Systems development IV: Reproductive and renal Flashcards
In what ways can there be problems with development of kidneys and genitalia?
Renal agenesis- kidneys don’t develop; could be uni or bilateral
Abnormal shaped kidneys
Abnormal ureter
Pelvic or horseshoe kidney
Duplication or atresia of uterine canal- within the female
Hypospadias- abnormal urethra development through the penis in males
Bladder exstrophy- bladder develops outside of the body
What is the pronephros?
Most immature form of the kidney- doesn’t contribute to any of the adult structures that we have but acts as a template for other structures to form around
What is the mesonephros?
Acts as an early filtering system and contributes to development of metanephros
Where does the mesonephros receive blood from?
From the aorta through capillaries
What does the mesonephros start to form which is like in the kidneys?
Capsules
What happens when blood reaches mesonephros?
It is filtered through its tubules
What is the metanephros?
Most developed and persists as definitive adult kidney
What is there at the very beginning of kidney development?
The intermediate mesoderm
What forms from the intermediate mesoderm?
A duct forms (cranially to caudally)- the pronephric duct
What forms between the intermediate mesoderm and the pronephric duct?
Pronephric tubules
What are the pronephric duct and tubules known collectively as?
Pronephros
What the pronephric duct continue to develop caudally to form?
Mesonephric duct
What does the mesonephric duct attach to?
Cloaca
What develops from the mesonephric duct?
Mesonephric tubules (The two together are the mesonephros)
What happens to the pronephros when the mesonephros is fully formed?
It is almost completely disintegrated
Which two things happen at the same time after the mesonephros is fully formed?
From the cloaca we start to have a bud forming cranially which gives rise to the metanephric ducts.
The mesonephros starts disintegrating and changes to form new structures
Why does the mesonephric duct completely disintegrate in women but not men?
In females, mesonephric duct completely disintegrates because this duct normally gives rise to the testes (the Wolffian duct)
What does the metanephric duct forming upwards and inwards give rise to?
Mesenchyme of the adult kidneys- metanephric blastema
What does the metanephric duct give rise to?
Ureteric bud
What does the mesenchyme go on to form?
The kidneys
What does the mesenchyme of the metanephros give rise to?
Collecting duct system up to the DCT
What does the ureteric bud give rise to?
Renal pelvis, major calyx and minor calyx
What causes renal agensis?
Early degeneration of steric bud
Which side is more likely to be affected by renal genesis?
Left is more common
What is bilateral Potter’s syndrome?
When there’s very little amniotic fluid around the foetus-
the foetus is squashed, arms and legs are unable to move around, fingers are short
lungs can’t develop because fluid is required around the baby in order for the lungs to grow and expand; lungs are filled with amniotic fluid
Condition isn’t compatible with life
What causes pelvic kidney?
Metanephros starts caudally and moves cranially so has to move up and if there’s a problem with this movement, it results in a pelvic kidney rather than a kidney in the lions
What causes horseshoe kidneys?
Fusion of metanephric areas
- Fused pole of kidney lies under the insertion of the inferior mesenteric artery
- This occurs because the kidneys develop with their vasculature and as the kidneys move upwards, they bring their vasculature up with them
Where do kidneys initially form?
Near the tail of the embryo
Where do vascular buds from kidneys go?
They grow towards and invade common iliac arteries
What causes the kidneys to ascend to their final position in the lumbar region?
Growth of the embryo in length
What happens to kidneys blood supply as they ascend?
Rather than drag their blood supply with them as they ascend, the kidneys send out new and slightly more cranial branches and then induce the regression of more caudal branches
How is a double kidney formed?
Complete division of metanephric diverticulum
What commonly presents with double kidney?
2 ureters on the same side that lead down to the bladder or a bifid ureter whereby there are 2 from one kidney. In most cases the 2 ureters will unite before opening into the bladder however it’s possible for both to drain in or only one
What are children with bifid ureters prone to?
UTIs or obstruction
Where does the bladder develop?
Outside the abdominal wall- the umbilical cord usually inserts just above
What does bladder exstrophy usually occur as a result of?
Failure of development of cloaca and resorption of this tissue into the abdominal wall
What does the cloaca form?
The rudimentary bladder- also known as urogenital sinus
What does the cloaca/urogenital sinus give rise to?
