Embryology intro Flashcards
diff b/w baby and mom development duration
38 weeks for baby, 40 for mom (40 weeks from LMP)
embryonic period
weeks 3-8, embryo w/ organogenesis
weeks 1-2
zygote-morula-blastocyst; fertilization and implantation
fetal period
weeks 9-38, fetus- growth and maturation
birth defect
congenital abnormality present at birth
malformation
structural abnormality secondary to intrinsic process like genetic abnormality
deformation
abnormality secondary to extrinsic process
sequence
multiple abnormalities developing in order
syndrome
multiple abnormalities in no known sequence
abnormal development in weeks 1-2
not susceptible to teratogens, secondary to inherited genetics
abnormal development in embryonic period
most vulnerable time! susceptible to all types, major anomalies when development is disrupted while structure is only a few cells
abnormal development in fetal period
susceptible to all types, minor anomalies b/c structures are almost fully formed
common “directions” of development
cranial to caudal, proximal to distal
fns performed by placenta
fetal lungs, kidneys, GI tract
fetus interaction (body processes) w/ amniotic fluid
breathes the fluid, urinates into fluid, does NOT defecate in utero
process during week 1 in order
fertilization- zygote division- morula- early blastocyst- late blastocyst- implantation in uterus
differentiate 2 components of late blastocyst
inner cell mass- becomes fetus
trophoblast- becomes placenta and fetal membranes
week 2 processes
inner cell mass into epiblast (embryo) and hypoblast (disappears), amniotic cavity appears, primitive streak forms
primitive streak
dorsal, caudal midline in epiblast - precursor to 3 germ layers
dorsal view
“birds eye”- cranial up at the top and caudal at the bottom
transverse view
cross section- top is posterior/dorsal, bottom is anterior/ventral
week 3 development- 3 main processes
gastrulation (trilaminar embryo w/ 3 layers), somite formation, neurulation
gastrulation
epiblast becomes ectoderm, 2 new layers form under epiblast at primitive streak: mesoderm and endoderm
ectoderm
epidermis, teeth, nervous system
mesoderm
muscle, bone, connective tissue, vessels and blood, dermis
endoderm
epithelium of GI and respiratory tracts
mesenchyme
aggregates of undifferentiated cells, mostly from mesoderm
somites
horizontal body segments, form during week 3 from mesoderm
3 somite divisions
dermatome- skin, myotome- muscle, sclerotome- bone
3D embryo structure beginning of week 4
flat!!! during week 4, folding begins in 2 directions
longitudinal folding, visualize longitudinal section
cranial and caudal ends fold ventrally- heart moved from cranial to new thorax and begins to beat
transverse folding, visualize cross-section view
lateral sides fold ventrally and fuse at the ventral midline
creates GI tract and body cavity precursor (coelom)
new germ layers begin to differentiate
major events of week 4
beginning of transverse and longitudinal folding, germ layer differentiation
