Neuroembryology

Question 1

Ectoderm: generates ————
Mesoderm: generates ———
Endoderm: generates the———

Answer 1

Ectoderm: outside, surrounds other
layers later in development, generates skin and nervous
tissue.
Mesoderm: middle layer, generates most of the muscle, blood and connective tissues of the body
and placenta.
Endoderm: eventually most interior
of embryo, generates the
epithelial lining and associated glands of the gut, lung, and
urogenital tracts.

Question 2

Neural Induction:

Ectoderm located adiacent to the
midline becomes thickened to form an elongated plate of thickened epithelial cells called the ———.
• Ectoderm exposed to ——(from
endoderm and mesoderm below), develops into ——
• • However, the node secretes BMP-4
antagonists: (e.g. ——-) that allow a region of the ectoderm to develop into———.

Answer 2

Ectoderm located adiacent to the
midline becomes thickened to form an elongated plate of thickened epithelial cells called the neural plate.
• Ectoderm exposed to BMP-4 (from
endoderm and mesoderm below), develops into skin
• • However, the node secretes BMP-4
antagonists: (e.g. noggin, chordin, & follistatin) that allow a region of the
ectoderm to develop into nerve tissue.

Question 3

Neurulation:
folding and closure of the neural plate
• Folding and closure of the neural tube occurs first in the ———
region.
• The neural tube then “zips” up
toward the —- and toward the —-, leaving two openings which are
the —— and ——.

Answer 3

Neurulation:
folding and closure of the neural plate
• Folding and closure of the neural tube occurs first in the cervical
region.
• The neural tube then “zips” up
toward the head and toward the tail, leaving two openings which are
the anterior and posterior neuropores.
• The anterior neuropore closes around day 25.
• The posterior neuropore closes around day 28.

Question 4

Failure of neuropores to close can cause neural
tube defects
anterior neuropore: ———
posterior neuropore: ————

Answer 4

Failure of neuropores to close can cause neural
tube defects
anterior neuropore: anencephaly posterior neuropore: spina bifida

Question 5

The early neural tube is a ——— epithelium
• The “apical” portion abuts the ——-
• The “basal” portion abuts the ——-
• Cell division occurs in the —— portion.

Answer 5

The early neural tube is a pseudostratified epithelium • The “apical” portion abuts the central canal
• The “basal” portion abuts the surrounding tissue (e.g. somites, notochord, etc.).
• Cell division occurs in the apical portion.

Question 6

Day —
•Neural plate invaginates

Answer 6

18

Question 7

Day — to —
•Groove begins to close forming the neural tube

Answer 7

Day 21-23

Question 8

Closure of the anterior neuropore
•Day — to —
•Proceeds from both directions
•From the ——— caudally
•From the future ——— cranially
•Failure  ———

Answer 8

Closure of the anterior neuropore
•Day 23-25
•Proceeds from both directions
•From the rhombencephalon caudally
•From the future optic chiasm cranially
•Failure  anencephaly

Question 9

•Closure of the posterior neuropore
•Day — to —
•Proceeds craniocaudally
•Site of closure is roughly opposite somites — /— (~— level)
•Failure  ———

Answer 9

•Closure of the posterior neuropore
•Day 25-27
•Proceeds craniocaudally
•Site of closure is roughly opposite somites 30/31 (~S2 level)
•Failure  meningomyelocele

Question 10

Neural crest derivatives include

Answer 10

Neural crest derivatives
●Neurons of the spinal posterior nerve root ganglion.
●Neurons of the sensory ganglion of the 5th, 7th, 8th, 9th, and 10th cranial nerves.
●Neurons of the sympathetic ganglia.
●Schwann cells that form the neurolemmal sheaths of all peripheral nerves.
●Specific cells of the adrenal medulla.
●Chromaffin tissue
●Pigment cells (melanoblasts) of the skin.

