Implantation of the Hu embryo

Question 1

What starts the decidualization (endoderm become ripe for fert) of the uterine stroma?

Answer 1

P and E

that the corpus luteum secretes after fertil

Question 2

What enters the uterus?

Answer 2

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

Question 3

Decidualization

Answer 3

Morphological and biochemical differentiation of uterine stromal cells

1. Accumulation of glycogen and lipids
2. Change in ECM
3. Prolactin and IGFBP-1
4. Activate COX2 and PGE2
5. Recruitment of dNK cells into the decidua

Critical for trophoblast invasion and formation of the placenta

Question 4

Hatching

Answer 4

• 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

Question 5

Epithelium of uterus starts forming what day 20-21

Answer 5

Formation of pinopods or microvilli on the surface of the luminal epithelium

Important for trophoblasts to bind

Question 6

Stages of implantation

Answer 6

1. Apposition
2. Adhesion
3. Invasion

Question 7

The extent of decidualization corresponds to what?

Answer 7

the degree of invasiveness of trophoblasts

*but decidualization begins prior to implantation due to high P and E in luteal phase

Question 8

What prevents immune rejection of the fetus?

Answer 8

Areas of immune contact

1. Syncytiotrophoblast
   - no MHC antigens
2. 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

Question 9

When can you detect HCG in mother? Embryo?

Answer 9

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

Question 10

Leading cause of maternal death in first trimester

Answer 10

Ectopic pregnancy

2nd leading cause of maternal mortality overall

Question 11

Risk of ectopic pregnancy (most likely in Ampulla of fallopian tube)

Answer 11

1/50-250 pregnancies (.5-2%)

1. tubule disease
2. Prior hx of ectopic
3. INfertility and ART
4. CIgarrette smoking
5. Vaginal douching

Question 12

Tx for ectopic pregnancy

Answer 12

1. Medical
   - methotrexate
2. Surgical
   - laparotomy vs laparoscopy
3. Expectant

Question 13

What makes B HCG?

Answer 13

Trophoblast

trophoectoderm of the blastocyst

Question 14

At what value does the serum HCG have to be for intrauterine preg to be ruled out?

Answer 14

Discriminatory zone

1500 (2000)

Question 15

Implantation refers to attachment of fertilized egg to uterine lining, when does this occur?

Answer 15

6-7 days after conception.

Question 16

What cycle day do you see hCG in embryo? Mother?

Answer 16

day 18 - morula in uterus

day 21 -
Implantation

Question 17

What happens on day 20-24 of the menstrual cycle that primes the epithelium of the uterus to accept implantation of the blastocyst?

Answer 17

1. Frame pinopodes, small fingerlike projections, form on the apical surface of the endometrial epithelium
   - dependent upon progesterone and suppressed by estrogen
2. Endometrium bcomes more vascular and edematous

Question 18

Apposition

Answer 18

1st stage of implantation

Loose unstable connxn btwn trophoectoderm microvilli and endometrial lining (pinopodes)

Question 19

Adhesion

Answer 19

2nd stage of implantation
(first is apposition)

Stronger connection made by ligand receptor intxns

• Integrins
• Heparin

Question 20

1st and 2nd and 3rd stage of implantation

Answer 20

1. Apposition
2. Adhesion
3. Invasion

Question 21

Invasion

Answer 21

3rd stage of implantation

Blastocyst adheres to epithelium ->
trophoblastic cells rapidly proliferate and differentiate into syncytiotrophoblasts and cytotrophoblasts

Question 22

What do syncytiotrophoblast secrete that assist in the dislogement of epithelial cells, and promote invasion thru basement membrane?

Answer 22

TNF-a: interferes with expression of cadherins and b-catenin

Autocrine factors + proteases