Development of the Reproductive System Part 2 Flashcards
Initially embryos have two pairs of genital ducts, What are they?
Mesonephric (wolffian) ducts.
Paramesonephric (müllerian) ducts.
Describe the Paramesonephric duct in an early embryo. (How it arises, and it’s path)
It arises as an invagination of the epithelium on the anterolateral surface of the urogenital ridge.
Cranially the duct opens into the abdominal cavity with a funnel-like structure
Caudally, it first runs lateral to the mesonephric duct, then crosses it ventrally to grow caudomedially.
In the midline it comes in close contact with the other Paramesonephric duct, separated only by a septum, but later fused to form the uterine canal.
The caudal tip of the combined ducts projects into the posterior wall of the urogenital sinus, where it causes a small swelling, the Paramesonephric or müllerian tubercle.
Where do the mesonephric ducts open in the early embryo?
They open into the urogenital sinus on either side of the müllerian tubercle.
How does the SRY gene cause the regression of the paramesonephric (müllerian) duct?
SRY either indirectly or directly, upregulates factors that elevate the concentration of müllerian inhibiting substance (MIS) produced by Sertoli cells, which leads to the regression of the paramesonephric ducts.
Which cells upregulate the genes for the enzymes that synthesize testosterone?
Leydig cells
What does testosterone do in early embryonic development?
It mediates the virilisation of the mesonephric ducts to form vas deferens, seminal vesicles, efferent ductules, and epididymis.
It can also be converted to dihydrotestosterone, which modulates differentiation of the make external genitalia
What gene is responsible for ovarian differentiation?
WNT4
How is oestrogen involved in sexual differentiation?
Under its influence, the paramesonephric (müllerian) ducts are stimulated to form the uterine tubes, uterus, cervix, and upper vagina.
In addition, oestrogens act on the external genitalia at the indifferent stage to form the labia majora, labia minora, clitoris, and lower vagina.
