embryology Flashcards
(28 cards)
what is a zygote?
a fertilised ovum
what is a morula?
a solid mass of cells at 4-6 days
what is a blastocyst?
a hollow ball of cells- inner cell mass and outer(trophoblast) at 6-10 days
what is the embryo’s life support/nutrient supply?
the placenta
how is the baby’s blood replenished from the mothers?
the circulations don’t mix as they are separated by a thin barrier, it is permeable to most molecules but not cells
what is the bilaminar embryo?
at 10-12 days the implanted trophoblast contains an embryo with 2 cell layers
what is the epiblast?
the layer in the bilaminar embryo which gives rise to embryonic ectoderm, mesoderm and endoderm
what is the hypoblast
the layer in the bilaminar embryo which participates in formation of endoderm and extraembryonic mesoderm
what does the embryo develop during gastrulation?
an axis (bilateral symmetry), the 3 embryonic cell layers and a groove- the primitive streak
how is the mesoderm formed?
some ectodermal cells are introduced to and migrate thru the primitive streak towards the hypoblast
how is the endoderm formed?
an interaction between the mesoderm and hypoblast.
what is the trilaminar embryo?
the mesodermal cells push thru the primitive streak and spread out to form a 3rd layer
what is organogenesis?
during weeks 3-8 the major organs develop from the 3 basic germ layers
when is the neural groove evident?
20 days
what is the neural tube the forerunner of?
CNS
what defect can occur where the neural groove persists?
spina bifida
what is weird about the neural crest?
it is derived from ectoderm but has the characteristics of mesenchyme
how does the trilaminar embryo begin to take shape?
the front and back ends begin to fold under the middle, the embryo folds around the yolk sac, and important organs appear
at which week does and embryo become a fetus?
week 9
what are stem cells?
unspecialised cells that can develop into more specialised cells
describe adult stem cells
committed to cell lines
what embryonic stem cells are totipotent?
inner cell mass
what embryonic stem cells are pluripotent?
cells in the 3 germ layers
what does the ectoderm consist of?
outer- skin, mucous membranes, brain, spinal cord, tooth enamel
