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Objectives
• Describe the development of meninges.
• Describe the development of brain vesicles
from the neural tube.
• Describe the development of the different
parts of brain.
• Describe the development of brain
ventricles and choroid plexuses
• Describe the development of the cranial
nerves and their ganglia.
• Describe the congenital anomalies of brain
and spinal cord.
Meninges:
• The meningeal layers originate from:
• Paraxial mesenchyme in the trunk and caudal regions of the head.
• Neural crest in regions rostral to the mesencephalon.
• The meninges may be divided in development into the
pachymeninx (dura mater) and leptomeninges (arachnoid mater,
subarachnoid space with arachnoid cells and fibres, and pia mater).
• All meningeal layers are derived from loose mesenchyme which
surrounds the developing neural tube, termed primary meninx.
• Rhombencephalon:Hindbrain
• Rhombencephalon consists of the
myelencephalon, most caudal of the brain
vesicles,and metencephalon, which extends
from the pontine flexure to rhombencephalic
isthmus.
• Myelencephalon:
• It is brain vesicle that
gives rise to medulla
oblongata.
• It differs from the
spinal cord in that its
lateral walls are
everted.
• Alar and basal plates
separated by sulcus
limitans can be clearly
distinguished
• The basal plate, similar to that
of spinal cord contains motor
nuclei. These nuclei are divided
into three groups:
• (1) Somatic efferent.
• (2) Special visceral efferent.
• (3) General visceral.
• Somatic efferent group
continues rostrally into
mesencephalon as somatic
efferent motor column.
• In myelencephalon, it includes
neurons of hypoglossal (XII)
nerve.
• In the metencephalon and the
mesencephalon, the column
contains neurons of abducens
(VI) ,trochlear (IV), and
oculomotor(III) nerves.
• Special visceral efferent group extends into the metencephalon,
forming special visceral efferent motor column.
• Its motor neurons supply striated muscles of pharyngeal arches.
• In myelencephalon, the column is represented by neurons of
accessory (XI),vagus (X), and glossopharyngeal (IX) nerves.
• The general visceral efferent group contains motor neurons that
supply involuntary musculature of the respiratory tract, intestinal
tract, and heart.
• The alar plate contains three
groups of sensory relay nuclei:
• (1)Somatic afferent (general
sensory) receives sensations
of pain, temperature, and
touch from pharynx by way of
glossopharyngeal nerve (IX).
• (2) Special afferent receives
from taste buds of tongue,
palate, oropharynx, epiglottis
and from vestibulocochlear
nerve (VIII) for hearing and
balance.
• (3) General visceral afferent,
group receives interoceptive
information from respiratory
gastrointestinal tract and
heart by vagus nerve (X).
• Roof plate of myelencephalon consists of a single layer of
ependymal cells covered by pia mater The two combined
are known as tela choroidea.
• Proliferation of vascular mesenchyme forms sac-like
invaginations that project into the underlying ventricular
cavity and form the choroid plexus, which produces
cerebrospinal fluid.
• Metencephalon:
• Similar to myelencephalon it is
characterized by basal and alar
plates.
• Two new components form:
• (1) Cerebellum, a coordination center
for posture and movement .
• (2) Pons, the pathway for nerve
fibers between spinal cord , cerebral
and cerebellar cortices.
• Basal plate of metencephalon
contains three groups ofmotor
neurons:
• (1) Somatic efferent , which gives rise
to the nucleus of the abducens
nerve.
• (2) Special visceral efferent
containing nuclei of the trigeminal
and facial nerves.
• (3) General visceral efferent, with
axons that supply the submandibular
and sublingual glands.
• Marginal layer of basal plates of
metencephalon makes a bridge
for nerve fibers connecting
cerebral cortex and cerebellar
cortex with the spinal
cord.Hence, this portion of the
metencephalon is known as pons
(bridge).
• In addition to nerve fibers, pons
contains pontine nuclei, which
originate in the alar plates of
metencephalon and
myelencephalon.
• Alar plates of the metencephalon
contain three groups of sensory
nuclei:
• (1) Somatic afferent which
contains neuronsof the
trigeminal nerve.
• (2) Special afferent.
• (3) General visceral afferent.
• Cerebellum
• Dorsolateral parts of alar
plates bend and form rhombic
lips which join and form the
cerebellar plate.
• In a 12-week embryo, this
plate shows a small midline
vermis, and two lateral
hemispheres.
• A transverse fissure soon
separates the nodule from
vermis and lateral flocculus
from hemispheres.
• This flocculonodular lobe is
phylogenetically the most
primitive part of the
cerebellum.
• Initially cerebellar plate
consists of
neuroepithelial, mantle,
and marginal layers.
• Cells formed by the
neuroepithelium migrate
to surface of the
cerebellum to form
external granular layer.
• In the sixth month of
development external
granular layer gives rise to
various cell types. These
cells migrate toward the
differentiating
Purkinjecells and give rise
to granule cells.
• Basket and stellate cells
are produced by
proliferating cells in the
cerebellar white matter.
