Abdominopelvic Development Flashcards
What mesoderm forms the kidneys and gonads?
Intermediate mesoderm
What two things does the intermediate mesoderm split into?
Nephrogenic region
Genital ridge
Note:
Found posterior to the intraembryonic cavity, but in contact with it.
What are the 3 nephros? Which one becomes the actual kidney?
Pronephros
Mesonephros
Metanephros (kidney!)
What does the pronephros become?
Nothing. It starts out in the cervical region and then rescinds.
What does the mesonephros become?
It first helps filtrate in the thoracic and lumbar region. The mesonephros rescinds, but the mesonephric duct stays connected to the cloaca.
What does the metanephros become?
Kidneys!
Starts out in the pelvis and then ascends.
What is the ureteric bud and its purpose?
It is an outgrowth of the mesopephric duct. It extends into the intermediate mesoderm and INDUCES the formation of the metanephros into kidneys.
Note:
It is the sole signal for the kidneys’ formation.
As the metanephric kidneys ascend, what happens to the mesonephric ducts?
They descend, carrying the UNDIFFERENTIATED gonads with them.
How does the blood supply of the kidneys and mesonephric ducts change as they move?
The kidneys get blood supply from a more superior source, aka the aorta. They lose their lower arteries.
The mesonephric ducts just keep their OG blood supply from the aorta.
What can happen to the blood supply of the kidney as it develops early?
It can get multiple renal arteries, some of which are retained at birth.
What do we call the extra renal arteries?
Polar arteries, if they enter via the superior or inferior poles of the kidney.
What is agenesis of the kidney? What causes it?
Failure of a kidney to develop.
Caused by failure of the ureteric bud to form.
What happens if the ureteric bud kinda splits in two but not fully off just a single stalk?
You can get a bifid ureter going from your kidney, and the other kidney will fail because the blood supply will not rescind from its lower region.
What happens if the ureteric bud splits in two partially but share the same stalk overall?
You can have two kidneys on a single side whose ureters will combine inferiorly.
What happens if you have two distinct ureteric buds on one side with two distinct stalks?
Two kidneys with two distinct ureters on a single side.
What happens if a kidney moves to the opposite side while its ascending?
Your kidneys could fuse on one side!
What happens if your kidney ascend but they are right next to each other?
They can fuse in the pelvis, preventing them from ascending further.
Why can horseshoe kidneys not ascend?
They get stuck at the inferior mesenteric
What is a polycystic kidney?
It is a inherited disease that causes many cysts to form on the kidney, leading to renal insufficiency.
What two ducts are important in reproductive embryology and are found next to the genital ridge?
Mesonephric duct
Paramesonephric duct
What do Y chromosomes produce?
SRY, previously known as testes-determining factor.
What is the default gender of the embryo unless signaled?
Female!
What is the origin of the testes?
Mesonephric ducts (Wolffian) (male meso)
Note:
Paramesonephric will rescind.
What is the origin of the ovaries?
Paramesonephric ducts (Mullerian)
Note:
Mesonephric will rescind
Do mesonephric ducts enter the urogenital sinus together or separate? Why?
Separate!! They form the sperm tubules.
Do paramesonephric ducts enter the urogenital sinus together or separate? why?
Together! Ovaries are connected.
What kind of fusion produces a normal uterus?
PARTIAL fusion of the paramesonephric ducts.
Note:
Although the ovaries are separate, they are connected by the uterus.
What is a septate vagina?
There is a septum in-between the vaginal openings, so each vaginal opening only leads to one uterus.
What is a septate uterus?
A septum between the uterus, so you can have one vaginal opening but its a 50/50 chance which ovary it leads to.
What is the hymen?
It is a remnant of the fusion of the urogenital sinus and fused paramesonephric ducts.
Looks like a membrane over the vaginal opening.
What keeps the gonads attached to the anterior body wall?
Gubernaculum
As the emrbyo lengthens, what does the gubernaculum tether the gonads to?
