Development Of The Brain Flashcards
1
Q
When and where does the neural plate and neural groove develop?
A
Week 3
On posterior aspect of the Trilaminar embryo
2
Q
What induces the development of the neural plate and neural groove?
A
Notochord
3
Q
When does Neurulation begin?
A
Week 4
22-23 days
4
Q
What does the cranial 2/3rds of the neural plate form?
A
Future brain
4th pair of somites
5
Q
What does the caudal 1/3 of the neural plate form?
A
Future spinal cord
6
Q
What does the 5th somite form?
A
Neural tube
7
Q
When does the cranial neuropore close?
A
Day 25
8
Q
When does the caudal neuropore close?
A
Day 27
9
Q
What is the origin of the neural plate and neural groove?
A
Neuroectoderm
10
Q
What does the brain develop from? And when?
A
3rd week from neural tube
11
Q
What is the neural tube?
A
Cranial to 4th pair of somites
12
Q
What are primary brain vesicles formed from?
A
Fusion of neural fold in cranial regions
&
Closure of rostral neuropore
13
Q
What are the primary brain vesicles?
A
Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)
14
Q
What happens during the 5th week?
A
Secondary brain vesicle form
15
Q
What are the secondary brain vesicles?
A
Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon
16
Q
What secondary brain vesicles are formed from the
Forebrain?
A
Telencephalon
Diencephalon
17
Q
What secondary brain vesicles are formed from the
Midbrain?
A
None - stays as the Mesencephalon
18
Q
What secondary brain vesicles are formed from the
Hindbrain?
A
Metencephalon
Myelencephalon
19
Q
What are the adult derivates that come from the
Telencephalon?
A
Walls: cerebral hemispheres
Cavities: lateral ventricles
20
Q
What are the adult derivates that come from the
Diencephalon?
A
Wall: Thalami
Cavities: Third ventricle
21
Q
What are the adult derivates that come from the
Mesencephalon?
A
Walls: midbrian
Cavities: aqueduct
22
Q
What are the adult derivates that come from the
Metencephalon?
A
Walls: Pons & cerebellum
Cavities: upper part of 4th ventricle
23
Q
What are the adult derivates that come from the
Myelencephalon?
A
Walls: medulla
Cavities: lower part of the fourth ventricle
24
Q
What happens during the 5th week?
A
Secondary brain vesicles form
Embryonic brain grows rapidly
Bends ventrally with the head fold
25
What does the bending of the brain produce?
Midbrain flexure
Cervical flexure
26
What is the cervical flexure?
Hindbrain- SC junction
27
What produces the pontine flexure?
Unequal growth
28
What is the pontine flexure?
Meten - myelencephalon junction
This is what eventually moves cerebellum up and over the pons
29
What is the first flexure to form?
Mesencephalic flexure
30
Where is the junction of the cervical flexure?
At level of superior rootlet of C1
| Roughly at foramen magnum
31
What does the pontine flexure do?
Divide the hindbrain into
Metencephalon (pons and cereb.)
&
Myelencephalon (medulla)
32
What does the cavity of the hindbrain produce?
Fourth ventricle
Central canal in medulla
33
In the caudal myelencephlon what do neuroblasts in the alar plate do?
Migrate into marginal zone
Form nuclei Gracilus & Cuneatus
34
What are nuclei Gracilus and Cuneatus?
Sensory nuclei that associate w/ paired, afferent tracts
35
What are the pyramids of the myelencephalon?
Ventrally located structures consisting of CST fibers
36
What does the pontine flexure do in the rostral myelencephalon?
Causes walls of medulla to move laterally, thinning the roof plate
Cavity is now made and will be part of future 4th ventricle
37
What are the alar plates of the myelencephalon compared to the basal plates?
Alar plates are more lateral
| Makes motor nuclei develop medial to sensory
38
What do the neuroblasts in the basal plate of the medulla develop into?
