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The Nervous System: Pathology > Embryology and Congenital Malformations > Flashcards

Embryology and Congenital Malformations Flashcards

(101 cards)

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1
Q

From what layer of cells does the neural tube develop from

A

The ectoderm

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2
Q

When does neural tube formation begin

A

Beginning of the third week (during gastrulation)

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3
Q

What occurs in neuralisation

A

The ectoderm thickens forming the neural plate at the cranial end of the embryo (ad grows down to caudal end)

The lateral edges then become elevated and move together to from neural folds

The neural folds migrate in the middle of the embryo and fuse together forming the neural tube

The neural tube extends in both cranial and caudal direction

The cells cells on the crest of the neural tube detach

The neural tube closes

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4
Q

What does the cranial end of the embryo go on to develop

A

The future brain

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5
Q

What does the cauda end of the embryo develop into

A

Future spinal cord

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6
Q

What does detached cells to the neural tube from and develop into

A

Form neural crest leading to the formation of the peripheral nervous system

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7
Q

What is is essential for normal development and function

A

Neural tube closure - completes the process

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8
Q

When does neural tube closure begin and end for cranial and caudal

A

Begins day 18

Cranial closes - 25 days (18-20 somite stage)

Caudal closes -27 days

Completely closed by the 4th week

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9
Q

How many closure sits are present in humans

A

5

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10
Q

Failure of neural tube to close properly results in neural tube defects

A 
Anencephaly
Encephalocoele
Spina bifida
Craniorachischisis
Iniencephaly
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11
Q

What is the presentation of anencephaly

A

The skull is absent and so is cerebral hemisphere of the brain

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12
Q

When does anencephaly occur

A

23-26 days after conception

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13
Q

What is the cause of Craniorachischisis

A

Failure of neural tube closure along entire neuroaxis

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14
Q

What is the presentation of encephalocoele

A

Hernatio of cerebral tissue through a defect in the skull

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15
Q

What causes encephalocoele

A

Failure in closure of rostral neural tube

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16
Q

What is the affect of encephalocoele

A

Variable degree of neurological deficits

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17
Q

What is the affect of anecephaly

A

Incompatible with life

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18
Q

What is the two shapes of encephalocoele

A

Occiittal encephalocele (most frequent)

