Development of Kidneys and Urinary Tract Flashcards
What are the three sets of excretory organs in development of the kidneys and urinary tract?
- Pronephros
- Mesonephros
- Metanephros
When does the pronephros appear?
Start of week 4
When does the pronephros regress?
End of week 4
Is the pronephros functional?
No
When does the mesonephros appear?
End of week 4
When does the mesonephros regress?
End of week 8
Is the mesonephros functional?
Yes
Does the mesonephros have a water conserving mechanism?
No
Where does the mesonephric duct have a very important role?
In the development of the male reproductive tract
What does the mesonephric duct sprout?
The ureteric bud
What is the ureteric bud?
The primordium of the collecting system of the definitive kidney
When does the metanephros appear?
Week 5
When does the metaneophros regress?
It doesn’t
Is the metanephros functional?
Yes, from the end of the first trimester
What is the metanephros?
The definitive kidney
What does the collecting system develop from?
The ureteric bud
What does the excretory system develop from?
The metanephric tissue cap
What do the embryonic kidney and gonad originate from?
The urogenital ridge
What is the urogenital ridge?
A region of the intermediate mesoderm
Label this diagram
- A - Paraxial mesoderm
- B - Intermediate mesoderm
- C - Somatic mesoderm
- D - Intraembryonic coelom
- E - Splanchnic mesoderm
Label this diagram
- A - Urogenital ridge
- B - Mesonephric duct
- C - Mesonephros
- D - Gonad
What does the organisation of the intermediate mesoderm lead to in the development of the kidneys and urinary tract?
3 systems developing sequentially
What does the disapperance of one system in the development of the kidneys and urinary tract mark?
The start of then next
Where does the first system in the development of the kidneys and urinary appear?
In the cervical region
What is the first kidney system?
The pronephros
What does the pronephros produce?
The pronephric duct
Where does the pronephric duct extend?
From the cervical region to the cloaca
What does the pronephric duct do?
Drives the development of the next stage, becoming the mesonephric duct
Label this diagram, including what the red and yellow represents
- A - Cloca
- B - Pronephros
- C - Mesonephros
- D - Duct
- E - Metanephros
What does the mesonephros do?
Sprouts tubules that develop caudal to the pronephric region
What makes up the embryonic kidney?
The tubules sprouted by the mesonephros and the mesonephric duct
What does the mesonephric duct sprout?
The ureteric bud
What does the ureteric bud do?
Induces the development of the definitive kidney
Where does the mesonephric duct have an important role?
In the development of the reproductive system in the male
Label this diagram
- A - Mesonephros
- B - Mesonephric duct
Where does the ureteric bud sprout from?
The mesonephric duct
What does the uteric bud do?
Induces the development of the definitive kidney within the intermediate mesoderm of the caudal region of the embryo that lies closest to it
What happens once the ureteric bud has induced the development of the definitive kidney?
It expands and branches into differentiated intermediate mesoderm, the metanephric blastema
What does the metanephric blastema form?
The definitive kidney’s structure
What does the ureteric bud drive?
The development of the definitive kidney
What is the collective system derived from?
The ureteric bud itself
What is the excretory component derived from?
The intermediate mesoderm
What is the development of the excretory component from the intermediate mesoderm under the influence of?
The ureteric bud
Draw a diagram illustrating the role of the ureteric bud
Where does the metanephric kidney first appear?
In the pelvic region
What happens once the metanephric kidney has appeared in the pelvic region?
It undergoes an apparent caudal to cranial shift, crossing the arterial fork formed by vessels returning blood from the foetus to the placenta
Do the kidneys actually move in development?
No
Why do the kidneys not actually move in development?
Because development is cranial to caudal, and the trunk just extends downwards, making it appear as though the kidneys move
What causes renal agenesis?
The ureteric bud fails to interact with the intermediate mesoderm
What does renal agenesis affect?
One (unilateral) or both (bilateral) kidneys
What are some congential abnormalities of kidney position and renal vessels?
- Renal agenesis
- Migration defect
- Duplication defects
- Cystic kidney disease
- Abnormal renal vessels
- Exstrophy of the bladder/urachal anomalies
- Hypospadias
What can cause a migration defect?
- 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. If they get caught on the arterial fork, they can fuse and form a horseshoe kidney
Why may the kidney end up much lower than it should be if it fails to cross the arterial fork?
