Embryo Implantation Flashcards
Pregnancy
Upon fertilisation, pregnancy is initiated when the conceptus has successfully signalled its presence to the mother and continues with the development of one or more offspring, known as the embryo or fetus, in a mother’s uterus
Where does fertilisation occur?
In the ampulla region of the fallopian tube
What is a gastrula?
Hollow cup-shaped structure having 3 layers of cells in which the germ layers of the embryo form
What are the 3 stages of embryo implantation?
- Blastocyst apposition
- Blastocyst attachment
- Blastocyst invasion
What and when is the window of implantation?
When the endometrium becomes receptive
Mid-secretory phase
Days 19-23
What is the role of the zona pellucida?
- Supports the communication between oocytes and follicles during oogenesis
- Protects oocytes, eggs, and embryos during development
- Regulates interactions between ovulated eggs and free-swimming sperm during and after fertilisation
- Prevents the pre-embryo adhering to the fallopian tube
What happens to the endometrium during the window of implantation?
- Apical microvilli shortens
- Loss of surface negative charge
- Thinning of the thick mucin coat
- Formation of pinopodes
What is glycocalyx?
anti-adhesive gel-like layer formed by MUC1 (heavily glycosylated mucin) which defers blastocyst implantation
What are pinopodes?
Cytoplasmic projections arising from the apical surface of the endometrial epithelial cells
What is decidualisation
differentiation of elongated, fibroblast-like mesenchymal cells in the uterine stroma to rounded, epithelioid-like cells during the mid-luteal phase of the menstrual cycle
What molecules are involved in blastocyst attachment?
LIF, integrins, selectins, E-cadherins
How long is the embryogenic phase?
14 days
How long is the embryonic phase?
6 weeks
How long is the fetal phase?
220 days
What is the role of the decidualised endometrium?
- Protects the embryo from maternal immune rejection
* Regulates trophoblast invasion and placental formation
