantois and the urachus?
Allantois in the embryo; becomes urachus in foetus.
What is the adult remnant of the urachus?
The median umbilical ligament
What does the urorectal septum divide the cloaca into?
The anorectal canal and the urogenital sinus
What are the 3 sections of the urogenital sinus, from cranial to caudal?
- Bladder
- Pelvic part
- Phallic part
What happens to the mesonephric duct in both males and females (3 steps)?
- Mesonephric ducts reach urogenital sinus
- Ureteric buds sprout from ducts
- Smooth musculature begins to appear and urogenital sinus expands
What happens to the mesonephric duct in males, once the urogenital sinus begins to expand? What drives this process?
- As UGS expands past junction of mesonephric duct and ureteric bud, each develops own entrance to sinus - buds no longer branch off ducts
- Prostate and prostatic urethra develop
- Mesonephric ducts become vas deferens
All driven by androgens
What happens to the mesonephric ducts in females, once the urogenital sinus has begun to expand? What drives this process?
As UGS expands, ducts begin to regress - no longer needed for kidney development, and not needed as vas deferens.
Ureteric buds open out onto UGS.
Driven by absence of androgens.
