Development of the Nervous System Flashcards
Where does primary neurulation extend from?
Brain to the lumbar spinal cord
What is the caudal eminence?
The caudal eminence induces the creation of the sacral and coccygeal parts of the spinal cord. It is part of secondary neurulation.
Almost all cells of the NS come from neuroepithelium (neural tube), except for:
Microglia, which are developed monocytes from mesenchyme.
Where do the brain vesicles begin to form?
Above the 4th somites
3 brain vesicles
Prosencephalon - forebrain
Mesencephalon - midbrain
Rhombencephalon - hindbrain
When does the forebrain and hindbrain divide?
Wk 5
What does the prosencephalon divide into?
Telencephalon and diencephalon
What does the rhombencephalon divide into?
Metencephalon and myelencephalon
Cervical flexure demarcates:
Demarcates the hindbrain from SC
Pontine flexure demarcates:
Divides the hindbrain into metencephalon and myelencephalon.
Cephalic flexure demarcates:
Bend between midbrian and forebrain
What develops from weeks 6-32? (2)
Basal ganglion
Cortical structure
Components of telencephalon (6)
Cerebral cortex Subcortical white matter Olfactory bulb and tract Basal ganglia Amygdala Hippocampus
Components of diencephalon (4)
Thalamus
Hypothalamus
Epithalamus
Eyes (CN II)
Holoprosencephaly
Results from incomplete separation of cerebral hemispheres.
Many facial abnormalities can happen.
Causes of Holoprosencephaly (3)
Genetic
Maternal diabetes
Teratogens
What are the sources of the anterior and posterior lobes of the pituitary?
Anterior: first arch ectoderm
Posterior: neuroectoderm
What part of the neural tube will become the SC?
Caudal to the 4th somites
What is the sulcus limitans?
It separates the alar and basal plates within the SC
Zones of the spinal cord
Ventricular zone (stem cell layer) Intermediate zone (grey matter) Marginal zone (white matter)
Nerve fibers from the basal plate (3)
Motor to skeletal muscle and preganglionic ANS:
GSE
SVE
GVE
Nerve fibers from the alar plate (4)
Sensory within CNS: GVA SVA GSA SSA
Syringomyelia is:
What is it associated with?
Fluid filled cavity develops within the SC.
Hydrocephalus.
What is deformed in Chiari malformations?
Deformity of the hindbrain
Chiari type I
Herniation of cerebellar tonsils thru foramen magnum.
Often can be asymptomatic, but can have sx that align with problems in lower CNs.
Chiari type II
Herniation of cerebellar tonsils and medulla thru foramen magnum.
Hydrocephalus.
Lower CN problems.
Dandy Walker Malformation (Cyst)
Large posterior fossa cyst continuous with 4th ventricle.
Hypoplasia of cerebellum.
Atresia of foramina of Luschka and Magendie.
Hydranencephaly
Absence of cerebral hemisphere, but brainstem intact.
Excessive head growth after birth.
Little/no cognitive development.
Cytodifferentiation of cerebrum (lamina I-VI, superficial to deep)
Lamina I - mainly dendrites.
Laminae II-III - mainly neurons.
Laminae IV - receives inputs from thalamus.
Lamina V - projects into structures like the brainstem, SC and basal ganglia.
Lamina VI - projects primarily into the thalamus.
Lissencephaly
AKA smooth brain.
Problem with neuronal migration during wks 12-24.
Child may have apnea, poor feeding or abnormal muscle tone.
Microcephaly
Sign, not a dx.
Can be from lack of brain development or injury to previously normal developing brain.
Can be caused by genetics, infection, brain injury, etc.
Cortical layers are laid down:
Inside out (deep to superficial)
How is cerebellum developed?
Dorsal parts of alar plates –> cerebellar swellings –> project into 4th ventricle and fuse
Position of SC in adult and infants:
Adults: L1-L2
Infants: L2-L3
Neural crest cells give rise to:
Neurons on DRG
Sensory ganglia of cranial nerves
Schwann cells
Smpathetic ganglia
CNS myelination
Starts in lower brainstem with the older tracts first.
Done by oligodendrocytes. Begins 6 mo to puberty.
PNS myelination
Motor roots before sensory roots.
Schwann cells.
Begins 4th mo.
Spina bifida occulta
Meningocele
Meningomyelocele
Myelocele
Spina bifida occulta: imcomplete closure of vertebra.
Meningocele: protrusion of meninges.
Meningomyelocele: protrusion of the meninges and can contain SC.
Myelocele: SC is open to the outside.
Anencephaly
Top of the head is exposed