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USMLE Neurology > Embryology > Flashcards

Embryology Flashcards

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USMLE® Step 1 flashcards
1
Q

What is gastrulation (occurs in 3rd week)?

A

The 3 primary germ layers form (ectoderm, mesoderm, endoderm)

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2
Q

What process does the notochord initiate?

A

Neuralation
- Induces overlying ectoderm to become neural plate

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3
Q

What does the notochord form into later?

A

Nucleus pulposus

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4
Q

The ectoderm forms a layer around the other germ layers, why is this?

A

It forms into the skin later

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5
Q

Somites are formed from what germ layer and then turn into what structures?

A

Formed from mesoderm and turn into bone muscle and cartilage

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6
Q

The neural plate (ectoderm) folds inwards to create what?

A

The neural plate folds inwards to create the neural fold it then folds in further to create the neural tube

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7
Q

What does the neural plate give rise to?

A

The neural tube and neural crest cells

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8
Q

At what day does the neural plate form and at what day does it become the neural tube?

A
  • Day 18 = Neural plate
  • Day 21 = Neural tube
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9
Q

The alar plate is located dorsally and relays what information?

A

Sensory

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10
Q

The basal plate is located ventrally and relays what information?

A

Motor

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11
Q

What is the alar (dorsal, sensory) plate regulated by?

A

TGF-B (including bone morphogenic protein, BMP)

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12
Q

What is the basal (ventral, motor) plate regulated by?

A

SHH

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13
Q

What are the 3 primary vesicles of the brain?

A
  • Forebrain
  • Midbrain
  • Hindbrain
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14
Q

What are the 5 secondary vesicles?
- What primary vesicles are these derived from?

A
  • Telencephalon (forebrain)
  • Diencephalon (forebrain)
  • Mesencephalon (midbrain)
  • Metencephalon (metencephalon)
  • Myencephalon (hindbrain)
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15
Q

What does the telencephalon become?

A
  • Cerebral hemispheres
  • Basal ganglia
  • Lateral ventricles
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16
Q

What does the diencephalon become?

A
  • Thalamus
  • Hypothalamus
  • Retina
  • 3rd ventricle
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17
Q

What does the mesencephalon become?

A
  • Midbrain
  • Cerebral aqueduct
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18
Q

What does the metencephalon become?

A
  • Pons
  • cerebellum
  • Upper part of 4th ventricle
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19
Q

What does the myelencephalon become?

A
  • Medulla
  • Lower part of 4th ventriclde
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20
Q

The neuroepithelia in the neural tube become what?

A
  • CNS neurons
  • CNS glial cells (astrocytes, oligodendrocytes and ependymal cells)
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21
Q

What cells/structures are derived from the neural crest?

A
  • PNS neurons (DRG, autonomic ganglia [sympathetic, parasympathetic, enteric])
  • PNS glial cells (schwann cells, satellite cells)
  • Adrenal medulla
  • Melanocytes
  • Face/ brachia arch mesenchyme
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22
Q

What cells in the NS are derived from the mesoderm?

A

Microglia (like macrophages)

23
Q

What is Holoprosencephaly?

A

Failure of embryonic forebrain (prosencephalon) to seperate into 2 cerebral hemispheres - 1 hemisphere

24
Q

What gene mutation is thought to cause Holoprosencephaly?

A

SHH (usually occurs in weeks 3-4)

25
Q

What other developmental defects and diseases are associated with Holoprosencephaly?

A
  • Cleft lip/palate
  • Cyclopia
  • Pituitary dysfunction (diabetes insipidus)
  • Patau syndrome
  • Maternal alcohol use
26
Q

What substance is associated with Holoprosencephaly?

A

Alcohol

27
Q

What will be see o MRI in Holoprosencephaly?

A
  • Monoventricle
  • Fusion of basal ganglia
28
Q

What is Lissencephaly and what is it caused by?

A

Smooth brain that lacks sulci and gyri
- Failure of neuronal migration

29
Q

What conditions is Lissencephaly associated with?

A
  • Microcephaly
  • Ventriculomegaly
  • Hydrocephalus
30
Q

What are the 3 posterior fossa malformations?

A
  • Chiari I malformation
  • Chiari II malformation
  • Dandy-Walker malformation
31
Q

What is Chiari I malformation?

A

Ectopia of cerebellar tonsils inferior to foramen magnum

32
Q

What can a Chiari I malformation present with?

A
  • Asymptomatic often in childhood
  • Headaches
  • Cerebellar symptoms
  • Spinal cavitations - syringomyelia
33
Q

What structures are herniated in Chiari II malformation?

A
  • Cerebellum (vermis and tonsils)
  • Medulla
34
Q

What can Chiari II malformation cause?

A
  • Noncommunicating hydrocephalus
  • Aqueductal stenosis
  • Lumbosacral myelomeningocele (may present with paralysis/sensory loss at and below the level of the lesion)
35
Q

What is a Dandy-Walker malformation?

A

Agenesis of cerebellar vermis -> cystoc enlargement of 4th ventricle that fills the enlarged posterior fossa

36
Q

What conditions is Dandy-Walker malformation associated with / what does it cause?

A
  • Noncommunicating hydrocephalus
  • Spina bifida
37
Q

What does the 1st pharyngeal arch form on the tongue?

A

Ant 2/3s (sensation via V3, taste via VII)

38
Q

What do the 3rd and 4th pharyngeal arches form on the tongue?

A

Posterior 1/3 (sensation and taste via CNIX)

39
Q

What does the Hyoglossus muscle do?

A

Retracts and depresses tongue

40
Q

What does the Genioglossus do?

A

Protrudes tongue

41
Q

What does the Styloglossus do?

A

Draws sides on tongue upwards to create a trough for swallowing

42
Q

What are the muscles of the tongue?

A
  • Hyoglossus
  • Genioglossus
  • Styloglossus
  • Palatoglossus
43
Q

What does the palatoglossus do and what is it innervated by?

A

Elevates posterior tongue during swallowing

44
Q

What fails to fuse in a neural tube defect?

A

Neuropores

45
Q

When are neuropores meant to fuse by (what week)?

A

4th

46
Q

What are NT defects caused by (what incr risk from mother)?

A

Diabetes and folate deficiency

47
Q

What will amniotic fluid show in NT defects?

A

`- Incr AFP (also in serum)
- Incr AChE (acetylcholinesterase)

48
Q

Which type of neural tube defect will have a normal AFP level in mother?

A

Spina bifida occulta

49
Q

What is spina bifida occulta and what are the unque features of it?

A
  • Neuropore doesnt close but no herniation
  • Dura is intact
  • Lower vertebral levels
  • Skin dimple or tuft of hair at level
50
Q

What herniates through the bony defect in meningocele?

A

Meninges but not neural tissue

51
Q

What herniates through the bony defect in myelomeningocele?

A

Meninges and neural tissue (eg caudia equina) herniate through boney defect

52
Q

What is myeloschisis (rachischisis)?

A

Exposed, unfused neural tissue w/o skin/meningeal covering

53
Q

What is anencephaly?

A

Failure of rostral neuropore to close -> no forebrain, open calvarium

54
Q

What finding will the mother have if her child has anencephaly?

A

Polyhydramnios

USMLE Neurology (19 decks)

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