embryology part 1 Flashcards
what are the 2 processes involved in fertilisation
Capacitation and Acrosome reaction
What is capacitation
secretions from uterus lining and fallopian tubes destabilise the acrosome (sperm head) causing the membrane to become more fluid and the flagella more active, sperm begins to make way through the corona radiata.
what is the acrosome reaction
ZP3 surface proteins on the zona pellucida bind with the acrosome causing it to release enzymes that digest a pathway through zona pellucida.
what is fast block
fusion of acrosome with oocyte plasma membrane depolarises plasma membrane preventing polyspermy.
whats is slow block
depolarisation of fast block causes the an influx of calcium into oocyte triggering cortical granules to fuse with oocyte plasma membrane rendering ZP3 inactive and preventing further zona pellucida breach.
what process does the oocyte undergo once the acrosome has fused
meiosis II
what is implantation
the blastocyst embeds into the lining of the uterus wall.
when does implantation occur
generally 6-10 days after fertilisation, can be 4-14.
Which hormone, secreted by the trophoblast, is important in maintain the endometrium after implantation of the blastocyst?
Human chorionic gonadotrophin
When does the embryonic period end?
End of week 8
what is cleavage
rapid cell division after fertilisation
how many cells are in a blastomere
2
how many cells are in a morula
16
what is a blastocyst
a fluid
filled hollow sphere composed of a single layer of flattened
cells called trophoblast cells (form placenta). On one side is a small cluster of cells (the inner mass, or embryonic disc) from which the embryo
develops.
what are the 2 layers of trophoblast
cytotrophoblast (inner)
synctiotrophoblast (outer)
which trophoblast layer invades mother’s blood supply
synctiotrophoblast
what does the inner cell membrane divide to become
bilaminar disc, comprised of upper epiblast and lower hypoblast.
what is gastrulation
The process by which bilaminar disc folds to become the trilaminar disc
what are the 3 layers of the trilaminar disc
endoderm, mesoderm and ectoderm
what structure forms in the epiblast to begin gastrulation
primitive streak
at what end of the primitive streak is the primitive pit
cranial end