Question 11

Anencephaly
•Absence of —— and ——

Answer 11

Anencephaly
•Absence of brain and calvarium

Question 12

Anencephaly is also called

Answer 12

/MEROANENCEPHALY

Question 13

Any disruption between when the neural plate begins to fold and when it fuses to form the neural tube leads to ———

Answer 13

craniorachiscisis

Question 14

————, the most severe NTD

Answer 14

craniorachiscisis, the most severe NTD

Question 15

Encephaloceles / Cranial Meningoceles
•Distinguished from anencephaly because they have an ———- over the cranial neural tube closure defects

Answer 15

epidermal covering

Question 16

Defect in the skull with protrusion of leptomeninges +or - brain

Answer 16

Encephaloceles / Cranial Meningoceles

Question 17

Primary brain vesicles are

Answer 17

Prosencephalon
Mesencephalon
Rhombencephalon

Question 18

Secondary brain vesicles and their respective cavities

Answer 18

Telencephalon - Lateral Ventricles
Diencephalon - third ventricle
Metencephalon - Fourth Ventricle
Mylencephalon - Fourth Ventricle and Central Canal
Spinal portion- central canal

Question 19

Adult brains structures from the secondary brain vesicles

Answer 19

Telencephalon: cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei)
Diencephalon: Diencephalon
(thalamus, hypothalamus,
epithalamus), retina
Mesencephalon: Brain stem: midbrain
Metencephalon : brain stem: pons, cerebellum
Myelencephalon: brain stem: medulla, spinal cord

Question 20

The brain & the spinal cord develop from the neuroectoderm during the — week (day — to —) of embryonic life.
•A neural plate gives rise to (a) —— (b) —— (c)——.
•Leaves two openings at the ends- —— & ——

Answer 20

The brain & the spinal cord develop from the neuroectoderm during the 4th week (day 22-23) of embryonic life.
•A neural plate gives rise to (a) neural groove (b) neural fold (c)neural tube.
•Leaves two openings at the ends- anterior & posterior neuropore

Question 21

The anterior neuropore closes on day —; posterior closes how many days later.

•The walls thicken to form the —-/ & ——
•while the canal of the tube is converted into the ——- of the brain and the ——-of the spinal cord

Answer 21

The anterior neuropore closes on day 25; posterior closes 2 days later.

•The walls thicken to form the brain & spinal cord
•while the canal of the tube is converted into the ventricular system of the brain and the central canal of the spinal cord

Question 22

neural tube caudal to— to —th somite develop into spinal cord
•———neuroepithelium in the wall constitute the ventricular zone or ependymal layer. It gives rise to all ____- & ——— cells.
•The outer parts of these cells differentiates into a ——- zone which gives rise to ——- matter.

Answer 22

neural tube caudal to 4-6th somite develop into spinal cord
•Pseudostrtified, columnar neuroepithelium in the wall constitute the ventricular zone or ependymal layer. It gives rise to all neurons & glial cells.
•The outer parts of these cells differentiates into a marginal zone which gives rise to white matter.

Question 23

Then a mantle layer develops between the ——- zone and the ——— zone which give rise to the —- matter of the spinal cord

•Both ——— cells and —— cells develop from the neuroepithelial layer

Answer 23

Then a mantle layer develops between the neuroepithelial zone and the marginal zone which give rise to the gray matter of the spinal cord

•Both neuronal cells and glial cells develop from the neuroepithelial layer

Question 24

Differentiation of the spinal cord (s.c.)

•Proliferation & differentiation of the s.c , A shallow longitudinal groove appears- the ———; it seperates the dorsal part, the —— plate-(future ————)
• from the ventral part, the —— plate- (future ————)
•Enlargements of the alar & basal plates produce the ——— & the ———respectively

Answer 24

Differentiation of the spinal cord (s.c.)
•Proliferation & differentiation of the s.c , A shallow longitudinal groove appears- the sulcus limitans; it seperates the dorsal part, the alar plate-(future posterior horn of gray matter)
• from the ventral part, the basal plate- (future anterior & lateral horn)
•Enlargements of the alar & basal plates produce the posterior median septum & the anterior median fissure respectively

Question 25

Development of meninges
•Mesenchyme around the neural tube condenses to form a membrane- primordium ———.
•External layer of the membranes form the —— - called——-.
•Internal layer forms the —— & —— mater – called ——-.
•Fluid filled spaces appear within the leptomeninges to form the ——— space
•Embryonic CSF production begins — week

