EMBRYO LEC - NEURULATION

Neurolation

transforms the flat ectodermal neural plate into a cylindrical neural tube

what marks the beginning of neurolation

formation of the neural plate induced by signals from the underlying notochord and mesoderm

stage of development of neurolation

after gastrulation

what is the embryo called during neurolation

neurula

what do neural tube cells become

specialized precursors of neurons and glial cells

neural plate

becomes CNS

surface ectoderm

becomes epidermis

neural crest

lies between CNS and epidermis; forms PNS structures and others

what morphogens are important in neurolation

transforming growth factor - beta and sonic hedgehog

what transcription factors are key in neural plate development

Sox1, sox 2, and sox3

functions of the sox family

induce neural plate identity and inhibit epidermal gene expression

primary neurolation

forms most of the neural tube

secondary neurolation

forms posterior spinal cord from mesenchymal condensation and cavitation

stages of primary neurolation

elongation and folding of neural plate

bending of neural plate

convergence of neural folds

closure of the neural tube

what regulates the median hinge point

Shh from the notochord induces MHP cells to become wedged shaped

how dues Shh affect bone morphogenic protein?

it binds and inhibits BMPs, allowing bending and Median Hinge Point formation

what is critical for dorsolateral hinge point (DLHP)formation?

noggin

ends of the neural tube called

anterior and posterior neuropores

anterior neuropore failure

anencephaly

posterior neuropore failure

spina bifida

what are morphogens

extracellular signaling molecules that pattern tissues based on their concentration gradient

high Bone morphogenetic protein results to

epidermis

low bone morphogenetic protein

neural plate = CNS

What secrets bone morphogenetic proteins?

ectoderm and lateral mesoderm

what proteins antagonize bone morphogenetic proteins (BMPs)?

noggin, chordin, and follistatin

what does noggin do?

inhibits BMP signaling; crucial for Dorsolateral hinge point formation and neural fold bending

what does the primary neurolation form?

brain and spinal cord form cervical to lumbar regions

what does secondary neurulation form?

sacral and coccygeal spinal cord

what tissue is involved in primary neurulation

ectoderm

what tissue is involved in secondary neurulation?

messenchymal tissue from the tail bud

what happens during elongation and folding

neural plate lengthens along the cranio-caudal axis and begins to fold at the midline

what occurs during bending?

median hinge point forms; central plate cells become wedge shaped due to sonic hedgehog

what happens during convergence

lateral neural folds move toward the midline; DLHPs form with help from noggin

what happens during closure?

neural folds fuse to form the neural tube; the ectoderm seals above, and neural crest cells delaminate

neural tube closure begins at?

cervical region

in which direction does closure proceed?

bidirectionally - cranially and caudally

what are neuropores

open ends of the forming neural tube

what is the anterior neuropore?

the rostral opening - closes first

what is the posterior neuropore?

the caudal opening - closes last

what is craniorachischisis?

a severe neural tube defect where the entire neural tube fails to close

what happens in secondary neurolation

messenchymal cells condense to form a medullary cord that undergoes cavitation to form the caudal neural tube

what is the medullary cord

a solid rod of mesenchyme that cavitates to form the neural tube in the tailbud

what is a neural plate

thickened ectoderm that will give rise to the CNS

what is the neural groove?

central depression in the neural plate

what are neural folds

elevated lateral edges of the neural plate

what is the neural crest

a band of cells between the neural plate and surface ectoderm; migrates to form multiple tissues

what nutrient prevents neural tube defects

Folic Acid of Vitamin B9

what happens in spina bifida occulta

mild form where vertebral arch doesnt form properly; often asymptomatic

what happens in spina bifida cystica

more severe; involves a fluid filled sac protruding from the back

moderate bone morphogenetic protein results to

neural crest = PNS