Motor neurons
39
How do the nuclei of the basal plate organize?
GSE
SVE
GVE
(GVE - closest to sulcus limitans)
40
How are neuroblasts in the alar plates of the medulla arranged?
GVE
SVA
GSA
SSA
(SSA is farthest from sulcus limitans)
41
What will some neuroblasts of the alar plates do?
Migrate ventrally and form neurons in the Olivary nuclei *
42
Of the basal columns, what does the GSE column consist of?
* Nucleus of CN 12 in caudal most rhombencephalon
* CN 6 more cranially in rhombencephalon
• Cn 4 in most cranial rhombencephalon
◦ Will later be displaced into caudal midbrain
• CN 3 in mesencephalon
43
Of the basal columns, what does the SVE column consist of?
* 3 nuclei serving ns. 5, 7 ,9-11 confined in rhombencephalon
* Cn 5 and 7 = cranially located in rhombencephalon
* CNs 9, 10, 11 = caudally located in rhombencephalon, supplied by Nucleus Ambiguus
44
Of the basal nuclei, what does the GVE column consist of?
• 2 nuclei in rhombencephalon
◦ Salivatory nucleus
‣ Pre-g parasympathetic to salivary and lacrimal glands
◦ Dorsal Nucelus of vagus
‣ Caudal to salivatory nucelus
‣ Pre-g parasympathetic to CN 10 to innervate viscera
• In mesencephalon
◦ Edinger-WEstphal nucleus
‣ CN3 - constrict eye
45
Of the alar columns, what does the GVA column consist of?
* Nucleus receiving interocetpive info
| * Via CN 9 and 10
46
Of the alar columns, what does the SVA column consist of?
• Nucleus of Tractus Solitarius
◦ Taste impulses
◦ Via CN 7, 9, 10
47
Of the alar columns, what does the GSA column consist of?
• Neurons receiving impulses from general sensation from:
◦ CN 5 - areas of face
◦ Cn 7 - areas of face
◦ Cn 5, 7, 9, 10 - oral, nasal, external auditory, and pharyngeal/laryngeal cavities
48
Of the alar columns, what does the SSA column consist of?
• Cochlea and Vestibular Nuclei ◦ Cn 8
| ◦ Special senses of balance and hearing
49
In the Metencephalon what does the pontine flexure do?
Forces walls of pons laterally, spreading grey matter in floor of 4th ventricle
50
How does the cerebellum develop?
From the metencephalon’ s dorsal parts of alar plates
Cerebellar swellings project into the fourth ventricle and fuse in median plane
Overgrown rostral 4th ventricle and overlaps pons and medulla
51
What covers the ependymal roof of the fourth ventricle?
What is this derived from?
Pia mater
Hindbrain Mesenchyme
52
What forms the tela choroidea?
Pia + ependymal roof
53
What is the tela choroidea?
Sheet of Persia covering the lower part of the 4th ventricle that invaginates the 4th ventricle to form the choroid plexus
54
What is the epithelial lining of the choroid plexus derived from?
Neuroepithelium
55
What does the stroma of the choroid plexus develop from?
Mesenchymal cells
56
Where do plexuses similar to the choroid plexus develop?
Roof of 3rd ventricle
Medial walls of lateral ventricles
57
What forms the median and lateral apertures?
Invagination of the 4th ventricle’s roof in 3 location and the subsequent rupture of it
58
What is the function of the median and lateral apertures?
Permit CSF to enter subarachnoid space from the 4th ventricle
59
How do the superior and inferior colliculi form?
From midbrain neuroblasts of alar plates migrating into the tectum (Roof)
60
What do neuroblasts of the basal plate of the midbrain form?
Tegmental nuclei
61
What are the tegmental nuclei in the midbrain?
Red nuclei
Reticular nuclei
CN 3 and 4 nuclei
62
What is the superior colliculi pathway?
