special topic 1 - embryonic development Flashcards
when does gastrulation occur
week 3 of embryonic development
what are the amnion and chorion
the amnion is the innermost membrane surrounding the foetus and containing the amniotic fluid.
the chorion is the outermost membrane that protects the amnion and embryo, and is connected to the uterine lining. has chorionic villi for nutrient exchange from placenta to uterus.
the ectoderm gives rise to (main categories)
the skin and all nervous tissue
what are blastomeres? they are ____potent?
early embryonic cells formed during cleavage.
blastomeres are ____potent?
totipotent
cleavage is:
the early rapid cell division following fertilisation, resulting in increasingly smaller cells called blastomeres
the mesoderm gives rise to (main categories)
connective tissues and internal organs
structure of the sperm
very small, with a head containing genetic material and a tail to swim. head has a sac with enzymes to allow it to burrow into the egg.
what is the corona radiata, what is its function in fertilisation
a layer of follicular cells surrounding the zona pellucida and egg. provides a barrier that the sperm must penetrate.
where and when does fertilisation occur (what phase)
in the fallopian tubes, 12-24 hours after ovulation, in metaphase II
when is a morula formed, what are its characteristics
3-4 days after fertilisation.
loosely packed ball of 16-32 cells.
what is the zona pellucida, why is it important
a thick glycoprotein membrane surrounding the egg,
is slippery/not sticky so ensures egg doesn’t get stuck in fallopian tubes which would result in ectopic pregnancy
what is embryogenesis
formation of embryo from a fertilised egg (0-8 weeks)
what does embryogenesis achieve
patterning, axis definition, rudiments of organs, gastrulation
what is patterning
cells in the embryo become organised and acquire identity, forming the ‘plan’ of the developing body
what are the 4 major axis
anterior - head
posterior - bottom
dorsal - back
ventral - stomach
what germ layer would the skeleton arise form
mesoderm
when can we call a fertilised egg a zygote?
when the male and female pronuclei fuse
what is the difference between a polar body and a secondary oocyte or ovum, and why?
the polar body is the product of female meiosis I or II that is much smaller with less cytoplasm. isn’t typically fertilised.
secondary oocyte/ovum are much larger with more cytoplasm so that they are nutrient and organelle rich to support development.
order the levels of cell potency, least to most.
nulli(uni)potent, multipotent, pluripotent, totipotent
what can a multipotent cell give rise to
cells of a particular tissue or organ
the endoderm gives rise to
the innermost structures; the gut
differentiated cells have _______ division potential
limited
stem cells are defined as….
cells that divide to form one daughter that goes on to differentiate, and one daughter that maintains stem cell properties
structure of a blastocyst
outer trophoblast cells, blastocyst cavity, inner cell mass (gives rise to embryo)
when does the zona pallucida disappear
when embryo enters uterus
role of enzymes in implantation
allows the blastocyst to stick in the endometrium, and ensures uterine lining doesn’t slough off.
trophoblast cells give rise to ______
the embryonic portion of the placenta (fetal placenta)
hCG is secreted by what, and does what?
secreted by trophoblast cells, signals pregnancy
what does the fetal placenta consist of?
the amnion and chorion
what does the bilaminar embryonic disk consist of, what does it give rise to.
epiblast and hypoblast cells.
epiblast cells eventually give rise to the three germ layers, while hypoblast forms the endoderm yolk sac. (endoderm, but not final endoderm).
what does the yolk sac do
provides nutrition for embryo while placenta is still developing
what is the connecting stalk, what axis of the embryonic disc is it connected to
the connecting stalk attaches the embryonic disc to the trophoblast at the uterine wall, at the posterior side of the disc.
where does the primitive streak form and what direction does it travel
forms on the dorsal side, from the posterior to anterior side
what is the primitive streaks structure and function
it is a groove on the surface of the bilaminar disc’s epiblast.
it allows for organisation of the embryo, defining its midline and axis.
allows for invagination in gastrulation
what is invagination/gastrulation
epiblast cells migrate through the primitive streak and move inward, forming the final endoderm and the mesoderm. the remaining epiblast cells become the ectoderm.
what happens to the yolk sac and connecting stalk in embryonic folding
they get squished together and together will form the umbilical cord
how is embryonic folding able to occur
cells are moving, changing shape and size, and dividing
describe embryonic folding and when it occurs.
occurs around week 3-4, and consists of head to tail folding in towards each other, and lateral folding. results in the internal gut cavity tube, and the ectoderm around it enclosing the internal structure.
we need stem cells for _____
renewal, growth, repair
what condition results in very fragile skin, what is it, what does it do
epidermolysis bullosa.
single gene defect.
defect in collagen 7, which sticks epidermis to dermis, results in fragile skin that sloughs off very easily.
explain the attempt to create skin sheets for epidermolysis bullosa, why are stem cells important in this ( + stem cell % aim)
skin biopsies are taken, edited to fix the collagen 7 defect, and grown into larger skin sheets with collagen 7. important for these to have stem cells to be a long-lived product. aiming for 5% stem cell retention
