11/20 Development Of Urinary System Flashcards
Formation of multiple sets of kidneys is in weeks?
4-8
Relocation of kidneys in urinary development happens in week?
9
Significant urine formation in urinary development happens in week?
11
Nephrogenesis occurs when prenatally?
Through week 36
When is the critical period for kidneys?
Most of human gestation (through week 36)
Fewer nephrons is associated with an increased risk for?
Hypertension
After birth, the glomerular filtration rate increases rapidly due to
decreased renal vascular resistance and increased renal blood flow
What is the general process of renal development?
Clusters of cells and ducts form, connected to cloaca
Columns of tissues use ducts and develop primitive, temporary nephrons
Kidneys form in pelvic region (at caudal end of ducts) and develop permanent nephrons
Kidneys relocate to their final positions
Cloaca is divided and part of it forms urinary bladder
During the urogenital ridge stage of renal development what is the state of sexual development?
Embryo is in undifferentiated state of sexual development, phenotypically identical regardless of genetics
What is the urogenital ridge and what does it contain?
Elevated intermediate mesoderm on either side of the dorsal aorta, along the posterior abdominal wall
Contains: Nephrogenic cord, Gonadal ridge
What does endoderm do in the urogenital ridge of renal development?
Endoderm forms epithelial lining and glands of the urinary bladder
Neural crest cells may play a minor role
How many sets of kidneys develop in weeks 4-5? How many of these become the permanent kidneys?
3 sets develop
1 set becomes permanent kidneys
What is the pronephroi set of kidneys? where are they?
Practice set of kidneys, used to develop a duct system
• On same plane as pericardial cavity
What are the three sets of kidneys that develop? In which weeks?
Weeks 4-5
Pronephroi, mesonephroi, metanephroi
What are the mesonephroi set of kidneys?
Temporary set of kidneys, used until the metanephroi are complete
What are the metanephroi set of kidneys?
Permanent set of kidneys
When are the pronephroi present? What is the purpose?
Present only in week 4
Purpose is to create tubular structures to be used later
What do the pronephroi contain?
Nonfunctional cell clusters in cervical region
Pronephric ducts
What are the pronephroi nonfunctional cell clusters made of? Do they persist?
made of pronephric tubules that degenerate
Where do the pronephric ducts run? Do they persist?
run from pronephric tubules to cloaca
persist and are used by mesonephroi
When are the mesonephroi present?
Appear late week 4
Degenerate after week 11
What is significant about week 11 in relation to renal function?
Urine formation contributes to amniotic fluid
What do the mesonephroi consist of?
Long columns of tissue caudal to pronephros
Made of mesonephric nephrons and tubules
Are the mesonephroi functional?
temporarily functional until metanephroi take over in week 11
Where do the mesonephric ducts run?
From mesonephric nephrons and tubules to cloaca
When do metanephroi appear? Become functional?
Appear in early week 5
Take a month to become functional, and take over urine production from mesonephroi in week 11
What do metanephroi develop from?
Develop from intermediate mesoderm in two ways:
Ureteric bud and metanephric blastema
What is the ureteric bud?
lateral outgrowth of mesonephric duct near cloaca
What is the metanephric blastema?
Renogenic tissue surrounding ureteric bud
Interactions between what forms the metanephroi?
Ureteric bud epithelium and cells within metanephric blastema
What is metanephroi development dependent on?
Retinoic acid
Renogenic malformations can be caused by retinoic acid excess or deficiency?
Excess and deficiency can both cause malformations
What are some other developing tissues that are dependent upon proper levels of retinoic acid?
Neural tube development
What does the ureteric bud form?
Forms collecting system (collecting duct through renal pelvis)
What do the metanephric blastema form?
Forms nephrons
What is the inheritance of bilateral renal agenesis? Is it compatible with life?
Multifactorial inheritance, typically incompatible with life
What is the treatment for bilateral renal agenesis?
Dialysis, renal transplant
What is bilateral renal agenesis associated with? What are the issues this causes?
Potter syndrome
Major bilateral kidney issues, leading to…
Oligohydramnios, leading to…
Fetal compression, leading to…
Various issues like
- talipes equinovarus
- craniofacial anomalies
- pulmonary hypoplasia
What is the inheritance of unilateral renal agenesis? Is it compatible with life?
Multifactorial inheritance (mutations)
Usually asymptomatic due to compensatory hypertrophy of contralateral side
What is the treatment for unilateral renal agenesis?
Lifelong assessment of kidney function
How can you tell bilateral renal agenesis versus unilateral renal agenesis apart on a fetal sonogram?
Bilateral renal agenesis will lack both renal arteries
Unilateral renal agenesis will lack one renal artery, will be suspected in neonates with a single umbilical artery in umbilical cord
What is the final morphology of allantois?
Urachus, then median umbilical ligament
What is the final morphology of umbilical arteries?
Bilateral internal iliac and superior vesical arteries, medial umbilical ligaments
What are the steps for development of the collecting system via the ureteric bud?
Ureteric bud elongates and penetrates the metanephric blastema, then is renamed the ureteric bud stalk
Branching of ureteric bud forms:
renal pelvis, then the major calyces, then the minor calyces, and finally collecting ducts
What is something that can go wrong during development of the collecting system via the ureteric bud?
Duplication of the collecting system (e.g. bifid ureter)
What are the steps for development of the nephrons via the metanephric blastema?
Renal vesicles develop in the ampulla of each collecting duct
Each renal vesicle elongates into an S-shaped renal tubule to meet with its collecting duct
A glomerulus migrates into the open distal end of each (still elongating) renal tubule
Renal tubule invaginates distally and forms Bowman’s capsule
Renal tubule lengthens proximally and differentiates into the rest of the nephron (proximal convoluted tubule, loop of Henle, distal convoluted tubule, connecting tubule)
where do the kidneys lie before relocation?
close together in the pelvis with hilum facing anteriorly
What are the steps for the relocation of the kidneys?
