Lecture 7: Embryogenesis Flashcards
Weeks 1-8 of human pregnancy are known as what? What happens during this pd? What follows?
Embryogenesis. Organ primordia (organs in their
earliest recognizable stage of development) are established. Fetal pd.
Timing of development: the two-cell stage is reached ? hours post-fertilization, 4-cell stage ?, 16-cells ? and the late
morula stage ? Cells undergoing cleavage in the early stages are called what?
~30 hours, ~ 40 hours, ~3 days, ~ 4 days. Blastomeres.
Inner cells of the morula constitute the what? This gives
rise to tissues in the embryo proper and the outer cells give rise to the what that later contributes to the placenta. Fluid then penetrates into the intercellular spaces of the ICM to form a what?. At this time the embryo is a what? The outer cells flatten and form the wall of the
blastocyst.
ICM. Trophoblast. Blastocoel. Blastocyst.
Trophoblast cells contribute to what tissues?
Extraembryonic
ICM gives rise to what?
The embryo (they’re pluripotent ESCs)
What on trophoblast cells interact with carbohydrate
receptors on the uterine epithelium to mediate attachment of the blastocyst to the uterus?
L-Selectins.
The trophoblast diffn’s into two layers. What are they?
On day 8, the blastocyst is partially embedded in the endometrium and the trophoblast differentiates into two layers: 1) cytotrophoblast—an inner layer of mononucleated
cells and 2) syncytiotrophoblast—an outer multinucleated
layer that lacks distinct cell boundaries. The syncytiotrophoblast continues to expand into the uterine wall
On day 9, cells of the ICM also differentiate into what two layers?
Hypoblast and epiblast. Meanwhile, the trophoblast invades maternal capillaries to establish uteroplacental
circulation.
The epiblast layer gives rise to all tissues in the ? proper, whereas the hypoblast layer and trophoblast
contribute to ?.
embryo, extraembryonic tissues.
What process establishes three germ layers in the 3rd week of development?
Gastrulation.
Gastrulation begins with the formation of the ? on the surface of the epiblast. What’s considered the ‘organizer; that drives gastrulation?
primitive streak. The primitive (Henson’s) node.
Invaginating epiblast cells through the prim streak give rise to what two layers? Cells remaining in the epiblast form which layer?
Endoderm and mesoderm. Ectoderm.
The process by which the neural plate forms the neural tube?
Neurulation.
The events of neurulation divide the ectoderm into three major domains. Describe them.
The internally positioned neural tube, which will form the brain and spinal cord; Externally positioned surface ectoderm that will primarily form skin
(epidermis); the neural crest cells that migrate to new locations to give rise to many cell types.
Failure to close the posterior neuropore results in what?
Failure to close at the other 2 sites results in an open anterior
neuropore and a lethal condition called what in which the forebrain remains in contact with amnionic fluid and degenerates? Complete
failure of closure along the entire neural tube results in
what?
Spina bifida. Anacephaly. Craniorachischisis.
