Week 1 CNS & Skull Embryology- Ach Flashcards

1
Q

What three embryonic sources does the entire nervous system derive from?

A

Neural tube
Neural Crest
Placodes
(all ECTODERM) in origin

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2
Q

Describe development of neural tube

A
  • Notochord stimulates ectoderm differentiation into neural plate
  • Neural folds
  • Neural groove
  • Week 4 fusion of neural tube, begins centrally and moves both directions
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3
Q

What are neuropores?

A

Located on each end of the neural tube

-communicated with amniotic fluid

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4
Q

What is the space with in the neural tube called?

A

Neural canal

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5
Q

What does the neural tube form?

A

Brain AND spinal cord

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6
Q

What are neural crest cells and what do they form?

A
  • they are motile neuroectodermal cells
  • migrate through out embryo
  • Forms PNS, and a wide variety of non-neuronal structures
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7
Q

What does the neural canal form?

A

Ventricles of the brain and Central canal of the spinal cord

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8
Q

What are the layers of the neural tube?

A
  • Ventricular layer
  • Intermediate layer
  • Marginal layer
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9
Q

What does the ventricular layer of the neural tube become?

A
  • Rapidly dividing neuroepithelial cells
  • Differentiate into neurons and glial cells
  • Become ependyma (single layer of cells lining the central canal of the spinal cord)
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10
Q

What does the intermediate layer of the neural tube become?

A
  • Will become GRAY MATTER of the spinal cord (dorsal, ventral and lateral horns)
  • NOTE: CONTAINS ALL SPINAL CORD NERVE CELL BODIES
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11
Q

What does the marginal layer of the neural tube become?

A

Becomes the WHITE matter of the spinal cord

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12
Q

What is the difference between the mitotic ability of Neurons and glial cells?

A
  • Glial cells can divide

- Neurons loose their ability when they develop processes (some rare examples they do)

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13
Q

What plates form with-in the intermediate layer of the neural tube?

A

Alar and basal plates

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14
Q

What divides the alar and basal plates?

A

Sulcus limitans

-longitudinal groove in the lumen

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15
Q

What does the alar plate form and where is it located?

A

Alar is dorsal

  • forms second order neurons
  • SENSORY/AFFERENT neurons (primarily of the dorsal horn)
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16
Q

What does the basal plate form and where is it located?

A

Basal is ventral
-Forms motor neurons of the VENTRAL (large motor neurons tha innervate skeletal muscle) and LATERAL horns (pre-ganglionic neurons of the sympathetic nervous system)

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17
Q

Why are the roof and floor plates of the neural tube important?

A

Contain NO neuroblasts

-Become routes for axons to cross the midline of the spinal cord!!!

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18
Q

Where would you find the cell bodies of motor neurons in the ventral horn? (embryonically)

A

BASAL PLATE

-will send out neurites (multiple cytoplasmic processses) that become axon/dendrites

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19
Q

Where would you find the cell bodies of sensory neurons in the dorsal horn? (embryonically)

A

ALAR PLATE

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20
Q

Where are the dorsal root ganglia derived from?

A

Neural crest

Note: the neurons are PRIMARY afferents

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21
Q

What cell myelinate the CNS and PNS

A

CNS- Oligodendrocytes

PNS- Schwann cells

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22
Q

When does myelination begin?

A

4 months of prenatal development

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23
Q

Why do you see a positive Babinski sign in infants?

A

Toes extend due to incomplete myelination. (if present in adults indicated CNS pathology)

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24
Q

At birth where is the end of the spinal cord located?

A

L2 or L3

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25
Q

In the adult where does the spinal cord terminate?

A

inferior border of L1

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26
Q

What are the three primary brain vesicles?

A

Prosencephalon (Forebrain)
Mesencephalon (Midbrain)
Rhombencephalon (Hindbrain)

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27
Q

What are the primary brain vesicles?

A

Prosensephalon
Mesensephalon
Rhombensephalon

28
Q

What are the secondary vesicles of the proensephalon? And what adult structures do they become?

A

Telencephalon- cerebral hemispheres

Dienceophalon- Thalmus

29
Q

What are the secondary vesicles of the mesencephalon? And what adult structures do they become?

A

Does not divide again

Becomes the midbrain

30
Q

What are the secondary vesicles of the Rhombencephalon? And what adult structures do they become?