Answer 25

Development of meninges
•Mesenchyme around the neural tube condenses to form a membrane- primordium meninx.
•External layer of the membranes form the Dura mater- pachymeninx.
•Internal layer forms the pia & arachnoid mater – leptomeninges.
•Fluid filled spaces appear within the leptomeninges to form the subarachnoid space
•Embryonic CSF production begins 5th week

Question 26

Positional changes of the spinal cord

•Embryo- extends entire length & spinal nerves exit ——— foramina near their levels of origin
•——- & ——— grow more rapidly than the spinal cord. Caudal end of s.c. lie at progressively higher levels.
•6 months intrauterine at — level
•At birth at — level
•Adult at — level

Answer 26

Positional changes of the spinal cord
•Embryo- extends entire length & spinal nerves exit intervertebral foramina near their levels of origin
•Vertebral column & dura mater grow more rapidly than the spinal cord. Caudal end of s.c. lie at progressively higher levels.
•6 months intrauterine S1
•At birth L3
•Adult L1

Question 27

SPINA BIFIDA
•spinal bifida usually occur in the ——— region.
•But sometimes at the ——— and ——— levels

Answer 27

SPINA BIFIDA
•spinal bifida usually occur in the sacrolumbar region.
•But sometimes at the thoracic and lumbar levels

Question 28

SPINAL BIFIDA CYSTICA is also called

Answer 28

(MENINGOCOELE)

Question 29

Development of the brain
•Neural tube cranial to — somite develops into brain.
•3 primary brain vesicles:

•Durning the — week 20 brain vesicles appear. Forebrain forms ——— & ———
•Hindbrain partly divides into ——— and ———

Answer 29

Development of the brain
•Neural tube cranial to 4th somite develops into brain.
•3 primary brain vesicles
•-prosencephalon (forebrain)
•Mesencephalon (midbrain)
•Rhombencephalon (hindbrain)
•Durning the 5th week 20 brain vesicles appear. Forebrain forms telencephalon & diencephalon
•Hindbrain partly divides into metencephalon and myelencephalon

Question 30

Brain flexures
•— week –rapid growth. 2 flexures develop ventrally which are:
And a dorsal flexure called:.

Answer 30

Brain flexures
•4th week –rapid growth. 2 flexures develop ventrally
•Midbrain flexure- in midbrain region &
• Cervical flexure- demarcates hindbrain from spinal cord
•Unequal growth between the 2 leads to a dorsal pontine flexure being formed.

Question 31

TELENCEPHALON
•The telencephalon consist of
•Cerebral vesicles:”2 ———-” primordia of the cerebral hemispheres
•Its median portion forms the ant part of ———-
•At first, the cerebral vesicles communicate with cavity of 3rd ventricle thru ———- with expansion the cerebral hemispheres meet in the midline.
•The mesenchyme trapped btw them -the———
•Later, ——— develops as a swelling in the floor of each cerebral hemisphere

Answer 31

TELENCEPHALON
•The telencephalon consist of
•Cerebral vesicles:”2 lateral diverticula” primordia of the cerebral hemispheres
•Its median portion forms the ant part of 3rd ventricle
•At first, the cerebral vesicles communicate with cavity of 3rd ventricle thru interventricular foramina with expansion the cerebral hemispheres meet in the midline.
•The mesenchyme trapped btw them -the falx cerebri
•Later, corpus striatum develops as a swelling in the floor of each cerebral hemisphere

Question 32

DIENCEPHALON
•Swellings develop in the lateral wall of the — ventricle
•The ——— develops rapidly and bulges into the cavity of the 3rd ventricle
•The hypothalamus arises by proliferation of ——— in the ——— zone diencephalon
•The epithalamus develops form the roof and dorsal portion of the lateral walls of ——-

Answer 32

DIENCEPHALON
•Swellings develop in the lateral wall of the 3rd ventricle  epithalamus, thalamus and hypothalamus.
•The thalamus develops rapidly and bulges into the cavity of the 3rd ventricle
•The hypothalamus arises by proliferation of Neuroblasts in the intermediate zone diencephalon
•The epithalamus develops form the roof and dorsal portion of the lateral walls of diencephalon

