Embryo: Development of the Nervous System Flashcards
1
Q
Formation of 3 germ layers (endoderm, mesoderm, and ectoderm)
A
Gastrulation
2
Q
What week does Gastrulation begin?
A
Week 3
3
Q
Components of gastrulation
A
- formation of 3 germ layers
- Primitive streak
- Notochordal process
4
Q
What germ layer is the primitive streak made up of?
A
Embryonic ectoderm
5
Q
3 parts to the primitive streak?
A
- Primitive node
- Primitive groove
- Primitive pit
6
Q
What region of the embryo does the primitive streak occur at?
A
Caudal region of the embryo
7
Q
What region of the embryo does the primitive node occur at?
A
Rostral region of the embryo
8
Q
What germ layer is the notochordal process made of?
A
Mesoderm
9
Q
What does the notochordal process become?
A
It is the template for formation of the vertebral column and induces the formation of the neural plate
10
Q
When does neurulation begin?
A
Day 22-23
11
Q
Notochord induces neural plate formation: ?
A
- Neural plate
- Neural groove
- Neural folds
- Neural tube
12
Q
What does the notochord release to form the neural plate?
A
Sonic Hedge Hog (Shh)
13
Q
What is the neural plate (germ layer)?
A
Thickening of ectoderm
14
Q
What is the space called when the neural folds have not yet met each other?
A
Neural groove
15
Q
Neurulation
- In the end, the surface ectoderm becomes?
A
Developing epidermis
16
Q
Neurulation
- In the end, the neural crest becomes?
A
Developing spinal ganglion
17
Q
Neurulation
- When the neural folds met up, it is now called?
A
Neural tube
18
Q
What are the germ layers involved with the neural plate?
A
Neuroectoderm, surface ectoderm, and neural crest
19
Q
What germ layer is the neural tube made of?
A
Neuroectoderm
20
Q
Neurulation
- What day does the rostral neuropore close?
A
Day 25
21
Q
Neurulation
- What day does the caudal neuropore close?
A
Day 27/28
22
Q
What does primary neurulation give rise to?
A
Brain and down to the lumbar region of the spinal cord
23
Q
What day does primary neurulation begin?
A
Day 22-23
24
Q
What day does secondary neurulation begin?
A
Day 20-42
25
What is the group of cells from neuroectoderm that forms the sacral and coccyx region of the spinal cord ?
Caudal eminence
26
What are the cells of the nervous system that come from neuroectoderm?
- Dendrite
- Protoplasmic astrocyte
- Fibrous astrocyte
- Oligodendrocyte
- Ependyma and Epithelium of choroid plexus
27
What are the cells of the nervous system that come from mesoderm?
**Microglial cell
| from blood monocytes
28
Neural tube forms portion of the brain cranial to the ? somites
Fourth
29
What are the three primary brain vesicles?
- Prosencephalon
- Mesencephalon
- Rhombencephalon
30
Prosencephalon is what part of the brain?
Forebrain
31
Mesencephalon is what part of the brain?
Midbrain
32
Rhombencephalon is what part of the brain?
Hindbrain
33
What week do the forebrain and hindbrain divide?
5th week
34
Prosencephalon gives rise to?
Telencephalon and
| diencephalon
35
Rhombencephalon gives rise to?
Metencephalon and
| myelencephalon
36
What area do we find in the region of the telencephalon?
Lateral ventricle
37
What area do we find in the region of the diencephalon?
Third ventricle
38
What area do we find in the region of the Mesencephalon?
Cerebral aqueduct
39
What is bonded between metencephalon and
| myelencephalon?
Fourth ventricle
40
Spinal cord has opening to the ?
Central canal
41
Have ? that give rise the adult formation of the brain
Flexures
42
Telencephalon consists of?
Cerebral hemisphere
43
Diencephalon consists of?
Thalamus and hypothalamus
44
Mesencephalon consists of?
Midbrain
45
Metencephalon consists of?
Pons and cerebellum
46
Myelencephalon consists of?
Medulla
47
Cervical flexure develops in what week?
Week 5
48
Demarcates the hindbrain from the spinal cord
Cervical flexure
49
Divides hindbrain into caudal myelencephalon and rostral metencephalon
Pontine flexure
50
What flexure develops later?
Pontine flexure
51
Bend between midbrain and forebrain
Cephalic flexure
| persists and gives our brain the adult structure
52
What week are basal ganglion and cortical structure developing?
Between weeks 6 to 32
53
What is a collection of different cell bodies or nuclei?
Basal Ganglion
54
Basal ganglion includes?
Caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra
55
Telencephalon consists of?
```
– Cerebral cortex
– ** Subcortical white
matter (including internal capsule) (made of ectoderm)
– Olfactory bulb and tract
– Basal ganglia
– Amygdala
– Hippocampus
```
56
Diencephalon consists of?
– ** Thalamus (made of ectoderm)
– Hypothalamus
– Epithalamus
– Eye (optic nerve)
57
Midbrain consists of?
– Cerebral peduncles
– Superior and inferior colliculi
– 2 cranial nerves
58
Medulla oblongata consists of?
- Olive
| - Pyramid
59
What are the adult structures of the brain?
- Telencephalon
- Diencephalon
- Midbrain
- Cerebellum
- Pons
- Medulla oblongata
60
What results from incomplete separation of cerebral hemispheres?
Holoprosencephaly (HPE)
61
Holoprosencephaly
– Most associated with ?
– Reduction of ?
–Eyes close together aka ?
- facial abnormalities
- frontonasal prominence
- Hypotelorism
62
Causes of Holoprosencephaly
- Genetic and environmental factors
- Maternal diabetes
- Teratogens (alcohol) (can cause the cyclopia)
- Retinoic acid
63
Clinical features of Holoprosencephaly
- Microcephaly (small head), microphthalmia (small eyes), ocular hypotelorism, midfacial hypoplasia, and cleft lip with or without cleft palate
- ** Intellectual disability (mental retardation) or developmental delay
- Epilepsy, hydrocephalus, dystonia, movement disorder, autonomic
dysfunction, and
hypothalamic/pituitary dysfunction
64
Holoprosencephaly spectrum
1. Median cleft lip and palate
- Mild
2. Cebocephaly
- One nose
3. Ethmocephaly
- Nose from frontal nasal prominence does not migrate correctly = Probiscus
4. Cyclopia
- Most severe
- Usually die
65
Pituitary Gland
| - First arch ectoderm gives rise to:
– Roof of mouth
**– Contributes to anterior lobe of pituitary gland
– Hypophysial
diverticulum (Rathke’s
pouch)
66
Pituitary Gland
| - Posterior lobe of pituitary gland is from?
** Neuroectoderm
67
Posterior lobe of pituitary gland is from neuroectoderm and comes from?
– Diencephalic floor
– Neurohypophysial
diverticulum
68
So the anterior lobe of pituitary is ? and posterior lobe is ?
- Surface ectoderm
| - Neuroectoderm
69
Formation of Spinal Cord and Brain Regions:
Neural tube is caudal or inferior to the ?
Fourth pair of somites
70
Formation of Spinal Cord and Brain Regions:
Neural canal consists of?
Central canal (at the center)
71
Formation of Spinal Cord and Brain Regions:
- Separates alar and basal plates?
Sulcus limitans
72
Formation of Spinal Cord and Brain Regions:
• Alar plate
- Gives rise to ? horn
- Gives rise to ? neurons that are contained and stay in the CNS
- Dorsal
| - Sensory
73
Formation of Spinal Cord and Brain Regions:
• Basal plate
- Gives rise to ? neurons which leave to go out to skeletal muscle
- Also gives rise to ?
- Motor
| - Preganglionic Autonomics
74
Formation of Spinal Cord:
| - Zones?
1. Ventricular zone
2. Intermediate zone (mantle layer)
3. Marginal zone
75
- Which zone is gray matte?
| - Which zone is white matter?
- Intermediate zone
| - Marginal zone
76
Which zone has stem cells that give rise to neurons?
Ventricular zone
77
Stem cells give rise ?
Ependymoblasts
78
Ependymoblasts give rise to ? and ?
Ependymal cells and choroid plexus
| - which line the ventricles or central canal
79
Which layer do you get migration of neurons in this area? Formation of neurons, astocytes, microglia.
Intermediate zone
80
Which layer has white matter and axon tracts. Axons of neurons leaving. Oligodendrites there and myelinate axons of CNS
Marginal zone
81
Pattern Maintained Into Brainstem:
Which ventricle moves structures laterally?
4th
82
Gives rise to dorsal horns and is sensory
Alar plate
83
Gives rise to ventral horns and is motor
Basal plate
84
Pattern Maintained Into Brainstem:
- Thinned the roof of the 4th ventricle so have sensory laterally and motor more towards the midline
Pontine flexure
85
Pattern Maintained Into Brainstem:
•? - found closest to the midline
- CN ?
