Special Lectures: Embryology Flashcards
the first event of human development
fertilization
the step after fertilization
cleavage
the step after cleavage
blastula formation
the step after blastula formation
gastrulation
the step after gastrulation
organogenesis
the step after organogenesis
embryonic folding
whats the main function of fertilization?
to have 2 haploid cells fuse to make a diploid cell ( n + n = 2n)
what process to sperm undergo in fertilization and why
they undergo capacitation, they lose inhibitory molecules making them swim faster and chemotactic and thermostatic - heat-seeking the fertilization site.
what is the cell called when egg and sperm properly fuse
a pronuclei
when does first cleavage occur
30 hours after fertilization
what cells multiply in the cleavage stage
blastomeres
what happens when the blastomere cells cleave
the mass does not get larger, mutliple cells become smaller filling the same space
what occurs at day 4 of this
the cluster of cells is called morula - raspberry
how many cells make up a blastocyst
4-5
why is a blastocyst different to a blastomere
blastocysts are densely packed, have a cavernous inside
what are the names for the inside and outside cells in a blastocyst?
inner cells - embryoblasts
outer cells - trophoblasts
blastocyst
a specifically mammalian blastula
blastula
general term used in any organism
when does implantation occur
6 days after fertilization
what happens if the egg implants in the uterine tube? why is this bad?
ectopic pregnancy - embryo cant form a placenta
what landmark event marks the start of the second week of development?
development of the trophoblast
what do the trophoblast cells do during this stage?
outer cells will form the placenta and extra embryonic tissue
two types of trophoblast cells
syncytiotrophablast cells and cytotrophoblast cells
what do these trophoblast cells excrete help with
- produce enzymes that help the embryo implant and bury into the endometrium
what hormone do these trophoblast cells excrete
human chorionic gonadotropin - pregnancy test in urine
what do these trophoblast cells give rise to?
embryo side of placenta - chorionic villi (fetal placenta)
during the development of the bilaminar embryonic disc, what are shown in blue
epiblasts - rise to ectodermal tissue
during the development of the bilaminar embryonic disc, what are shown in yellow
hypoblasts - rise to endodermal tissue
what starts to form in the bilaminar embryonic disc
amnion and amniotic cavity
what starts forming 9 days after fertilization
development of amnion and yolk sac
what is the function of the amnion? (5pts)
- protects baby
- fluid filled
- regulates temperature
- prevents embryo drying out
- prevents tissue sticking to surfaces
aminocentesis test
checks for infections, mutation, and overall fetus health with shed skin in amnionic sack
what provides nutrients in the first few weeks
yolk sac (pre-placenta)
what type of germ tissue and what will the yolk sack eventually form?
endodermal tissue, helps form gut
what network forms and why?
lacunar network forms to link the maternal blood supply
whats the benefits o connecting baby to mums blood supply
- nutrient supply
- waste removal
- gas exchange
when does the yolk sac form
around day 12
what stage occurs at the end of the second week?
gastrulation
what attaches to the embryo in gastrulation
connecting stalk
in gastrulation, there is the development of the
primitive streak
describe the movement of the concentration gradient
cells from outer ectodermal layer on dorsal side moving in and under (invagination) towards future anterior end
gastrulation results in the beginning of
the mesodermal layer
what process forms after gastrulation
notochordal process
what is the location/what is notochordal process
new mesodermal, rod of cells in new mesodermal layer (under primitive streak)
what is the function of the notochordal process?
instructs other cells what to do by induction (inducing cells) a kind of juvenile cell communication
what is signalled in the notochodral process
neuronal tissue is signaled to thicken and begin neural plate
3 germ layers
ectoderm, mesoderm, endoderm
ectoderm is
outside, usually blue, forms outside structures - skin, nervous tissue
mesoderm is
middle, usually red, forms middle structures like dermis, skeletal system, muscular
when does the mesoderm begin to form
during gastrulation
endoderm is
inside, usually yellow, forms the gut, thyroid
neurolation is the beginning of
organigenisis (organ formation)
backbone =
notochord
what does the neural plate do in the neurolation stage
neural plate folds up and forms neural folds which join and sink under ectodermal layer forming a tube
the tube formed by neural plate folds is called
neural tube - starts the backbone
the notochord (backbone) signals what to start what
the lateral mesoderm to start the formation of somite structures
somites are the start of?
ribs, skeleton, muscle of neck and back
the stage after neurulation
embryonic folding
what folds and why in embryonic folding
lateral side folding as amniotic cavity pinches yolk sac and then surrounds embryo
what will the yolk sac become
the gut
what else begins to be formed during embryonic folding
umbilical chord
what does the cell transition to in embryonic folding
2D to 3D
what is the role of pharyngeal arches
give rise to head and neck structures
why is hollow blastocyst important
hollowness allows cells to re-orient
