Fertilization and Implantation Flashcards
What is capacitation?
Sperm start out with many seminal plasma proteins which allow it to bind to the female tract
Sperm loses proteins which causes it to unbind and reveals molecules that can bind to zona pellucida
What 3 barriers must be breached for fertilization?
Corona radiata (Expanded cumulus)
Zona pellucida
plasma membrane of oocyte
Which receptor does sperm bind to?
ZP3 receptor which triggers acrosomal reaction
What is the acrosomal reaction?
1) Sperm plasma membrane fuses with acrosomal membrane to release contents of acrosomal vesicle
2) enzymes in the acrosomal vesicle digest the zona pellucida
3) sperm can enter the holes created in the zona pellucida
What protein receptor does sperm bind to once reaching the plasma membrane of the oocyte?
Izumo
What happens once sperm and egg fuse?
Cortical reaction
1) Release of Ca2+
2) Alteration of ZP proteins
3) Hyaluronic acid and other proteoglycans are released and hydrated
4) Zona pellucida forms a physical barrier
When the outer cells of morula increase cell adhesions what does this do?
Forms trophoectoderm
Increases Na+ transport and osmosis to form a blastocele
What is hCG?
Secreted by trophoblast and synctiotrophoblasts
structure closely related to LH
What does hCG do?
Prevents involution of the corpus luteum
-prevents menstruation
-Leads to increased secretion of progesterone and estrogen
Autocrine growth factor
-stimulates trophoblast growth and development
-stimulates placental growth
Describe the apposition stage of implantation
Contact between endometrium and trophoblasts
Describe the attachment phase of implantation
Trophoblast cells adhere to the luminal endometrial epithelium
- Increased vascular permeability
- Intracellular matrix composition
- Stromal cell morphology
Describe the invasion stage of implantation
Degradation of endometrial cells
Trophoblast fusion and formation of syncytiotrophoblasts
Syncytiotrophoblast protrudes through basement membrane and reaches endometrial stroma
What is decidulaization?
Response of maternal stromal cells to invasion and progesterone
Forms an epithelial-like sheet that inhibits migration of hte implanting embryo
What happens to make primary villi?
Proliferation of syncytiotrophoblast and cytotrophblasts to lacunae
What happens to make secondary villi?
Mesenchyme cells from extraembryonic mesoderm invade villi
