Development of the Reproductive System Flashcards
What is the indifferent stage of gonadal development?
Initial stage
Undifferentiated gonads - cannot distinguish male and female
Where do the gonads begin development?
Genital ridges = pair of longitudinal ridge derived from intermediate mesoderm and overlying epithelium
From where do germ cells migrate into the gonads?
Endoderm lining of yolk sac
When do the germ cells migrate to the gonads?
Weeks 4-6
How are the primitive sex cords formed?
Proliferation of epithelium of genital ridge
Penetrates intermediate mesoderm
Which gene on the Y chromosome stimulates the formation of the testis cords?
SRY gene
What is the tunica albuginea?
Fibrous connective tissue layer that forms over testis cords
What do the testis cords form?
Rete testis
Germ cells
Sertoli cells
When do the seminiferous tubules form?
During puberty
How do the seminiferous tubules form?
Testis cords acquire lumen
What do the seminiferous tubules do?
Site of sperm production
Where are the Leydig cells in the developing embryo?
Between testis cords
What do the Leydig cells do?
Produce testosterone
What happens to the primitive sex cords in the female embryo?
Degenerate
What forms the cortical cords in the female embryo?
Proliferation of epithelium of gonads
How do the primordial follicles of the ovaries form?
Cortical cords break into clusters, surrounding each oogonium with layer of epithelial follicular cells
What is an oogonium?
Germ cell
When do the primordial follicles form?
Month 3
What are the two pairs of ducts, ending at the cloaca, that all embryos have at the initial stage of urogenital development?
Mesonephric/Wolffian ducts
Paramesonephric/Mullerian ducts
What happens to the mesonephric ducts in male embryos?
Mesonephric ducts develop into primary male genital ducts in presence of testosterone Give rise to - Efferent ductules - Epididymis - Vas deferens - Seminal vesicles
What happens to the paramesonephric ducts in male embryos?
Degenerate in presence of anti-Mullerian hormone
Which cells in the male embryo produce anti-Mullerian hormone?
Sertoli cells
What is the remnant of the paramesonephric ducts in males?
Appendix testis
What happens to the mesonephric ducts in female embryos?
Degenerate in the absence of testosterone
What is the remnant of mesonephric ducts in female embryos?
Gartner’s duct
What happens to the paramesonephric ducts in female embryos?
Develop in absence of anti-Mullerian hormone Form - Uterine/Fallopian tubes - Uterus - Cervix - Upper 1/3 of vagina
What forms the lower 2/3 of the vagina?
Sinovaginal bulbs, derived from pelvic part of urogenital sinus
How do the external genitalia form during the indifferent stage of reproductive embryological development?
Mesenchymal cells from primitive streak migrate to cloacal membrane > form pair of cloacal folds
Cranially, cloacal folds fuse > genital tubercle
Caudally, cloacal folds divide into
- Urethral folds, anteriorly
- Anal folds, posteriorly
Genital swellings develop either side of urethral folds
What drives the formation of indifferent genitalia into male external genitalia?
Androgens from testes, mainly dihydrotestosterone (DHT)
What forms the phallus in male embryos?
Genital tubercle
What forms the urethral groove in male embryos?
Urethral folds
What is derived from the urethral groove in male foetuses?
Penile urethra
From what is the scrotum derived?
Genital swellings > scrotal swellings
What drives formation of indifferent genitalia into female external genitalia?
Oestrogens
What forms the clitoris in female embryos?
Genital tubercle
What forms the labia minora in female foetuses?
Urethral folds
What forms the labia majora in female foetuses?
Labia majora
What forms the vestibule into which the urethra and vagina open?
Urogenital groove
What is the gubernaculum?
Ligamentous structure tethering gonads to scrotum/labia
When do the testes pass through the inguinal canal?
During week 28
By when do the testes reach the scrotum?
Week 33
What is the adult remnant of the gubernaculum in males?
Scrotal ligament
What is the adult remnant of the gubernaculum in females?
Ovarian ligament
Round ligament of uterus
