01-22: Implantation Flashcards
When does fertilization occur in the upper ampulla?
within 12 hours after ovulation
What stage of fertilization happens at the END OF DAY 1?
2-cell stage in isthmus
What stage of fertilization happens at DAY 3?
- Morula in isthmus
- Corona radiata lost
What stage of fertilization happens at DAY 4?
Blastocyst in uterus
What stage of fertilization happens at DAY 5?
Loss of ZP
What stage of fertilization happens at DAY 6?
Beginning of implantation
The ZP surrounds the developing embryo until ____________________
the embryo reaches the uterus
What is the process of shedding the ZP?
Blastocyst hatching
ZP functions
-
What are the 4 stages of implantation?
1- Expanded blastocyst attaches to the endometrial epithelium
2- Blastocyst penetrates uterine epithelium
3- Blastocyst invades the tissues underlying the epithelium
4- Maternal vascular supply is eroded
What does the erosion of the maternal vascular supply do?
- creates spaces within the implanted material
- allows BV to bleed into the spaces so that the embryo can feed of the oxygen and nutrients for the next 9 months
What is the initial contact of the expanded blastocyst to the endometrial epithelium?
initial contact between the endometrial surface and the embryonic pole of the blastocyst
What is the embryonic pole of the blastocyst?
side of the blastocyst where the ICM is located
What facilitates the attachment of the blastocyst to the endometrial epithelium?
Adhesion molecules expressed by:
- Endometrium
- Trophoblast
What is the leukemia-inhibiting factor expressed by?
the endometrium
**respective receptors on the trophoblast may be important
During blastocyst penetration into the uterine epithelium, what does the trophoblast separate into?
- Cellular cytotrophoblast
- Multinucleated syncytiotrophoblast
What is the cellular cytotrophoblast closest to?
ICM
What is the multinucleated syncytiotrophoblast closest to?
the endometrium
Where does the syncytiotrophoblast projections penetrate?
the endometrial basal lamina
**then they begin to invade the endometrial stroma
When do trophoblastic lacunae appear?
After the syncytiotrophoblast projections begin to invade the endometrial stroma
What are the trophoblastic lacunae filled with?
Eroded endometrial BV with maternal blood
**Trophoblast = less invasive at this point
What is the response of the endometrial stroma cells to the invading blastocyst called?
the decidual reaction
Where are the decidual cells derived from?
endometrial stroma cells that accumulate glycogen and lipid droplets
What is the result of the decidual reaction?
a massive cellular matrix completely surrounds the embryo and fills most of the endometrium
During the decidual reaction, what do infiltrating leukocytes in the endometrium secrete?
IL-2
What does IL-2 in the decidual reaction?
prevents the mother’s immune system from recognizing the embryo as a foreign body
What is one of the primary functions of the decidual reaction?
provide an immunologically privileged site to protect the developing embryo from being rejected
Where do ectopic pregnancies commonly occur?
Almost 80% = in uterine tube
0.2% - abdominal cavity
0.3% - cervical cavity
0.5% - ovary
1.0% - rectouterine pouch
2.0% - intestinal
17% - fimbrial
25% - isthmic
54% - ampullary
What is an ectopic pregnancy?
when the fertilized egg develops outside the environment
