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Embryology PHM > Development of Nervous system > Flashcards

Development of Nervous system Flashcards

1
Q

Part of neural tube forming the brain extends up to which somites.

A

4th pair of somites

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2
Q

Point at which neural tube first closes

A

Cervical region along 4th to 6th somite pairs

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3
Q

Describe origin and destination of mantle layer of spinal cord

A

Originates from neuroblasts that form a layer around the neural epithelium
Destined to form gray matter

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4
Q

Describe formation of layers of spinal cord

A

The neuroepithelial layer is formed by pseudostratified columnar neuroepithelial cells. These cells divide and some of them differentiate into neuroblasts.
Neuroblasts divide to form a layer around the neural tube called mantle layer
They then send out their fibers which form the marginal layer that will give rise to white matter

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5
Q

By which week does neural tube have 3 layers?

A

Week 5

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6
Q

How is sulcus limitans produced?

A

Differential thickening of neural tube wall

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7
Q

Basal plate of neural tube gives rise to

A

Ventral and Lateral gray horns

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8
Q

Function of roof and floor plates

A

act as pathways for decussating fibers and connect the plates on the opposite sides(basal and alar plates)

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9
Q

True or false: Neuroblasts are a result of meiosis of neuroepithelial cells

A

False: Neuroblasts are a result of mitosis of neuroepithelial cells

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10
Q

What temporary changes to neuroblasts undergo when they migrate to the mantle layer?

A

Become apolar and rounded

*NOTE: Permanently loose the temporary dendritic processes they once sent off to lumen of neural tube

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11
Q

What type of neuron is a neuroblast?

A

multipolar

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12
Q

Precursors of glial cells

A

Glioblasts

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13
Q

How does the fate of glial cells change from when they are in the mantle layer and when they are in the marginal layer?

A

In the mantle layer, they differentiate into oligodendroblasts and astroblasts

In the marginal layer, they will differentiate into microlial

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14
Q

Origin of ependymal cells

A

arise from neuroepithelial cells when they stop giving off neuroblasts and glioblasts, then they give rise to ependymal epithelium

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15
Q

What type of neuron is a spinal ganglia

A

unipolar

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16
Q

True or false: Spinal ganglia are initially bipolar, but processes fuse and they become unipolar

A

True

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17
Q

Explain formation of sympathetic ganglia.

A

Cells from neural crest cells in the thoracic region migrate behind aorta and align themselves along developing spinal cord in groups connected by longitudinal nerve fibers. These form the ganglia along the spinal cord

Other neural crest cells go in front of the developing aorta to form preaortic ganglia

Other neural crest cells travel to organs to form organ ganglia.

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18
Q

Difference between preganglionic and postganglionic fibers.

A

Preganglionic are myelinated but postganglionic nerves are not myelinated

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19
Q

Origin of cortex and medulla of adrenal glands

A

cortex is from mesoderm

medulla is from ectoderm neural crest cells

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20
Q

Difference in distribution of chromaffin cells in adults and embryos

A

Chromaffin cells are scattered throughout in the embryo, but in the adults, they are limited to the adrenal medulla

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21
Q

Embryologic origin of postganglionic parasympathetic fibers

A

Postganglionic parasympathetic fibers come from post ganglionic ganglia which originate from neural crest cells

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22
Q

when does myelination begin?

A

month 4

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23
Q

Why do spinal nerves run obliquely from spinal cord to vertebrae levels?

A

Due to disproportionate growth in IUL. After month 3, the vertebra and pia mater extend much faster than the spinal cord itself

24
Q

Explain changes in the length of the spinal cord at various stages.

