S2.1 Development Of The Urinary System Flashcards
Where does development of the kidneys begin?
Intermediate mesoderm
What is the pronephros?
The first kidney system that appears (week 4)
Drives the development of the mesonephric duct
What is the mesoneprhos?
The mesonephros and mesonephric duct make up the embryonic kidney.
The mesonephric duct sprouts the ureteric bud, which induces development of the definitive kidney.
What is the metanephros?
When the ureteric bud expands and branches into the metanephric blastema forming the kidneys definitive structure
Describe the ascent of the kidneys
The metanephric kidney first appears in the pelvic region. It then undergoes an apparent caudal to cranial shift, crossing the arterial fork.
NB the kidneys don’t actually ascend just the trunk extends downwards
How are accessory renal arteries formed?
As the kidneys ascend, they receive their blood supply from new branches and the original disappear. However if the original remain, they form accessory renal arteries
What is renal agenesis?
The ureteric bud fails to interact with the intermediate mesoderm so can’t form kidney
What migration defects can occur to the kidney?
If a kidney fails to cross the arterial fork, it ends up much lower than it should be.
During their ‘ascent’ the kidneys lie extremely close to one another. Their inferior poles can fuse and form a horseshoe kidney which gets stuck under the IMA.
What is a duplication defect?
Splitting of ureteric bud forming a double ureter. Can cause incontinence.
How is the urogenital sinus formed?
The cloaca is divided by the urorectal septum into the urogenital sinus (future bladder and urethra) and anorectal canal (future rectum and anal canal).
The lumen of the allantois becomes obliterated to become the urachus; the median umbilical ligament in adults.
How is the male bladder formed?
Mesonephric ducts reaches urogenital sinus
Ureteric Bud Sprouts from MD
Smooth musculature appears
UBs and MDs make independent openings in UGS
Prostate formed.
MD is maintained in males, forming the vas deferens, UB forms the ureters.
How is the female bladder formed?
Same way as in males, but without male hormones, the Mesonephric duct regresses. Therefore females do not form prostates or vas deferens
What are the different parts of the male urethra?
Pre-Prostatic
Prostatic
Membranous
Spongy
What is hypospadias?
A defect in fusion of urethral folds. The urethra opens onto the ventral surface, rather than at the end of the glans.
