Download 14 Nervous - Biology Courses Server

For the real amazement, if you wish to be
amazed, is this process. You start out as a
single cell derived from the coupling of a
sperm and an egg; this divides in two, then
four, then eight, and so on, and at a certain
stage there emerges a single cell which
has as all its progeny the human brain. The
mere existence of such a cell should be one
of the great astonishments of the earth.
People ought to be walking around all day,
all through their waking hours calling to
each other in endless wonderment, talking
of nothing except that cell.
Lewis Thomas (1979)
Nervous Development
This chapter will briefly introduce the key developmental principles
associated with the formation of the nervous system and the relationships it
forms with other body systems.
• You should be familiar with the basic structure of the nervous system
– central nervous system consisting of brain and spinal cord and
peripheral nervous system comprised of cranial nerves and spinal
nerves.
• You should understand the basic design of the special senses – the
eye and the internal ear.
• Understand the process of neurulation and the early development of
the key components of the nervous system.
• Recognize how the neural tube and neural crest contribute to the
formation of the central and peripheral nervous system.
• Understand the basic development of the eye from the neural tube,
optic placode, and surrounding mesenchyme.
• Understand how the internal ear emerges from the otic placode and
its association with the neural tube.
157
Review of Nervous System Anatomy
Be comfortable with the following basic anatomy
Basic structure of the nervous system
Central nervous system
Brain
Spinal cord
Peripheral nervous system
Cranial nerves
Spinal nerves
Autonomic nervous pathways
Basic eye anatomy
Fibrous tunic
Sclera
Cornea
Vascular tunic
Choroid coat
Ciliary body
Iris
Sensory tunic
Retina
Photosensitive layer
Pigment layer
Basic internal ear anatomy
Boney labyrinth
Membranous labyrinth
Cochlear division
Vestibular division
E m b r y o l o g y
158
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Origin of Nervous System
Review of neurulation
Neural plate
Neural groove
Neural fold
Body ectoderm
Neural tube
Rostral neuropore
Caudal neuropore
Neural crest
Neural canal
159
Development of the Neural Tube
Ventricular zone
Neuroblasts
Future ependymal glioblasts
Marginal zone
Future white matter glioblasts
Astrocytes
Oligodendrocytes
Intermediate zone
Neuroblasts from ventricular zone
Differentiate into neurons
Mesenchyme
Microglial cells
Dura mater
Crest cells
Pia-arachnoid mater
E m b r y o l o g y
160
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Development of Spinal Cord
Lateral wall intermediate zone
Alar plate
Dorsal gray horn
Basal plate
Ventral gray horn
Lateral gray horn
Sulcus limitans
Roof plate
Floor plate
161
Peripheral Nervous System Development
Establishing the peripheral nervous pathways
Neural Crest Cells
Pseudounipolar sensory neurons
Cell bodies
Relation to neural tube
Relation to somite
Relation to gut tube
Section depicting sensory neuron growth, left S2-S4, right T1-L2
Autonomic postganglionic motor neurons
Sympathetic trunk migrations
Sympathetic collateral migrations
Sympathetic adrenal migrations
Parasympathetic terminal migrations
Enteric migrations
Section depicting neural crest migration, left S2-S4, right T1-L2
Association with smooth muscle and gland cells
Sympathetic postganglionic
Parasympathetic postganglionic
Section depicting postganglionic neuron growth, left S2-S4, right T1-L2
E m b r y o l o g y
162
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Neural Tube Cells
Skeletal motor neurons
Cell bodies
Relation to somite
Autonomic preganglionic motor neurons
Cell bodies
Section depicting skeletal motor neuron growth, left S2-S4, right T1-L2
Sympathetic preganglionic
Parasympathetic preganglionic
Association with migrating neural crest cells
Section depicting preganglionic neuron growth, left S2-S4, right T1-L2
163
Resulting Structure of Peripheral Nervous System
Embryonic migrations and neuronal connections
Section depicting complete neuronal development, left S2-S4, right T1-L2
E m b r y o l o g y
164
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Section depicting complete neuronal development for levels C1-C8, T3-S1, and S5-Co1
165
Development of the Brain
Brain vesicles
Three primary vesicles
Prosencephalon
Mesencephalon
Rhombencephalon
Five secondary vesicles
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
Brain flexures
Ventral flexures
Midbrain flexure
Cervical flexure
Dorsal flexure
Pontine flexure
E m b r y o l o g y
166
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Ventricles
Telencephalon
Lateral ventricles
Diencephalon
Third ventricle
Mesencephalon
Cerebral aqueduct
Metencephalon and myelencephalon
Fourth ventricle
Wall of neural tube in brain
Expansion of roof plate
Shifting of alar and basal plates
Addition of new cell columns
167
Cranial Nerve Development
Somitic motor cranial nerves
Basal plate origin
Oculormotor nerve
Trochlear nerve
Abducens nerve
Hypoglossal nerve
Pharyngeal arch cranial nerves
Crest, lateral horn, and new column origin
First arch - trigeminal nerve
Second arch - facial nerve
Third arch - glossopharyngeal nerve
Fourth and sixth arches - vagus nerve
Lateral plate mesoderm nerve
Accessory nerve
Special sensory cranial nerves
Olfactory nerve
Optic nerve
Vestibulocochlear nerve
E m b r y o l o g y
168
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
Arch 1
Arch 2
Arch 3
Arch 4
Arch 1
Arch 2
Arch 3
Arch 4
D e v e l o p m e n t
Neural tube, notochord,
prechoral mesoderm
Neural crest
Premuscular mesoderm
Muscle migration and
development
Motor neuron
development
Peripheral ganglia
development
169
Development of Parts of the Brain
Medulla
Pons and cerebellum
Midbrain
Diencephalon
Cerebrum
E m b r y o l o g y
170
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Development of the Eye
Eye components from neural tube
Optic groove and vesicle
Optic stalk
Optic cup
Outer layer of optic cup
Inner layer of optic cup
Intraretinal space
Eye components from surface ectoderm
Lens placode
Lens pit
Lens vesicle
Mesenchyme and neural crest
171
Development of basic eye components
Optic cup derivatives
Outer layer of optic cup - pigment layer of the retina
Inner layer of optic cup - neural layer of the retina
Ciliary body
Epithelium from optic cup
Smooth muscle from mesenchyme
Iris
Epithelium from optic cup
Connective tissue from neural crest
Smooth muscle from optic cup epithelium
Lens vesicle derivatives
Subcapsular lens epithelium
Primary and secondary lens fibers
E m b r y o l o g y
172
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n
N e r v o u s
D e v e l o p m e n t
Mesenchymal derivatives
Central artery of the retina and hyaloid canal
Tunica vasculosa lentis
Lens capsule
Suspensory ligaments of lens
Anterior and posterior chambers
Choroid and sclera
Neural crest derivatives
Vitreous humor
Choroid and sclera
Surface ectoderm derivatives
External corneal epithelium
Conjuntiva
173
Development of the Ear
Key components
Otic placode
Otic pit
Otic vesicle
Morphogenesis of the otic vesicle
Dorsal utricular part
Endolymphatic duct and sac
Utricle
Semicircular ducts
Absorption focus
Ampulla
Ventral saccular part
Saccule
Cochlear duct
Surrounding mesenchyme
E m b r y o l o g y
174
L e c t u r e
M a n u a l
b y
M a r k
N i e l s e n