Development of Nervous system Flashcards
Central nervous system
formed in week 3 as neural plate
neural plate -> neural tube -> brain and spinal cord
Peripheral nervous system
derived from:
- Neural crest cells: peripheral ganglia, Schwann cells, afferent nerve fibers
- Neural tube: preganglionic autonomic fibers, fibers innervating skeletal muscle
- Mesoderm: dura mater, CT around peripheral nerve fibers
Development of neural tube
week 3-4
- Neural plate: thickening of neural ectoderm
- Neural groove: formed by neural plate folding
- Neural fold: fuse in midline, neural crest differentation
- Neural tube: neural folds fuse + separate from surface ectoderm
Neural tube
- cranial part: brain
- caudal part: spinal cord
- cavity: central canal of spinal cord + ventricles
- anterior neuropore: lamina terminalis
- posterior neuropore
Neural crest
gives rise to:
- pseudounipolar ganglion cells (spinal, cranial nerve ggl)
- Schwann cells
- Multipolar ganglion cells (autonomic)
- Leptomeninges
- Chromaffin cells of suprarenal medulla
- Pigment cells
- Odontoblasts
- Skeletal + connective components of pharyngeal arches
- Aorticopulmonary septum of heart
- Parafollicular cells
Placodes
thickenings of cephalic surface ectoderm
- Lens placode: lens, induced by optic vesicle
- Nasal placode: olfactory nerve, induce formation of olfactory bulb
- Otic placode: organ of Corti, spiral ggl, cristae amullares, maculae utriculi and sacculi, vestibular ggl, vestibulocochlear nerve
Stages of neural tube development: primary brain vesicles
week 4
- proencephalon:otic vesicles, telencephalon+diencephalon
- mesencephalon
- rhombencephalon: metencephalon + myelencephalon
- cephalic flexure
- cervical flexure
Stages of neural tube development: secondary brain vesicles
week 6
- Telencephalon: cerebral hemispheres, olfactory bulb
- Diencephalon
- Mesencephalon: cerebral aqueduct
- Metencephalon: rhomboic lips -> cerebellum, pons
- Myelencephalon: medulla
Cells of neural tube wall
neuroepithelial cells that gives rise to:
- Neuroblasts: neurons in CNS
- Glioblasts:
- macroglia: astrocytes, radial glial cells, oligodendroglia
- ependymal cells: ependymocytes, tanycytes, choroid plexus cells - Microglia
Layers of early neural tube wall
- Spinal cord:
- ventricular zone(neurepith. layer): ependymal cells lining central canal, neurons and glial cells of spinal cord
- intermediate zone(mantle layer): grey matter of spinal cord, alar and basal plates
- marginal zone: white matter of spinal cord - Brain
- ventricular zone: ependymal cells lining ventricles, neurons and glial cells of brain
- intermediate zone: cerebral cortex, basal ganglia
- marginal zone: molecular layer of cortex
- cortex: grey matter of cerebral hemispheres
Alar plate
dorsolateral thickening of intermediate zone of neural tube
gives rise to: sensory neuroblasts of dorsal horn
receives axons -> dorsal roots from dorsal root ganglion
becomes dorsal horn of spinal cord
Basal plate
ventrolateral thickening of intermediate zone of neural tube
gives rise to: motor neuroblasts of ventral and lateral horns
axons exit from spinal cord and form ventral roots
becomes ventral horn of spinal cord
Sulcus limitans
longitudinal groove in lateral wall of neural tube
appears week 4
separates alar ad basal plates
disappears in adult but remains in rhomboid fossa
Position changes of the spinal cord
week 8 spinal cord length = vertebral canal
at birth conus medullaris to L3, in adult L1-L2
disparate growth results in caudal equina + filum terminale
Development of Myelencephalon: Alar plates
Sensory neuroblasts give rise to:
- dorsal column nuclei
- inf. olivary nuclei
- solitary nucleus
- spinal trigeminal nucleus
- cochlear and vestibular nuclei
Development of Myelencephalon: Basal plates
Motor neuroblasts give rise to:
- hypoglossal nucleus
- nucleus ambiguus
- dorsal nucleus of vagal nerve
- inf. salivatory nucleus
Development of Myelencephalon: Roof plate
- forms roof of 4th ventricle
- is the tela choroidea
- invaginated by pal vessels -> choroid plexus
Development of Methencephalon: Pons
- Alar plate sensory neuroblasts:
- solitary nucleus
- vestibular and cochlear nuclei
- spinal and principal trigeminal nuclei
- pontine nuclei - Basal plate motor neuroblasts:
- abducent nucleus
- facial nucleus
- motor trigeminal nucleus
- sup. salivatory nuclei - Base of pons