BIOL116- Development to death

what layers surround the secondary oocyte?

corona radiata (granulosa cells) and the zona pellucida

how does the sperm enter the layers of the secondary oocyte?

the acrosome releases enzymes enabling it to penetrate the layers

what happens when the sperm and oocyte fuse?

a cortical reaction is triggered, hardening the zona pellucida to prevent polyspermy, the secondary oocyte completes meiosis II

on day 5 post fertilisation, what does the morula turn into?

the blastocyst

what happens to the blastocyst?

it break out of the zona pellucida and differentiates into the trophoblast and inner cell mass

what will the trophoblast and inner cell mass in the blastocyst turn into?

trophoblast- placenta

inner cell mass- embryo

where does the blastocyst implant on day 7?

the endometrium

what happens when the embryo shifts from pre-embryonic to embryonic phase?

the endoderm and ectoderm form, with the embryonic disc separating them

fraternal twins

two separate eggs fertilised by two separate sperm

identical twins

splitting of early embryonic cells post-fertilisation

Neurulation

formation of the neural tube, where nervous system stems from and becomes the spinal cord

why is folate (vitamin B9) important around 4 weeks?

because neural tube closure is dependent on it

what happens if there isnt enough folate present in week 4?

spina bifida- where the spinal cord and backbone don't close completely

What does the amnion do?

fills with amniotic fluid to cushion the fetus

What does the allantois turn into?

the blood vessels of the umbilical cord

What does the yolk sac produce?

early blood cells and germ cells

What does the chorion do?

makes hCG and becomes the fetal side of the placenta

what is the function of the umbilical cord?

carries oxygenated blood through a vein to the fetus and returns deoxygenated blood through arteries to the placenta