Question 33

HINDBRAIN
•The ——- flexure demarcates the hindbrain from the spinal cord

•The pontine flexure divides the hindbrain into
•——— “caudal”  develops into medulla oblongata

•———- “rostral-toward the front”  develops into the pons and cerebellum.
•The cavity of the hindbrain becomes the — ventricle and the ——- in the caudal part of the medulla

Answer 33

HINDBRAIN
•The cervical flexure demarcates the hindbrain from the spinal cord

•The pontine flexure divides the hindbrain into
•Myelencephalon “caudal”  develops into medulla oblongata

•Metencephalon “rostral-toward the front”  develops into the pons and cerebellum.
•The cavity of the hindbrain becomes the 4th ventricle and the central canal in the caudal part of the medulla

Question 34

Neuroblasts arise from ——-
and form———

Answer 34

Neuroblasts arise from neuroectoderm
and form all the neurons within the CNS

Question 35

Glioblasts arise from ——— and form the ———- cells of the CNS. Which include:

Answer 35

Glioblasts arise from neuroectoderm and form the supporting cells of the CNS. These supporting cells include:

1. Astrocytes
2. Radial glial cells – provide guidance for migrating neuroblast.
3. Oligodendrocytes, which produce the myelin of the CNS.
4. Ependymocytes, which line the ventricles and the central canal.
5. Tanycytes
6. Choroid plexus cells, which produce CSF..

Question 36

Microglia (Hortega cells) arise from ——- within the ——— and migrate into the CNS along with the vasculature. These cells are the ——— of the CNS.

Answer 36

Microglia (Hortega cells) arise from monocyte within the bone marrow and migrate into the CNS along with the vasculature. These cells are the macrophages of the CNS.

Question 37

MYELENCEPHALON

•Neuroblasts from alar plates in the mylencephalon migrate into the marginal zone and form isolated areas of the grey matter  ——-“medial” and ——— “laterally

Answer 37

MYELENCEPHALON

•Neuroblasts from alar plates in the mylencephalon migrate into the marginal zone and form isolated areas of the grey matter  gracile nuclei “medial” and cuneate nuclei “laterally

Question 38

METENCEPHALON

•The cerebellum develops from thickenings of dorsal parts of the —— plates

• Neuroblasts in the ——— zone of the alar plates migrate and differentiate into the neurons of the cerebellar cortex

Answer 38

METENCEPHALON

•The cerebellum develops from thickenings of dorsal parts of the alar plates

• Neuroblasts in the intermediate zone of the alar plates migrate and differentiate into the neurons of the cerebellar cortex

Question 39

Metencephalon

Cells from the alar plate give rise to the ——— nucleus “largest nucleus”, ———nuclei, the ——— & —— nuclei and ——- nuclei of the ——— nerve.

•Bands of nerve fibers cross the median plane and form a bulky ridge——

Answer 39

Cells from the alar plate give rise to the dentate nucleus “largest nucleus”, pontine nuclei, the cochlear & vestibular nuclei and sensory nuclei of the trigeminal nerve.

•Bands of nerve fibers cross the median plane and form a bulky ridge  pons

Question 40

Cerebellum

•It enlarges & fuse in the medial plane overlapping the —— and ——
•Phylogenetically (evolutionary) - 3 parts
•——— (oldest): ——- lobe
•——— : ——— & ——— lobe
•———- (newest part): —— lobe

Answer 40

Cerebellum

•It enlarges & fuse in the medial plane overlapping the pons and medulla
•Phylogenetically (evolutionary) - 3 parts
•Archicerebellum (oldest)- flocculonodular lobe
•Paleocerebellum- vermis & anterior lobe
•Neocerebellum (newest part)-posterior lobe

Question 41

MIDBRAIN

•The neural canal that passes through the midbrain narrows forming ——— “ a canal that connect the 3rd and the 4th ventricles”
•Neuroblasts migrate from the alar plates of the midbrain into the tectum “roof” and aggregate to form——— and ——— concerned with the visual and auditory reflexes

Answer 41

MIDBRAIN

•The neural canal that passes through the midbrain narrows  cerebral aqueduct “ a canal that connect the 3rd and the 4th ventricles”
•Neuroblasts migrate from the alar plates of the midbrain into the tectum “roof” and aggregate to form  superior and inferior collicluli  concerned with the visual and auditory reflexes