• The cortex of the
cerebellum, consisting of
Purkinjecells, Golgi II
neurons, and neurons
produced by the external
granular layer, reaches its
defi nitive size after birth
.
• The deep cerebellar
nuclei, such as dentate
nucleus, reach their final
position before birth.
• Mesencephalon (Midbrain):
• In mesencephalon each basal
plate contains two groups of
motor nuclei:
• (1) Somatic efferent
represented by oculomotor
and trochlear nerves.
• (2) General visceral efferent
represented by nucleus of
Edinger-Westphal.
• Marginal layer of each basal
plate enlarges and forms crus
cerebri.
• Alar plates of mesencephalon
appear as two longitudinal
elevations separated by a
shallow midline depression.
With further development, a
transverse groove divides
elevations into superior and
inferior colliculi.
• Prosencephalon
(forebrain):
• It isconsists of
telencephalon which forms
cerebral hemispheres and
diencephalon, which
forms optic cup and stalk,
pituitary, thalamus,
hypothalamus, and
epiphysis.
• Diencephalon:
• It develops from median
portion of prosencephalon
and consist of a roof plate
and two alar plates but
lack floor and basal plates.
• Roof plate of
diencephalon
give rise to
choroid plexus
of the third
ventricle.
• The most caudal
part of roof
plate develops
into pineal
body, or
epiphysis.
• Alar Plate, Thalamus,
and Hypothalamus:
• Alar plates form
lateral walls of
diencephalon.
• Hypothalamic sulcus
divides the plate into
a dorsal region
forming the
thalamus and a
ventral region
forming the
hypothalamus.
• Cranial Nerves:
• By the fourth week of
development, nuclei for all
12 cranial nerves are
present.
• All except the olfactory (I)
and optic (II) nerves arise
from brainstem, and of
these only the oculomotor
(III) arises outside the
region of the hindbrain.
Cranial Nerve
Olfactory (I)
Brain Region
Telencephalon
Type
SVA
Innervation
Nasal epithelium (smell)
Optic (II)
Diencephalon
SSA
Retina (vision)
Oculomotor (III)
Mesencephalon
GSE
Sup., inf., med. Rectus, inf.
oblique, levator palpebrae sup.
m.
GVE (ciliary
ganglion)
sphincter pupillae, ciliary m.
Trochlear (IV)
Metencephalon
(exits
mesencephalon)
GSE
Sup. oblique m.
Trigeminal (V)
Metencephalon
GSA (trigeminal
ganglion)
Skin, mouth, facial m., teeth,
ant. two-thirds of tongue
GVA (trigeminal
ganglion)
proprioception: skin, muscles,
joints
SVE
(branchiomotor)
M. of mastication, mylohyoid,
ant. belly of digastric, tensor
velipalatini, post. belly of
digastric m.
Abducens (VI)
Metencephalon GSE
Lateral rectus m.
Facial (VII)
Metencephalon SVA (geniculate Taste ant. two-thirds of
ganglion)
tongue
GSA (geniculate Skin ext. auditory meatus
ganglion)
GVA (geniculate Ant. two-thirds of tongue
ganglion)
SVE
M. of facial expression,
(branchiomotor) stapedius, stylohyoid, post.
belly of digastric
GVE
Submandibular, sublingual,
and lacrimal glands
Vestibulocochlear Metencephalon SSA (vestibular Semicircular canals, utricle,
(VIII)
and spiral
saccule (balance) spiral
ganglia)
organ of Corti (hearing)
Myelencephalon
Glossopharyngeal (IX)
Vagus (X)
Myelencephalon
SVA (inferior
ganglion)
Post. one-third of tongue (taste)
GVA (superior
ganglion)
GSA (inferior
ganglion)
SVE (branchiomotor)
Parotid gland, carotid body and
sinus, middle ear
External ear
GVE (otic ganglion)
Parotid gland
SVA (inferior
ganglion)
GVA (superior
ganglion)
Palate and epiglottis (taste)
Stylopharyngeus
Base of tongue, pharynx, larynx,
trachea, heart, esophagus, stomach,
intestines
External auditory meatus
GSA (superior
ganglion)
SVE (branchiomotor) Constrictor m. pharynx, intrinsic m.
larynx, sup. two-thirds esophagus
Spinal Accessory (XI) Myelencephalon
GVE (ganglia at or
Trachea, bronchi, digestive tract,
near viscera)
heart
SVE (branchiomotor) Sternocleidomastoid, trapezius m.
Hypoglossal (XII)
GSE
Myelencephalon
M. of tongue (except palatoglossus
Congenital Malformations Of CNS
Spina bifida
Meningoencephalocele
Anencephaly
• Due to failure of
closure of the rostral
end of the neural
tube.
• Failure of complete
development of the
brain , skull and scalp
Microcephaly
Congenital hydrocephalus
• Abnormal
Accumulation of
CSF inside the
brain cavities
1) Spina bifida cystica
2) A-Spina bifida with
meningocele
Myelocele: •