Labioscrotal swellings.
What happens to the testes and gubernaculum in males as it descends?
Testes will descend parallel to the an outpouching of peritoneum called the processus vaginalis. It is the embryonic origin of the tunica vaginalis.
The gubernaculum becomes the ligament of the testes.
What happens to the ovaries and gubernaculum in females as it descends?
The gubernaculum pulls the ovary inferiorly but gets stopped by the uterus.
The gubernaculum becomes the round ligament of the uterus and ovary.
What happens if the processus vaginalis does not close?
Predisposed to indirect inguinal hernias.
Chance for hydrocele formations
What do the mesonephric ducts form in a male?
Efferent ductules, epididymis, ductus deferens, seminal vesicles, and ejaculatory ducts.
What do the paramesonephric ducts form in a male?
Prostatic utricle/appendix of the testes.
What do the mesonephric ducts form in a female?
Gartner cysts
Epoophoron
What do the paramesonephric ducts form in a female?
Oviduct
Uterus
Cervix
Superior vagina
What partitions the cloaca?
Urorectal septum, dividdng the rectum from the urogenital sinus.
What is the allantois?
A remnant of the connection between the urogenital sinus and umbilical cord.
What does the urogenital sinus form?
It gets the mesonephric ducts and allantois
As a result, it also forms the bladder, urethra, and vagina.
What does the allantois eventually become?
The urachus, which connects the bladder to the umbilical cord. Eventually becomes the median umbilical ligament.
What are the various abnormalities of the urachus?
Uracheal sinus = blind pouch at the umbilicus
Uracheal fistula = channel between umbilicus and bladder.
Uracheal cysts = fluid-filled pouches
Note:
Uracheal fistula at birth = baby peeing out of their bellybutton.
What is the genital tubercle? What does it become in males?
Eventual penis.
The urethra will develop inferior to it, eventually getting wrapped by the corpus spongiosum.
What does the genital tubercle become in females?
Clitoris
What is an ectopic ureter?
It is when the urogenital sinus and/or uretic bud causes the ureter to enter the urogenital sinus at the wrong spot. Essentially, you could pee from your vagina or straight into your urethra, bypassing your bladder.
Note:
This would cause leaky pee, since you’re not keeping it contained in the bladder.
What is the origin of the external genitalia?
Genital tubercle
Urethra folds
Genital swellings
How does external genitalia form in males?
The urethral folds all zip up on the median and go to the genital tubercle to form the shaft and glands. The genital swellings become the scrotum.
How does external genitalia form in females?
The urethral folds remain separate, forming the labia minora on each side of the vestibule.
The genital swellings become the labia majora.
The genital tubercle becomes the clitoris.
What are hypospadias?
Failure of the urethral folds to close appropriately, leaving openings.
Likely cause is increased estrogen during development.
Note:
THIS ONLY HAPPENS IN MALES.
What are epispadias?
Urethra opens onto the dorsal shaft of the penis.
Caused by failure of anterior body wall to close.
What other abnormality commonly accompanies epispadias?
Bladder exstrophy.
What is the key enzyme that is needed for male development?
5-alpha-reductase. Converts testosterone to DHT, which is more potent.
What is the key enzyme that is needed for female development?
Aromatase, which converts testosterone to estrogen.
What causes the initial formation of male genitalia?
DHT spike.
What causes the further development of male sexual characteristics?
Testosterone spike at puberty.
What happens to a girl with a lack of aromatase?
More masculine, but still female.
What happens to a guy with a lack of aromatase?
Hypermasculinity, due to excess testosterone.
What is a hermaphrodite?
Genetically male or female, showing same sex genitalia but opposite sexual characteristics.
What are male hermaphrodites generally insensitive to?
Androgens, aka testosterone.
Note:
They will develop male internal genitalia since initial is determined by DHT. However, they will be hyper-feminine and typically grow up as girls.
