Embryology basics Flashcards
how long is the gestation period and how is it divided
there are 3 trimesters over the 9 months
name of weeks 0-3
conceptus/embryo
name of weeks 3-8
embryonic period
name of weeks 9-40
fetal period
what are the 6 phases of embryogenesis
gametogenesis fertilisation cleavage gastrulation formation of body plan organogenesis
describe gametogenesis
gamete cells are produced by mitosis and meiosis, leads to genetic variation
what is a gamete cell
a cell with inly 23 chromosomes(half of set)
describe spermatogenesis
male gametes are produced(sperm/spermatozoa), occurs during puberty and never stops
describe oogenesis
female gametes produced(oocytes), starts during development and ends at menopause
by weeks 28-30 primary oocytes begin meiosis but are in arrest until puberty
describe fertilisation
fusion of sperm and oocyte, forms a zygote
what is a zygote
a diploid cell created by fusion of M and F gametes, its a single cell with sex determination 46 XX or XY
describe cleavage
period of rapid cell division, with no increase in size. eventually forms blastocyste
describe gastrulation
formation of germ layers, establishes left and right sides of the body putting things in the correct place
what are the 3 germ layers
ectoderm, mesoderm and endoderm
describe the formation of the body plan phase
embryonic folding occurs, the endoderm folds to create the gut tube and the ectoderm folds to become the skin/body wall. creating a tube-within-a-tube
describe organogenesis and when it is in place
formation of organs and organ systems, basis of these in place by end of embryonic period
describe the changes in weight and growth during the foetal period
mainly grows in length during 2nd trimester, most weight added during 3rd trimester
describe changes to the body during foetal period
tissues mature and become functional, bone laid down, connections to CNS made, overt sexual difference
describe the orientation of the body in terms of a foetus
cranial = head/top caudal = feet/bottom dorsal = back ventral = front
what are the primary processes during the transition from a zygote to a human
cell division, cell attachment, apoptosis and cell differentiation, induction and cell migration
induction = one cell causes another to differentiate
what are the secondary processes of zygote to human
axis formation/polarity (which way is up)
folding/rotation (allows formation of organ structures)
how is development controlled
genetic expression
preferential expression of maternal or paternal gene
environmental factors (smoking etc.)