Question 42

Congenital anomalies
•———- - defects in the formation of the cranium

Answer 42

Congenital anomalies
•Cranium bifidum

Question 43

Congenital anomalies
•Cranium bifidum- defects in the formation of the cranium
•When defect is small usually only meninges herniate and anomally is a ————- or ————
•Cranium bifidum with its associated anomalies occurs how many in how many births

Answer 43

Congenital anomalies
•Cranium bifidum- defects in the formation of the cranium
•When defect is small usually only meninges herniate and anomally is a cranial meningocoele or cranial bifidum with meningocoele
•Cranium bifidum with its associated anomalies occurs once in 2000 births

Question 44

When cranial defect is large, meninges and part of the brain herniate forming ————

•If protruding brain contains part of the ventricular system- —————

Answer 44

When cranial defect is large, meninges and part of the brain herniate forming meningoencephalocoele

•If protruding brain contains part of the ventricular system- meningohydroencephalocoele

Question 45

Failure of anterior neuropore to close causes ———— anomaly

Answer 45

Anencephaly meroanencephaly:

Question 46

Anencephaly meroanencephaly:
Failure of anterior neuropore to close
• Brain and calvarium are absent & Replaced by a ————- - a tangle of glial and connective tissue
• Remnants of ——— and ——— may be present & so infant is born alive
• Occurs how many in every —— births
“ — to — times commoner in females
• Always associated with ——- (absence of calvaria)
• May be associated with ——— (when defective neural tube closure is extensive)

Answer 46

Anencephaly meroanencephaly:
Failure of anterior neuropore to close
• Brain and calvarium are absent & Replaced by a cerebrovasculorum - a tangle of glial and connective tissue
• Remnants of brainstem and pituitary may be present & so infant is born alive
• Occurs once in every 1000 births
“ 2-4 times commoner in females
• Always associated with acrania (absence of calvaria)
• May be associated with rachischisis (when defective neural tube closure is extensive)

Question 47

Hydrocephalus can be caused by congenital or acquired factors
•Congenital causes includes: ——,——
•Acquired: ———, ———, ———, ———, etc

Answer 47

Hydrocephalus can be caused by congenital or acquired factors
•Congenital causes includes: Spina bifida, Craniosynostosis, etc
•Acquired: Haemorrhage, meningitis, head trauma, tumours, etc

Question 48

Microcephaly

——— & ——- is small but face is normal
•caused by ———— resulting
In Microcephaly

Answer 48

Calvaria & brain is small but face is normal
•Early closure of the Sutural lines limits the Development of The brain, resulting
In Microcephaly

Question 49

MACROCEPHALY

●Megalencephaly is increased size of the ——- itself.

●Large heads can run in normal families but inherited megalencephaly can be associated with significant problems like——-

Answer 49

MACROCEPHALY

●Megalencephaly is increased size of the brain itself.

●Large heads can run in normal families but inherited megalencephaly can be associated with significant learning difficulties, neurological abnormalities, and seizures.

Question 50

Mental retardation
•Congenital impairment of intelligent
•Causes:

Answer 50

Mental retardation
•Congenital impairment of intelligent
•Causes
●Action of mutant gene
●Chromosomal abberation(trisomies 21, 18, 13) Down, Edward, Patau respectively
●Maternal alcohol abuse
●Disorders of carbohydrate, protein, fat
●Maternal and fetal infections
●Toxins(lead)

Question 51

Hydrocephalus
There may be Other congenital Anomalies like ——- and ——-

Answer 51

Cleft lip & palate

Question 52

•———— Is a cephalic disorder in which the prosencephalon (the forebrain of the embryo) fails to develop into two hemisphere.

Answer 52

HOLOPROSENCEPHALY
.

Question 53

HOLOPROSENCEPHALY
. Caused by mutation in the gene encoding the ——— protein.

Answer 53

HOLOPROSENCEPHALY
. Caused by mutation in the gene encoding the sonic edge protein.

