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N - C > Neuro Embryology > Flashcards

Neuro Embryology Flashcards

1
Q

What does the Ectoderm form?

A

Epidermis

Nervous system

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2
Q

What does the Mesoderm form?

A

Bone
Muscle
Blood cells
etc

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3
Q

What does the endoderm form?

A

Gut
Pharynx
Lungs

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4
Q

What is the hypoblast?

A

Lining of the yolk sac

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5
Q

What does the epiblast form?

A

Generates all 3 germ layers from the primitive streak

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6
Q

How is the neural plate formed?

A

Thickening of ectoderm anterior to the primative node

primitive streak at one end of the trilaminar disc; neural plate at the other

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7
Q

After its formation the neural plates edges thicken and move upwards.
What does this form?

A

Neural folds

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8
Q

What is the groove in the centre of plates between the converging neural folds called?
What does this do?

A

Neural groove

divides the future left and right sides of the embryo

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9
Q

How is the neural tube formed from the neural folds?

A

Neural folds migrate towards echoer and fuse at the midline.

Neural tube zips up

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10
Q

The neural tube remains open at the anterior and posterior ends.
When do these ends close?

A

Anterior (cranial) neuropore
-about day 25

Posterior (caudal) neuropore
-about day 27

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11
Q

Describe the morphological cell changes in neurolation

A

Neural plate forms by notochord signalling ectodermal cells to become columnar

Neural tube starts to fold by cells becoming pyramidal, then triangular (notochord signals)

Fusion is by wound healing mechanisms

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12
Q

How does the ectodermal cells forming the neural tube separate from those that go onto form the epidermis?

A

Once the neural tube is fused this breaks off from the ectoderm and the remaining cell layer will form the epidermis

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13
Q

Describe neural tube closure

A

Essential for normal development and function.

  • Initiated at several points along A-P axis
  • Proceeds in cranial and caudal directions
  • Begins day 18
  • Completed by end of 4th week (around day 27)
  • Up to 5 closure sites in humans
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14
Q

Failure of neural tube to close properly leads to neural tube defects (NTDs).
Name the 3 we need to know about

A

Anencephaly
Encephalocoele
Spina bifida

These are some of the most common congenital abnormalities of the CNS

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15
Q

What is Anencephaly?

A

AKA Exencephaly or Meroencephaly

1:1500 births (4x more common in females

Failure of anterior neuropore to close so telencephalon never develops.
Skull doesnt form over area because brain doesnt form

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16
Q

What is craniorachischisis?

A

Craniorachischisis is the most severe form of neural tube defect in which both the brain and spinal cord remain open to varying degrees. It is a very rare congenital malformation of the central nervous system.

Failure of anterior neuropore and rostral neural tube to close

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17
Q

What is encephaloceole?

A

1:4000 births

Herniation of cerebral tissue through a defect in the skull
Failure in closure of rostal neural tube
Most frequent in occipital region

Variable degree of neurological deficits (depending on size and location)

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18
Q

What are the two forms of encephalocoele?

A

Occipital- encephalocoele

Fronto-nasal encephalocoele

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19
Q

What is spina bifida?

A

Defective closure of the caudal neural tube.

Affects tissues overlying the spinal cord.

Spina bifida = non-fusion of vertebral arches

Neural tissue may or may not be affected

Severity ranges from minor abnormalities to major clinical symptoms

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20
Q

What is Spina Bifida occulta?

A

Most minor form

failure for embryonic halves of vertebral arch to grow normally and fuse

Occurs in L5 and L6 vertebrea of 10% of otherwise healthy people

Usually no clinical symptoms

May result in dimple with small tuft of hair

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21
Q

What is spina bifida cystica?

A

Protrusion of spinal cord and/or meninges through the defect in the vertebral arches

Three types:

  • Spinal bifida with meningocele
  • Spina bifida with meningomyelocle
  • Myeloschisis
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22
Q

What is spinal bifida with meningocele?

A

Rarest form

Protrusion of meninges and cerebrospinal fluid

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23
Q

What is spina bifida with meningomyelocle?

A
  • Nerve roots and/or spinal cord included in the sac
  • Neurological deficits (loss of sensation and muscle paralysis
  • Area affected determined by level of lesion
  • Often associated with hydrocephalus
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24
Q

What is myeloschisis?

A

Most severe form of spina bifida.

Spinal cord in affected area open due to failure of neural folds to fuse.
-> exposed to amniotic fluid as a result causing degeneration

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25
Q

How are Neural tube defects diagnosed?

A

Prenatal Diagnosis:
-Maternal blood screening
(Indicated by high level alpha-fetoprotein (AFP) in serum)

-Amniocentisis
(high levels AFP in amniotic fluid)

-Ultrasound
(Ancephaly from 12 weeks, spina bifida from 16-20 weeks

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26
Q

How can AFP be detected in maternal blood for Neural tube defect diagnosis?

A

AFP from foetal liver leaks into amniotic fluid then into maternal blood.

Best detected at 16-20 weeks

27
Q

What reduces risk of neural tube defects?

A

Folic acid supplements

400ug/day causes 50-70% decrease in risk

28
Q

What are the risk factors for neural tube defects?

A

Genetic predisposition

Nutritional (e.g. too little folate, too much vitamin A)

Environmental (e.g. hyperthermia, taking certain drugs ( e.g. sodium valproate))

29
Q

Why shouldnt you eat liver when pregnant?