A

At month 3, it reaches C1
By end of month 5, it reaches S1
By birth, it reaches L3

25
Q

Causes of neural tube defects

A
  1. Hypervitaminosis for Vit A
  2. Hyperthermia or hypothermia
  3. Valproic acid (an anticonvulsant)
  4. Folic acid/ vit B9 deficiency
26
Q

Diagnosis of neural tube defects

A

elevated levels of alpha fetoprotein in amniotic fluid or mother’s serum

ultrasonography

27
Q

Spina bifida

A

nonfusion of vertebral arches

28
Q

Enumerate SPINA BIFIDA OCCULTA

A

Neural tissue not affected
Defect covered by skin with tuft of hair
Usually occurs at level of L5 to S1

Asymptomatic

29
Q

Explain Spina bifida with meningocele

A

protrusion of meninges with CSF
Can be easily fixed with surgery and child doesn’t usually have symptoms

  1. Spina bifida with meningomyelocele
    protrusion of meninges and spinal cord or nerve roots (is more common and severe)
    Symptoms include: paralysis, sensory loss below the sac and hydrocephaly
    Can be “treated” with surgery, but child will need special care
30
Q

Spina bifida with meningomyelocele

A

protrusion of meninges and spinal cord or nerve roots (is more common and severe)
Symptoms include: paralysis, sensory loss below the sac and hydrocephaly
Can be “treated” with surgery, but child will need special care

31
Q

The most severe spina bifida

A

Myeloschisis - nerve tissue is fully bare and a dermal or meningeal covering is absent

32
Q

Absence of spinal cord

A

Amyelus

33
Q

myelocystomeningocele

A

spinal cord dilates

also called syringomyelocele

34
Q

Anencephaly

A

neural folds do not fuse at cranial region. it’s a type of spinal bifida. always fatal

35
Q

Rachischisis

A

entire spine does not close

36
Q

List order in which brain flexures appear

A

Midbrain
Cervical
Pontine
Forebrain/Cepalic flexure

37
Q

Formation of corpus striatum

A

In month 2, bases of cerebral hemispheres thicken and extend download into foramina of monro

38
Q

Internal capsule divides the corpus striatum into?

A

Lentiform nucleus

Caudate nucleus

39
Q

When does brain get its characteristic sulci and gyri?

A

Final part of IUL

40
Q

Cerebral cortex develops from

A

PALLIUM

which is divided into neopallium and archipalleum

41
Q

Development of Olfactory bulb

A

interaction between neural crest cells and floor of telencephalon causes the floor to differentiate into the olfactory bulb

42
Q

The first commissure to appear is the

A

anterior commissure

43
Q

When does corpus callosum appear?

A

week 10

44
Q

Roof plate of diencephalon forms which structures?

A

Choroid plexus of 3rd ventricle

Pineal gland

45
Q

Which structure of diencephalon includes mamillary bodies?

A

Hypothalamus

46
Q

Which plate of diencephalon forms pars narvosa of pituitary gland?

A

alar plate’s downward extension as the infundibulum

47
Q

Holoprosencephaly

A

loss of midline structures resulting in brain and face malformations

Causes

  1. excess alcohol intake
  2. defect in SHH gene
  3. lack of cholesterol synthesis required for SHH gene to influence its effects
48
Q

Schizencephaly

A

large clefts in cerebral hemispheres

49
Q

Most commonly affected bone in ossification defects of skull

A

occipital bone

50
Q

Meningoencephalocele

A

defect in occipital bone large enough so that part of the brain bulges through

51
Q

Meningohydroencephalocele

A

defect in occipital bone so that brain and ventricles protrude

52
Q

A mother goes for her ultrasound and the clinician notices hydramnios. What is a possible cause?

A

Fetus could be having anencephaly because they lack swallowing mechanism

53
Q

Aqueductal stenosis

A

obstruction of aqueduct of Sylvius leading to hydrocephalus

54
Q

Enumerate on the Arnold-Chiari malformation

A

defect of cerebellum in which there is caudal displacement and herniation through foramen magnum, or incomplete development of cerebellum

are 4 types
type 1: cerebellum protrudes into foramen magnum due to spina bifida cystica
type 2: cerebellum and brain stem extend into foramen magnum
type 3: most serious. cerebellum goes past foramen magnum and into the spinal cord
type 4: incomplete cerebellum

Can be asymptomatic if its type 1
Serious symptoms arise from type 2,3 and 4
most of the times accompanies spina bifida cystica

55
Q

Cerebellum forms from which structures

A

rhombic limbs which form cerebellar plates

Embryology PHM (9 decks)

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