Reproductive Embryology Flashcards
What is the default developmental status for the reproductive system?
Female
What 3 tissues do the gonads develop from embryologically?
Gonadal ridge: intermediate mesoderm at 6 weeks
- Epithelium penetrates mesenchyme to form primitive sex chords
Mesodermal epithelium: covers posterior abdominal wall
Primordial germ cells: migrate from the yolk sac at around 5-6 weeks and induce development of differential gonad.
Where does the indifferent gonad develop?
Are they interperitoneal or retroperitoneal?
Retroperitoneal; in the gonadal ridge areas
When does differentiation occur?
When testis determining factor is released by the Y chromosome in males or not released in females.
What is androgen insensitivity syndrome?
Can result in genetic male with normal female appearance. Testis present but often intra-abdominal, vagina is blind ended pouch.
What accompanies the gonad descent in both males and females?
What does it travel through?
What does this become in females?
The gubernaculum, travels through inguinal canal.
In females becomes the round ligament of uterus and ovarian ligament
Describe the process of gonad descent in males
The testes descend along the gubernaculum through the inguinal canal, pulling with them a loop of peritoneum.
The space inbetween the fold of peritoneum is called the processus vaginalis which eventually fuses.
The part of the peritoneal fold left behind is called the tunica vaginalis which sits alongside the testes in the scrotum. A small amount of fluid between the layers allows free movement of the testes.
Describe 2 types of maldescent of the testes
Cryptorchidism: testicle does not fully descend, often stuck in inginal canal (most common). Most fully descend by 3 months after birth.
Ectopic testicle: testicle descends through the inguinal canal but does not end up in the scrotum. Can end up in the thigh, perineal region, abdo wall.
Both of these increase the risk of testicular cancer.
What does the gubernaculum attach to in females?
Attaches to the uterus forming the round ligament and ovarian ligament.
Where does ovarian descent stop?
Stops at the broad ligament of the uterus.
Which genital ducts develop in the male?
How does this occur?
What do the ducts develop into?
Which duct does not develop in the males? What can it become?
Mesonephric ducts develop in males:
- Testosterone production drives development of mesonephric ducts at around 8 weeks.
- Develops into:
- Epididymis
- Seminal vesicle
- Ejaculatory duct
- Ductus deferens
Paramesonephric ducts do not develop in males as anti-mullerian hormone produced by Sertoli cells causes it to regress.
Can form the appendix of testicle
Which genital ducts develop in the female?
How does this occur?
How does this process cause the uterine ducts to communicate with the peritoneal cavity?
What ducts do not develop in the female? What can they become?
Paramesonephric ducts develop in the female in the absence of testosterone or anti-mullerian hormone.
- They form the uterine ducts and join together to form the uterus and vagina
- Formed from invagination of coelomic epithelium, the end of the tube remains open, communicating with the peritoneal cavity.
- This is how ectopic pregnancies can occur
The mesonephric ducts do not develop in the female, they degenerate spontaneously and remnants (opoopherons) can form cysts around ovaries or vagina.
How does cloacal division occur?
The urogenital septum separates the cloaca into the rectum and urogenital sinus.
The urogenital septum forms the perineal body as it meets the pelvic floor. Stabilises the posterior vaginal wall and is attachment point for anal sphincter.
How does the vagina develop?
Develops from the uterovaginal primordium and the sinovaginal bulb of the urogenital sinus.
These meet and form the vaginal plate which canalises to form the vaginal lumen.
- Failure to canalise can lead to vaginal atresia or transverse septa
Name some vaginal and uterine malformations
Uterus didelphys with double vagina
Uterus arcuatus
Uterus bicornis
Uterus bicornis unicollis (1 rudimentary horn)
Atresia of cervix
Atresia of vagina
What do the following structures of the indifferent embryological external genitalia become in males and females?
Genital tubercle
Labioscrotal swelling
Urogenital/urethral fold
Genital tubercle:
- Clitoris in females
- Penile glans and erectile tissue in males
Labioscrotal swelling:
- Labia majora
- Scrotum
Urogenital/urethral fold:
- Labia minora
- Spongy urethra in males