Superior colliculi —> branchium of the sup. Colliculi —> lateral genicular nucleus —> sight
63
What is the inferior colliculi pathway?
Inferior colliculi —> branchium of the inferior colliculi —> medial geniculate nucleus —> hearing
64
What forms the substantia nigra?
EITHER basal or alar plates of midbrain
| Still debated
65
How does the crus cerebri form?
Fibers growing form the cerebral cortex form the cerebral peduncles
66
How does the cerebral aqueduct form? What does it do?
Neural canal narrows
Connects 3rd and 4th ventricles
67
What odes the diencephalon form?
Thalami from 3 swellings in the lateral walls of the third ventricle
(Thalami = thalamus, epi, hypo)
68
What does the epithalamus sulcus do?
Separates thalamus and epithalamus
69
What does the hypothalamic sulcus do?
Separates thalamus and hypothalamus
70
How does the thalamus develop?
Develops on each side of third ventricle and fuses at midline forming interthalamic adhesion or Mass Intermedia
71
How often does the interthalamic adhesion form?
70% of the time
20% of the time, Massa Intermedia is absent
72
What forms the hypothalamus?
Neuroblasts in the intermediate zone of the diencephalon
73
What develops in the hypothalamus?
Endocrine and homeostatic nuclei develop
Mammillary bodies form on ant. Surface
74
What makes the majority of the 3rd ventricle?
Diencephalon
75
How does the epithalamus develop?
From roof and dorsal portion of the lateral walls
| Swelling originally quite large but become small
76
How does the pineal gland develop?
Develops as a median diverticulum of the caudal part of the roof of the diencephalon
Will proliferate in its walls, converting it into a solid, cone-shaped gland
77
What does the pineal gland do?
Regulate sleep and wake cycles
78
What two diverticulum does the pituitary gland develop from?
Hypophyseal diverticulum
| Neurohypophyseal diverticulum
79
What is the hypophyseal diverticulum derived from?
Surface ectoderm since it is an upgrowth of roof of stomodeum
80
What is the neurohypophyseal diverticulum derived from?
Neuroectoderm since it is a downgrowth from the diencephalon
81
Where is the hypophyseal diverticulum located during week 3?
Wk 3 = near floor of diencephalon
82
What is the infundibulum?
Stalk that passes between the developing bones of the cranium to the posterior pituitary gland
83
How is the anteiror pituitary gland attached to the brain?
It’s not!
84
When does the hypophyseal diverticulum’s connection to the oral cavity degenerate?
Week 6
85
How does sella turcica develop?
Forms around the pituitary gland and makes that nice little saddle
86
What two things will the hypophyseal diverticulum make?
Pars anterior
Pars tuberalis
87
What will the neurohypophyseal diverticulum make?
Median eminence
Infundibulum
Pars nervosa
88
What is the derivation of the anteiror pituitary gland?
Oral surface ectoderm
89
What is the derivation of the posterior pituitary gland?
Neuroectoderm
90
What does the telencephlonconsist of?
Median part
| 2 telencephalic/cerebral vesicles
91
What do the telencephalic/cerebral vesicles give rise to?
Cerebral hemispheres
92
What does the median cavity of the telencephalon form?
Anterior 3rd ventricle
93
What appears at the closure of the rostral neuropore?
Optic vesicles appear; will give rise to retina and optic nerves
94
How do cerebral hemispheres communicate with the 3rd ventricle?
Intervetnricular foramina
95
Why do the cerebral hemispheres become C -shaped?
Due to cortex rapidly proliferating while deep nuclei do not
Thus impacting shape of ventricles
96
What forms at the medial wall of the cerebral hemisphere where is it continuous with the roof of the third v?
Choroid plexus
97
What covers the diencephalon, midbrain and hindbrain?
Cerebral hemispheres will meet each other int he midline and medial surfaces flatten
98
What gives rise to the falx cerebri?
Mesenchyme trapped in the longitudinal fissure after the cerebral hemispheres meet each other medially
99
What is holoprosencephaly (HPE)?
