1.1 development of the reproductive system - 2 Flashcards
what is the cloaca?
early development, GI, urinary & repro tracts all end in this single structure
what is the urogenital sinus created from? by what?
created from hindgut by urorectal septum (wedge of intermediate mesoderm)
what is the UGS continuous with?
urachus (median umbilical ligament)
what happens to the mesonephric ducts and UGS in males?
mesonephric ducts reach UGS ureteric bud sprouts from MD smooth musculature begins to appear in UGS UGS expands UB & MD both open into UGS prostate and prostatic urethra form
what happens to mesonephric ducts and UGS in females?
MD reach UGS
MD sprouts UB (future kidney)
UGS begins to expand, MD regresses (UB maintained)
UB opens into UGS
what are paramesonephric ducts?
Mullerian duct
what do paramesonephric ducts appear as?
invaginations of epithelium of urogenital ridge
what do the paramesonephric ducts make contact with caudally?
with cloaca (urogenital sinus)
what happens to the paramesonephric ducts cranially?
opens into abdominal cavity
where are primordial gonads located?
superficial and medial to mesonephric tissue
what forms the primitive medullary cords and sex cords?
PMC: columns of cells from mesonephros
MC: columns of cells from coelomic epithelium
if the germ cells are male, what happens to the sex cords? what does it meet?
vigorous growth of sex cords in medullary region of gonad
to meet mesonephric cords - forming testis cords
what enters the testis cords? giving rise to what?
germ cells, giving rise to seminiferous tubules (sperm forms within)
what do the mesodermal cells in males give rise to?
Sertoli cells
what do Sertoli cells express?
SRY gene - only in males
if the germ cells are female, then what doesn’t develop?
medullary cords
which region of the gonad develops in females?
cortical region
what do germ cells become surrounded by in females? what does it form?
germ cells become surrounded by mesenchymal cells to form primordial follicles
what are the germ cells surrounded by mesenchymal cells with primordial follicles called?
oogonia
what is oogonia surrounded by?
a single layer of granulosa cells
what is not expressed in female germ cells?
SRY gene
if no germ cells arrive, then what happens to the development of the primitive sex cords?
not initiated
what happens when the development of primitive sex cords isn’t initiaed?
no gonadal ridges form
so mature gonads do not develop
what does male internal genitalia form from?
Wolffian / mesonephric ducts
what do female internal genitalia form from?
Mullerian / paramesonephric ducts
what happens to the Wolffian ducts in females?
regress spontaneously
what does the Mullerian duct develop into in females?
oviducts (fallopian tubes)
uterus
cervix
upper vagina
what develops if there are no gonads at all?
Mullerian ducts (female = default gender)
In males, which cells secrete testosterone?
interstitial cells
which cells secrete MIH in males? (mullerian inhibitory hormone)
Sertoli cells
what happens as a results of testosterone & MIH secretion?
Mullerian ducts regress
Wolffian ducts develop
what joints with mesonephric (Wolffian ducts)? where?
seminiferous cords
joins at the rete testis
what happens to the remainder of each duct in males (Wolffian & Mullerian)?
forms epididymis, vas deferens, seminal vesicles
internal genitalia
what is it called if an organ has the potential to develop into either male or female sexual organs?
bi-potential e.g. gonads & ducts systems
what are the basic components of the external genitalia?
genital tubercle (GT)
genital folds
genital swellings
what forms the labia minora and majora in females?
urethral folds (minora) and genital swellings (majora)
what forms the clitoris in females?
genital tubercle
what stimulates the development of female external genitalia?
nothing - default gender
what happens to the female (genital) urethral folds? what does this result in?
no fusion
urethra opens into vestibule (outside)
what forms the spongy urethra in males?
GT elongates, genital folds fuse (either side, envelop - scrotum) - urethra opens up at tip of glans penis
what drives the formation of spongy urethra in males?
testis-driven androgen hormones: dihydrotestosterone
what forms when the urethral folds close in males?
shaft of the penis
what forms the scrotum in males?
genital swellings fuse
what forms the glans penis in males?
genital tubercle expand
