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MSK exam 1 AP > Development of the spinal cord EMBRYOLOGY > Flashcards

Development of the spinal cord EMBRYOLOGY Flashcards

1
Q

the notochord secretes what?

A

noggin and chordin

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2
Q

what do noggin and chordin do

A

induce the overlying ectoderm to differentiate in a very specific manner

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3
Q

what does the notochord signals the development of?

A

spinal cord (ectoderm)

vertebral column (mesoderm)

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4
Q

Day 19

A

Neurulation starts

neural ectoderm forms –> called the neural plate

is signalled by the notochord

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5
Q

what does the neural plate give rise to?

A

central nervous system

neural crest cells

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6
Q

Day 20

A

lateral edges start to fold towards one another forming neural groove

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7
Q

Day 22, 23

A

lateral edges fuse

forming neural tube

fusion begins in the cervical/neck region of the embryo and progresses cranially and caudally

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8
Q

what day does the caudal neuropore close?

A

Day 27

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9
Q

what day does the cranial neuropore close

A

Day 25

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10
Q

what does the neural tube give rise to ?

A

spinal cord and brain

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11
Q

if there was a defect during formation of the neural tube epithelium, which of the following cell types would be unaffected?

A

dorsal root ganglion b/c they are part of the peripheral nervous system

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12
Q

Neural crest cells

A

gives rise to all cells of the PERIPHERAL NS

Sensory ganglia of cranial and spinal nerves
Autonomics
-(all peripheral parasympathetic and sympathetic ganglia)
-sympathetic chain ganglia
-prevertebral sympathetic ganglia
-parasympathetic ganglia

Schwann cells

Meninges

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13
Q

classic signs of neural crest cell deformities

A

peripheral nervous system defects

craniofacial defects

heart defects

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14
Q

what are the 3 different regions that form in the neural tube as a result of neuron migration from the neuroepithelium?

A

Ventricular

mantle

marginal zones

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15
Q

Ventricular zone

A

middle inner layer

embryo–> thick, pseudostratified neuroepithelium

adult –> very reduced b/c neurogenesis has stopped–> composed of a simple layer of EPENDYMAL cells

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16
Q

Mantle layer

A

where the cell bodies take up residence

mantle in adults forms the gray matter

motor neurons migrate ventrally (form basal plate)
sensory neurons migrate dorsally (forma alar plate)

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17
Q

basal plate in adults

A

motor neurons have migrated ventrally to form this area

forms ventral motor horn in adult
cell bodies of origin for motor nuclei are located here

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18
Q

Alar plate

A

sensory neurons have migrated dorsally to form this region

becomes the dorsal sensory horn (where sensory information enters the spinal cord)

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19
Q

marginal layer

A

outermost layer, composed of nerve processes

where axons and dendrites are located, which can be myelinated

WHITE MATTER IN adults

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20
Q

spinal nerve

A

motor and sensory components

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21
Q

motor part of nerve

A

cell bodies located in the basal plate of the mantle layer

form ventral motor root of the spinal nerve

eventually merging with the sensory component

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22
Q

sensory part of nerve

A

cell bodies located in the dorsal root ganglia

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23
Q

what is the dorsal root ganglion formed from

A

neural crest cell

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24
Q

dorsal root ganglion

A

send peripheral process outward which forms the dorsal sensory root of the spinal nerve

send central process into the alar plate

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25
Q

mixed spinal nerve

A

ventral nerve root and dorsal nerve root
31 pairs

cervical first
then thoracic
lumbar
sacral
coccygeal
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26
Q

spinal cord differential growth

A

8 weeks - spinal cord extends the entire length of the vertebral column (so when spinal cord segments and spinal nerves form they line up with vertebrae across from it)

in newborn the spinal cord ends at LV4-LV5

in the adult the spinal cord ends at about LV1-LV2

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27
Q

where does the spinal cord end in the adult

A

at LV1-LV2

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28
Q

what is the somite doing?

A

guiding formation of spinal nerves

sends out signals!!

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29
Q

each spinal nerve has…

A

its own somite

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30
Q

somites give rise to

A

dermatomes

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31
Q

dermatomes

A

strip of skin innervated by one spinal nerve

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32
Q

somite splits into myotome too!

