Embryo Basics Flashcards
What weeks make up the embryonic period? and what is the main function of it?
weeks 3-8 and organogenesis
what weeks make up the fetal period and what goes on?
weeks 9-38
growth and development
what type of stem cells start development?
pluripotent cells
of congenital abnormalities, what percent do teratogens cause?
7-10 percent
define birth defect
abnormality present at birth
define malformation
developmental structure abnormality from intrinsic factor
define deformation
development structure abnormality from extrinsic factor
what can happen during the embryonic period?
this period is most sensitive to teratogens and since its the start of organ dveelopment if something goes wrong it can cause a major anomaly
what can happen during fetal period?
not as sensitive to teratogens…will lead to minor anomalies since there are more normal cells already present
name three things the placenta functions as in utero
lungs kidneys and Gi tract
week one development steps
fertilization to zygote to morula to blastocyst then implantation
what are the two parts of the blastocyst?
inner cell mass and trophoblast
what does the inner cell mass become?
embryo
what does the trophoblast become?
placenta
what four things form in week 2?
epiblast, hypoblast and amniotic cavity and primitive streak
what happens to the epiblast and hypoblast?
epiblast becomes embryo and hypoblast dies off
what is the primitive streak that develops in week 2?
this is the midline
what three things develop in week 3?
ectoderm, mesoderm, endoderm
somites
nervous system
what is the formation of the three germ layers called in week 3?
gastrulation
explain gastrulation process
cells from the spiblast migrate and become the ecto and mesoderm…then epiblast becomes the ectoderm
what does the ectoderm lead to?
skin, teeth and CNS
what does the mesoderm lead to?
muscle, bone, connective tissue, blood and vessels, deep layers of skin
what does the endoderm lead to?
epithelial lining of respiratory and GI tracts
which of the three layers do somites arise from?
mesoderm
how many somite pairs are there?
35-37
what three things does a somite divide into?
scleratome, myatome and dermatome
what is the dermatome of a somite?
skin
what is the scleratome of a somite?
bone
what is the myatome of a somite?
muscle
what happens in week 4?
organogenesis…folding longitudinal and transverse
what results from longitudinal folding in week 4?
heart moves from cranial position toward the thoracic trunk
what results from the transverse folding in week 4?
transvers folds bilaterally come together to meet ventrally and make the thorax, pelvis and abdomen and body cavities, and GI tract
what happens in weeks 5-8?
more organ development…by week 8 most all organs are present for normal life and you look like a human
