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MSK Exam 1 > Neurulation & Development of the PNS > Flashcards

Neurulation & Development of the PNS Flashcards

1
Q

___ incudes neuroectoderm to form Neural Plate

A

Notochord

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2
Q

What week does Neurulation begin?

A

Beginning of week 3

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3
Q

What makes up the ectoderm during neurulation?

A
  • Neuroectoderm
  • Surface Ectoderm
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4
Q

__-__ spine formation occurs during Primary Neurulation

A

Cervical-Lumbar (coccygeal and sacral regions undergo secondary neurulation)

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5
Q

What day does the neural plate form?

A

Day 17

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6
Q

During Primary Neurulation, the Notochordal Plate is __ to the Notochord, which is ___ to the Neural Plate

A
  • Inferior/below
  • Inferior/below
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7
Q

Need ___ in order to close the rostral & caudal neuropore

A

Folate

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8
Q

What signifies the end of Primary Neurulation?

A

Closure of the caudal neuropore at somite 31 (NT extends past this caudally into sacral and coccygeal regions)

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9
Q

What day does the Caudal Neuropore close?

A

Day 26

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10
Q

What day does the Rostral Neuropore close?

A

Day 24

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11
Q

What develops from the tail bud?

A
  • Caudal-most NT
  • Neural crest cells
  • Somites
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12
Q

Secondary Neurulation

A
  • Formation of the neural tube from the tail bud
  • Involves the making of a medullary cord and its subsequent hollowing into a neural tube
  • Closing of caudal neuropore is merged with the forming tail bud
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13
Q

Medullary cord grows ___ to primitive streak

A

Inferior

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14
Q

Steps of Secondary Neurulation

A

(1) Tail bud condenses into a solid mass, the medullary cord
(2) Medullary cord develops a lumen
(3) Lumen of medullary cord becomes continuous with more cranial neural canal – merges with central canal or neural tube (consists of mixed cells of mesodermal and ectodermal origin)

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15
Q

What days does Secondary Neurulation occur?

A

Days 20-40

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16
Q

Neural Crest Cells

A
  • Neuroectodermal cells positioned along dorsal neural folds; present bilaterally along entire cranial-caudal NT
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17
Q

Neural Crest cells undergo ___

A

EMT

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18
Q

EMT

A
  • Epithelial-mesenchymal-transition
  • Lose contacts and become migratory
  • Migrate ventrally along length of embryo
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19
Q

__ Neural Crest contributes to septation of the heart

A

Cardiac

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20
Q

Neural Crest Derivatives

A
  • Melanocytes
  • Odontoblasts
  • Schwann cells
  • Spinal & Autonomic ganglia
  • Enteric nervous system
  • Suprarenal (adrenal) medulla
  • Characteristic facial features
  • Pharyngeal arch (Malleus, Incus, Stapes, Styloid process, facial bones, Meckels cartilage, Hyoid cartilage, Laryngeal cartilage, Trachael rings)
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21
Q

What are the derivatives of Cardial Neural Crest cells?

A
  • Aortic arch arteries
  • Aorta
  • Aortic-pulmonary septum
  • Pulmonary artery
  • Outflow tract
  • Pharyngeal arches
  • Right and left dorsal aortas
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22
Q

What are 5 Neurocristopathies?

A
  • Goldenhar Syndrome (hemifacial macrosomia)
  • Micrognathia
  • TCS (Mandubulofacial Dystosis)
  • Hirschsprung Disease
  • Piebaldism
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23
Q

Goldenhar Syndrome (hemifacial macrosomia)

A
  • Jaw and cheekbones on one side of the body are underdeveloped
  • Associated with eye and ear abnormalities, sometimes cleft lip
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24
Q

Micrognathia

A

Lower jaw is underdeveloped or completely absent

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25
Q

TCS (Mandibulofacial Dystosis)

A
  • Autosomal dominant disorder of craniofacial development
  • Often affects jaw, cheekbones, ears, and ears
  • Characteristics: downward slanting eyes, very small chin and jaw, hearing loss, and vision loss
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26
Q

