embryology of the nervous system

blastocyte

cluster of cells

week 3 critical period

developing neural tube

ectoderm

top layer

sensory organs, epidermis layer, nervous system

mesoderm

middle layer

dermis, muscle, skeleton, circulatory, excretory structures

endoderm

bottom layer

gut, liver, internal organs, respiratory system

what does the neural tube develop into

brain and spinal cord (CNS)

what do the neural crest cells form

PNS

somite development

correlate with myotome / dermatome distribution

come from the mesoderm

form vertebral bodies

mantle layer of neural tube

gray matter

marginal zone of neural tube

white matter

alar plate

dorsal aspect of neural tube

location of sensory information in dorsal horn

afferent fibers (to CNS)

basal plate

ventral aspect of neural plate

location of motor information in ventral horn

efferent fibers (away from CNS)

week 4 critical period

superior / inferior neuropore closes

what does the prosencephalon (forebrain) become

telencephalon and diencephalon

what does the mesencephalon (midbrain) become

mesencephalon

what does the rhombencephalon (hindbrain) become

metencephalon and myelencephalon

when does myelin start / complete

starts: month 4-5

complete: 2-3 years old

Schwann cells

support cells in PNS

create myelin

oligodendrocyte

support cells in CNS

create myelin

anencephaly

superior neuropore defect that causes bony defects of skull and malformation of cerebral hemispheres

cause of spina bifida

lack of closing inferior neuropore

spina bifida occulta

bony defect L1 and below

doesn’t effect nervous system

spina bifida meningocele

bony defect with fluid filled sac on outside of infant back

protrusion of meningeal layer

mild degree of deficit

spina bifida meningomyelocele

bony defect and spinal cord / peripheral nerves extended into sac

nervous tissue involvement

higher than L1 = spinal cord involvement (more severe)

what is the caudal equine part of

PNS

hydrocephalus

accumulation CSF within the ventricle in the brain

hydrocephalus from chiari malformation

parts of the brain stem and cerebellum protrudes down through the foramen magnum

where does the spinal cord end

L1 / L2