Development of Reproductive system Flashcards
Gametes are derived from…
Primordial Germ Cells
What are Primordial Germ cells?
Germ cells that have yet to reach the Gonads where they undergo Mitosis and Meiosis to produce Gametes.
Describe the process of PGC production and migration?
2nd week: Produced in the Epiblast, then moves into the wall of the yolk sac
4th week: Cells migrate from the yolk sac to the developing gonads via the dorsal mesentery. They arrive there by the end of the 5th week
What forms the Male external genitalia?
Penis and Scrotum
What forms the Male internal genitalia?
Testes Duct system: Epididymis, Vas Deferens, Urethra Seminal vesicles Prostate Bulbo-urethral glands
What forms the Female external genitalia?
Vagina
Vestibule
Labia minora and majora
Clitoris
What forms the Female internal genitalia?
Ovaries
Duct system: Fallopian tube, Uterus, Cervix, Vagina
Describe the Urogenital ridge…
A region of intermediate mesoderm which gives rise to the embryonic Kidney (mesonephros and mesonephric duct) and Gonad.
Outline the development of the Mesonephric system in the male and female:
- Mesonephros descends, forming the Mesonephric (Wolffian) Duct as it does.
- The Mesonephric Duct reaches the Urogenital sinus, where it then sprouts the Ureteric bud.
- Urogenital sinus expands and smooth muscle appears…
Male:
- Ureteric bud and Mesonephric Ducts make independent openings in the Urogenital sinus
- Ureteric bud connects the primitive Kidney to the bladder
- Mesonephric duct opens into the Prostate and prostatic urethra
Female:
- Mesonephrics duct regresses (no male androgen to maintain it)
- Ureteric bud opens into the Urogenital sinus, to connect the primitive Kidneys and bladder
Describe the Wolffian duct
aka Mesopnephric duct
Derived from the mesonephros (developing Kidney).
Male genitalia form from this duct as a result of male hormones:
- Sertoli cells of the testis secrete MIH (Mullerian Inhibiting Hormone) which prevents development of the female reproductive duct (Paramesonephric/Mullerian duct).
- Leydig cells of the testis secrete Testosterone which stimulates development of the Wolffian duct.
It opens into the UGS, prostate and prostatic urethra.
Regresses spontaneously in the female.
Describe the Mullerian duct
aka Paramesonephric duct
These ducts appear as invaginations of the epithelium of the Urogenital ridge.
Female genitalia for from this duct as a result of a lack of male hormones:
- No MIH… therefore the Mullerian duct is not inhibited
- No Testosterone… Wolffian duct degenerates
Connects the abdominal cavity with the cloaca.
What Gene determines the development of the Male reproductive system?
SRY - Sex determining Region Y
An important gene found on the Y chromosome which codes for a transcription factor - leading to male development, and inhibits female development.
Describe the development of the Male external genitalia
Starts as ‘indifferent’. Basic components: Anus, Urogenital sinus, Genital tubercle, folds and swellings
In the Male:
- Genital tubercle elongates (forms the Glans)
- Genital folds fuse to become the spongy urethra
- Genital swellings fuse to form the scrotum
This development occurs as a result of Dihydrotestosterone
Describe the development of the female external genitalia
Starts as ‘indifferent’. Basic components: Anus, Urogenital sinus, Genital tubercle, folds and swellings
In the female:
- Genital tubercle becomes the Clitoris
- Genital fold becomes the Labia Minora
- Genital swellings becomes the Labia Majora
Describe the descent of the Testis
Starts retroperitoneally and descends towards the future scrotum by invaginating the peritoneum.
Gubernaculum attached to the inferior testis shortens, pulling the testis lower during the pregnancy.
The testis passes through the inguinal canal into the scrotum in the 9th month.
The Processus Vaginalis - a remnant of evaginated peritoneum - also passes through inguinal canal and forms a serous bilaminar structure on the anterior testis.
