Implantation

Question 1

what are steps of implantation

Answer 1

fertilization –> development in the oviduct, migration to uterus (5 days) –> implantation into the uterus –> placentation (placenta forms) –> fetal development

Question 2

name and describe types of losses of pregnancies

Answer 2

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

Question 3

describe uterine cell types

Answer 3

lumen = where embryo goes
endometrium = surrounds lumen
myometrium = muscular layer surrounds endometrium
perimetrium = structure to uterus

Question 4

describe uterine organization

Answer 4

epithelium and endometrium = parts that build up and slough off - contains uterine glands (poke down into endometrium) and spiral arteries
myometrium under = muscle layer

Question 5

describe reproductive cycle - what hormones involved

Answer 5

Estradiol
Progesterone

Question 6

describe reproductive cycle - estradiol

Answer 6

increase just before ovulation
all granulosa cells in growing follicle make estradiol
promotes proliferation of uterine tissues and layers = endometrium and epithelium

Question 7

describe reproductive cycle - progesterone

Answer 7

peak progesterone = helps develop and differentiate uterine layers
progesterone falls bc no fert = layers slough off = period

Question 8

describe non reproductive cycle - uterine changes during follicular (pre ovulatory) phase

Answer 8

growth of uterine epithelium (estradiol)
due to proliferation of endometrial stromal cells (progesterone and estradiol)
growth of spiral arteries

Question 9

describe non reproductive cycle - uterine changes during pre menstrual phase

Answer 9

thinning of spiral arteries (low progesterone)
blood supply falls apart bc no fert

Question 10

describe non reproductive cycle - uterine changes during menstrual phase

Answer 10

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

Question 11

what produces progesterone required by uterus - explain

Answer 11

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

Question 12

what maintains corpus luteum

Answer 12

embryo
human chorionic gonadotropin = hcg, binds to lh receptor
made by embryo
embryos tells it to make progesterone

Question 13

Describe implantation - steps

Answer 13

apposition –> attachment –> invasion

Question 14

what is diapause

Answer 14

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

Question 15

describe Factors implicated in blastocyst-uterine attachment

Answer 15

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

Question 16

which factors on blastocyst side for attachment

Answer 16

erbB4 = egfr receptor
L selectin

Question 17

which factors on endometrial surface side for attachment

Answer 17

integrin
hb egf
osteopontin

Question 18

how does embryo invade uterine endometrium

Answer 18

cytotrophoblast
syncytiotrophoblast

Question 19

how does embryo invade uterine endometrium - PANEL A

Answer 19

blastocyst cells must force way into epithelial surface of endometrium = digest or split cells apart to get through epidermis to endometrium

Question 20

how does embryo invade uterine endometrium - PANEL B

Answer 20

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

Question 21

how does embryo invade uterine endometrium - PANEL C

Answer 21

syncytiotrophoblast invades maternal deciduum (derived from endometrium)

Question 22

how does embryo invade uterine endometrium - PANEL D

Answer 22

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

Question 23

describe chorionic villi

Answer 23

blood vessels going up into placenta
all around= cytotrophoblast
fetal blood and maternal blood exchange nutrients = in close contact

Question 24

what does placental development do

Answer 24

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

Question 25

describe stem cells derived from blastocyst

Answer 25

icm –> embryonic stem cells
can give rise to all cells of embryo if put them back into blastocyst

Question 26

describe stem cells derived from fibroblasts

Answer 26

from skin - treat with define factors = induced pluripotent stem cells
can give rise to all cells of body if properly maintained

Question 27

describe stem cells derived from muscle stem cell

Answer 27

Adult stem cells
corresponds to specific tissue

Question 28

describe how we can make an embryo with stem cells - gen

Answer 28

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

Question 29

how to make synthetic embryo - steps

Answer 29

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

Question 30

how to make synthetic embryo - results

Answer 30

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

Question 31

what else are people exploring for synthetic embryos

Answer 31

also exploring using only embryo stem cells or induced pluripotent stem cells and get them to be whole range of cells and generate embryo

Question 32

Synthetic embryos ethical considerations

Answer 32

easier to make synthetic embryos = if can = avoid ethical issues but if almost indistinguishable from natural embryo = conflicted again

Question 33

what makes up corpus luteum

Answer 33

mural and thecal cells express lh receptor = of large follicles, these cells make up corpus luteum

Question 34

what does corpus luteum have

Answer 34

corpus luteum has lh receptor

Question 35

what looked for in pregnancy test

Answer 35

hcg looked for in pregnancy test

Question 36

what does embryo do - progesterone

Answer 36

embryo looking after own interest = maintains environment
ensures uterine epithelium maintained in healthy condition