A

Metenecephalon-pons and cerebellum

Myelencephalon- Medulla

31
Q

What does the telencephalon become?

A

Cerebral hemispheres

32
Q

What does the diencephalon become

A

Thalmus

33
Q

What does the mesencephalon become?

A

Midbrain

34
Q

What does the Metencephalon become?

A

Pons and cerebellum

35
Q

What does the myelencephalon become?

A

Medulla

36
Q

What constitutes the brain stem?

A

Midbrain
Pons
Medulla

37
Q

What is the hypophysis? And where does it come from?

A

PITUITARY gland!!

-dual ectodermal origin (neuro and oral ectoderm)

38
Q

What is the infundibulum?

A

Neuroectoderm that becomes the neurohypophysis (posterior lobe of the pituitary gland)

39
Q

What is Rathke’s Pouch?

A

Oral ectoderm that becomes the adenophypophysis (anterior lobe of the pituitary gland)

40
Q

What is the choroid plexus?

A

Produces CSF

forms in all ventricles

41
Q

Craniorachischisis

A

complete failure of the neural tube to close resulting in exposure of the malformed tissue to the outside of the head and body

42
Q

Congenital Megacolon (Hirschsprung’s Disease)

A

Neural crest cells fail to migrate into the colon

  • fecal retention
  • ballooning of colon
43
Q

Waardenburg Syndrome

A

occures with diffuse disruption of migration of neural crest cells

  • abnormall appearance of face, deafness
  • lack of pigmentation
  • Digestive problems
44
Q

Anencephaly and meroanencepaly

A

Failure of the rostral neuropore to close and subsequent failure of the cranial vault to form

45
Q

Occipital encephalocele

A

Defect in occipital bone, brain and meninges protrude through

46
Q

Spina Bifida (Myelomeningocele)

A

Failure of CUADAL neuropore to close

47
Q

Syringomyelia

A

Formation of “empty tube” in the spinal cord

-pathogenesis unknown

48
Q

Holoprosencephaly

A

forebrain does not divide into two hemispheres

49
Q

Hydrocephalus

A

dilations of the ventricles due to CSF overproduction, obstruction of flow, or failure to reabsorb

50
Q

Prenatal- alcohol exposure

A

Teratogenic at all times of gestation, effects depend on time of exposre

51
Q

Carniosynostosis

A

PREMATURE closure of one of more sutures that produces a misshapen skull.

52
Q

Brachycephaly

A

fusion of coronal suture

flat-head

53
Q

Oxycephaly, turricephaly or acrocephaly

A

Fusion of coronal and lamboidial sutures produces “tower skull”

54
Q

Plagiocephaly

A

fusion of coronal and lamboidal sutures unilaterally

-produces an asymmetrical skull

55
Q

Scaphocephaly

A

fusion of the sagittal suture produces a long front-to-back diameter skull

56
Q

Microcephaly

A

is a small head due to brain that fails to grow

57
Q

Cranioschisis

A
  • failure of rostral neuropore to close

- skull defect through which the meninges and/or brain herniate

58
Q

Apert Syndrome

A

Autosomal dominant genetic disorder characterized by craniosynostosis and other congenital abnormalities (syndactylyl of hands and feet, mental retardation)

59
Q

Acrania

A

No skull

60
Q

Where are the bones of the skull derived from?

A

Paraxial mesoderm

Neural crest

61
Q

What type of ossification occurs in the skull base?

A

Endochondrial ossification

62
Q

What type of ossificaiton occurs in the cranial vault

A

Membranous ossification

63
Q

What is special about the occipitial bone?

A
  • Part of bone is intramembranous ossificaiton

- Part of bone is endochonrial ossification

64
Q

What is the neurocranium?

A

brain case, base of skull

65
Q

What is the viscerocranium

A

Face, contains taste, sight and smell organs

66
Q

What contributes to mesenchyme of the neurocranium?

A

BOTH somites (paraxial mesoderm) and NEURAL CREST contribue to mesenchyme

67
Q

What contributes to mesenchyme of the viscerocranium?

A
  • forms around the gut tube, rostral to the notocord
  • Neural crest cells migrate into the paryngeal arches where they form mesenchyme to form the bones of the face, hyoid and middle ear bones.