implantation basics Flashcards
What is the definition of pregnancy?`
After fertilisation when the conceptus succesfully signals its presence to the mother, and continues to develop succesfully in the mother’s uterus
What is the definition of fertilisation?
The fusion of 2 haploid gametes to form a diploid zygote
What is the definition of infertility?
After 1 year of regular, unprotected sex - the women has not become pregnant.
What is the incidence of infertility in the UK?
1/6
At what region of the fallopian tubes does 4-8 cell cleavage occur?
Isthmus
What are 3 crucial requirements for implantation?
- receptive endometrium (Window of implantation)
- healthy embryo at blastocyst stage
- mutual communicatio bt mother and embryo
What are the three stages of implantation, and on what days do they occur?
- apposition, Day6/7
- adhesion, Day 7/8
- invasion, Day 8/9
What cell structure is found opposite the uterine epithelium at apposition?
Inner cell mass
What happens during gastrulation?
Spherical blastocyst changes to hollow cup shaped structure with 3 layers of cells. These cells form the germ layers of the embryo.
What are the 3 germ layers of the embryo?
Ectoderm, endoderm and mesoderm
What is the cell potential of ectoderm cells?
Skin, neurons, pigments
What is the cell potential of endoderm cells?
Digestive tract, lungs, thyroid
What is the cell potential of mesoderm cells?
muscle, kidney tubules, red blood cells
Through histological tests you find the endometrium of a woman has long apical microvilli and a highly negative surface charge. Will this woman have succesful embryo implantation?
No - her endometrium is not in a receptive state
When do pinopodes form?
During day 19-21, in the window of implantation. Pinopodes assist blastocyst invasion of endometrial epithelium
What is decidualisation?
Decidualisation is the change of uterina stroma cells to become receptive to blastocyst invasion
What specific changes occur during decidualisation?
Uterine stroma differentiate from elongated fibroblast like mesenchymal cells to rounded epithelioid like structures.
What unique abilities do decidualised stroma have that non decidualised stroma don’t?
They can regulate trophoblast invasion by resisting inflammation and oxidative attacks, and dampen the maternal immune system.
Which cells in the endometrium are stimulated by estradiol?
Endometrial epithelial cells
Which cells in the endometrium are stimulated by progesterone?
Uterine stroma cells.
What is the effect of a progesterone receptor antagonist (less than 7 weeks)?
Abortive
At what point in pregnancy does progesterone supply change from corpus luteum to placenta?
12 weeks
What role does hCG have in progesterone regulation?
hCG prolongs progesterone secretion
Where is hCG produced?
In early embryo produced by trophoblast cells, later secreted by the placenta.
