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

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2
Q

What induces the development of the neural plate and neural groove?

A

Notochord

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3
Q

When does Neurulation begin?

A

Week 4

22-23 days

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4
Q

What does the cranial 2/3rds of the neural plate form?

A

Future brain

4th pair of somites

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5
Q

What does the caudal 1/3 of the neural plate form?

A

Future spinal cord

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6
Q

What does the 5th somite form?

A

Neural tube

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7
Q

When does the cranial neuropore close?

A

Day 25

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8
Q

When does the caudal neuropore close?

A

Day 27

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9
Q

What is the origin of the neural plate and neural groove?

A

Neuroectoderm

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10
Q

What does the brain develop from? And when?

A

3rd week from neural tube

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11
Q

What is the neural tube?

A

Cranial to 4th pair of somites

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12
Q

What are primary brain vesicles formed from?

A

Fusion of neural fold in cranial regions
&
Closure of rostral neuropore

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13
Q

What are the primary brain vesicles?

A

Forebrain (prosencephalon)

Midbrain (mesencephalon)

Hindbrain (rhombencephalon)

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14
Q

What happens during the 5th week?

A

Secondary brain vesicle form

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15
Q

What are the secondary brain vesicles?

A
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
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16
Q

What secondary brain vesicles are formed from the

Forebrain?

A

Telencephalon

Diencephalon

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17
Q

What secondary brain vesicles are formed from the

Midbrain?

A

None - stays as the Mesencephalon

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18
Q

What secondary brain vesicles are formed from the

Hindbrain?

A

Metencephalon

Myelencephalon

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19
Q

What are the adult derivates that come from the

Telencephalon?

A

Walls: cerebral hemispheres

Cavities: lateral ventricles

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20
Q

What are the adult derivates that come from the

Diencephalon?

A

Wall: Thalami

Cavities: Third ventricle

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21
Q

What are the adult derivates that come from the

Mesencephalon?

A

Walls: midbrian

Cavities: aqueduct

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22
Q

What are the adult derivates that come from the

Metencephalon?

A

Walls: Pons & cerebellum

Cavities: upper part of 4th ventricle

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23
Q

What are the adult derivates that come from the

Myelencephalon?

A

Walls: medulla

Cavities: lower part of the fourth ventricle

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24
Q

What happens during the 5th week?

A

Secondary brain vesicles form

Embryonic brain grows rapidly

Bends ventrally with the head fold

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25
Q

What does the bending of the brain produce?

A

Midbrain flexure

Cervical flexure

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26
Q

What is the cervical flexure?

A

Hindbrain- SC junction

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27
Q

What produces the pontine flexure?

A

Unequal growth

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28
Q

What is the pontine flexure?

A

Meten - myelencephalon junction

This is what eventually moves cerebellum up and over the pons

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29
Q

What is the first flexure to form?

A

Mesencephalic flexure

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30
Q

Where is the junction of the cervical flexure?

A

At level of superior rootlet of C1

Roughly at foramen magnum

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31
Q

What does the pontine flexure do?

A

Divide the hindbrain into

Metencephalon (pons and cereb.)

&

Myelencephalon (medulla)

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32
Q

What does the cavity of the hindbrain produce?

A

Fourth ventricle

Central canal in medulla

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33
Q

In the caudal myelencephlon what do neuroblasts in the alar plate do?

A

Migrate into marginal zone

Form nuclei Gracilus & Cuneatus

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34
Q

What are nuclei Gracilus and Cuneatus?

A

Sensory nuclei that associate w/ paired, afferent tracts

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35
Q

What are the pyramids of the myelencephalon?

A

Ventrally located structures consisting of CST fibers

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36
Q

What does the pontine flexure do in the rostral myelencephalon?

A

Causes walls of medulla to move laterally, thinning the roof plate

Cavity is now made and will be part of future 4th ventricle

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37
Q

What are the alar plates of the myelencephalon compared to the basal plates?

