Lecture 15: Establishing the Basic Body Plan Flashcards
notochord formed from what layer
mesenchymal cells
where does the notochord originate
the primitive node, mesenchymal cells migrating cranially
where does notochord end
prechordal plate
what is the main function of the notochord
primary inductor of the embryo
what does the notochord induce in the overlying ectoderm
formation of the neural plate
what gives rise to the CNS
neuroectoderm
when does the neural groove form
day 18
where does fusion of neural tube begin
cranially
when do the anterior and posterior neuropore close
anterior: day 24-25
posterior: day 27
fate of neural tube
forebrain: cerebral hemispheres
midbrain: adult midbrain
hindbrain: pons, cerebellum, medulla oblongata
Rest becomes spinal cord
what are neural crest cells
neuroectodermal cells at the crest of the neural folds that detach as neural tube separates from ectoderm. migrate to each side
neural crest cells become
DRG, ganglia of ANS, CN V VII IX and X, peripheral nerve sheaths, melanocytes, adrenal medulla, facial muscles/bones
names of mesoderm
embryonic (somatic) = paraxial, intermediate, lateral and
extraembryonic (splanchnic) = continues with it
where are the endo and ectoderm not separated by mesoderm
oropharyngeal membrane (prechordal plate) and cloacal membrane
when are somites formed
end of week 3
what does the paraxial mesoderm become
paired blocks called somites
where do somites first appear
cranially
how many pairs of somites by the end of week 5
42-44
what do somites become
axial skeleton, skeletal muscles, dermis
how does the body cavity form
coelomic spaces in lateral mesoderm and cardiogenic mesoderm. spaces coalesce to form intraembryonic coelom
embryonic coelom becomes
pericardial cavity (heart), pleural cavity (lungs), peritoneal cavity (abdominal organs)
when does angiogenesis begin
start of week 3
where does angiogenesis begin
extraembryonic mesoderm, yolk sac, connecting stalk, chorion
how are blood islands formed
mesenchymal cells in yolk sac called angioblasts aggregate
how is the endothelium of blood vessels formed
angioblasts flatten to form endothelium, these fuse to form blood vessels
initial blood cells formed from
endothelial cells called hemocytoblasts
heart and great vessels formed from
mesenchyme (cardiogenic area)
how/when is the primitive heart tube formed
paired endocardial tubes form and fuse
when does the heart begin to beat
end of week 3
allantois
outpouching of yolk sac into the connecting stalk, becomes bladder
