Urinary System Development Flashcards
What part of the mesoderm is most important for the development of the urogenital system?
the intermediate mesoderm
What are the two parts of the urogenital ridge of the intermediate mesoderm?
- nephrogenic ridge (gives rise to urinary system)
2. Gonadal or genital ridge (gives rise to genital system)
The developing urinary system consists of three successive development phases, which are:
- pronephros
- mesonephros
- metanephros
When does the pronephric kidney develop? How long does it last?
Around the 2nd week of conception and really only lasts about a week.
THe pronephric kidney doesn’t last very long, but what part of it is super important?
the pronephric duct, which drains the pronephric kidney into the cloaca
WHat happens to the pronephric duct?
it remains and becomes the mesonephric duct (or Wolffian duct)
The mesonephros gives rise to what structures that eventually become really important in the male testis?
the mesonephric tubule - they become the efferent ductules of the male testis
What does the mesonephric duct gives rise to in the male only?
the ductus deferens
What does the mesonephric duct give rise to in both males and females?
the ureteric bud
What is another name for the ureteric bud?
metanephric diverticulum
What does the ureteric bud do?
It grows out from the mesonephric duct into the intermediate mesoderm (metanephrogenic mesoderm) to initiate the formation of the definitive kidney (the metanephros)
What does the ureteric bud give rise to?
ureter
renal pelvis
minor and major calyces
colecting ducts (tubules) up to the arch of the collecting duct
What is the rest of the nephron derived from?
the metanephric mesoderm that the ureteric bud grows to join
WHat induces the metanephric mesoderm to form the nephron?
signalling from the arched collecting duct (derivative of the ureteric bud)
Where are the metanephric kidneys initially located?
deep in the pelvic region
How do they get up into the abdominal region?
they appear to “ascend”, but in reality, the caudal embryo just rapidly grows away from them
How does this “ascent” affect blood supply?
They initially receive blood supply from the common iliac arteries, but as the caudal region of the body grows, the kidneys receive their blood supply from progressively more superior parts of the abdominal aorta
What does this mean in terms of anatomic variations?
this means it’s relatively common to have a kidney receive blood from multiple arteries off the aorta - some just don’t undergo apoptosis like they should.
What will result in renal agenesis?
failure of the ureteric bud and metanephric mesoderm to interact
Renal agenesis is unilateral on what side? in what gender?
left side
males
What newborn exam finding should make you concerned about renal agenesis?
having only one umbilical artery
What will result in a duplicated or branched ureter?
if the ureteric bud bifurcates prior to interaction with the metanephric mesoderm
note - this can also result in a divided kidney or multiple kidneys on one side (supernumerary kidney)
What can non-rotation or abnormal rotation of the kidney result in?
a kidney with a hilus that faces laterally instead of medially - doesn’t cause any issues
What is a pelvic kidney?
When the metanephric kidneys fails to migrate from the pelvis and thus fuses to form on epelvic kidney - functions normally
What is a crossed ectopic kidney?
it’s when one kidney migrates over to the other side and fuses with the other
What blocks the ascent of a horseshoe kidney?
the IMA
What structure will divide the cloaca into the rectum and urogenital sinus?
urorectal septum
The urogenital sinus is continuous with what structure that extends into the umbilical cord?
the allantois
The allantois will eventually form what?
the urachus
Describe the urachus
it’s a fibrous cord that extends from the bladder to the umbilicus
What does the urachus form in the adult?
the mediaN umbilical fold (covered by peritoneum
What are the three parts of the urogenital sinus?
vesicle part
pelvic (middle) part
phallic part
What does the vesicle part of the urogenital sinus form?
the urinary bladder (continuous with the allantois)
What does the pelvic part of the urogenital sinus form?
the bladder neck
prostatic urethra in males
entire urethra in females
What does the phallic part of the urogenital sinus form?
the penile urethra in males
What is the term for the region where the urorectal septum fuses with the tissue of the proctodeum?
the perineal body
What forms the trigone of the bladder?
the incorporation of the mesonephric ducts into the bladder wall
as the mesonephric ducts are incorporated into the posterior wall of the urogenital sinus, they ultimately reach the pelvic part that gives rise to the prostatic urethra. the ureters terminate in the posterior lateral wall of the vesical portion.
The proximal male urethra is part of the original urogenital sinus, but what is the distal male urethra derived from?
ectoderm - there is an ectodermal cord that grows inward form the glans
The connective tissue and smooth muscle of the urinary bladder is derived from what?
splanchnic (visceral) mesenchyme (mesoderm)
What is a urachal cyst?
when the chord of tissue that comprises the urachus has a region that doesn’t close completely, the epithelium will secrete per usual and a cyst will develop
these cysts can become infected
What is a urachal sinus?
when the urachus remains open in the region of the umbilicus - the epithelium will secrete out of it
What is a urachal fistula?
this is when the urachus remains open all the way from the bladder to the umbilicus - this means urine will come out
Failure of lateral plate mesoderm folding will cause what?
extrophy of the bladder in severe cases
epispadias in the male fetus
What causes megacystis in male infants?
they can have posteior urethral valves in the area hwere the ejaculatory ducts enter the prostatic urethra and they can block the outflow of urine from the bladder
this causes the bladder to enlarge and you get hydronephrosis and renal failure
What other developmental issue will be seen in megacystis?
lung hypoplasia because they’re not peeing so there is not amniotic fluid to cushing them
What region of mesoderm will give rise to the adrenocortical primordia?
the cranial part of the urogenital ridge (intermediate mesoderm)
What will migrate down into this region to form the adrenal medulla?
neural crest cells
What accounts for the relatively large size of the fetal adrenal gland compared to that of adults?
there is a fetal cortex that is really big and then regresses during the first year after birth to give way to the permanent cortex