Male- Bladder (except trigone), prostate gland, bulbourethral gland and urethra
Female- Bladder (except trigone), bulbourethral gland, urethra, lower 2/3 of vagina
What does the trigone develop from?
The mesonephric and ureteric bud commit together to form the trigone at the back of the bladder
What do the gonads arise from?
The intermediate mesoderm within the urogenital ridges of the embryo
What do the genital ducts arise from?
Paired mesonephric (male) and paramesonephric ducts (female)
What does the mesonephric/Wolffian ducts give rise to?
Seminal vesicle, ductus deferens, epididymis, efferent ducts and rete testis
What does the paramesonephric duct give rise to?
Uterine tubes and uterus (and upper 1/3 of vagina)
Up until when are gonads and reproductive tracts indifferent?
7 weeks of development
What influences differentiation of the gonads and reproductive tract?
Presence or absence of SRY (on the Y chromosome)
If positive- development proceeds along male path
What effect does SRY have on gonad development?
The gonad develops into a testis containing spermatogonia, Leydig cells and Sertoli cells
What do Leydig cells produce and what does it support?
Testosterone - supports growth of the mesonephric ducts
What would happen to the mesonephric ducts without testosterone?
They would regress
What is testosterone converted to and what does this support?
Dihydroxytestosterone (DHT) which supports the development of the prostate gland, penis and scrotum
What do sertoli cells produce?
Anti-mullerian hormone which induces regression of the paramesonephric ducts
How do the gonads develop in the absence of SRY?
The gonads develop into an ovary with oogonia and stromal cells
Since there’s no testoreone produced, mesonephric ducts regress
Since there’s no MIS, the paramesonephric ducts persists to give rise to the oviducts, uterus nd upper 1/3 of the vagina
Where do testes originate?
In the lumbar region but then they descend
What is descent of the testes due to?
Tethering of the testes to the anterior body wall by the gubernaculum-
With growth and elongation of the embryo coupled with shortening of the gubernaculum, the testes are pulled through the body wall, then inguinal canal and finally into scrotum
What leads to undescended testes?
Problems with tethering of testes to anterior abdominal wall
What does the uterus usually form as a result of?
Fusion of the structures resulting from the paramesonephros
What is the arcuate uterus?
When one side proliferates more than the other side
What is bicornuate uterus?
Not fully fused and there is a dip at the top
What other problems with uterus development are there?
You can have 2 separate uteruses opening into 1 vagina or 2 with 2 cervixes
What does the urethra originate as a result of?
Fusion of urethral folds
Where is the urethral meatus normally?
At the tip of the penis
What happens in hypospadias?
The fusion is incomplete and the urethral meatus can be located further down the shaft of the penis
When does differentiation of external genitalia occur?
After 7 weeks
What does the genital tubercle become in male and female?
Male- phallus
Female- Clitoris
What does the urogenital sinus become in male and female?
Male- Scrotum
Female- Urethral orifice and labia majora
What is persistent mullerian duct syndrome?
Presentation of symptoms with abdominal pain
A uterus and rudimentary fallopian tube will be present
Occurs in genetic males with mutations in MIS or MIS receptor
- Because of testosterone and DHT production, there are normal male external genitalia and male genital ducts
Because there is effectively no Mullein inhibition, paramesonephric ducts persist
Testes may lay either where ovaries would normally be found within broad ligament or one or both may descend into scrotum
Who does androgen insensitivity (testicular feminisation) syndrome occur in?
Genetic males with mutations in the androgen receptor
How does androgen insensitivity syndrome develop?
There is a lack of virilisation due to inability of AR to bind testosterone or DHt
XY sex reversal with relatively normal female external genitalia but undescended testes
Mesonephric ducts are rudimentary or lacking due to loss of testosterone
Normal production of MIS from Sertoli causes Mullein duct regression, so no oviducts, uterus or upper 1/3 of vagina
Who does congenital adrenal hyperplasia occur in?
Genetic females often due to defects in 21-hydroxylase essential for cortisol synthesis- lack of feedback to pituitary causes overproduction of ACTH and overactivity of adrenal gland
What does increased production of weak androgenic hormones from the adrenal gland result in in congenital adrenal hyperplasia?
Weak virilization of external genitalia:
Enlarged clitoris
Partial or complete fusion of labia majora
What are the internal genitalia like in CAH?
They are female:
Testes absent as no SRY
No mesonephric ducts
No MIS so mullerian duct structures are intact
