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Year 2 - Nervous > Embryology > Flashcards

Embryology Flashcards

1
Q

What week does gastrulation occur and therefore what week does CNS begin to appear

A

3

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2
Q

Neural tube initially remains open at its anterior and posterior ends as what

A

Anterior and posterior neuropores

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3
Q

What week do the 3 primary brain vesicles form

A

4

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4
Q

What week do the 3 primary vesicles subdivide into 5 secondary vesicles

A

5

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5
Q

What flexure divides the mesencephalon and rhombencephalon

A

Cephalic

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6
Q

What flexure divides the rhombencephalon and spinal cord

A

Cervical

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7
Q

What flexure divides the metencephalon and myelencephalon

A

Pontine

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8
Q

What week does CSF formation begin

A

5

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9
Q

What do neural crest cells form

A

PNS neurons and glia

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10
Q

What week does cortical folding occur to form sulci and gyri

A

26

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11
Q

Name 3 neural tube defects (due to failure of neural tube to close)

A

Anencephaly/exencephaly
Encephalocele
Spina bifida

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12
Q

What causes anencephaly

+ what is the resulting damage

A

Failure of anterior neuropore to close

Skull fails to form, brain tissue degenerates

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13
Q

What is craniorachischisis

A

Failure of neural tube to close along entire neuroaxis

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14
Q

What causes encephalocele

+ what is it

A

Failure of anterior neural tube to close

Herniation of cerebral tissue through a defect in the skull

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15
Q

What causes spina bifida

A

Failure of caudal neural tube to close

Non-fusion of the vertebral arches

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16
Q

Name the 2 types of spina bifida

A

Spina bifida occulta

Spina bifida cystica

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17
Q

Name other congenital brain abnormalities

A

Lissencephaly - smooth brain (no gyri or sulci)

Polymicrogyria

Microcephaly

Agenesis corpus callosum

Porencephaly

Schizenecephaly

Diastematomyelia (split cord malformation)

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18
Q

When does neural tube fuse/close

-when does it begin + when is it completed by

A

Begins day 18 and complete by end of 4th week

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19
Q

When the 3 germ layers (ectoderm, mesoderm, endoderm) have formed, cells from primitive streak continue to sink down to form what

A

Notochord (solid tube of cells in the midline)

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20
Q

What does the notochord do

A

sends out signals to ectodermal cells in the midline, causing the cells there to thicken and influencing a neural plate to form

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21
Q

Neural plate eventually sinks down and forms a dip in the midline of the ectoderm layer then…

A

Surface ectoderm comes together centrally and encloses the neural tube

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22
Q

Name the 3 primary brain vesicles

A

forebrain/rosencephalon,

midbrain/mesencephalon,

hindbrain/rhombencephalon

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23
Q

Name the 5 secondary brain vesicles

A

Forebrain:
Telencephalon,
Diencephalon,

Midbrain:
Mesencephalon,

Hindbrain:
Metencephalon, Myelencephalon

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24
Q

Optic vesicles grow laterally from which brain vesicle of the neural tube

A

Diencephalon

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25
Q

Optic vesicles eventually develop into what

A

Eyeballs

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26
Q

When the optic vesicles reach surface ectoderm, it sends signals to the surface ectoderm inducing what to happen

A

surface ectoderm to thicken –> forming the lens placode

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27
Q

Define placode

A

thickening of embryological tissue

28
Q

Optic cup is connected to neural tube by what

A

Optic stalk (future CN II)

29
Q

10th layer of retina is formed by inner or outer layer of optic cup

Other 9 layers of the retina are formed by inner or outer layer of optic cup

A potential space therefore sits between the inner 9 layers and the outer 10th layer which is important clinically because it gives rise to…

A

outer

inner

Diseases like retinal detachment

30
Q

5 histological layers of the cornea

A 
Epithelium
Bowman's membrane
Stroma
Descemet's layer
Endothelium
31
Q

What type of epithelium covers the cornea

A

Stratified squamous non-keratinised

32
Q

What is bowman’s membrane

A

Basement membrane of corneal epithelium

33
Q

What is the stroma of the cornea made of

A

REGULARLY ARRANGED COLLAGEN FIBRES –> making cornea TRANSPARENT

34
Q

What is descemet’s layer

A

Basement membrane of the endothelium

35
Q

Endothelium v epithelium

A

Endothelium is just epithelium lining the inside of a surface

36
Q

If cornea is avascular, where does it get its nutrition from

A

from AH and blood vessels at the side of it

37
Q

Which of the 3 germ layers does the CNS develop from

A

Ectoderm

38
Q

Telencephalon becomes the (3)

