Nervous System Development Flashcards
primordial dilation’s of the neural plate (cranial end)
called the primary brain vesicles
F= prosencephalon (fore-brain)
M = Mesencephalon (mid-brain)
H = rhombencephelon (hind brain)
where does the spinal cord develop?
below the level of the hindbrain
primordial dilations aka
primary brain vesicles
neuroepithelial layer
-derived from and characteristic
initially the wall of the neural tube is formed from the neuroepithelial cells and these divide and form a THICK pseudostratified epithelium called neuroepithelium layer
cytodifferentiation of the brain and spinal cord
neuroepithelial layer is proliferating and forming a thick pseudostratified epithelium and as a result we have neurogenesis and gliogenesis
when is neurogenesis more prominent?
during embryonic development
ventricular cells
cells that form the brain and spinal cord
ventricular zone
inner layer of developing spinal cord AND WILL GIVE RISE TO ALL NEURONS AND MACROGLIAL CELLS
inner layer
ventricular zone - which lines the canal and gives rise to other layers
these are remaining cells of the ependyma
ependymal cells
these cells line the central canal of the spinal cord and ventricles of the brain
Intermediate zone
mantle zone
- formed by neuroblasts
- becomes the gray zone/material of the spinal cord
outer layer
marginal zone
- formed by neuronal processes that give rise to the white matter of the spinal cord
T/F microglial are derived from the ventricular zone of the neural tube
FALSE
They are a macrophage - so mesenchymal
three types of glial cells and where they arise from
- Macroglia-oligodendrocyte - from gliablast (from neuroepithelial cells differentiated)
- Macroglia- Astrocytes (from the glialblast - from the neuroepithelial cell)
- Microglia*NOT DERIVED FROM NEUROEPITELIAL CELLS - from resident macrophage of the bone marrow so it is mesenychmal in origin
macroglia
providing nutrition, physical support, and synthesizing myelin
- includes the oligodendrocytes and astrocytes
dorsal root ganglion
DERIVED FROM THE NEURAL CREST CELLS
These are sensory cells that give rise to the cell body of the sensory neuron that is housed in the dorsal root ganglion
This is in the PNS.
schwann cells are originated from?
neural crest cells and produce the myeline for the PNS
Differentiation in the spinal cord
Ventral thickening - basal plates = motor horn cells
Dorsal thickening = alar plates= sensory area
Sulcus limitans= groove on each side that separates alar from basal
Roof and floor plates = no neuroblasts, pathway for nerve fibers to cross from one side to the other
roof and floor plates
no neuroblasts, pathways for nerve fibers crossing to the contralateral side
sulcus limitans
a groove on each side that separates the a from basal
marginal zone
white matter, so AXONS from the cell bodies in the brain, spinal cord, and dorsal root ganglion
where do the cell bodies of the ventricular zone end up?
intermediate zone or mantle zone, what is left over differentiates into the epedyma cells and lines the central canal of the spinal cord and the ventricles of the brain
alar plates
DORSAL gray horns with sensory/afferent
differentiate into inter neurons and receive first input from the sensory neurons of the peripheral nervous system
basal plate
ventral/motor/efferent
differentiates into voluntary motor neurons to innervate skeletal muscle
intermediate zone
lateral horns/motor/efferent
differentiates to autonomic or involuntary motor neurons
what forms the ventral roots?
nerve fibers outgrowth of the basal plate
direction neural crest cells migrate in spinal cord and what does this form?
migrate dorso-laterally to give rise to the dorsal root ganglion (DRG)
where do the cell bodies of dorsal go?
interneurons
central processes of DRG
grow into dorsal horns
distal processes of DRG
meet the ventral roots to form a spinal nerve
conus medullaris
termination of the spinal cord
*but still have nerves running beneath
spinal cord at 3rd month
spinal cord extends entire length of vertebral column - spinal nerves passing at level of origin
spinal cord at 6 months
due to differential growth, the cord ends AT HIGHER LEVELS - the 1st sacral vertebral
spinal cord at birth
spinal cord ends at the level of the 2nd or 3rd lumbar vertebra
divisions of the forebrain (prosencephalon)
telencephalon and diencephalon
T/F the midbrain (mesencephalon) divides during brain development
F stays the same - does not divide
hindbrain (rhombencephalon) divisions
metencephalon and myelencephalon
telencephalon (walls and cavity associated with)
rise to the cerebral hemispheres and cavity associated is the lateral ventricles
diencephalon
thalami, etc. and wall associated with is the third ventricle
mesencephalon
associated with midbrain and the cavity is the cerebral aqueduct
metencephalon
(from hindbrain/rhombo) and associated with the pons and cerebellum and the cavity associated is the upper part of the 4th ventricle
myelencephalon
associated with the walls of the medulla (also contributing to the spinal cord) and the cavity is the lower part of the fourth ventricle
pituitary gland develops from what
- surface ectoderm - ectoderm invagination of the ectodermal stomatodeum (primitive oral cavity) called Rathke’s pouch or ADENOHYPOPHYSIS
- neuroectoderm - downward extension of the diencephalon (hypothalamus/thalamus) called the neurohypophysis
Further development of Rathke’s pouch by surface ectoderm (pituitary development)
- pars distalis - anterior lobe of the pituitary gland
- pars tuberalis - surrounds the infundibulum (connecting stalk of hypothalamus and posterior part)
- pars intermedia - adjacent to posterior lobe - questionable significance
further development of the neuroectoderm part of the pituitary gland
- median eminence
- pars nervosa
- infundibular - downgrowth of the neuroectoderm of the diencephalon
how does the pituitary gland have two different tissue types?
TWO DIFFERENT ORIGINS
- surface ectoderm - pars distalis- Rathke’s pouch and the primitive oral cavity (stomodeum)
- neuroectoderm - infundibulum - pars nervosa which is a down growth of the diencephalon so hormones from the hypothalamus travel to the pars nervosa via axons