Hirschsprung Disease

A
  • Enteric nervous system doesn’t develop
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27
Q

Piebaldism

A
  • Autosomal dominant disorder
  • Characterized by the congenital absence of melanocytes in affected areas of the skin and hair
  • Affected individuals present at birth with a white forelock and relative stable, persistent depigmentation of the skin with a characteristic distribution
  • Due to mutations of the KIT proto oncogene that encodes a tyrosine kinase that is important in nearl crest cells; mutated KIT affects differentiation and migration of melanoblasts from the neural crest
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28
Q

Meningomyelocele

A
  • NTD that can occur anywhere along the vertebral column, but most common in lumbar and sacral region
  • involved a malformation of the vertebral arch, meninges, and nervous tissue, covered in a membraneous sac
  • Does not lead to immediate death
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29
Q

Cranial Neural Tube Defects

A
  • Typically found in the cervical region of the vertebral column
  • May lead to immediate death of the fetus
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30
Q

Why is melanoma so deadly?

A

It reactivates cell’s migratory genes

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31
Q

What are the meninges?

A
  • Membranes covering the spinal cord and brain
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32
Q

What do the meninges develop from?

A
  • Neural Crest Cells
  • Mesenchyme
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33
Q

What day(s) do the meninges develop?

A

Days 20-35 (3 to 4 weeks)

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34
Q

How is the Meninx Primitiva formed?

A
  • When NCC and mesenchyme migrate and surround NT
  • Results in formation of the primordial meninges
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35
Q

What 2 things does the Primitive Meninx differentiate into (days 34-48)?

A
  • Ectomeninx
  • Endomeninx
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36
Q

Ectomeninx between 45-60 days:

A

(1) Ectomeninx becomes more compact and forms spaces for future venous sinuses (collect blood from brain to drain out)
(2) Endomeninx becomes more reticulated and subarachnoid space/cisterns appear

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37
Q

What does the spinal ectomeninx give rise to after it dissociates from the vertebral bodies?

A

Spinal epidural space – necessary for epidurals

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38
Q

Ectomeninx is the future:

A

Dura

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39
Q

Endomeninx is the future:

A

Arachnoid and Pia

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40
Q

Dermal Sinus Tract

A
  • Forms during Primitive Meninx differentiation
  • Abnormal tract connecting the epithelium and the spinal neural structures and containing epithelial and/or neural elements
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41
Q

Neural Tube Closure

A
  • Does not occur simultaneously along the length of the NT
  • Closure starts in middle of embryo
  • Cranial regions are more advanced than caudal regions
  • Initiated at several locations along the AP axis
  • Results in formation of the cranial and caudal neuropores
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42
Q

During NT closure why are the cranial regions so advanced compared to the rest?

A

Because the cells are growing faster than they can close causing cranial and caudal neuropores that are closed last (zipped from middle to cranial, and middle to caudal)

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43
Q

How many closure sites are there in NT closure?

A

5

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44
Q

Failure of any of the NT closure sites results in:

A

NTDs (cranial and/or spinal)

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45
Q

What factors impact the development of NTDs?

A
  • Genetic
  • Nutritional
  • Environmental
46
Q

4,000 pregnancies per year affected by:

A

NTDs

47
Q

Encephalocele

A
  • Protrusion of brain tissue (in which the NT is closed) through an opening in the skull
48
Q

Craniorachischisis (Anencephaly)

A
  • NT is open onto surface of the neck and back
  • Occurs at Closure Site 1
  • Non-viable
49
Q

300,000 infants are born with this worldwide each year:

A

Spina Bifida Aperta

50
Q

What are the 4 types of Spina Bifida?

