Implantation Flashcards
what are steps of implantation
fertilization –> development in the oviduct, migration to uterus (5 days) –> implantation into the uterus –> placentation (placenta forms) –> fetal development
name and describe types of losses of pregnancies
pre implantation loss = 20-40%
1st trimester loss <12 weeks, around implantation = 30%
2nd trimester loss 12-24 weeks = 1-2%
stillbirth = 0.4% (3rd trimester)
less, most losses due to major anueploidies
describe uterine cell types
lumen = where embryo goes
endometrium = surrounds lumen
myometrium = muscular layer surrounds endometrium
perimetrium = structure to uterus
describe uterine organization
epithelium and endometrium = parts that build up and slough off - contains uterine glands (poke down into endometrium) and spiral arteries
myometrium under = muscle layer
describe reproductive cycle - what hormones involved
Estradiol
Progesterone
describe reproductive cycle - estradiol
increase just before ovulation
all granulosa cells in growing follicle make estradiol
promotes proliferation of uterine tissues and layers = endometrium and epithelium
describe reproductive cycle - progesterone
peak progesterone = helps develop and differentiate uterine layers
progesterone falls bc no fert = layers slough off = period
describe non reproductive cycle - uterine changes during follicular (pre ovulatory) phase
growth of uterine epithelium (estradiol)
due to proliferation of endometrial stromal cells (progesterone and estradiol)
growth of spiral arteries
describe non reproductive cycle - uterine changes during pre menstrual phase
thinning of spiral arteries (low progesterone)
blood supply falls apart bc no fert
describe non reproductive cycle - uterine changes during menstrual phase
necrosis and shedding of uterine epithelium and proximal layer of endometrium
basal layer of endometrium and embedded uterine glands remain to seed next cycle of growth and proliferation (return to basal layer of mesometrium, regenerates endometrium and epithelial layer as result of increase in estradiol) = CYCLE
what produces progesterone required by uterus - explain
remains of the ovulated follicle (corpus luteum)
absence of progesterone = shedding
need progesterone rich environment of epithelium and endometrial cells for embryo to implant
corpus luteum = remains of follicle that ovulated oocyte = produces progesterone that maintains tissue layers of uterus
what maintains corpus luteum
embryo
human chorionic gonadotropin = hcg, binds to lh receptor
made by embryo
embryos tells it to make progesterone
Describe implantation - steps
apposition –> attachment –> invasion
what is diapause
up to blastocyst
long period developmental arrest
sits at blastocyst stage then implants
skunk = 200 days
does not happen in humans but does in many species
describe Factors implicated in blastocyst-uterine attachment
Blastocyst must form good adhesion and then implant
factors = lif (leukemia inhibiting factor), cg, hbegf (heparin binding epidermal growth factor)
Specific molecules = some expressed on uterine epi or embryo epi = helps form good attachment
enables embryo to attach to uterus
firm attachment is first step in implantation
which factors on blastocyst side for attachment
erbB4 = egfr receptor
L selectin
which factors on endometrial surface side for attachment
integrin
hb egf
osteopontin
how does embryo invade uterine endometrium
cytotrophoblast
syncytiotrophoblast
how does embryo invade uterine endometrium - PANEL A
blastocyst cells must force way into epithelial surface of endometrium = digest or split cells apart to get through epidermis to endometrium
how does embryo invade uterine endometrium - PANEL B
cells of trophectoderm fuse to generate syncytiotrophoblast (sct, st)
all one = whole bunch of cells fused together = one giant cell with hundreds of nuclei (multinucleated)
te cells proliferate then fuse to form st, which facilitates implantation
how does embryo invade uterine endometrium - PANEL C
syncytiotrophoblast invades maternal deciduum (derived from endometrium)
how does embryo invade uterine endometrium - PANEL D
cytotrophoblast cells derived from trophectoderm push into sct to generate chorionic villi
instead of fusing = formed into columns, formed by individual cytotrophoblasts - all stack up and push way in
ALL EMBRYONIC CELLS NOT MATERNAL
describe chorionic villi
blood vessels going up into placenta
all around= cytotrophoblast
fetal blood and maternal blood exchange nutrients = in close contact
what does placental development do
brings maternal and fetal blood in proximity
maternal blood outside
decidua = maternal portion of placenta
villi w/ cytotrophoblast = fingers going into sct and inside fingers = fetal blood cells
describe stem cells derived from blastocyst
icm –> embryonic stem cells
can give rise to all cells of embryo if put them back into blastocyst
describe stem cells derived from fibroblasts
from skin - treat with define factors = induced pluripotent stem cells
can give rise to all cells of body if properly maintained
describe stem cells derived from muscle stem cell
Adult stem cells
corresponds to specific tissue
describe how we can make an embryo with stem cells - gen
could also make from trophectoderm blastocyst = been able to discriminate between stem cells
1 = cell of icm (become embryo, primitive epiblast)
2= stem cells from primitive endoderm cells
can get stem cells destine to be all parts of embryo then combine
how to make synthetic embryo - steps
Embryonic stem cells , extraembryonic endoderm cells, trophoblast stem cells = take cells and put into little culture well = pyramid = STEP 1 AGGREGATION CULTURE
then treat with proper things = cocktail of drugs and growth factors to activate ot block certain signalling pathways = goal to get cells to organize themselves into embryos = STEP 2 EPS-BLASTOID SELF ORGANIZATION
STEP = IVC BEYOND IMPLANTATION
how to make synthetic embryo - results
etx embryo = aggregated - formed aggregated cells types
looks similar to natural embryo
stained with antibody that recognizes protein expressed in visceral endoderm
comes from extraembryonic extoderm
what else are people exploring for synthetic embryos
also exploring using only embryo stem cells or induced pluripotent stem cells and get them to be whole range of cells and generate embryo
Synthetic embryos ethical considerations
easier to make synthetic embryos = if can = avoid ethical issues but if almost indistinguishable from natural embryo = conflicted again
what makes up corpus luteum
mural and thecal cells express lh receptor = of large follicles, these cells make up corpus luteum
what does corpus luteum have
corpus luteum has lh receptor
what looked for in pregnancy test
hcg looked for in pregnancy test
what does embryo do - progesterone
embryo looking after own interest = maintains environment
ensures uterine epithelium maintained in healthy condition
