Embryonic Development Flashcards
Ecto -»
nervous system, skin
a new embryo develops three layers….
- outer layer: Ectoderm
- mid-layer = Mesoderm
- inner layer = Endoderm
Meso
bones, muscles, blood vessels
endo -»
organs, glands
over the first 2 weeks….
… embryo changes from a sphere of cells to an elongated “worm”, still 3 layered.
then the dorsal ectoderm begins to thicken and forms the hard Neural Plate
then edges of the plate form ridges (Neural Folds) that curl toward each other along a longitudinal line
i.e. from Rostral (head) end to Caudal (tail) end, until they touch and fuse
where is the dorsal Ectoderm
along the back of the worm
Neural Plate
future nervous system
key developmental structure that serves as the basis for the nervous system
Neural Folds
are formed by the edges (ends) of the Neural Plate
they curl toward each other along a longitudinal line
push the ends of the plate up and together, folding into the Neural Tube
By week 4…
… edges of the Neural Folds have fused, forming Neural Tube lined with Ectoderm, embedded in Mesoderm
Neural Tube
is the embryo’s precursor to the central nervous system
Spinal Bifida
Neural Folds fail to fuse -» serious brain and cord defects: deformation, retardation, death
Rostral end of the Neural Tube
Brain, dividing into Forebrain, Midbrain, and Hindbrain
Caudal end of the Neural Tube
Spinal Cord
Neural Crest
surface of ridges that later break away from tube -» Ganglia of ANS and Peripheral Neurons & Glia
Hollow center of tube will form….
…. 4 chambers (Ventricles) in brain and Central Canal of Cord, later filled w/CSF
