Group 1 - Set 3/4 - Embryology of Urogenital system COMPLETE *** Flashcards
Embryology: Describe how the cloaca is converted into 2 separate openings in mammals (4)
the urorectal septum grows caudally towards the cloacal membrane
this separates the cloaca into 2 separate openings
one opening is for the gastrointestinal tract
one opening is for the urinary tract
Embryology: What are the 3 divisions of mesoderm?
- What does it form?
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm
everything apart from the skin and lining of the gut
Intermediate Mesoderm: What 3 bilaterally symmetrical sections does it divide into from cranial to caudal?
pronephros
mesonephros
metanephros
Mammalian Embryo: The nephros develop cranially to caudally, as a wave of development down the embryo as it grows.
What is the first Nephros to form?
- What does it eventually do?
pronephros
it regresses
Mammalian Embryo: After the Pronephros atrophies, what happens?
- What does it do as the embryo grows?
- Describe the structure of the Mesonephros
- What do they function as?
- How do the mesonephric ducts form?
- What do they connect to?
- Where do they grow to?
the mesonepros develops
it regresses
it consists of segmental mesonephric tubules draining into mesonephric ducts
a kidney
spontaneously in the mesoderm
they connect to the segmental mesonephric tubules inside the mesonephros
they grow towards the cloaca
When the Mesonephric ducts connect with the cloaca, what has happened?
- Where does the urine flow and why?
the urine produced in the mesonephros can now drain into the cloaca
down the allantois into the allantoic cavity as the cloacal membrane is still intact
While the Mesonephros is developing and the ducts connecting to the cloaca, what is happening in the background?
- What will these ultimately become?
metanephric masses are growing
mammalian kidneys
In fish and amphibians, how is the development of Mesonephros different?
the mesonephros does not regress and remains as the functional kidney
In Mammals, when the mesonephros regresses, what does it become in the embryo?
the gonads and adrenal cortex
The Metanephric ducts invade the Metanephric masses.
- What does this stimulate?
- at the same time, what has the Urorectal septum done?
the formation of the nephrons and blood supply in the metanephric masses
it has divided the cloaca into an exit for the go tract and a common urogenital opening
Describe what happens as the mesonephros is degrading and the metanephros masses are growing
paired metanephric ducts grow out of the mesonephric ducts towards the metanephric masses
The mesonephros has now fully degraded and left behind gonads and adrenal cortex.
- In males, what have the mesonephric ducts become?
- Now what do we have?
the ductus deferens
a male
Backtrack to where the Mesonephros is still active and the metanephric ducts have just connected with the Metanephric masses.
- What else is forming alongside the Mesonephric ducts in females?
- Where do they form?
- Do these form in males to?
paramesonephric ducts
as grooves sinking into the mesoderm of the abdominal wall
yes but they will eventually regress
To become a female, what has to happen? (2)
the paramesonephric ducts approach but do not fuse with the gonads
the mesonephric ducts within the gonads regress
In the female, what do the caudal ends of the paramesonephric ducts do?
- What does this create?
- then what does the caudal end do?
they fuse to different extents
a uterus
it induces a bud from the endoderm of the cloaca and forms a cervix and vagina
Formation of final positions of Ureters and Ductus Deferens in males:
- describe the path of the Ductus deferens as it descends towards the scrotum
- What happens as the mesonephric ducts (ductus deferens) collapse over the bladder as they loop over?
- Do we get this in females too?
- How is the trigone tissue different to the bladder wall tissue?
- How is the trigone of the bladder clinically relevant?
it loops over the ureters as the testes descend
they leave a trail of mesoderm tissue creating the trigone of the bladder
yes but it is smaller as the mesonephric ducts regress
the trigone is derived from mesoderm but the bladder is derived from endoderm
bladder neoplasia starts in the trigone
Developmental Defects: What happens with ectopic ureters?
- What does this lead to?
one or both furthers enter the urethra downstream of the bladder sphincter
urinary incontinence
Developmental Defects: Free Martins Heifer
- When does this happen?
- Why does it produce a sterile heifer? (4)
- Which hormones might the heifer produce? (2)
- What behaviour is the CNS programmed to exhibit?
when a heifer is born twin to a bull
because a common blood supply between the twins allows XY germ cells to migrate to female ovaries
and the female is exposed to testosterone
so the paramesonephric ducts dont develop completely
and the ovaries dont develop a full complement of XX germ cells
testosterone
androstenedione
male behaviour
Developmental Defects: Free Martins Heifer
- What visible gross abnormalities would you see? (3)
- What abnormalities would you feel on rectal palpation? (2)
enlarged clitoris
under developed vulva
long hairs near vulva
small or absent uterus
small ovaries
