Reproduction - fertilisation, maternal recognition of pregnancy & placental development Flashcards
What is the first stage of fertilisation?
Sperm enters the tract, bypasses the cervix>uterus>oviduct within minutes.
In the uterus it undergoes capacitation
What is capacitation?
This is destabilisation of the membrane.
- Glycoprotein molecules coating sperm head are removed
- Zona pellucida binding proteins are exposed
- Membrane fluidity is increased to aid acrosomal breakdown.
What happens in the sustained transport stage?
The sperm reaches the oviduct, where capacitation is completed. Hyperactive motility is reached, seen with wide tail slashing.
An increase in Ca2+ helps it do this
Where do the egg and sperm meet?
In the ampulla-isthmus junction
How does the sperm and egg attach?
The sperm attaches to the zona pellucida via ZP3 and acrosomal enzymes digest a small hole and expose the equatorial segment
What happens once the hole is digested in the zona pellucida?
The sperm moves into the perivitelline space, where it is surrounded by plasma microvilli and cortical granules.
The sperm equatorial segment fuses with the membrane and the cortical granules block the hole preventing polyspermy.
This forms the zygote
What happens to the zygote?
It cleaves into blastomere cells (2 - 4 - 8 - 16).
At the 16 cell stage it becomes a morula
What happens to the morula?
The cells for two distinct layers:
Inner cell mass
Trophoblasts
Outer cells pump sodium inot the blastocyst and create a blastocyst
When does it attach to the uterine wall?
The blastocyst moves down the oviduct, protected by the zona pellucida and then hatches, latching onto the wall
Why is the corpus luteum important for maternal recognition?
It produces progesterone which is important to proliferate the endometrium for nutrition, prevents smooth muscle contraction and develops mammary gland growth/blocks cycles
What is the pregnancy recognition factor of the cow?
bIFN tou
What is the pregnancy recognition factor of the ewe?
oIFN tou
What is the pregnancy recognition factor of the sow?
Oestradiol - 17B
What is the pregnancy recognition factor of the mare?
3 proteins/oestrogen and something else
What is the pregnancy recognition factor of the queen?
PRL (thought)
