fetal development Flashcards
what does the fusion of the sperm and secondary oocyte form
a zygote
where does the zygote form
in the ampulla - taking ~ 24hrs
what hormone influences the endometrium receptiveness to implantation of the blastocyst
human chorionic gonandotrophin hCG
what do villi in maternal blood vessels enable
enable the blood vessels to transfer nutrients + waste
until how many weeks post-fertilisation is considered the pre-embryonic stage
up to 2 weeks post-fertilisation
how many weeks is considered the embryonic phase
2-8 weeks
how many weeks is considered a fetus
after 8 weeks
describe the primitive streak
a thickened linear band of epiblast that appears at the beginning of the 3rd week.
what does the primitive streak then become
primitive node - cranial end proliferates
what is the primitive pit
a narrow primitive groove in the primitive node
what does longitudinal folding of the embryo cause
brings about flexion and development of the head and tail folds
what does transverse folding of the embryo cause
forms the lateral body - turns embryo from flattened disc into cylinder
what does the trilaminar plate fold into
c-shaped cylindrical embryo
what changes occur to the fetus during 8-12 weeks
rapid weight gain, eyelids meet and fuse, urine formation and passing, swallowing, external genitalia recognisable, primitive reflexes, erythropoiesis begins
what changes to fetus occur between 12-16 weeks
rapid skeletal development + limb movement, rapid growth, thumb sucking, in females ovaries differentiated
what changes occur to fetus weeks 16-20
weight gain, fetal movements start, vernix and lanugo, skin cells renewed, brown adipose tissue forms, males - testes begin to descend
what changes occur to fetus weeks 20-24
most organs functioning, eyes complete, sleep + activity, ears developing, response to sound, primitive reflexes, surfactant secreted from lungs
what changes occur to fetus weeks 24-28
legally viable, eyelids opened, respiratory movements apparent, white fat = 3.5% of body weight
what changes occur to fetus weeks 28-32
white fat = 8% of body weight, males - testes descend into scrotum, lanugo disappears from the face
what changes occur to fetus weeks 32-36
weight gain 25g/day, lanugo disappears from body, nails reach tips of fingers/ toes, head hair lengthens
what changes occur to fetus from weeks 36- births
body round + plump, skull fully formed but soft and pliable