A

High level of vitamin A

30
Q

What are the 3 primary brain vesicles?

A

Prosencephalon
Mesencephalon
Rhombencephalon

31
Q

What does the Prosencephalon divide into?

A

Telencephalon

Diencephalon

32
Q

What does the Rhombencephalon divide into?

A

Metencephalon

Myelencephalon

33
Q

What are the 5 secondary brain vesicles?

A 
telencephalon
diencephalon
mesencephalon
metencephalon
myelencephalon
34
Q

When does the cephalic flexure develop?

Where does it develop?

A

End of 3rd week

Between midbrain (mesencephalon) and hindbrain (rhombencephalon)

35
Q

When does the cervicle flexure develop?

Where does it develop?

A

End of 4th week

Between hindbrain and spinal cord

36
Q

When does the pontine flexure develop?

Where does it develop?

A

5th week

In hindbrain (between metencephalon and myelencephalon)

37
Q

What does the telencephalon go onto form?

A

Cerebral hemispheres
Hippocampus
Basal ganglia

38
Q

What does the diencephalon go onto form?

A

Thalamus
Hypothalamus
Pituitary gland
Pineal

39
Q

What does the mesencephalon go onto form?

A

Midbrain

Superior and inferior colliculi

40
Q

What does the metencephalon go onto form?

A

Cerebellum

Pons

41
Q

What does the myelencephalon go onto form?

A

Medulla

42
Q

What does the lumen of the telencephalon form?

A

Lateral ventricles

43
Q

What does the lumen of the diencephalon form?

A

3rd ventricle

44
Q

What does the mesencephalon lumen form?

A

Cerebral aqueduct

45
Q

What does the metencephalon and myelencephalon lumen form?

A

4th ventricle

46
Q

When does CSF start to be produced?

A

During 5th week

Produced predominantly by choroid plexus in 3rd and 4th lateral ventricles

47
Q

Describe hydrocephalus during development

A

Hydrocephalus = Accumulation of CSF

Results in enlarged brain and cranium
Frequently due to blocked aqueduct
Prevents CSF from lateral and 3rd ventricle passing to 4th ventricle

48
Q

What are the causes of hydrocephalus during development?

A

Genetic
Prenatal viral infection
Intraventricular haemorrhage
Spinal bifida cystica

49
Q

What is the cell type of the neural tube?

A

Initially a single layer of rapidly dividing neuroepithelial cells

Then pseudostratified epithelium

Divide at ventricular surface

50
Q

Neuroepithelium produces most cells of the CNS.

What cell type does it not produce?

A

Microglia

Mesenchymal cells that migrate into CNS

51
Q

Describe the positional changes of the spinal cord during development

A

3rd month - extends the entire length of the vertebral column

Vertebral column and the fixed dura mater grow more rapidly -> cord at progressively higher levels (L2 or L3, L1 in adults)

Initially spinal nerves found at level of origin.
Become elongated forming cauda equina

Pia mater forms terminal filum

52
Q

What are sympathetic and parasympathetic ganglia formed by?

A

Neural crest cells

53
Q

How are sulci and gyri formed?

A

Surface of cerebral hemispheres initially smooth

Rapid growth results in the development of sulci and gyri.

Pattern becomes more complex as brain enlarges

54
Q

What is Lissencephaly?

A

“Smooth Brain”

  • Rare brain disorder.
  • Caused by defective neuronal migration.
  • Gyri and sulci fail to develop
  • Results in severe mental impairment, failure to thrive, seizures and abnormal muscle tone
  • Many affected children die before age 10
55
Q

What is polymicroglia?

A

Excessive number of small gyri

Variable degree of neurological problems (e.g. mental retardation, seizures, motor deficits etc)

56
Q

What is microencephaly?

A

“Small Brain”

Genetic, Drugs, Infection

Intellectual impairment, delayed motor functions/speech, hyperactivity seizures, balance and coordination problems etc

57
Q

What is Aegenesis corpus callosum?

A

Corpus callosum fails to develop.

Can occur alone or with other abnormalities

Effects range from subtle to severe

Cognitive and social difficulties -> intellectual impairment, seizures, hypotonia etc

58
Q

What is Porencephaly?

A

CSF filled cysts or cavities

Usually from postnatal stroke or infection

Delayed growth and development, seizures hypotonia, intelectual impairment

59
Q

What is Schizencephaly?

A

Large clefts or slits in the brain

Genetic, in utero stroke, infection

Paralysis, Seizures, intellectual impairment, developmental delay

60
Q

What is Diastermatomyelia?

A

Split cord malformation

Spinal cord split longitudinally into 2 parts

Usually associated with vertebral anomalies
Bony or cartilaginous process “fixes” cord in place

Scoliosis, weakness of lower extremities, hairy patch over lower back, foot deformities, loss of sensation

61
Q

What are the causes of intellectual impairment?

A

Often no obvious gross brain defects

  • Genetic (e.g. Down’s)
  • Radiation
  • Infectious agents (e.g. rubella, toxoplasmosis, CMV)
  • Birth trauma
  • Postnatal insults (head injury, infections (e.g. meningitis), lead exposure)

MATERNAL ALCOHOL ABUSE
-Foetal alcohol syndrome

62
Q

When does the development of the nervous system begin?

A

Week 3

63
Q

What forms the neurons and glia of CNS?

A

Neural tube

64
Q

What forms the neurons and glia of the PNS?

A

neural crest cells

plus non-neuronal cells

N - C (35 decks)

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