A

a group of muscles innervated by one spinal nerve

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33
Q

when do the ventral and dorsal rami form?

A

when the somite splits into dorsal and ventral portions

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34
Q

epimere

A

innervatd dorsal ramus

forms back structures

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35
Q

hypomere

A

innervated by ventral ramus

forms rest of trunk and limbs

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36
Q

spina bifida occulta

A

results when vertebral arches os spinal cord fail to fuse.
typically does not involve meninges or nervous tissue

often marked by a small patch of hair over the lumbosacral spinal cord region

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37
Q

spina bifida with meningocele

A

involves the meninges

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38
Q

spina bifida with meningomyelocele

A

involves meninges and spinal cord

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39
Q

spina bifida with myeloschisis

A

the most severe form of spina bifida

neural plate fails to elevate and fold

very underdeveloped

40
Q

sclerotome of the somite forms the …

A

axial skeleton (vertebral column, sternum, ribs, portion of the skull)

organizes loosely around neural tubea

41
Q

dermotome of the somite

A

just deep to the ectoderm

dermis

42
Q

myotome of the somite

A

skeletal muscle

43
Q

what about somites??

A

arises from paraxial mesoderm

44
Q

vertebral column resegmentation

A

sclerotome divides into cranial and caudal portions

caudal half fuses with cranial half of sclerotome below it
this fusion forms the vertebrae

after resegmentation myotome actually now spans two vertebral levels

45
Q

what is the nucleus pulposus formed from

A

notochord

46
Q

annulus fibrosis

A

formed from mesenchymal cells which remain between the cranial and caudal portions of the original sclerotome

47
Q

hemivertebrae

A

most often causes congenital scoliosis

half a vertebrae b/c only one vertebrae ossified

48
Q

Klippel-Feil syndrome

A

results in fusion of vertebrae (most often cervical)

fusion happens when resegmentation doesn’t take place (doesn’t split)

results in a short neck and restricted neck movements

49
Q

what do ribs develop from?

A

develop from costal processes of the 12 thoracic vertebrae

50
Q

sternum

A

NOT FROM SOMITE

but rather from LATERAL plate mesoderm

forms from the fusion of two sternal bars

51
Q

pectus excavatum

A

depression in chest (anterior thoracic wall sunken-in)

caused by ribs growing in excess

52
Q

pectus carinatum

A

anterior thoracic wall protrudes

“pigeon” chest

ribs grow in excess

53
Q

all skeletal muscle comes from the …

A

myotome of the somite

54
Q

myotome splits into…

A

dorsal and ventral portions

dorsal–>

55
Q

epimere

A

dorsal part after myotome split

innervated by dorsal primary rami

gives rise to intrinsic back muscles
(erector spinae, splenius, transversospinal group, intersegmental group)

56
Q

hypomere

A

ventral part after myotome splits

innervated by ventral rami

gives rise to anterior and lateral neck musculature, trunk muscles and limbs

57
Q

why do our muscles have multiple myotomes and more than one level of innervation

A

b/c a myotomes can split!

58
Q

splitting of myotomes longitudinally

A

trapezius and sternocleidomastoid muscles

59
Q

skeletal muscle myogenesis

A

1) mesoderm cells differentiate into myoblasts (primordial muscle cells)
2) myoblasts ellongate and fuse together to form myotubes
3) contractile filaments appear in the cytoplasm of the myotube, now called a muscle fiber with sarcomeres

60
Q

why are skeletal muscle multinucleate?

A

b/c multiple myoblasts fuse

61
Q

Poland syndrome

A

Absent or underdeveloped pectoralis muscles

usually unilateral, right side affected

most cases include syndactyly of the fingers

cause is unknown but believed to involve loss of blood supply to chest wall during development

62
Q

somatic layer of LATERAL PLATE mesoderm will give rise to what?

A

connective tissues of limbs

-bones
tendons
ligaments
dermis
blood
blood vessels
63
Q

axial skeletal comes from

A

paraxial mesoderm

64
Q

surface ectoderm gives rise to

A

epidermis

65
Q

myotome of somites gives rise to

A

all skeletal muscle of limbs

66
Q

upper limb limb buds show up when?