A

Alar plates are more lateral

Makes motor nuclei develop medial to sensory

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38
Q

What do the neuroblasts in the basal plate of the medulla develop into?

A

Motor neurons

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39
Q

How do the nuclei of the basal plate organize?

A

GSE
SVE
GVE

(GVE - closest to sulcus limitans)

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40
Q

How are neuroblasts in the alar plates of the medulla arranged?

A

GVE
SVA
GSA
SSA

(SSA is farthest from sulcus limitans)

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41
Q

What will some neuroblasts of the alar plates do?

A

Migrate ventrally and form neurons in the Olivary nuclei *

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42
Q

Of the basal columns, what does the GSE column consist of?

A
  • 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

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43
Q

Of the basal columns, what does the SVE column consist of?

A
  • 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
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44
Q

Of the basal nuclei, what does the GVE column consist of?

A

• 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

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45
Q

Of the alar columns, what does the GVA column consist of?

A
  • Nucleus receiving interocetpive info

* Via CN 9 and 10

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46
Q

Of the alar columns, what does the SVA column consist of?

A

• Nucleus of Tractus Solitarius
◦ Taste impulses
◦ Via CN 7, 9, 10

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47
Q

Of the alar columns, what does the GSA column consist of?

A

• 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

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48
Q

Of the alar columns, what does the SSA column consist of?

A

• Cochlea and Vestibular Nuclei ◦ Cn 8

◦ Special senses of balance and hearing

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49
Q

In the Metencephalon what does the pontine flexure do?

A

Forces walls of pons laterally, spreading grey matter in floor of 4th ventricle

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50
Q

How does the cerebellum develop?

A

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

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51
Q

What covers the ependymal roof of the fourth ventricle?

What is this derived from?

A

Pia mater

Hindbrain Mesenchyme

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52
Q

What forms the tela choroidea?

A

Pia + ependymal roof

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53
Q

What is the tela choroidea?

A

Sheet of Persia covering the lower part of the 4th ventricle that invaginates the 4th ventricle to form the choroid plexus

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54
Q

What is the epithelial lining of the choroid plexus derived from?

A

Neuroepithelium

55
Q

What does the stroma of the choroid plexus develop from?

A

Mesenchymal cells

56
Q

Where do plexuses similar to the choroid plexus develop?

A

Roof of 3rd ventricle

Medial walls of lateral ventricles

57
Q

What forms the median and lateral apertures?

A

Invagination of the 4th ventricle’s roof in 3 location and the subsequent rupture of it

58
Q

What is the function of the median and lateral apertures?

A

Permit CSF to enter subarachnoid space from the 4th ventricle

59
Q

How do the superior and inferior colliculi form?

A

From midbrain neuroblasts of alar plates migrating into the tectum (Roof)

60
Q

What do neuroblasts of the basal plate of the midbrain form?

A

Tegmental nuclei

61
Q

What are the tegmental nuclei in the midbrain?

A

Red nuclei
Reticular nuclei
CN 3 and 4 nuclei

62
Q

What is the superior colliculi pathway?

A

Superior colliculi —> branchium of the sup. Colliculi —> lateral genicular nucleus —> sight

63
Q

What is the inferior colliculi pathway?

A

Inferior colliculi —> branchium of the inferior colliculi —> medial geniculate nucleus —> hearing

64
Q

What forms the substantia nigra?

A

EITHER basal or alar plates of midbrain

Still debated

65
Q

How does the crus cerebri form?

A

Fibers growing form the cerebral cortex form the cerebral peduncles

66
Q

How does the cerebral aqueduct form? What does it do?

A

Neural canal narrows

Connects 3rd and 4th ventricles

67
Q

What odes the diencephalon form?

A

Thalami from 3 swellings in the lateral walls of the third ventricle

(Thalami = thalamus, epi, hypo)

68
Q

What does the epithalamus sulcus do?

