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Histo (VM1 Fall) > Exam 2 - Lecture 27 (Devel. of Nervous System) > Flashcards

Exam 2 - Lecture 27 (Devel. of Nervous System) Flashcards

1
Q

What is another name for monozygotic twins?

A

identical twins

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2
Q

What are the 3 ways/stages in which monozygotic twins can occur?

A
  1. Early blastomeres split apart (2-8 blastomeres when divided)
  2. 2 inner cell masses develop in the blastula
  3. 2 primitive streaks form in the same inner cell mass
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3
Q

In the earliest possible stage that monozygotic twins develop, what is the state of amniotic cavities and placenta?

A

Separate amniotic cavities, no placental overlap

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4
Q

In the middle stage that monozygotic twins develop, what is the state of amniotic cavities and placenta?

A

Shared placenta (surrounded by same trophoblasts), separate amniotic cavities

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5
Q

In the latest possible stage that monozygotic twins develop, what is the state of amniotic cavities and placenta?

A

Same placenta (surrounded by same trophoblasts), same amniotic cavities

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6
Q

Which stage of monozygotic twin formation is the most common in humans?

A

2nd stage (2 inner cell masses develop in the blastula)

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7
Q

What is the least common and worst stage of monozygotic twin formation?

A

3rd stage (2 primitive streaks form); one twin almost always dies; can lead to cojoined twins

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8
Q

What is an amorphous globosus?

A

Free, asymmetrical twins

  • Amorphous glob surrounded by hair
  • Inside has c.t. and a tooth
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9
Q

What matter is on the inside portion of the spinal cord?

A

Gray

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10
Q

What matter is on the outer portion of the spinal cord?

A

White

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11
Q

What cells are in the grey matter?

A

Neuronal cell bodies and glial cells

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12
Q

What structures are predominantly found in white matter?

A

Axons and myelin

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13
Q

What gives white matter its white appearance?

A

High lipid content of myelin

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14
Q

What two things join to form a spinal nerve?

A

Dorsal root and ventral root

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15
Q

Where do ascending tracts of the nervous system go?

A

Spinal cord –> brain

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16
Q

Where do descending tracts of the nervous system go?

A

Brain –> spinal cord

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17
Q

What is the first organ system to initiate differentiation?

A

CNS

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18
Q

What forms postnatally in puppies and kittens that form prenatally in foals and calves?

A

cerebellum

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19
Q

If there is a disruption in the formation of the brain and spinal cord, what other 3 things can be affected?

A

vertebrae, head, face

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20
Q

When does the neural tube begin developing?

A

2-3 days after gastrulation

21
Q

From what germ layer is the neural tube derived?

A

ectoderm

22
Q

What are the 4 steps of neural tube formation?

A
  1. Notochord releases factors to begin differentiation of surface ectoderm
  2. Surface ectoderm differentiates into the neural plate
  3. Neural folds come up to meet each other while neural groove descends into embryo as a neural tube
  4. Neural crest cells separate and also descend into the embryo
23
Q

What is the purpose of the cavity of the neural tube?

A

Communicates with amniotic cavity via rostral and caudal neuropores; helps get rid of waste and bring in nutrients

24
Q

What is derived ONLY from cranial neural crest cells?

A

Sensory ganglia of cranial nerves V VII, and X.

25
Q

What 3 things are derived from BOTH cranial and spinal neural crest cells?

A
  1. Schwann cells
  2. Enteric ganglia
  3. Parasympathetic ganglia
26
Q

What 3 things are derived ONLY from spinal neural crest cells?

A
  1. All dorsal root ganglia
  2. Sympathetic ganglia
  3. Adrenal medulla
27
Q

What is a ganglion?

A

Collection of neuronal cell bodies outside of the CNS.

28
Q

Where are ependymal cells located in the neural tube?

A

Line the cavity

29
Q

Where is the neural canal located in the neural tube?

A

In the center

30
Q

Where is the mantel layer located in the neural tube?

A

Includes alar plates and basal plates on either side of the neural canal

31
Q

Where is the alar plate located in the neural tube and what is its function?

A

Mass of cells closest to the roof plate; sensory

32
Q

Where is the basal plate located in the neural tube and what is its function?

A

Mass of cells closest to the floor plate; motor and autonomics)

33
Q

What is the marginal layer of the neural tube?

A

Axons projecting out from mantel layer

34
Q

What plate is the dorsal horn derived from?

A

Alar plate

35
Q

What plate is the ventral horn derived from?

A

Basal plate

36
Q

What two plates do not really move that much and what is the result?

A

Roof and floor plates; result in the dorsal median sulcus and ventral median fissure

37
Q

Where is the dorsal root ganglion derived from?

A

Neural crest cells

38
Q

What are the steps of ventral root formation?

A

Neurons in the ventral horn project their axons out to meet a target.

39
Q

What are the steps of dorsal root formation?

A

Neuronal cell bodies in the dorsal root ganglion project their axons to the dorsal horn and also out to the periphery to meet a target.

40
Q

How can multiple nerves innervate the same muscle?

A

Muscle bundles of the early spinal cord can fuse together to form a single muscle, but each bundle is attached to its own spinal nerve.

41
Q

What are the 4 steps to how the spinal cord changes in position?

A
  1. Root of sacral nerves join with bundles of muscle just on the outside of the vertebrae
  2. Vertebral column begins to grow faster than the spinal cord
  3. Spinal cord moves cranially
  4. Roots of nerves elongate, forming “cauda equina”
42
Q

What are the 3 types of spina bifida discussed in class?

A
  1. Spinal bifida occulta
  2. Meningomyocele
  3. Myeloschisis
43
Q

What is the most benign form of spina bifida and what happens?

A

Spinal bifida occulta; vertebral arch is missing, typically on one vertebrae (can sometimes be on 2 consecutive vertebrae)

44
Q

What happens in spina bifida?

A

Development of vertebral arch is impacted

45
Q

What is the most common type of spina bifida in animals and what happens to the animal?

A

meningomyocele; paralysis

46
Q

What happens in meningomyocele?

A

Spinal cord and meninges protrude up into the space where the vertebral arch should be

47
Q

What is the most severe form of spina bifida and what happens?

A

Myeloschisis; neural tube doesn’t close (animal can never walk)

48
Q

What is the fate of animals with spina bifida?

A

Are typically euthanized because of the difficulties associated with the condition.

Histo (VM1 Fall) (27 decks)

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