Embryonic Development Flashcards
what is the cloaca
a dilation of the hindgut from where the urogenital and GI develop from
why does the cloaca have no surrounding mesoderm
so that there is no blood supply to the cloacal membrane so that it can rupture to give an orifice
what is the urogenital ridge
an area of intermediate mesoderm from which the kidneys and gonads arise from
where do primordial germ cells come from
the yolk sac wall
what determines how the gonads will develop
the karyotypes of the primordial germ cells
describe the duct differentiation for males
the testis produce mullerian inhibiting hormones causing the paramesonephric duct to regress
they also produce androgen which cause development of the mesonephric ducts
describe the duct differentiation for females
there is no MIH so the paramesonephric ducts develop
due to the lack of androgens the mesonephric ducts regress
describe the fusion of the paramesonephric ducts in female development
the 2 ducts move towards each other and fuse. as they do this they make contact with the urogenital sinus below, these 2 tissues then develop into the uterus and vagina
describe the production of male external genitalia
the genital tubercle elongates, the genial folds fuse together to form the spongy urethra
what androgen drives the production of external Male genitalia
dihydrotestosterone
describe the production of external female genitalia
there is no fusion
the genital tubercle becomes the clitoris
the genital swellings become the labia majora and labia minora
describe the descent of the testes
they descend down the gubernaculum, bringing down layer of abdominal muscle with them
describe the descent of the ovaries
they descend down the gubernaculum, but not as far down as the testes - therefore some remnants of the gubernaculum remain as the round ligament and ligament to the ovary