- Motor neurons going directly to muscles that come from somites are always found in the midline
- GSE
| - CN III, IV, VI, XIII (3,4,6,12)
86
Pattern Maintained Into Brainstem:
• Laterally but still in basal plate - have parasympathetic nuclei lateral to ?
GSE
87
Pattern Maintained Into Brainstem:
•? - go to pharyngeal arches (CN ?- found laterally)
- SVE
| - CN 5,7,9,10
88
Pattern Maintained Into Brainstem:
• Have ? and ? close to sulcus limitans and ? and ? more laterally
- GVA and SVA
| - SSA and GSA
89
Myelencephalon
• Alar plate gives rise to: ?
- Cuneate
| - Gracile nuclei
90
Myelencephalon:
Cuneate and gracile nuclei are involved with?
Proprioception, vibratory sense and 2 point discrimination, and discriminative touch
91
Myelencephalon:
• Basal plate gives rise to: ?
- Hypoglossal nuclei closest to midline
92
Myelencephalon:
| • Alar plate gives rise to: ?
extra one
- ** Hypoglossal nucleus
- ** Dorsal motor vagal nucleus = GVE
- ** Nucleus Ambiguous = CN 9 and 10
93
Myelencephalon:
• Basal plate gives rise to: ?
- ** Solitary nucleus = gets visceral afferent info
- Vestibular nuclei
- Cochlear nuclei
- Spinal trigeminal tract and nucleus = sensory
94
Metencephalon:
• Basal plate gives rise to: ?
- Abducens nucleus
- Facial motor nucleus
- Trigeminal motor nucleus
- Superior salivatory nucleus
95
Metencephalon:
- Sulcus limitans gives rise to?
Vestibular and cochlear nuclei
96
Mesencephalon:
- Alar plate germ layer?
- Basal plate germ layer?
- Ectoderm
| - Mesoderm
97
Mesencephalon:
- Alar plate gives rise to?
- Inferior and superior colliculus (ectoderm)
98
Mesencephalon:
- Basal plate gives rise to?
- Edinger-Westphal nucleus
- Red nucleus
- Oculomotor nucleus and trochlear nucleus
(all mesoderm)
99
Mesencephalon:
• In upper midbrain, anytime you see red nucleus, you also see ? and ?
oculomotor and superior colliculus
100
Mesencephalon:
• In Inferior midbrain, you see ?
Trochlear nucleus
101
Classifications
•?: somatic muscle
* ?: autonomics to smooth and cardiac muscle and glands
* ?: muscles derived from the pharyngeal arches
• ?: sensory in the skin, joint capsule, tendon, muscle
– Ectoderm
• ?:sensory of visceral structures
– Endoderm
* ? : hearing, balance (CN 8) and sight (CN 2)
* ? : taste and smell: chemical senses
- GSE (General somatic efferent)
- GVE (General visceral efferent)
- SVE (Branchial or Special visceral efferent)
- GSA (General somatic afferent)
- GVA (General visceral afferent)
- SSA (Special somatic afferent)
- SVA (Special visceral afferent)
102
Ventricles are continuous with the ? in the spinal
| cord
central canal
103
Location of frontal or anterior horn?
Frontal lobe
104
Location of inferior or temporal horn?
Temporal region
105
Location of occipital or posterior horn?
Occipital region
106
Diseases associated with issues of ventricles?
* Syringomyelia
* Hydrocephalus
* Cerebral palsy
107
Kinds of Cerebral Palsy
- Spastic
- Dyskinetic
- Ataxic
- Mixed
108
Cerebral palsy
– Spastic: damage adjacent to the ventricles
– Dyskinetic
•? : damage to the basal ganglion
•? : damage to the basal ganglion and VL thalamus
– Ataxic: damage to the ?
– Mixed
- Athetoid
- Dyskinetic
- Cerebellum
109
Cerebral Palsy
| - Spastic - damage to the ?
cortical spinal tract (motor tract)
| spasticity = upper motor neuron issues
110
In homunculus, what is the most medial?
Legs and feet
111
Axons come right next to ? ventricles as they descend into the posterior limb of intenral capsule
lateral
112
Syringomyelia
- Excess fluid in the ?
- Form structures called Syrnx found in vertebral level ?
- Disease highly associated with ?
- Causes?
- central canal
- C2-T9 (but can go higher or lower)
- Chiari Type 1
- Some are idiopathic, trauma, infection ...
113
* Too much fluid in the brain
* Many causes are abnormal development
* Communicating and obstructive types
Hydrocephalus
114
What kind of cerebral palsy?
- Toe walking and scissor gait (toes pointed in)
- Hypertone
- Ventricles enlarge and hit motor tract
Spastic
115
What kind of cerebral palsy?
