From A Cell To An Embryo Flashcards
What is capacitation?
Penultimate step in the maturation of spermatozoa, required for them to be fertile
What happens during capacitation?
- glycoprotein coat removed causing cell membrane to become more permeable to calcium ions
- these activate strong tail lashing & make the acrosome reaction possible
What happens when sperm meet the zona pellucida of the egg?
Acrosome reaction
What happens during an acrosome reaction?
- acrosome membrane and plasma membrane fuse at many points
- acrosomal contents spill out & can digest the zona pellucida
What is the acrosome?
Organelle that develops over the anterior half of the head in the spermatozoa
What happens after the acrosome reaction?
Sperm burrow towards egg and fuses with membrane (fusion causes wave of calcium entry which keeps repeating)
Effect of calcium waves?
- cortical granules released (alter ZP so block sperm & fusion)
- meiosis of oocyte resumes
Reasons for assisted fertilisation?
Blocked/absent oviducts, blocked Vasa deferentia/efferentia, impotence, low male fertility, female age
Stages of assisted fertilisation
- superovulation
- oocyte harvesting
- sperm harvesting
- capacitation of sperm (artificially)
- mixing of sperm & oocytes
- observation of early development
- embryo transfer
What’s an ICSI?
Intra-cytoplasmic sperm injection
What is cleavage?
Mitosis with no growth
Trophoblast
Cells forming outer layer of blastocyte (provide nutrients to the embryo and develop into part of placenta)
Blastocyte
Posses an inner cell mass (ICM) which subsequently forms the embryo, and an outer layer (the trophoblast)
What happens during implantation? (after the blastocyte hatches though zona pellucida)
The trophoblast of the hatched blastocysts invades the uterine epithelium