Fronto-nasal encephalocele

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19
Q

What is the presentation of Iniencephaly

A

Occipital and spine defect with extreme retroflexion of the head

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20
Q

What is the cause of spina biffida

A

Defective closure of the caudal neural tube

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21
Q

What does spina bifida affect

A

Tissue overlying spinal cord

Potential may affect neural tissue

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22
Q

What is the two forms of spin bifida

A

Spina bifida occulta - minor/closed

Spina bifida cystica - severe/open

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23
Q

What is the cause of spina bifida occulta

A

Failure of the embryonic halves of the vertebral arch to grow normally and fuse

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24
Q

What is the presentation of spina bifida occulta

A

Dimple with a small tuft of hair typically occurring and L5 /L6 vertebrae

No clinical symptoms

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25
What is the cause of spina bifida cystic
Protrusion of spinal cord and/or meninges through the defect in the vertebral arches
26
What is the three forms of spina bifida cystic
Spina bifida with meningocele Spina bifida with meningomyelocele Myeloschisis
27
What occurs in Spina bifida with meningocele
protrusion of meniges and cerebrospinal fluid through a defect in spine
28
What occurs in spina bifida with meningomyelocele
Open spinal cord with meningeal cyst with nerve roots/spinal cord included in the sac
29
What are the neurological defecits of spina bifida with meningomyelocele
Loss of sensation and muscle paralysis Are affected determined by level of lesion
30
What is spina bifida with meningomyelocele associated with
Hydrocephalus
31
What occurs in myeloschisis
Spinal cord in affected is open de to failure of neural tubes to fold
32
What is the most severe spina biffida
Myeloschisis
33
What is taken in prenatal care to prevent neural tube deficits
Folic acod
34
What are the three prenatal diagnosis for neural tube defects
Maternal blood screening (16-20 weeks) Amniocentesis Ultrasound
35
What is the market found in amniocentesis and maternal blood screen for neural tube deficits
High levels of Alpha fetoprotein in serum/amniotic sac
36
What is the origin of AFP
From foetal liver leking into amniotic sac then into maternal blood
37
When is ancephaly and spina bifida best detected with an ultrasound
Ancephaly - from 12 weeks Spina bifida - from 16-20 weeks
38
What is the risk factors for neural tube deficits
Genetic predisposition Nutritional - to little folate - to much vitamin A Environmental - hyperthermia - sodium valproate
39
What do the brain vesicles formation co inside with
Closure of the anterior neuropore (roughly day 25 days)
40
What are the 3 primary brain vesicles formed by the end of the 4th week
Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain)
41
What is the secondary vesicles produced from the proscencephala
Telencephalon Diencephalon
42
What is the secondary vesicle produce from the rhombencephalon
Metencephalon Myencephalon
43
The primary vesicle mesencephalon doesn't further divide, what part of the brain develops from it
Midbrain
44
What part of the brain develops from the Telencephalon
Cerebral hemispheres Hippocampus Basal ganglia
45
What part of the brain develops from the diencephalon
Thalamus hypothalamus Pituitary gland Pineal
46
What part of the brain develops from the metecenphalon
Cerebellum | Pons
47
What part of the brain develops from the myelencephalon
Medulla
48
What is the three flexures in brain vesicle development
Cephalic Cervical Pontine
49
When and where is the cephalic flexure produced
End of the 3rd week between the mesencephalon (midbrain) and the rhombencephalon (hindbrain)
50
When and were is the cervical flexure formed
End of 4th week | between hindbrain and spinal cord
51
When and where is the pontine flexure formed
5th week | Between mesencephalon and myelecephalon (in the hindbrain)
52
What forms the ventricular system
Lumen of the neural tube
53
When does cerebral spinal fluid begin to from
5th week
54
Where is cerebral spinal fluid produced
By the choroid plexus
55
Where is the choroird plexus formed
Lines the lateral ventricle Lines the third ventricle 4th ventricle
56
Where does the cerebral spinal fluid drain
Into the subarachnoid space via the opening of the roof in the 4th ventricle some also flows through the central canal of the spinal cord
57
Where is CSF absorbed
Absorbed into the dural venous sinus system via the arachnoid villi
58
What is the 4 ventricle produced
Lateral ventricle 3rd ventricle Cerebral aqueduct 4th ventricle
59
What connects the lateral and third ventricle
Intraventricular foramina of monro
60
What is hydrocephalus
Accumulation of cerebral spinal fluid resulting in enlarged brain and cranium
61
What is the frequent cause of hydrocephalus
Blocked aqueduct preventing CSF passing from lateral and 3rd ventricle to fourth so cant drain properly
62
What is the aetiology of a blocked aquedcut
Genetic Prenatal viral infection Intracentricular haemorrhage Spina bifida cystica
63
When does production of neuronal cells ( neurones and gila) and their connections begin
During early embryogenesis and continue into post natal period
64
What is the neural tube initially
A single layer of rapidly dividing neuroepithelial cells
65
What is the epithelium of the neural tube
Pseudo-stratified epithelium
66
Where does neuroepithelial cells divide
The ventricular zone that lines the ventricular system
67
What kind of cells are principally neuroepithelial cells before they divide
Radial gilal cells
68
The neuroepihelai cells produce most cells of the CNS, name the cells produces
Neurone Astrocytes Ogliodendrocye
69
Once the radial gila/neuroepithelial cells are finished divided what do they become
Ependymal cells (type of gilal cells that line the ventricles)
70
What zone in the spine of you find differentiated neurones and axons
Mantle layer - differentiated neurones Marginal layer - axons
71
What is the exception of a neuronal cell not produced by the neuroepithelial cells and what is its origin
Microgilia - produced from mesenchymal cells that migrate into the CNS
72
What does the neuronal crest cells go on to develop
PNS neuronal cells Plus non neuronal cells: - Melanocytes - Bone and cartilage of the face and skull - Adrenal medulla - Meninges
73
What does the sensory and motor component of the spinal cord embryonically derived from
Sensory - Neural crest cells Motor - neural tube
74
What two process extend from the neuronal crest cells development of the spinal cord
Peripheral - due to body Central - due to dorsal horn of spinal cord
75
What is the initial position of the spinal cord in the 3rd month
The spinal cord extends the entire length of the vertebral column and initially spinal nerve found at level of origin
76
How does the position of the spinal cord change from 3rd month to birth
Spinal cord becomes elongate forming cud equine Pia matter then extend forming terminal filum
77
What does the autonomic nervous system sympathetic and parasympathetic ganglia embryonically derived from
Neuronal crest cells
78
What does rapid development of the cerebral hemispheres lead to the formation of
Sulci (grooves) and gyri (elevations) | With the pattens becoming more complex as the brain enlarges
79
What are to congenital abnormalities to do with sulci and gyro
Lissencephaly Polymicrogyria
80
What is the cause and presentation of lissencephaly
Caused by defective neuronal migration leading to the gyro and sulk failing to develop
81
What is the symptoms and signs seen with lishencephaly
Severe mental impairment Failure to thrive seizures abnormal muscle tone
82
What is the cause of polymicrogyria
Excessive number of small gyro
83
What is the symptoms and signs seen with pylormicrogyri
Neurological problems: Mental retardation, seizures, Motor defecits
84
Name 6 congenital abnormalities in the nervous system
Micricephaly Agenesis of corpus callous Porencephaly Schizencephaly Diastematomyelia Intellectual impairment
85
What is microcephaly
Abnormal smallness of the head, a congenital condition associated with incomplete brain development
86
What is the causes of microcephaly
Genetic drugs Infection eg zika virus
87
What is the symptoms of microcephaly
Intellectual impairment, Delayed motor functions/speech, Hyperactivity, Seizures, Balance/co-ordination problems
88
What is the subtle to severity of corpus callous
Cognitive and social difficulties to intellectual impairment, seizures and hypotonia
89
What is the characteristic of porencephaly
cysts or cavities within the cerebral hemisphere
90
What is the cause of porencephaly
Postnatal stroke | Infection
91
What is the symptoms of porecephaly
delayed growth and development seizures hypotonia intelectual impairment
92
What is the characteristics of schizencephaly
Large clefts or slits in the cerebral hemisphere
93
What is the cause of schizencephaly
Genetic In utero stroke Infection
94
What is the symptoms of schiecenchphaly
Paralysis seizures intellectual impairment developmental delay
95
What is Diastematomyelia
Split cord malformation where the spinal cord splits longitudinally into two parts
96
What is usually associated with Diastematomyelia
Vertebral abnormalities
97
What "fixes" the vertebral abnormalities in Diastematomyelia
Bones or cartilaginous process fixes the cord in place
98
What is the symptoms of Diastematomyelia
Scoliosis Weakness of lower extremities Hairy patch over lower back Foot deformities Loss of sensation
99
There is often no obvious gross defects in intellectual impairment, what is the potentially causes
Genetics Radiation Infectious agnets (rubella, toxoplasmosis, cytomegalovirus) Birth trauma Post natal insults (head injury, infections, lead exposure)
100
What is the commonest cause of intellectual impairment
Maternal alcohol abuse
101
What forms the vesicles
The expansion and the bending of the neural tube

The Nervous System: Pathology (25 decks)

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