- Slow writhing movements of the extremities and/or trunk
- Basal ganglia issue
Athetoid
116
What kind of cerebral palsy?
- Incoordination, weakness and shaking during voluntary movement
- Drunken sailor gait. Wherever lesion is, falls to that side of the lesion
Ataxic
117
Cerebral Palsy
| - Both limbs on one side of body
Hemiplegia
118
Cerebral Palsy
| - All 4 limbs equally
Quadriplegia
119
Cerebral Palsy
| - lower limbs more affected than upper limbs
Diplegia
120
Deformity of the hindbrain
Arnold-Chiari Malformation
121
Arnold-Chiari type I
• Herniation of ? through foramen magnum
• Usually no symptoms
- Head and neck pain, ? cranial nerves (problems with tongue, facial muscles, lateral eye movements, decreased ?, dizziness, coordinating movements)
- cerebellar tonsils
- lower
- hearing
Note:
- Tongue = hypoglossal
- Facial muscles = facial n. and exits at pontine medullary junction
- Lateral eye movement = Abducens at pontine medullary junction
- Decreased hearing and dizziness = CN 8
- Coordinating movements/ataxia = Cerebellum
122
Arnold-Chiari type II
• Herniation of ? and ? through foramen
magnum
• ?
• Lower cranial nerves (problems with tongue, facial muscles, lateral eye movements, decreased hearing, dizziness, paralysis
of sternocleidomastoid, coordinating movements)
- Medulla and Cerebellum
| - Hydrocephalus
123
Which Arnold-Chiari type doesn’t present until late adolescence and adult hood?
Type 1
124
Which Arnold-Chiari type presents in infancy or early childhood?
Type 2
125
- Which Arnold-Chiari type only has cerebellar tonsils herniating?
- Type 1
126
- Which Arnold-Chiari type starts with cerebellar tonsils herniating and then picks up vermis?
- Type 2
127
Which Arnold-Chiari type is highly associated with Syringomyelia?
Type 1
128
Which Arnold-Chiari type present with lower CN problems because traction and compression on these nerves?
Type 2
129
Which Arnold-Chiari type is almost always associated with spina bifida?
Type 2
130
```
The diagnosis of a
Chiari II malformation
can be made in utero
by fetal MRI, which
demonstrates the
lumbar ?
and cerebral Chiari II
malformation
```
myelomeningocele
131
Dandy Walker Malformation (Cyst):
• Large posterior fossa
cyst continuous with
?
* Hypoplasia of ?, partial or absence of ?
* Atresia of ?
• May be associated
with other abnormalities (like GI and heart issues)
- 4th ventricle
- cerebellum
- vermis
- foramina of Luschka and Magendie
132
Dandy Walker Malformation (Cyst):
- Atresia causing dilation of the ?
- cyst, 3rd ventricle, 4th ventricle and lateral ventricles
133
Dandy Walker Malformation (Cyst) on MRI
Cerebellum atrophy and compressed
134
Unknown cause, but thought to be due to obstruction of
blood flow to the areas
supplied by the internal
carotid arteries.
Hydranencephaly
135
Hydranencephaly:
• Absences of ? or represented by membranous sacs with
dispersed tissue
• ? is intact
• Excessively head growth
after birth
• ** Little to no cognitive
development
- cerebral hemispheres
| - Brainstem
136
At how many months of pregnancy is the cortex smooth?
5 months
137
By birth it has the cerebral cortex has folded
| in on itself to form ?
gyri (bumps) and sulci
| grooves
138
At how many months of pregnancy do you get bumps of gyri and grooves of sulci?
6-7 months
139
• ? (gyri and sulci) fold over insula
| - Formed by ?
Operculum
| - Formed by frontal, parietal and temporal lobes
140
Cytodifferentiation of Cerebrum:
- Lamina ? : contains mainly dendrites
I
141
Cytodifferentiation of Cerebrum:
- Lamina ? receives the majority of inputs from the thalamus
- Sensory or motor?
IV
- SENSORY
142
Cytodifferentiation of Cerebrum:
- Lamina ? projects primarily to the thalamus
VI
143
Cytodifferentiation of Cerebrum:
- Laminae ? and ? contains mainly neurons that project to other areas of the cortex
II and III
144
Cytodifferentiation of Cerebrum: projects mostly to subcortical structures such as the brainstem, spinal cord and basal ganglia
- Sensory or motor?