A

Day 25-26

67
Q

lower limb limb buds show up when?

A

day 27-28

later than upper limb
CRANIAL TO CAUDAL SEQUENCING

68
Q

what is the AER and where is it?

A

apical ectodermal ridge

signals limb growth

located at the apex of the limb bud

69
Q

hand and foot plates

A

form at week 5

distal ends of limb buds flatten to become paddle like

separated from limb bud by circular constriction

70
Q

what are digital rays

A

4 zones of APOPTOSIS along AER separate hand and footplates into 5 digital rays (five separate areas of AER)

6th week–> upper limb
7th week –> lower limb

71
Q

ectrodactyly

A

one missing digit or multiple missing digit

72
Q

brachydactyly

A

shortened digits

AER fail to lay down enough mesoderm

73
Q

polydactyly

A

too many digits

one extra apoptotic zone

74
Q

syndactyly

A

fusion of digits

not enough apoptotic cell death

osseous or dermal fusion of phalanges

75
Q

amelia

A

lack of limb formation

no AER formed or it doesn’t signal properly

76
Q

meromelia

A

partial limb formation (phocomelia)

77
Q

what is the main signal for proximal and distal growth in limbs?

A

AER

shoulder (proximal) to wrist (distal)

78
Q

what is the main signal for dorsal and ventral

A

dorsal (elbow and knee)

ventral (palm of hand, plantar surface of foot)

79
Q

anterior posterior axis of limb

A

defines thumb and great toe as anterior

little toe and little finger posterior

ZPA responsible for signalling this

80
Q

ZPA

A

zone of polarizing activity

releases retinoic acid which forms gradient that establishes anterior and posterior axis

81
Q

limb ossification

A

starts with endochondral ossification of lateral plate mesoderm

lay down mesenchymal model

then form cartilaginous model (week 5)

blood vessels migrate into and form primary site of ossification (7th week)

mesodermal cells differentiate into osteoblasts which then secrete bone matrix

NOTE some bones begin ossification after birth

82
Q

joint formation

A

site of contriction leads to signalling cascade that leads to cell death

clears out mesenchymal cells and forms the interzone

interzone forms joint cavity

mesodermal cells then form cartilage/capsule etc.

83
Q

when do secondary ossification centers form?

A

mostly after birth

important for growth

84
Q

muscle formation in the limb

A

5th week – myogenic cells from the myotome (hypomere portion) of the somite migrate into the limb bud (come in after cartilage)

myotomes pull in their ventral rami with them

muscles divide into anterior flexor and posterior extensor portions

85
Q

myotomes that migrate into the upper limb

A

C5- T1

86
Q

myotomes that migrate into the lower limb

A

L2-S3

87
Q

limb rotation

A

upper and lower limb initially in exact same position (thumb and great toe directed lateral)

lower limb rotates 180 degrees medially so that the great toe becomes medial, knee directed anterior in adult

ends with the flexor compartments dorsal and the extensor compartments as ventral

88
Q

Sensory limb innervation

A

sensory fibers are pulled into the limb as it elongates from the trunk

spinal nerves migrate along with dermatomes as they are pulled into developing limb

89
Q

how is sensory innervation distributed in limbs?

A

Radially

spiral effect in lower limb-b/c of limb rotation

90
Q

what is different about how dermatomes and myotomes form?

A

dermatomes are already established before limbs form

myotomes migrate in after limb has been established

91
Q

limb motor innervation

A

migrate into limb longitudinally

motor innervation spreads down the limb

so upper limb C5 near shoulder T1 near fingers

L2 near hip and S3 near foot

92
Q

phocomelia

A

absence of long bones

93
Q

congenital clubfoot

A

abnormal position of foot: sole inverted, foot adducted and plantar flexed

common cause is oligohydramnios (too little amniotic fluid)

94
Q

amniotic bands do what?

A

act as truncates

can circle and entrap portions of the fetus cutting off circulation as fetus develops and may cause amputations

95
Q

congenital hip dislocation

A

underdevelopment of acetabulum and head of femur

laxity of joint capsule

dislocation occurs before birth

common with breech deliveries

MSK exam 1 AP (7 decks)

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