Embryology

Question 1

Which one of the following correctly describes the order of embryological stages of CNS development?
a. Blastogenesis, gastrulation, dorsal induction, ventral induction, neural proliferation, neuronalmigration, and axonal myelination
b. Dorsal induction, ventral induction, gas-
trulation, neural proliferation, neuronal
migration, and axonal myelination
c. Gastrulation ventral induction, dorsal
induction, neural proliferation, neuronal
migration, and axonal myelination
d. Neural proliferation, gastrulation dorsal
induction, ventral induction, neuronal
migration, and axonal myelination
e. Ventral induction, gastrulation, dorsal
induction, neural proliferation, axonal
myelination, and neuronal migration

Answer 1

a. Blastogenesis, gastrulation, dorsal induction, ventral induction, neural proliferation, neuronalmigration, and axonal myelination

Question 2

Which one of the following statements regarding gastrulation is most accurate?
a. It is the process by which the bilaminar disc is converted into a trilaminar disc
b. It can result in lipomyelomeningocele if
disturbed
c. It is not dependent on bone morphoge-
netic protein expression
d. It starts with closure of the cranial
neuropore
e. It occurs from embryonic days 10-12

Answer 2

a. It is the process by which the bilaminar disc is converted into a trilaminar disc

Question 3

Which one of the following statements about
primary neurulation is most accurate?
a. Anterior neuropore closure approximately occurs on D19
b. Disjunction results in formation of the spinal canal below the posterior neuropore
c. Fusion of the neural folds starts at the anterior neuropore and proceeds caudally in a zip-like fashion until it reaches the
posterior neuropore
d. Notochord induces the overlying ectoderm to differentiate into a flat area of specialized neuroectoderm called the neural plate
e. SHH/morphogen secretion on D14 causes the neural plate to form median hinge points and start invaginating along its central axis to form a neural groove (with neural folds on either side)

Answer 3

d. Notochord induces the overlying ectoderm to differentiate into a flat area of specialized neuroectoderm called the neural plate

Question 4

Which one of the following statements about secondary neurulation and retrogressive differentiation is most accurate?
a. Important for the formation of the conus medullaris but not the filum terminale
b. Involves canalization of a caudal mensenchymal cell mass
c. Is completed by days 24-26 of embryonic development
d. Responsible for the formation of thoracic, lumbar, sacral, and coccygeal neural tube
e. Retrogressive differentiation is a mitotic process

Answer 4

b. Involves canalization of a caudal mensenchymal cell mass

Question 5

Which one of the following statements about
ventral induction is most accurate?
a. It includes development of the primary brain fissure
b. It includes development of the secondary brain vesicles and brain flexures
c. It includes formation of the neural plate
d. It includes formation of the notochord
e. It includes primary neurulation

Answer 5

b. It includes development of the secondary brain vesicles and brain flexures

Question 6

The disencephalon does not give rise to which one of the following?
a. 3rd ventricle
b. Mamillary bodies
c. Optic vesicle
d. Posterior pituitary
e. Superior colliculus

Answer 6

c. Optic vesicle

Question 7

Mesencephalon does NOT give rise to which one of the following?
a. Cerebral aqueduct
b. Edinger-Westphal nucleus
c. Pineal body
d. Red nucleus
e. Substantia nigra

Answer 7

c. Pineal body

Question 8

Which one of the following statements about
the rhombencephalon is most accurate?
a. It contains the cerebral aqueduct at
its center
b. It gives rise to diencephalon and myelen-
cephalon secondary brain vesicles
c. It gives rise to the inferior colliculi and pons
d. It is separated from the mesencephalon by
the isthmus rhombencephalii
e. Pontine flexure indents the rhomben-
cephalon ventrally

Answer 8

d. It is separated from the mesencephalon by
the isthmus rhombencephalii

Question 9

Which one of the following statements about
cerebellar development is most accurate?
a. Brainstem input to the cerebellum is via
parallel and climbing fibers
b. Commences at week 15
c. Golgi cells come to reside in the
molecular layer
d. Granule cells develop axons called Mossy
fibers
e. Granule cells migrate inward past Purkinje cells with the help of Bergmann glia

Answer 9

e. Granule cells migrate inward past Purkinje cells with the help of Bergmann glia

Question 10

Which one of the following is important in
dorsoventral patterning of the neural tube?
a. BF-1
b. BMP-4 and BMP-7
c. EMX1 and EMX2
d. FGF-8
e. HOX
f. SHH

Answer 10

f. SHH

Question 11

Which one of the following best describes
cells forming the mantle layer in the developing neural tube
a. Ependymal cells
b. Glioblasts
c. Neuroblasts
d. Postmitotic young neurons
e. Radial cells

Answer 11

d. Postmitotic young neurons

Question 12

Which one of the following statements about
cerebral cortex formation is most accurate?
a. Cortical layers are laid down from most
superficial to deep
b. Germinal matrix zone is superficial to the
ventricular zone
c. Intermediate zone contains axons of cor-
tical pyramidal neurons
d. Migration of cortical pyramidal neurons
occurs tangentially
e. The neocortex usually has four layers in
the adult

