5. Development Flashcards
which process converts neural plate –> neural tube?
neurulation
steps to neurulation
- lateral edges of neural plate fold DORSALLY
- midline neural groove forms
- folded edges meet & fuse at midline
- fusion begins day 22 (cervical region, 5th somite)
- neural groove is converted to neural tube
which day does neural fusion start?
at which region and somite?
fusion begins day 22 (cervical region, 5th somite)
- direction of fusion during neurulation
- on day 23, neuropores are (closed/open)
- cranially and caudally
- both cranial and caudal neuropores are still open to the amniotic sac
which neuropore closes first?
*cranial neuropore first (day 25)
and then caudal neuropore (day 28)
neural crest cells (aka “fourth germ layer”)
- from what layer is it formed?
- where do they originate?
- migration patterns?
- from ectoderm –> forms neural crest cells
- originates from lateral edges of neural plate
- migration
- cephalic region - sheet-like mass migration; pharyngeal arches
- trunk - chain migration
neural crest derivatives
- cranial nerve ganglia
- spinal (dorsal root) ganglia
- sympathetic chain and pre-aortic ganglia
- parasympathetic ganglia of GI tract
- schwann cells
- glial cells
- meninges (forebrain)
what does the neural tube develop into?
CNS
what do differentiating neuroblasts develop into?
these are primitive nerve cells; which these are responsible for neurons.
These migrate and form in mantle layer
layers of the spinal cord
- ventricular
- develops into neuroepithelium (pseudostratified)
- differentiates into neuroblasts
- neuroblasts form mantle layer
- gray matter
- marginal layer forms as nerve fibers emerge from neuroblasts
- white matter
neuroblasts form mantle layer and develop into…
gray matter
marginal layer forms as nerve fibers emerge from neuroblasts and differentiate into…
white matter
what are the plates of the spinal cord
- basal plate
- alar plate
- roof
- floor
basal plate of spinal cord develops into:
- ventral horn w/
- motor cells
These are primary order sensory cells
alar plate of spinal cord includes, and develops into:
second order sensory cells
- dorsal horn
- sensory cells
intermediate horn of spinal cord develops into:
autonomic nervous system (gray matter)
central canal develops into
cerebrospinal fluid
where do the ventral root and dorsal root come from?
- ventral root/ motor nerve fibers arise from cells in basal plate
- dorsal root/ sensory nerve fibers arise from sensory nerve cells
process of forming dorsal root?
(neural crest derivatives –> form outside the spinal cord (dorsal root ganglion) –> processes extend centrally to alar plate, and peripherally to join ventral root –> form sensory nerve cells
axonal growth:
direction and details
- axons grow towards their target (end) organs
- growth cone at apical end of developing axon is guided by molecular signaling
- towards - chemoattractants,
- away from- chemorepellants)
synaptogenesis
- synaptic connection forms when axon interacts w/ target
- not precise
apoptosis w/ regards to axonal growth and synaptogenesis?
50% of neurons produced during development undergo apoptosis
somites:
precursor; and develops into
- develop from paraxial mesoderm
- differentiate into:
- sclerotome: the part of each somite in a vertebrate embryo giving rise to bone or other skeletal tissue
- dermomyotome: the remaining part of the somite left when the sclerotome migrates
sclerotome: define
the part of each somite in a vertebrate embryo giving rise to bone or other skeletal tissue
dermamyotome: define
the remaining part of the somite left when the sclerotome migrates
purpose of resegmentation of sclerotomes
- resegmentation allows passage of spinal nerves between vertebrae
- accounts for segmental nerve distribution
- myotomes - motor innervation
- dermatomes - sensory innervation
myotome: define
what does myotome split into?
- dorsal part of each somite in a vertebrate embryo, giving rise to the skeletal musculature
- divides into:
- epimere: dorsal; deep back muscles
- hypomere: ventral; develops into hypaxial muscles
epimere:
develops into
inn. by
- the dorsal portion of the mesodermal mass in the early development of chordate embryos that gives rise to the skeletal muscles
- develops into deep back muscles
- inn by dorsal rami
hypomere:
develops into
inn. by
hypaxial musculature
- lateral and ventral body wall musculature
- limb musculature
- inn by ventral ramus
3 primary brain vesicles
- prosencephalon
- mesencehalon
- rhombencephalon