Week 1-8
embryonic period
Week 9-36
fetal period
Week 23
embryo is viable
ovum breaks out of perioteal membranes
mittlescherz
what sweeps ovum into tube
scary fallopian fimbriae
oocytes are viable for
24 hours after ovulation
sperms are viable
For 3 days!
reaction of uterine lumen to fertilized egg implanting
decidual reaction
yolk sac is on which side?
ventral
amniotic cavity is on which side?
dorsal
primitive streak starts
caudal and grows toward head
cells streaming from the primitive streak start which layer?
middle layer!
ectoderm
skin, nervous
mesoderm
connective, GU
endoderm
gut
extension of primitive streak rostrally is the origin of
notochord
notochord is
condensation of cells that induces the overlying ectoderm to differentiate into nervous system
lateral ectoderm becomes
skin, jerk.
ectoderm invaginates and pinches off to form
neural tube
neural crest
origin of nervous system,cells that delaminate and migrate fromadjacent to the neural tube
neural tube closure first occurs
in future neck, or else spina bifida, detectable by leak of CSF into amniotic fluid
paraxial mesoderm gives rise to
somites (skeleton, muscle)
intermediate mesoderm gives rise to
GU system
lateral mesoderm, 2 layers
top (next to ectoderm), bottom (next to endoderm)
top mesoderm becomes
body wall
bottom mesoderm becomes
visceral wall: internal around the gut
intraembryonic coelum
space between top and bottom mesoderm, becomes body cavities
blood island and heart form
via vasculogenesis in interembryonic coelum
where does the heart form
all the way anterior! (that’s in the head!)
at four weeks: folding
neural tube grows faster than other tissues and causes head and tail fold
what positions heart and connecting stalk (and allantois) to position on the ventral surface
neural tube folding over endoderm
at four weeks: yolk sac becomes
foregut, midgut, hind gut.
what creates the allantois?
tail fold bringing amniotic cavity into the embryo
does lateral folding happen at 4 weeks?
yes.
how many umbilical arteries?
two!
how many umbilical veins?
one!
Intra-embryonic coelum folding creates
future pericardial cavity, accompanying heart to ventral surface of the embryo.
dorsal aorta
the six precursors to the great vessels. Formed in pharyngeal folds
embryonic blood flow
placenta> umbilical vein> liver> inferior vena cava> right heart> foramen ovale> left atrium> aorta> internal iliacs> umbilical artery> bladder> placenta
umbilical artery
has LOW O2
umbilical vein
has high O2
most of liver
is mostly bypassed via ductus venosum
blood in inferior vena cava
mixes with venous return
foramen ovale
for bypassing the lungs!
embryonic pulmonary blood flow
right heart> pulmonary artery> ductus arteriosus> aorta
lung pressure is ____because lung is not functional
high
at birth, right heart pressure
falls due to lack of blood in the umbilical vein
at birth, foramen ovale
closes (due to higher pressure on the left), forcing right heart blood into lungs
at birth, ductus venosus
closes, becomes ligamentum venosum
at birth, ductus arteriosis
closes, becomes ligamentum arteriosum
at birth, umbilical arteries become
blood supply to the bladder
By 8 weeks
inch long embryo with all systems formed