Answer 12

c. Intermediate zone contains axons of cor-
tical pyramidal neurons

Question 13

Which one of the following is the first to form in the developing brain?
a. Anterior commissure
b. Genu of corpus callosum
c. Hippocampal commissure
d. Posterior commissure
e. Splenium of corpus callosum

Answer 13

a. Anterior commissure

Question 14

Which one of the following statements about
the developing spinal cord are most accurate?
a. Alar columns form the intermediolateral
horn
b. Alar columns form the ventral horns
c. Dorsally the floor plate marks where the
paired basal columns meet
d. Laterally, the alar and basal plates abut at a groove called the sulcus limitans
e. Ventrally the roof plate marks where the
paired alar columns meet

Answer 14

d. Laterally, the alar and basal plates abut at a groove called the sulcus limitans

Question 15

Embryological terms:
a. Ectoderm
b. Endoderm
c. Induction
d. Mesenchyme
e. Mesoderm
f. Neural crest
g. Notochord
h. Paraxial mesoderm
i. Primitive streak
j. Sclerotome
k. Somite

For each of the following descriptions, select the
most appropriate answers from the list above.
Each answer may be used once, more than once
or not at all.
1. Population of cells arising from the lateral
lips of the neural plate that detach during
formation of the neural tube and migrate
to form a variety of cell types/structures.
2. The first morphological sign of gastrulation.
2 EMBRYOLOGY 23
3. The process in which one embryonic region interacts with a second embryonic region, thereby influencing the behavior or differentiation of the second region.

Answer 15

1—f, Neural crest; 2—i, Primitive streak;
3—c, Induction

Question 16

Central nervous system formation:
a. Diencephalon
b. Mescencephalon
c. Metencephalon
d. Myelencephalon
e. Prosencephalon
f. Rhombencephalon
g. Telencephalon

For each of the following descriptions, select the
most appropriate answers from the list above.
Each answer may be used once, more than once
or not at all.
1. Contains cerebral aqueduct
2. Gives rise to the cerebellar hemispheres

Answer 16

1—b, Mesencephalon; 2—c, Metencephalon

Question 17

Embryology:
a. Days 2-3
b. Days 4-5
c. Day 6
d. Days 8-12
e. Days 14-17
f. Day 18
g. Day 20
h. Days 24-26
i. Days 26-28
j. Day 31
k. Day 35
l. Day 42

For each of the following descriptions, select the
most appropriate answers from the list above.
Each answer may be used once, more than once
or not at all.
1. Formation of the neural plate
2. Closure of the posterior neuropore
3. Five secondary brain vesicles

Answer 17

1—f, Day 18; 2—h, Day 26-28; 3—k, Day 35
Approximate timetable for CNS development is
shown below (exact numbers vary depending on
source).

Question 18

Neurulation:
a. Alar plate
b. Basal plate
c. Caudal neuropore
d. Cranial neuropore
e. Dorsal root ganglion
f. Neural fold
g. Neural groove
h. Notochord
i. Primary neurulation
j. Primitive node
k. Primitive streak
l. Secondary neurulation

For each of the following descriptions, select the
most appropriate answers from the list above.
Each answer may be used once, more than once
or not at all.
1. Origin of neural crest cells
2. Failure of closure results in spina bifida
3. Structure signaling to midline ectoderm to
form neural tube
4. Formed by neural crest cells

Answer 18

1—f, neural fold; 2—c, caudal neuropore;
3—g, neural groove; 4—e, dorsal root
ganglion

Question 19

Pharyngeal arch derivatives:
a. 1st pharyngeal arch
b. 2nd pharyngeal arch
c. 3rd pharyngeal arch
d. 4th pharyngeal arch
e. 5th pharyngeal arch
f. 6th pharyngeal arch
g. Ductus thyroglossus
h. Foramen caecum
i. Sinus cervicalis
j. Tuberculum impar
k. Tuberculum laterale

For each of the following descriptions, select the
most appropriate answers from the list above.
Each answer may be used once, more than once
or not at all.
1. Common carotid and internal carotid
artery and glossopharyngeal nerve
2. Recurrent laryngeal branch of CN X
3. Parts of CN V2 and V3
4. Facial nerve

Answer 19

1—c, 3rd pharyngeal arch; 2—f, 6th pharyngeal arch; 3—a, 1st pharyngeal arch; 4—b, 2nd pharyngeal arch

Question 20

Disorders of CNS development:
a. Adrenoleukodystrophy
b. Caudal regression syndrome
c. Dandy-Walker spectrum
d. Heterotopia
e. Intradural lipoma
f. Lipoma of filum terminale
g. Pelizaeus-Merzbacher disease
h. Schizencephaly
i. Segmental spinal dysgenesis
j. Split cord malformation
k. Sturge-Weber syndrome
l. Terminal myelocystocele

For each of the following descriptions, select the
most appropriate answers from the list above.
Each answer may be used once, more than once
or not at all.
1. Disorder of neural proliferation
2. Disorder of notochordal integration during
gastrulation
3. Disorder of ventral induction

Answer 20

1—k, Sturge-Weber syndrome; 2—j, Split cord malformation;
3—c, Dandy-Walker spectrum