Prenatal Development Flashcards
(38 cards)
When is genetic sex determined?
At the time of fertilization
First step in prenatal development
Primordial germ cells from the yolk sac/ allantois migrate into the gonadal ridge in the first trimester
What is the gonadal ridge classified as?
Bipotential (decides on sex based on genetic info)
How is the embryo a male?
Sperm with Y chromosome with SRY gene
What cells are present on the gonadal ridge?
Precursor cells (2)
Primordial germ cells
What do the precursor cells in the male become?
Sertoli cells that secrete desert hedgehog and anti-mullarian hormone
Desert Hedgehog
Tells the second precursor cells to become Leydig cells that produce Testosterone
What do the primordial germ cells in the male become?
Gonacytes that produce sperm throughout the male’s life
Mesonephric Duct (wolffian duct) in males
Gives rise to male internal genitalia
Testosterone is essential for development
Paramesophric duct (Mullarian duct) in males
Degernerates due to AMH
What happens after Leydig cells secrete testosterone?
Development of testis and regression of the mesonephros (temporary version of the kidney)
What does the remnant mesonephros give rise to in males?
Future efferent duct after combining with epithelial cords (future seminiferous tubules)
What does the mesonephric duct generate in males?
Epididymus and vas deferens
Dihydrotesterone
5a-reductase will convert testosterone into dihydrotesterone to develop into external genitalia because it’s 100 times more potent than testosterone
What does the genital tubercle become in males?
Glans penis
What does the urogenital/ genital folds become in males?
Fuse to form the ventral aspect of the penis
What does the labioscrotal/genital swelling do in males?
Become the scrotum
How is the female embryo developed?
Egg is fertilized with sperm with the XX genotype (SRY gene absent)- default pathway
For the female, what does the primordial germ cells give rise to?
The eggs
For the female, what do precursor cells become?
Granulosa (follicle cells) that secrete theca cells that secrete estrogen
Which structures regress in the female?
Mesonephros tubules and epithelial cords
Mesonephric duct as well because no testosterone
What does the Coelomic epithelium become?
Future cortex
What does the Paramesonephric duct become in females?
Develop into internal female genitalia (uterus, cervix, part of the vagina, oviduct) due to the absence of the AMH
For the female what does the Cranial and caudal urogentical sinuses develop into?
Bladder and vestibule respectively