A
  • Spina Bifida Occulta
  • Spina Bifida Occulta Meningocele
  • Spina Bifida Occulta Meningomyelocele
  • Spina Bifida Aperta Myeloschisis
51
Q

Spina Bifida Occulta

A
  • Failure of the posterior vertebral arch to close
  • Often tuft of hair present over site where vertebral arch did not close
  • Skin is closed
52
Q

Spina Bifida Occulta Meningocele

A
  • Protrusion of Dura Mater, Arachnoid Mater and CSF but no spinal cord protrusion
  • Skin is closed
53
Q

Spina Bifida Occulta Meningomyelocele

A
  • Protrusion of Dura Mater, Arachnoid Mater, CSF and spinal cord
  • Skin is closed
54
Q

Spina Bifida Aperta Myeloschisis

A
  • Protrusion of Dura Mater, Arachnoid Mater, CSF and spinal cord
  • Skin is OPEN
55
Q

Divisions of CNS

A
  • Brain, eyes, and spinal cord
  • Derivatives form from NEURAL TUBE
56
Q

Divisions of PNS

A
  • Cranial nerves and ganglia
  • Spinal nerves and ganglia
  • Autonomic nerves and ganglia
  • Enteric NS
57
Q

What does the PNS develop from?

A
  • Neural Crest Cells
  • Neuroectoderm
  • Ectodermal Placodes
58
Q

What two regions does the NT divide into?

A
  • Ventral
  • Dorsal
59
Q

What separates the Dorsal and Ventral regions of the NT?

A

Sulcus Limitans

60
Q

What is present at the uppermost part of the NT?

A

Roof Plate

61
Q

What is present at the lowest part of the NT?

A

Floor Plate

62
Q

Alar plate forms from what region of the NT?

A

Dorsal Region

63
Q

Basal plate forms from what region of the NT?

A

Ventral

64
Q

Alar plate extends __ and __ from the NT

A

Dorsally and Laterally

65
Q

Basal Plate extends __ and __ from the NT

A

Ventrally and Laterally

66
Q

What is the NT comprised of?

A

Germinal Neuroepithelium

67
Q

Neural crest cells migrate from which embryonic structure?

A

Neural Folds

68
Q

What are the 3 areas of Neural Tube differentiation?

A
  • Ventricular Zone
  • Mantle/Intermediate Zone
  • Marginal Zone
69
Q

Ventricular Zone

A
  • Stem cells positioned closest to lumen
  • Will divide and migrate
  • cells typically -blast
70
Q

Mantle/Intermediate Zone

A
  • Migrating cells that undergo differentiation into neurons and/or glia
  • Extend axons away from lumen toward outer surface
  • Presumative gray matter
71
Q

Marginal Zone

A
  • Poor in neuronal cell bodies
  • Contain axons that will eventually be myelinated
  • Presumative white matter
72
Q

What happens at the end of the 4th week?

A

Mantle layer reorganizes into the alar (dorsal) plate and basal (ventral) plate

73
Q

What connects the Alar Plates?

A

Roof Plate

74
Q

What connects the Basal Plates?

A

Floor Plates

75
Q

The alar and basal plates undergo differentiation due to what?

A

Signaling from roof plate and floor plate

76
Q

What happens to Neuroepithelial cells that migrate from marginal layer -> mantle layer -> ventricular layer -> mantle layer

A

(1) Neuroepithelial cell migrates from marginal layer to mantle layer
(2) In mantle layer it undergoes mitosis and can differentiate into 1 of the 3 different options:
- Neuron (mantle layer)
- Glioblast (mantle layer)
- Ependymal cell (occurs in ventricular layer)

77
Q

Mesenchymal cells can differentiate into __ cells

A

Microglial (this is not a glial or neural cell and thus do not come from the neuroepithelia)

78
Q

Neurons in dorsal aspect of neural tube become:

A

Sensory Neurons

79
Q

Neurons in ventral aspect of neural tube become:

A

Motor Neurons

80
Q

Which neurons form first, sensory or motor?

A

Motor

81
Q

___ gradient directs neuron identity

A

SHH

82
Q

Increased concentrations of SHH:

A

Motor neurons induced

83
Q

Decreased concentration of SHH:

A

Multiple interneurons induced – dependent on decreasing [SHH]

84
Q

What initiates Ventral specifications of the NT?