V
- MOTOR
145
Cytodifferentiation of Cerebrum:
- Older areas of the brain have ? layers of cerebrum and newer areas have ? layers
- 3
| - 6
146
Cytodifferentiation of Cerebrum:
Inside-out Sequence: Part 1
- First neurons produced from VENTRICULAR zone
- Form a superficial layer, the PREPLATE
- Axons from these neurons and form
INTERMEDIATE zone
147
Cytodifferentiation of Cerebrum:
Inside-out Sequence: Part 2
```
- Next neurons to be born migrate into
the middle of the preplate and divide
it into three parts:
• Marginal zone
• Cortical plate
• Subplate
```
- Early neurons of the cortical plate will form the deep layers (laminae VI and V) of the finished cortex
148
Cytodifferentiation of Cerebrum:
Inside-out Sequence: Part 3
• Later born neurons migrate radially from the ventricular zone across the intermediate
zone and subplate
• Through the earlier layers of VI and V and established laminae IV, then III and finally
II
149
Incomplete of failure of neuronal migration during 12-24 weeks
Lissencephaly or Agyria (smooth brain)
| smooth brain = mesoderm
150
Lissencephaly or Agyria (smooth brain)
| - Characterized by ?
– Microcephaly (mesoderm)
– Ventriculomegaly
– Wide Sylvian fissures (mesoderm) and minimal operculum (mesoderm) of insula
– Complete or partial agenesis of the corpus callosum (mesoderm)
151
Lissencephaly or Agyria (smooth brain)
- Infant have ?, ? or ?
- apnea, poor feeding or abnormal muscle
| tone.
152
Lissencephaly or Agyria (smooth brain)
- Patients later develop ?, ? and ?
- seizures
- mental retardation
- mild spastic quadriplegia
153
Microcephaly is a ?, not a
| diagnosis
sign
154
2 major mechanisms of Microcephaly
– Abnormal or lack of brain development during neurogenesis (mesoderm)
– Injury or insult to a previously normal brain
155
Etiology of Microcephaly
– Genetic
– Prenatal and perinatal brain injury
• Cytomegalovirus, rubella,
Toxoplasma gondii
– Craniosynostosis
– Postnatal brain injury
– Unknown
156
Cytodifferentiation of Cerebellum:
1. Cells from ventricle layer proliferate and migrate and form ? and ? out towards pia
2. ? - migrates over Purkinje cells and deep cerebellar nuclei cells that have already migrated out
3. Cells from germination center migrate back in and form ? and ?
1.
- deep cerebellar nuclei
- purkinje cell layer
2.
- External germination center
3.
- granular cells
- granular layer
157
What germ layer is the cerebellum?
Neuroectoderm
158
What vertebral level does the spinal cord end in for a newborn?
L2 or L3
159
What vertebral level does the spinal cord end in for a adult?
L1 or L2
160
Spinal Cord
- Neural crest cells give rise to ? and ? in the periphery
- spinal ganglion cells
| - sensory neurons
161
Spinal Cord
- Alar plate gives rise to sensory neurons in ?
- Neural crest gives rise to sensory neurons in ? (touch, pain, temperature)
- CNS
| - Periphery
162
What forms the PNS?
Neural crest and ectodermal placode
163
Cells that develop from the
| neural crest include:
– Neurons of dorsal root
ganglia (sensory)
– Sensory ganglia of cranial nerves (NC)
– Schwann cells (NC)
– Sympathetic ganglia
(Autonomic ganglia- come from NC because post synaptic. Pre = neuroectoderm and post = NC)
164
Development of the PNS
- Motor: come from ? in the ventral horn or spinal cord
- Sensory: come from ?
- neuroectoderm
| - NC
165
When does myelination form?
Late fetal period and continues into first postnatal year
166
What myelinates the CNS?
oligodendrocytes
167
What myelinates the PNS?
Schwann cells
168
Oligodendrocytes
- Location?
- When?
- Start in lower brain stem (myelinate older tracts first and newest last)
- 6th month through puberty
169
Schwann cells
- ? roots myelinated before ? roots
- When?
- Motor before sensory
| - 4th month
170
Which lobe of the brain is myelinated last?
Frontal Lobe
171
Neural tube disorder where there is failure of closure of CAUDAL neuropore?
Spina bifida
- Note: Occulta closes but closes late and Myelocele doesn't close at all
172
What can help prevent spina bifida?
Folic acid
173
Neural tube disorders where there is failure of closure of ROSTRAL neuropore to close?
• Anencephaly
(Meroanencephaly) - (didn't close at all)
• Encephalocele (with
brain tissue)
• Encephalocele (without
brain tissue)
