Histology 2

a depression, forming along the axis of the neural plate, giving rise to the neural folds

peripheral folds around the neural groove, fuse three days following their formation with the help of the neural crests

result of the fusing of the neural folds, separates from the overlying ectoderm

neural crest cells separate after pinching together to form the neural tube, whereupon they migrate into the embryo. They eventually give rise to:

• 1. dorsal root ganglia of the spinal chord
• 2. autonomic ganglia
• 3. parts of the ganglia of several cranial nerves
• 4. melanocytes
• 5. adrenal medulla
• 6. sheaths of peripheral nerves
• 7. dentin

condensed mesenchymal columns on either side of the notochord (form ~ at end of 3rd week of development), eventually breaking into cuboidal structures in a cranial and caudal direction. Give rise to most of the axial skeleton and its attendant musculature and overlying dermis

(CVS) first fully functional organ system of the embryo

mesodermally-derived mesenchymal cells proliferating to make the blood island formation; eventually canalize to form primitive blood vessels. Endothelium lining of CVS differentiated from cells lining blood islands, and are further differentiated to form various blood cells

most of the CVS arises from splanchnic mesoderm (early heart), paraxial and lateral mesoderm, and neural crest

develop from paired early vessels to form the heart tube, which becomes linked to other elements of the CVS; blood beings circulating near the end of week 3, heartbeat begins around day 21