Exam #1: Development--Self Study Flashcards

1
Q

What is neurulation?

A

Process by which the trilaminar embryo internalizes its developing nervous system (ectoderm)

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2
Q

Describe the process of neurulation.

A

Gastrulation= formation of the trilaminar disc

Neurulation=

1) Mesoderm forms the notochord
2) Notochord induces the overlying ectoderm to proliferate & become the neural plate
3) Induction causes the neural plate to fold & become a central neural groove/ lateral & raised neural folds
4) Neural folds approximate & fuse, forming the neural tube

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3
Q

What is the embryological defect that causes spina bifida?

A

Incomplete fusion of the neural tube (opening into the ectoderm)

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4
Q

What are the three sources of nervous tissue in the body?

A

1) Neural tube
2) Neural crest cells
3) Ectodermal placodes

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5
Q

What tissue & cell types are derived from the neural tube?

A

CNS
Somatic motoneurons
Preganglionic ANS neurons

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6
Q

Where do most neural crest cell migrate?

A

Pharyngeal arches of the developing head & neck

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7
Q

What tissue & cell types are derived from ectodermal placodes?

A

Lens of the eye
Inner ear
Pituitary gland
Some somatic sensory ganglia of cranial nerves

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8
Q

What are neural crest cells?

A
  • A narrow strip of cells at either edge of the neural plate

- Do NOT fuse with the neural tube; instead, lie ontop of it forming “neural crest”

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9
Q

What are the derivatives of neural crest cells? Specifically, what are the neural crest derivates of the head/ neck & body?

A

Head & Neck

  • Bones, cartilage, & muscles in the head / neck
  • Neurons of sensory ganglia in CN: V, VII, VIII, IX, X
  • Odontoblasts
  • Parafollicular cells of the thyroid gland
  • Cells of aortic & carotid bodies
  • PNS ganglia of CN

Body

  • Ganglia (ANS & DRG)
  • Schwann cells
  • Adrenal medulla
  • Melanocytes)
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10
Q

During early development, what are the three divisions of the neural tube?

A

1) Prosencephalon (forebrain)
2) Mesencephalon (midbrain & cerebral aqueduct of Sylvius)
3) Rhombencephalon (hindbrain)

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11
Q

When in gestation are the three major division of the neural tube further divided?

A

Week 5

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12
Q

Which of the three major divisions further divide?

A

Prosencephalon

Rhombencephalon

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13
Q

What does the prosencephalon divide into?

A

Telencephalon–>cerebral hemispheres & lateral ventricles
Diencephalon–>thalami & 3rd ventricle

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14
Q

What does the Rhombencephalon divide into?

A
Metencephalon= pons & cerebellum/ upper 4th ventricle
Mylencephalon= medulla oblongata/ lower 4th ventricle
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15
Q

What are the three flexures in the brain?

A

1) Cephalic flexure
2) Cervical flexure
3) Pontine flexure

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16
Q

What is the Cephalic Flexure?

A

Bend in the region of the mesencephalon

17
Q

What is the Cervical Flexure?

A

Bend between the Rhombencephalon & future spinal cord

18
Q

What is the Pontine Flexure?

A

Bend in the Rhombencephalon that forms the two distinct:

  • Metencephalon (pons & cerebellum)
  • Myelencephalon (medulla oblongata)
19
Q

What are CNS neurons & neuroglia derived from?

A

Neuroepithelium of the neural tube

20
Q

What is the neuroepithelium?

A

Cells of the neural tube that form three distinct layers:

1) Ventricular
2) Intermediate/ Mantle
3) Marginal

21
Q

Describe the formation of neurons in the CNS.

A

During weeks 4-20:

1) G1 ventricular
2) Migration to marginal & S-phase
3) Return to ventricular G2
4) Mitosis in ventricular
5) Migration to mantle & differentiation into neurons
6) Axon growth into the marginal layer

*****Migratory neurons that establish synaptic contacts remain; those that don’t undergo apoptosis

22
Q

Describe the formation of neuroglia in the CNS.

A

Following the same general process as neuroblasts, glioblasts migrate into the marginal layer

23
Q

How do the three zones of the neural tube translate into the mature spinal cord?

A
Ventricular= ependymal cells that line the ventricles 
Mantle= gray matter 
Marginal= white matter
24
Q

How do microglia differ from other glial cells in the CNS?

A

Derived from bone marrow i.e. hematopoietic stem cells that migrate to the CNS; these are the macrophages of the CNS

25
Q

How does the development of the PNS differ from the CNS?

A

All PNS cells are derived from neural crest cells i.e. neurons & neuroglia of the PNS are neural crest in origin

26
Q

How do the meninges differ in their development?

A

Pia & arachnoid mater= neural crest

Dura= mesoderm

27
Q

Describe the process of myelination. Specifically address: start & end/ cell types.

A
  • Myelination begins at 16 weeks gestation
  • Ends 3 years, except frontal lobes that continue till 20s
  • CNS= oligodendrocytes
  • PNS= Schwann cells
28
Q

What is Spina Bifida Occulta?

A
  • Incomplete closure of the neural tube in 1st month of gestation
  • Overlying bone (L5/ S1) will have subtle defects
  • Mildest form that is typically asymptomatic–maybe tuft of hair on skin in lumbar region
29
Q

What is Spina Bifida Cystica?

A
  • Incomplete closure of the neural tube in 1st month of gestation
  • Herniate of nervous tissue through the bony defect causes a visible cyst-like structure in the individuals back i.e. “cystica”
  • Two subtypes:
    1) Meningocele
    2) Meningomyelocele
30
Q

What is Spina Bifida Meningocele?

A
  • Herniation of meninges through body defect

- Spinal cord intact in spinal canal

31
Q

What is Spina Bifida Meningomyelocele?

A

Herniation of meninges & spinal cord through defect

32
Q

What is Spina Bifida Myeloschisis?

A

This is the most severe form of Spina Bifida that involves an externally open & flattened spinal cord

33
Q

What supplement in early pregnancy can reduce the risk of Spina Bifida?

A

Folic acid