A

Separates thalamus and epithalamus

69
Q

What does the hypothalamic sulcus do?

A

Separates thalamus and hypothalamus

70
Q

How does the thalamus develop?

A

Develops on each side of third ventricle and fuses at midline forming interthalamic adhesion or Mass Intermedia

71
Q

How often does the interthalamic adhesion form?

A

70% of the time

20% of the time, Massa Intermedia is absent

72
Q

What forms the hypothalamus?

A

Neuroblasts in the intermediate zone of the diencephalon

73
Q

What develops in the hypothalamus?

A

Endocrine and homeostatic nuclei develop

Mammillary bodies form on ant. Surface

74
Q

What makes the majority of the 3rd ventricle?

A

Diencephalon

75
Q

How does the epithalamus develop?

A

From roof and dorsal portion of the lateral walls

Swelling originally quite large but become small

76
Q

How does the pineal gland develop?

A

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
Q

What does the pineal gland do?

A

Regulate sleep and wake cycles

78
Q

What two diverticulum does the pituitary gland develop from?

A

Hypophyseal diverticulum

Neurohypophyseal diverticulum

79
Q

What is the hypophyseal diverticulum derived from?

A

Surface ectoderm since it is an upgrowth of roof of stomodeum

80
Q

What is the neurohypophyseal diverticulum derived from?

A

Neuroectoderm since it is a downgrowth from the diencephalon

81
Q

Where is the hypophyseal diverticulum located during week 3?

A

Wk 3 = near floor of diencephalon

82
Q

What is the infundibulum?

A

Stalk that passes between the developing bones of the cranium to the posterior pituitary gland

83
Q

How is the anteiror pituitary gland attached to the brain?

A

It’s not!

84
Q

When does the hypophyseal diverticulum’s connection to the oral cavity degenerate?

A

Week 6

85
Q

How does sella turcica develop?

A

Forms around the pituitary gland and makes that nice little saddle

86
Q

What two things will the hypophyseal diverticulum make?

A

Pars anterior

Pars tuberalis

87
Q

What will the neurohypophyseal diverticulum make?

A

Median eminence

Infundibulum

Pars nervosa

88
Q

What is the derivation of the anteiror pituitary gland?

A

Oral surface ectoderm

89
Q

What is the derivation of the posterior pituitary gland?

A

Neuroectoderm

90
Q

What does the telencephlonconsist of?

A

Median part

2 telencephalic/cerebral vesicles

91
Q

What do the telencephalic/cerebral vesicles give rise to?

A

Cerebral hemispheres

92
Q

What does the median cavity of the telencephalon form?

A

Anterior 3rd ventricle

93
Q

What appears at the closure of the rostral neuropore?

A

Optic vesicles appear; will give rise to retina and optic nerves

94
Q

How do cerebral hemispheres communicate with the 3rd ventricle?

A

Intervetnricular foramina

95
Q

Why do the cerebral hemispheres become C -shaped?

A

Due to cortex rapidly proliferating while deep nuclei do not

Thus impacting shape of ventricles

96
Q

What forms at the medial wall of the cerebral hemisphere where is it continuous with the roof of the third v?

A

Choroid plexus

97
Q

What covers the diencephalon, midbrain and hindbrain?

A

Cerebral hemispheres will meet each other int he midline and medial surfaces flatten

98
Q

What gives rise to the falx cerebri?

A

Mesenchyme trapped in the longitudinal fissure after the cerebral hemispheres meet each other medially

99
Q

What is holoprosencephaly (HPE)?

What can it cause?

A

Incomplete separation of the cerebral hemispheres

Defect in forebrain development causing facial anomalies bc reduction of the FNP

100
Q

What are the facial anomalies seen with Holoprosencephaly?

A
Cyclopes
Premaxillary agenesis
Proboscis
Single nostril
Hypotelorism (close set eyes)
Facial clefts
101
Q

How common is holoprosencephaly?