A

Cerebral hemispheres
Hippocampus
Basal ganglia

39
Q

Metencephalon becomes the (2)

A

Cerebellum

Pons

40
Q

Myelencephalon becomes the

A

medulla

41
Q

Lumen of neural tube forms the

A

ventricular system

42
Q

Name a genetic cause of hydrocephalus

A

Congenital aqueductal stenosis

43
Q

Neural tube is lined with what epithelium

A

Pseudostratifed

44
Q

Neural tube is initially a single layer of rapidly dividing neuroepithelial cells

Neuroepithelium goes on to produces most cells of the CNS including… (4)

A

Neurons
Astrocytes (glia)
Oligodendrocytes (glia)
Ependymal cells (glia)

45
Q

Microglia ARE NOT derived from neuroepithelial cells, instead they’re derived from…

A

MESENCHYMAL CELLS that migrate into CNS

46
Q

Neural tube also forms non-neuronal cells such as (2)

A

Melanocytes

Adrenal medulla

47
Q

Neural crest cells are derived from… and break away from it by undergoing a what transition

A

neural ectoderm

epithelial to mesenchyme transition

48
Q

Neural crest cells migrate through the neural tube to form things such as

A

DRG

Autonomic ganglia

49
Q

Neural crest cells form the motor or sensory component of spinal nerves

A

sensory

50
Q

Cortical folding (where the brain develops sulci and gyri) occurs at what week + purpose of this folding

A

26

Minimises brain volume and bring together brain regions that would otherwise be far apart

51
Q

Describe spina bifida occulta (a type of spina bifida)

  • failure of what to fuse
  • usually occurs in which vertebral levels
  • symptoms/signs
A

Most common but most minor

Failure of embryonic halves of vertebral arch to grow normally and fuse
Occurs in L5 & L6 vertebrae
No symptoms
SIGN SOMETIMES - dimple in back with a bushy growth of hair

52
Q

Spina bifida cystica is what

A

protrusion of spinal cord through the defect in the vertebral arches

53
Q

3 subtypes of spina bifida cystica

A

Spina bifida with meningocele
Spinda bifida with meningomyelocele
Myeloschisis (most severe)

54
Q

Prenatal diagnostic investigations of spina bifida (3)

A

Maternal blood screening
Amniocentesis
Ultrasound

55
Q

How can maternal blood screening diagnose spina bifida

A

Neural tube defect would be indicated by HIGH ALPHA FETOPROTEIN (AFP) in blood

56
Q

How early can spina bifida be detected in utero

A

16-20 wks

57
Q

How can amniocentesis diagnose spina bifida

A

high levels of alpha fetoprotein (AFP) in amniotic fluid (foetal liver leaks into amniotic fluid)

58
Q

Pregnant women are advised to take what to prevent neural tube defects

A

FOLIC ACID SUPPLEMENTS

59
Q

Risk factors of neural tube defects

A

Genetic predisposition, e.g. abnormal fold acid metabolism

Poor nutrition, e.g. too little folate, teratogens

Environmental, e.g. hypothermia, toxic drugs

60
Q

What is lissencephaly

A

‘smooth brain’

  • no formation of gyri or sulci
  • -> severe mental impairment
61
Q

What is polymicrogyria

A

excessive number of small gyri –> variable neuro problems

62
Q

What is microcephaly

A

Head circumference smaller than usual

-usually have a small brain and intellectual disability

63
Q

What isa genesis corpus callosum

A

Complete or partial absence of the corpus callosum

64
Q

What is porencephaly

A

CSF FILLED CYSTS OR CAVITIES in the brain

extremely rare

65
Q

What is schizencephaly

A

Loss of brain tissue –> large clefts/spaces in brain

often presents with seizures, mental retardation, hemiparesis

66
Q

What is diastematomyelia

A

Split cord malformation

-spinal cord splits longitudinally into 2

67
Q

Causes of brain defects

A 
Genetic 
Infection - e.g. rubella
Radiation
Maternal alcohol abuse
Drugs

Year 2 - Nervous (39 decks)

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