Implantation of the Hu embryo Flashcards
What starts the decidualization (endoderm become ripe for fert) of the uterine stroma?
P and E
that the corpus luteum secretes after fertil
What enters the uterus?
Morula
(which then becomes the blastocyst)
*the blastocyst invades and is completely buried in endometrium and no longer in direct contact with uterine cavity ~10 days after fertilization
Decidualization
Morphological and biochemical differentiation of uterine stromal cells
- Accumulation of glycogen and lipids
- Change in ECM
- Prolactin and IGFBP-1
- Activate COX2 and PGE2
- Recruitment of dNK cells into the decidua
Critical for trophoblast invasion and formation of the placenta
Hatching
- Blastocyst enters the endometrial cavity by
Escaping the ZP, day 5-7 after ovulation
(day 20-21 from last menstrual period)
Trophoblast becomes exposed and invades endo lining
Epithelium of uterus starts forming what day 20-21
Formation of pinopods or microvilli on the surface of the luminal epithelium
Important for trophoblasts to bind
Stages of implantation
- Apposition
- Adhesion
- Invasion
The extent of decidualization corresponds to what?
the degree of invasiveness of trophoblasts
*but decidualization begins prior to implantation due to high P and E in luteal phase
What prevents immune rejection of the fetus?
Areas of immune contact
- Syncytiotrophoblast
- no MHC antigens - Extravillous trophoblast
- express unusual HLA-C, G, E antigens (that may downregulate cellular immunity in local env. of placenta)
There is no large influx of T or B cells into placental that iwll provoke immune rejection
When can you detect HCG in mother? Embryo?
3 weeks after implantation
- serum is week one (lower levels)
- urine preg + around 4-5 weeks (need higher levels)
*HCG in embryo is made on day 18 after fert by morula in uterus
Leading cause of maternal death in first trimester
Ectopic pregnancy
2nd leading cause of maternal mortality overall
Risk of ectopic pregnancy (most likely in Ampulla of fallopian tube)
1/50-250 pregnancies (.5-2%)
- tubule disease
- Prior hx of ectopic
- INfertility and ART
- CIgarrette smoking
- Vaginal douching
Tx for ectopic pregnancy
- Medical
- methotrexate - Surgical
- laparotomy vs laparoscopy - Expectant
What makes B HCG?
Trophoblast
trophoectoderm of the blastocyst
At what value does the serum HCG have to be for intrauterine preg to be ruled out?
Discriminatory zone
1500 (2000)
Implantation refers to attachment of fertilized egg to uterine lining, when does this occur?
6-7 days after conception.
What cycle day do you see hCG in embryo? Mother?
day 18 - morula in uterus
day 21 -
Implantation
What happens on day 20-24 of the menstrual cycle that primes the epithelium of the uterus to accept implantation of the blastocyst?
- Frame pinopodes, small fingerlike projections, form on the apical surface of the endometrial epithelium
- dependent upon progesterone and suppressed by estrogen - Endometrium bcomes more vascular and edematous
Apposition
1st stage of implantation
Loose unstable connxn btwn trophoectoderm microvilli and endometrial lining (pinopodes)
Adhesion
2nd stage of implantation
(first is apposition)
Stronger connection made by ligand receptor intxns
- Integrins
- Heparin
1st and 2nd and 3rd stage of implantation
- Apposition
- Adhesion
- Invasion
Invasion
3rd stage of implantation
Blastocyst adheres to epithelium ->
trophoblastic cells rapidly proliferate and differentiate into syncytiotrophoblasts and cytotrophoblasts
What do syncytiotrophoblast secrete that assist in the dislogement of epithelial cells, and promote invasion thru basement membrane?
TNF-a: interferes with expression of cadherins and b-catenin
Autocrine factors + proteases