As the kidneys don’t actually move, its more the fork that snags the kidney as it develops, pulling it down
Draw a diagram illustrating what happens if the kidney fails to cross the arterial fork
Draw a diagram illustraing what happens if the kidneys fuse during their ascent
What causes duplication defects?
Splitting of the ureteric bud, either partial or complete
What is the systemic consequence of splitting of the ureteric bud?
An ectopic opening bypassing the bladder and causing incontinence
Where may the ectopic opening occur in duplication defects?
Into the vagina or urethra
Draw a diagram illustrating the consequence of a duplication defect
What do the kidneys require as they ascend?
A new arterial supply
Why do the kidneys require a new arterial suplply as they ascend?
Because the previous supply disappears
What happens if the arterial supply to the kidneys remain after it has descended?
They are accessory, or supernumerary arteries
What kind of arteries are the accessory arteries that remain after kidney ascention?
End arteries
Why are the arteries that remain after ascention end arteries?
Because the main renal artery will not branch to supply that area of the kidney if an accessory artery is present
What is the result of accessory end arteries in the kidney?
There is no collateral supply
What is the bladder derived from?
The hindgut- the caudal portion of the primitive gut tube
When is the bladder formed?
During embryonic folding in the fourth week of development
What is the caudal portion of the bladder?
A dilated, blind pouch called the cloaca
How is the cloaca separated from the outside?
By the cloacal membrane
What is the cloacal membrane?
One of the two mesoderm-less regions left present after gastrulation
What is the cloaca divided by?
The urorectal septum
What is the cloaca divided into?
The urogenital sinus and the anorectal canal
What is the urogenital sinus?
The future bladder and urethra
What is the anorectal canal?
The future rectum and anal canal
Label this diagram
- A - Urinary tract
- B - Gastrointestinal tract
- C - Reproductive tract
What is the allantois involved in?
The development of the bladder
What is the allantois?
A superoventral diverticulum of the hindgut
What does the allantois extend into?
The umbilical cord
What happens to the lumen on the allantois?
It becomes obliterated to become the urachus
What is the urachus in adults?
The median umbilical ligament
Label this diagram
- A - Hindgut
- B - Urorectal septum
- C - Urachus
- D - Bladder and urethra
- E - GI tract
Draw a diagram of the urogenital sinus
What are the stages in the development of the male bladder?
- Mesonephric ducts reach the urogenital sinus
- Ureteric bud sprouts from MD
- Smooth musculature begins to appear
- UGS begins to expand
- UBs and MDs make independant openings in UGS
- Prostate and prostatic urethra formed
What do the mesonephric ducts do once they have reached the urogenital sinus?
Drain embryonic urine into the cloaca
What does the ureteric bud become?
The ureter opening into the bladder
What does the smooth musculature that appears in the embryonic bladder become?
The trigone of the bladder
Is the MD maintained in the male?
Yes
Why is the MD maintained in the male?
Because it forms the prostate and ducts of the male reproductive system
Draw a series of diagrams illustrating the develoment of the male bladder
How does the development of the female bladder differ from that of the male?
The female bladder develops in much the same way, but without male hormones, the mesonephric duct regresses
What is the result of the regression of the mesonephric ducts in females?
Females do not form prostates or the tubes of the male reproductive system
Draw a series of diagrams illustrating the development of the bladder in a female
What is the female urethra formed by?
The pelvic part of the urogenital sinus
What is the male urethra divided into?
- Pre-prostatic
- Prostatic
- Membranous
- Spongy
What is the phallic part of the male urethra?
The spongy urethra
What is true of the first three parts of the male urethra?
They are analogous to the female urethra
What is exstrophy of the bladder?
A congenital anomaly in which part of the urinary bladder is present outside of the body
What does exstrophy of the bladder occur due to?
Maldevelopment of the lower abdominal wall, leading to rupture that causes the bladder to communicate with the amniotic fluid
What may exstrophy of the bladder be due to?
A urachal fistula
What is a urachal fistula?
A patent urachus, which normally becomes the median umbilical ligament, remains as a duct and so connects the bladder to the umbilicus
Draw a diagram illustrating a urachal fistula
What is hypospadias?
A defect in fusion of urethral folds
What happens in hypospadias?
The urethra opens onto the ventral surface, rather than the end of the glans
What is happening to the incidence of hypospadias?
It is increasing
Draw a diagram illustrating hypospadias