Question 54

Some cases of spinal bifida are accompanied by ———- malformation (part of cerebellum is displaced downward into the spinal column)

•——— malformation- incomplete formation or absence of central portion of cerebellum

Answer 54

Some cases of spinal bifida are accompanied by Arnold Chiari malformation (part of cerebellum is displaced downward into the spinal column)

•Dandy-Walker malformation- incomplete formation or absence of central portion of cerebellum

Question 55

———— (smooth brain)- failure of sulci and gyri to develop.

•———- - (split brain)- abnormal cleft or groove on surface of brain

•———— - CSF fills much of the space normally occupied by the brain

Answer 55

Lissencephaly (smooth brain)- failure of sulci and gyri to develop.

•Schizencephaly- (split brain)- abnormal cleft or groove on surface of brain

•Hydraencephaly- CSF fills much of the space normally occupied by the brain

Question 56

Development of hindbrain

•MYELENCEPHALON
•Closed part of medulla oblongata resembles the———.
•Neuroblast from alar plate migrate into marginal layer to form isolated masses-nuclei ——- & ——-.
•Rostral part opens out and roof becomes thinned out to give rise to future —— ventricle
•METENCEPHALON
•Walls of the metencephalon- —— and ——
•Its cavity forms the sup part of the — ventricle.

Answer 56

Development of hindbrain

•MYELENCEPHALON
•Closed part of medulla oblongata resembles the s.c.
•Neuroblast from alar plate migrate into marginal layer to form isolated masses-nuclei gracile & cuneatus.
•Rostral part opens out and roof becomes thinned out to give rise to future 4th ventricle
•METENCEPHALON
•Walls of the metencephalon- pons and cerebellum
•Its cavity forms the sup part of the 4th ventricle.

Question 57

Midbrain
•Undergoes less changes
•Neural canal- becomes ———
•Alar plate- forms midbrain ——- with 2 swellings - ——— & ———
•Basal plate- forms most structures of the midbrain ———
•Fibres from the cerebrum form the cerebral ——— anteriorly

Answer 57

Midbrain
•Undergoes less changes
•Neural canal- becomes cerebral aqueduct
•Alar plate- forms midbrain tectum with 2 swellings - superior & inferior collicui
•Basal plate- forms most structures of the midbrain tegmentum
•Fibres from the cerebrum form the cerebral peduncles anteriorly

Question 58

Diencephalon
•how many swellings dev in lateral wall of 3rd ventricle, which are:
•———, ——— & ——— seperated from each other by the ——— & ——— sulci.
•Thalamus develops rapidly bulging into wall of — ventricle reducing it to a narrow slit. They meet & fuse in midline in —% of brains as interthalamic adhesions

Answer 58

Diencephalon
•3 swellings dev in lateral wall of 3rd ventricle
•Epithlamus, thalamus & hypothalamus seperated from each other by the epithalamic & hypothalalmic sulci.
•Thalamus develops rapidly bulging into wall of 3rd ventricle reducing it to a narrow slit. They meet & fuse in midline in 70% of brains as interthalamic adhesions

Question 59

Telencephalon
•Develops from median part & 2 lateral vesicles- ———-.

•Expands & covers the ———, meet each other in the midline; mesenchyme form the covering meninges & the dural reflections.

•Deep nuclei are formed from ——— in floor of each hemisphere

Answer 59

Telencephalon
•Develops from median part & 2 lateral vesicles- cerebral hemispheres.

•Expands & covers the diencephalon, meet each other in the midline; mesenchyme form the covering meninges & the dural reflections.

•Deep nuclei are formed from swellings in floor of each hemisphere

Question 60

Telencephalon

•Commisures develop as groups of fibres connecting one ———- with another.

•These are ———, ———, ———. Growth produces —— & —— on the surface of the brain

•——— becomes a buried cortex in the depths of the lateral sulcus

Answer 60

•Commisures develop as groups of fibres connecting one cerebral hemisphere with another.

•These are corpus callosum, anterior commissure, hippocampal. Growth produces sulci & gyri on the surface of the brain

•Insula becomes a buried cortex in the depths of the lateral sulcus

Question 61

•Insula becomes a buried cortex in the depths of the ——- sulcus

Answer 61

Lateral