Implantation & 1st Trimester Flashcards
Compactation
Tight junctions formed between blastomere
Formation of morula
Hatching, Apposition & Adhesion
ICM contributes to chorion & placenta
Blastocyst enters uterine lumen 5 days after fertilization
Apposition= ICM aligns // to endometrium
Invasion
trophectoderm diff into cytotrophoblasts (inner cells on fetal side) & syncytiotrophoblasts (outer cells on maternal side)
EVT extravillous trophoblast
invasive trophoblasts
hypoxia inducible factor HIF- drives EVT formation
- HIF stimulated by hypoxic environment
Forms cytotrophoblastic shell over decidua
Aggressively infiltrate decidua
EVT remodels spiral a.!
Secretes VEGF like synctiotrophoblast (also hCG B) while EVT secrete hCG hyperglycosylated
Summary
cytotrophoblasts give rise to synctio & EVTs
STs form cell mass that will fomr placenta proper & secrete tons of hCG
CTs diff into EVTs due to low O2
EVTs highly invasive & secrete VEGF so invasion & remodeling of spiral a is successful
O2 T is low= 1st trimester, aggressive trophoblast invasion
O2 T is high= 2nd trimester through parturition, no invasion
Decidualization- Blastocyst
Junctional Zone
inner 1/3 of myometrium adj to basalis layer of endometrium
Highy packed w/ m. cells
Increased vascularity
Secretory phase in uterus
trophoblasts invade JZ
deep placentation
needed for normal placental f
Inadequate Remodeling of Spiral A.
trophoblastic remodeling did not extend into JZ
Decreased blood flow
Associated w/ preeclampsia >140/90
Restricts O2 & nutrient flow to developing fetus
Miscarriage
Spontaneous before 20th week
Preterm delivery after 20th
Most occur before 7th week
Recurrent early pregnancy loss- 3 or more consecutive pregnancies lost before 20th week of gestation
Live birth only 30% of pregnancies
Luteal Phase Defect
LPD
recurrent preg loss or infertility
Where endometriu fails to undergo proper diff or differentiates slowly.
Blastocyst invades but doesn’t implant adquaetly & abordted
Integrin fibronectin sys
integrin surface spanning binding proteins that adhere fibronectin
Fibronectin is glycoprotein
Integrins expressed in endometrium luminal epith
Drives apposition & adhesion
Vasoactive cmpds
VEGF, PGF & endothelins
Interact w/ proteins to form new vessels
For spiral a. angiogenesis
MMPs
MMP-9 implantation
GF & other enz stimulate production of MMP-9 during invasion
Acts on spiral a. & decidua to ease placentation
Inhibited by TIMPs
Prolactin
Marker for decidualization
Produced by stromal cells decidualized
acts on PRL R
secretory phase
Fetus-Maternal Exchange
Through syncytiotrophoblast
HCG
hCG
Total HCG- pregnancy test
B Hcg- doubles every 48-72 hrs during early pregnancy (if not high enough levels ectopic/inadeq implantation/spontaneous abortion)
HCG-H- secreted by EVTs, highest during early preg, if elevated past 20 wk= down’s
nicked hCG & hCG free B- ?
hCG-H
Low or undetectable by 20 wk in normal
hCG endocrine
- hCG rescue of CL
- binds to LH R of granulosa-lutein cells to maintain luteal progesterone
- bind to LH on theca-lutein to maintain luteal androgen output & contribute to progesterone
- suppress GnRH release
- reduce FSH & LH from pit
- inhibit recrutiment of more follicles
- CL responds to hCG
hCG paracrine
- stimulate EVTs
- maintain endometrial cell quiescence
- increase sacculation of endometrial glands
- increase glandular secretions
- after invasion stim further hypertrophy of spiral a.
hCG binding to LH R
Luteal Placental Shift of Pregnancy
Steroid production shifts from CL to placenta
7-9 weeks of gestation
If remove ovary before 6- abortion more likely
after 10th- no problem
Estriol production begins @ 8 week of gestation
Need to have progesterone to maintain pregnancy
Steroidogenesis in Maternal-Placental-Fetal