A

SHH secreted by notochord activates NKX2.2 and NKX6.2 to turn on the floor plate to increase the motor neuron identity of the neural tube; gradient forms with higher SHH and motor activation closer to the floor plate

85
Q

What is the role of NKX2.2 and NKX6.1?

A

Ventral Neuron formation

86
Q

SHH is released from what two structures?

A

(1) Notochord
(2) Floor Plate

87
Q

What counteracts the SHH gradient?

A

BMP/TGF-β

88
Q

What does BMP4 activate?

A

PAX3 and PAX7

89
Q

What initiates Dorsal specifications of the NT?

A

BMP4 and BMP7 (TGF-β family) activated PAX3 and PAX7 in the roof plate to activate dorsal associated neurons (remember they are not sensory themselves b/c sensory nerves are located in the dorsal root ganglion)

90
Q

Positional changes of the spinal cord from neonate to adult?

A
  • Neonate spinal cord is at the level of L3/L4
  • Adult spinal cord stops at L1/L2
91
Q

Filum Terminale

A
  • Originates at end of Medullary Cone
  • Travels down and attaches to C1
92
Q

Where is the Root of 1st sacral nerve present from embryo to adult?

A

S1

93
Q

How are the Intermediate columns formed?

A

Most dorsal cells of basal plate undergo segregation -> form the intermediolateral cell columns (T1-L3 and S2-S4 only) -> form the lateral horns (autonomic presynaptic cell bodies)

94
Q

Where are the visceral motor neurons of the sympathetic and parasympathetic divisions located?

A
  • Sympathetic: T1-L3
  • Parasympathetic: S2-S4
95
Q

What forms sensory ganglia in the head?

A

NCC and ectodermal placodes

96
Q

What do Neural Crest Cells form in the Trunk?

A

Sensory neurons in dorsal root ganglions, enteric nervous system, and schwann cells

97
Q

What do axons pass through to form a ventral root?

A

Cranial Sclerotome

98
Q

What do axons from the dorsal root ganglion do?

A

Extend from dorsal root ganglion to the dorsal horn (sensory nerves are not in the spinal cord themselves, they are stored in the dorsal root ganglion)

99
Q

What do cranial peripheral neurons consist of?

A

Sensory and parasympathetic (ANS) components

100
Q

When do cranial ganglia appear?

A

End of 4th week to the beginning of the 5th week

101
Q

What do ectodermal placodes give rise to?

A

Sensory structures (ears, vision, smell)

102
Q

What do Trigeminal nerves arise from?

A

NCC or Ectodermal Placodes

103
Q

What do CN VII and VIII arise from?

A

BOTH NCC and Ectodermal Placodes

104
Q

What is the pathway visceral motor neurons of the ANS in the trunk (both sympathetic and parasympathetic divisions) follow?

A

Two-chain pathway
(1) Preganglionic neuron and fibers
(2) Ganglionic neuron and postganglionic fibers

(Preganglion fiber from CNS synapses with Postganglionic fiber in the Autonomic Ganglion)

105
Q

What neurotransmitter is typically released from the preganglionic fiber in the sympathetic NS? Postganglionic fiber in the sympathetic NS?

A
  • Preganglionic: Ach
  • Postganglionic: NE
106
Q

In the ___ pathway, the preganglionic fiber is short & can have multiple targets, synapses in autonomic ganglion on postganglionic fiber that also can have multiple targets

A

Sympathetic

107
Q

What neurotransmitter is typically released from the preganglionic fiber in the parasympathetic NS? Postganglionic fiber in the parasympathetic NS?

A
  • Both release Ach
108
Q

In the ___ pathway, the preganglionic fiber is long & synapses on one target, synapses in autonomic ganglion located in muscle on postganglionic fiber

A

Parasympathetic

109
Q

What arises from the neuroectoderm in the ANS?

A

Preganglionic neurons (sympathetic and parasympathetic)

110
Q

What arises from the NCC in the ANS?

A
  • Ganglionic neurons and postganglionic fibers
  • Sympathetic: trunk and collateral ganglia
  • Parasympathetic: CN ganglia in the head and neck, terminal ganglia in the trunk

MSK Exam 1 (6 decks)

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