What can it cause?
Incomplete separation of the cerebral hemispheres
Defect in forebrain development causing facial anomalies bc reduction of the FNP
100
What are the facial anomalies seen with Holoprosencephaly?
```
Cyclopes
Premaxillary agenesis
Proboscis
Single nostril
Hypotelorism (close set eyes)
Facial clefts
```
101
How common is holoprosencephaly?
Severe and common defect
1: 250 fetuses (although most spont. Abort)
1: 15,000 neonates
102
What can cause Holoprosencephaly?
Over 12+ genetic loci have been implicated
All inhibit cholesterol synthesis
103
What are the cerebral commissures?
Groups of nerve fibers interconnecting the cerebral hemispheres
(White matter tracts)
104
What is the lamina terminalis found int he cerebral commissures?
At rostral end of forebrain
Where most of the white matter commissures form
105
Which commissures form first?
Anterior commissure
Hippocampal commissure
106
What does the anteiror commissure do?
Interconnects olfactory bulb w/ hemispheres
107
What does the hippocampal commissure do?
Connects hippocampal formations
108
How does the corpus callosum form?
| What does it do?
Anterior portions form first, posterior portions form in fetal life
Links hemispheres along their length
109
What does the lamina terminalis form?
Stretched and forms septum pellucidum
110
What is the septum pellucidum?
Thin plate of brain tissues containing nerve cells and fibers that separates the R and L lateral ventricles
111
What is the posterior commissure?
White matter tract connecting R and L temporal lobes
112
What is agenesis of corpus callosum?
Sxs?
Complete or partial absence of the corpus callosum
May be asymptomatic, seizure and mental deficits common
Assoc. w/ over 50 human congenital syndromes
113
How is gyri formed?
From infolding of the cortex
114
How do sulci and gyri develop?
Growth of cortex
115
What do sulci and gyri allow?
Increased surface area without increased the volume of the neurocranium
116
The brain at birth is only about what % of its adult volume?
25%
117
How does the brain grow postnatally?
Neurons increase in size
Myelination of axons
Additional growth and infolding if you learn to play musical instruments, etc.
118
When does the brain reach its final size?
7 years old
119
What are the zones of histogenesis for the cerebral cortex?
Ventricular
Intermediate
Marginal
&&&
*subventricular (!!!)
120
How are cortical layers of the cerebral cortex layer down?
From deep to superficial
Neurons will migrate thru deep and establish more superficial layers
Inside out development
121
What is lissencephaly?
Incomplete neuronal migration to cerebral cortex during 3-4 mos. gestation
Abnormal migration of those subventricular layers to outside
122
What is the incidence of Lissencephaly?
1:100,000 live births
123
What are the characteristics of Lissencephaly?
Smooth cerebral surface w/
Pachygyria
Agyria
Neuronal heterotopia
Enlarged ventricles and malformation of corpus callosum too
124
What is pachygyria?
Broad, thick gyri
125
What is agyria?
Lack of gyri
126
What is neuronal heterotopia?
Cell in aberrant positions compared to a normal brain
127
How does Lissencephaly present?
Initially - appear normal
Later - develop seizure, profound mental deficiency, and mild spastic quadriplegia
128
What is microcephaly?
Neurodevelopmental disorder where calvaria and brain are small but face is normal sized
129
What is the result of microcephaly?
Significant mental deficiencies due to brain underdevelopment
130
What does microcephaly result from?
Reduction in brain growth
No brain growth = no pressure of bones = small neurocranium
131
What is the incidence of microcephaly?
1:25,000 infants/yr in the US
132
What are the causes of microcephaly:?
Automakers recessive primary microcephaly
Ionizing radiation
Infectious agents (cytomegalovirus, rubella virus, toxoplasma gondii)
Maternal alcohol abuse
133
What do neural crest cells contribute to the development of?
Schwann cells