A

Severe and common defect

1: 250 fetuses (although most spont. Abort)
1: 15,000 neonates

102
Q

What can cause Holoprosencephaly?

A

Over 12+ genetic loci have been implicated

All inhibit cholesterol synthesis

103
Q

What are the cerebral commissures?

A

Groups of nerve fibers interconnecting the cerebral hemispheres

(White matter tracts)

104
Q

What is the lamina terminalis found int he cerebral commissures?

A

At rostral end of forebrain

Where most of the white matter commissures form

105
Q

Which commissures form first?

A

Anterior commissure

Hippocampal commissure

106
Q

What does the anteiror commissure do?

A

Interconnects olfactory bulb w/ hemispheres

107
Q

What does the hippocampal commissure do?

A

Connects hippocampal formations

108
Q

How does the corpus callosum form?

What does it do?

A

Anterior portions form first, posterior portions form in fetal life

Links hemispheres along their length

109
Q

What does the lamina terminalis form?

A

Stretched and forms septum pellucidum

110
Q

What is the septum pellucidum?

A

Thin plate of brain tissues containing nerve cells and fibers that separates the R and L lateral ventricles

111
Q

What is the posterior commissure?

A

White matter tract connecting R and L temporal lobes

112
Q

What is agenesis of corpus callosum?

Sxs?

A

Complete or partial absence of the corpus callosum

May be asymptomatic, seizure and mental deficits common

Assoc. w/ over 50 human congenital syndromes

113
Q

How is gyri formed?

A

From infolding of the cortex

114
Q

How do sulci and gyri develop?

A

Growth of cortex

115
Q

What do sulci and gyri allow?

A

Increased surface area without increased the volume of the neurocranium

116
Q

The brain at birth is only about what % of its adult volume?

A

25%

117
Q

How does the brain grow postnatally?

A

Neurons increase in size

Myelination of axons

Additional growth and infolding if you learn to play musical instruments, etc.

118
Q

When does the brain reach its final size?

A

7 years old

119
Q

What are the zones of histogenesis for the cerebral cortex?

A

Ventricular
Intermediate
Marginal

&&&

*subventricular (!!!)

120
Q

How are cortical layers of the cerebral cortex layer down?

A

From deep to superficial

Neurons will migrate thru deep and establish more superficial layers

Inside out development

121
Q

What is lissencephaly?

A

Incomplete neuronal migration to cerebral cortex during 3-4 mos. gestation

Abnormal migration of those subventricular layers to outside

122
Q

What is the incidence of Lissencephaly?

A

1:100,000 live births

123
Q

What are the characteristics of Lissencephaly?

A

Smooth cerebral surface w/
Pachygyria
Agyria
Neuronal heterotopia

Enlarged ventricles and malformation of corpus callosum too

124
Q

What is pachygyria?

A

Broad, thick gyri

125
Q

What is agyria?

A

Lack of gyri

126
Q

What is neuronal heterotopia?

A

Cell in aberrant positions compared to a normal brain

127
Q

How does Lissencephaly present?

A

Initially - appear normal

Later - develop seizure, profound mental deficiency, and mild spastic quadriplegia

128
Q

What is microcephaly?

A

Neurodevelopmental disorder where calvaria and brain are small but face is normal sized

129
Q

What is the result of microcephaly?

A

Significant mental deficiencies due to brain underdevelopment

130
Q

What does microcephaly result from?

A

Reduction in brain growth

No brain growth = no pressure of bones = small neurocranium

131
Q

What is the incidence of microcephaly?

A

1:25,000 infants/yr in the US

132
Q

What are the causes of microcephaly:?

A

Automakers recessive primary microcephaly

Ionizing radiation

Infectious agents (cytomegalovirus, rubella virus, toxoplasma gondii)

Maternal alcohol abuse

133
Q

What do neural crest cells contribute to the development of?

A

Schwann cells