Development of Repro System Flashcards
What detemines how the gonads will develop
The karyotype of the primordial germ cells will determine the pathway of the reproductive system -> detemines gonad development
What are primordial germ cells
Undifferentiated population of cells that are the seed for the next generation
Describe the movement of PGCs through the foetus to the gonads
PGCs arise in epiblast -> 3rd week migrate through primitive streak to residue within wall of yolk sac
Then at 4th week, they migrate into retroperitoneum along dorsal mesentery of hindgut
Then in 6th week they invade gonadal ridges
Why do gonads descend
Descend due to gubernaculum which attaches gonads to labio-scrotal folds
As abdominopelvic caivty increases in volume, gonads descend interiorly
What is the urogenital ridge
Region of intermediate mesoderm that gives rise to both the embyronic kidney and the gonad
What ducts are involved in male and female internal genitalia development
Paramesonephric ducts - appear as invaginations of epithelium of urogenital ridge. Run laterally to mesonephric ducts
Mesonephric ducts - first act as duct for embryonic kidney but become surplus to requirement once kidneys develop
What do the cloacal folds form
Cranially to cloacal membrane, cloacal folds unite to form the genital tubercle
Caudally to the cloacal membrane, the folds are divided into the genital and anal folds
What are the three basic components of the external genitalia
Genital tubercle
Genital folds
Genital swellings
What region of the gonads develop if the SRY gene is present and what region developms if the SRY gene is absent
If present, SRY causes medulla of the gonad to develop
If absent the surface epithelium develops
Which reproductive ducts develop if there are functioning testes and why do they develop
Wolffian/mesonephric duct development is supported by testes which produce androgens to support development
Testes also produce Mullerian inhibiting hormone which suppresses paramesonephric duct development
Describe the develpoment of the mesonephric duct into the vas deferens and epididymis
As duct regresses, epigenital tubules establish contact with cords of rete testis and form the efferent ductules of the testis
Mesonephric duct then persists to form the main male gential duct
The duct also elongates and becomes convoluted to form the epididymis
Duct obtains a thick coat to form ductus deferens
Describe the development of the external male genitalia
GT elongates rapidly to form the phallus and pulls the genital folds forward so that they fuse to form the spongy urethra -> GT develops into glans penis
Development is due to testis-derived hormones - especially dihydrotestosterone
Describe how the testes descend
Testes are pulled by gubernaculum down, behind the peritoneum to arrive at the scrotum
Processus vaginalis follows the course of the gubernaculum testis into the scrotal swellings
During descent, testes pass through inguinal canal and then enters the scrotal swelling behind the processus vaginalis which subsequently closes to form the tunica vaginalis
Which reproductive ducts develop if there is no functional testis
No hormones or androgens produced by testis so there is no Mullerian inhibiting hormone so no suppression of paramesonephric duct development so it develops
Without androgen production, mesonephric duct degenerates
Describe the development of the uterus
Paramesonephric ducts grow and become large -> grow into abdominal cavity and grow towards each other
The ducts then fuse - septum is present initially but this degenerates over time
The fused ends of the ducts then fuses with the urogenital sinus so that the uterus and vagina are continuous once system fully developed