As abdomen elongates the kidneys move apart, medially rotate 90°, and appear to ascend relative to other abdominal organs
Renal vessels continually form and regress during the relocation
By week 9, kidneys contact adrenal glands = adult position of kidneys
Where is the kidney in renal ectopia? (Ectopic kidney) What happened? What about the associated vasculature?
Often in pelvis (pelvic kidney) and often associated with malrotation of the kidney
• Vascular origin is variable
What is the embryological basis of renal ectopia?
Error(s) in the relocation process
Is renal ectopia compatible with life? What happens?
Typically asymptomatic, but can be associated with vesicoureteral reflux (VUR), which can lead to UTIs, kidney stones, hydronephrosis
• Excellent prognosis
What happens in renal fusion? (Horseshoe kidney) Where do the kidneys go? What about vasculature?
Inferior poles of both kidneys fuse together before or during relocation but often maintain separate excretory units and ureters
Usually lie in pelvic region because their ascent is prevented by the inferior mesenteric artery
* Vascular origin is variable
Is renal fusion (horseshoe kidney) compatible with life?
Typically asymptomatic, but should be evaluated for vesicoureteral reflux (VUR), obstructive uropathy, hydronephrosis
What is the difference between supernumerary aberrant and accessory renal vessels?
Aberrant renal vessels supply renal pole
Accessory renal vessels supply renal hilum
What is the arterial supply of supernumerary renal vessels?
Typically originate from aorta, so more common on LEFT side
Renal arteries are end arteries. If one is damaged/ligated then as a consequence….
The region it supplies is deprived of blood
Therefore, they’re not truly “accessory” vasculature since the kidney needs them!
When and where does the development of the adrenal glands (suprarenal glands) take place?
Develop bilaterally in week 6
Between root of dorsal mesentery and gonad, at T12 vertebral level
what is the final morphology of the suprarenal glands?
rest on the superior pole of kidneys
What does the adrenal cortex develop from?
Mesenchyme
What does the adrenal medulla develop from?
Neural crest cells
In the late embryonic period, the cloaca divides to separate into
Digestive, urinary, and reproductive structures
How does development of the urinary bladder begin?
In week 7, urorectal septum develops between hindgut and allantois
Urorectal septum grows caudally toward cloacal membrane, dividing cloaca into two parts, dorsal and ventral
What do the dorsal and ventral parts of the cloaca become when they are divided by the urorectal septum?
Dorsal part – becomes rectum, superior anal canal
Ventral part – becomes urogenital sinus
What are the parts of the urogenital sinus?
Vesical part, pelvic part, phallic part
What do the vesical, pelvic, and phallic parts of the urogenital sinus become?
Vesical part – forms most of urinary bladder
Pelvic part – forms female urethra, proximal part of male urethra
Phallic part – forms distal part of male urethra
What is the final stage of the development of the urinary bladder?
In weeks 5-12, as urinary bladder enlarges the distal mesonephric ducts are incorporated firmly into the bladder wall
Parts of the distal mesonephric ducts also form…
Some male reproductive structures
When distal mesonephric ducts are incorporated firmly into the bladder wall, what does this allow? What does this form?
This allows urine from mesonephroi and metanephroi to be expelled
This forms the trigone, a triangular region of the epithelium, between the openings for the urethra and the two vesicoureteric junctions.
What germ layer forms the epithelium of the majority of the urinary bladder?
Endoderm
What germ layer forms the epithelium of the trigone of the urinary bladder?
Intermediate mesoderm
What are the types of cystic kidney diseases?
Autosomal recessive polycystic kidney disease (ARPKD) - bilateral
Multicystic dysplastic kidney disease (MCDK) - unilateral
What is the etiology of Autosomal recessive polycystic kidney disease (ARPKD)? What happens?
Mutation of PKHD1 gene (encodes fibrocystin)
Multiple bilateral microcysts in collecting tubules and issues in the hepatobiliary ducts, leading to renal insufficiency
What is Autosomal recessive polycystic kidney disease (ARPKD) sometimes associated with? (25%)
Pulmonary hypoplasia due to oligohyramnios
What is the etiology of Multicystic dysplastic kidney disease (MCDK)? What happens?
Numerous non-communicating cysts and dysplastic tissue
Hypothesis: cysts are wide dilations of the loop of Henle
Typically unilateral and with fewer cysts than ARPKD
Is Multicystic dysplastic kidney disease (MCDK) compatible with life? Are there treatments?
better prognosis with compensatory hypertrophy (usually unilateral and fewer cysts)
Renal ultrasounds throughout childhood, Lifelong monitoring of renal lab values
Why are the fetal suprarenal glands so large?
Adrenal cortex provides DHEA (steroid precursors) essential for the placenta to synthesize estrogen
What does estrogen do during pregnancy?
Maintains uterine tissue and prepares for parturition
Stimulates mammary gland development
Plays role in fetal development
What does the ureteric bud stalk become?
Ureter
The end of each collecting duct induces the metanephric blastema to form what?
Small renal vesicles
where do renal vesicles develop?
in the ampulla of each collecting duct
what do renal vesicles elongate into?
an S-shaped renal tubule
what migrates into the renal tubule?
a glomerulus, through the open distal end
distal invagination of renal tubule forms what?
Bowman’s capsule
proximally, the renal tubule lengthens to form what?
the rest of the nephron (loop of Henle, proximal convoluted tubule, etc)
