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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
mixed spinal nerve
ventral nerve root and dorsal nerve root 31 pairs ``` cervical first then thoracic lumbar sacral coccygeal ```
26
spinal cord differential growth
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
27
where does the spinal cord end in the adult
at LV1-LV2
28
what is the somite doing?
guiding formation of spinal nerves sends out signals!!
29
each spinal nerve has...
its own somite
30
somites give rise to
dermatomes
31
dermatomes
strip of skin innervated by one spinal nerve
32
somite splits into myotome too!
a group of muscles innervated by one spinal nerve
33
when do the ventral and dorsal rami form?
when the somite splits into dorsal and ventral portions
34
epimere
innervatd dorsal ramus forms back structures
35
hypomere
innervated by ventral ramus forms rest of trunk and limbs
36
spina bifida occulta
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
37
spina bifida with meningocele
involves the meninges
38
spina bifida with meningomyelocele
involves meninges and spinal cord
39
spina bifida with myeloschisis
the most severe form of spina bifida neural plate fails to elevate and fold very underdeveloped
40
sclerotome of the somite forms the ...
axial skeleton (vertebral column, sternum, ribs, portion of the skull) organizes loosely around neural tubea
41
dermotome of the somite
just deep to the ectoderm dermis
42
myotome of the somite
skeletal muscle
43
what about somites??
arises from paraxial mesoderm
44
vertebral column resegmentation
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
what is the nucleus pulposus formed from
notochord
46
annulus fibrosis
formed from mesenchymal cells which remain between the cranial and caudal portions of the original sclerotome
47
hemivertebrae
most often causes congenital scoliosis half a vertebrae b/c only one vertebrae ossified
48
Klippel-Feil syndrome
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
what do ribs develop from?
develop from costal processes of the 12 thoracic vertebrae
50
sternum
NOT FROM SOMITE but rather from LATERAL plate mesoderm forms from the fusion of two sternal bars
51
pectus excavatum
depression in chest (anterior thoracic wall sunken-in) caused by ribs growing in excess
52
pectus carinatum
anterior thoracic wall protrudes "pigeon" chest ribs grow in excess
53
all skeletal muscle comes from the ...
myotome of the somite
54
myotome splits into...
dorsal and ventral portions dorsal-->
55
epimere
dorsal part after myotome split innervated by dorsal primary rami gives rise to intrinsic back muscles (erector spinae, splenius, transversospinal group, intersegmental group)
56
hypomere
ventral part after myotome splits innervated by ventral rami gives rise to anterior and lateral neck musculature, trunk muscles and limbs
57
why do our muscles have multiple myotomes and more than one level of innervation
b/c a myotomes can split!
58
splitting of myotomes longitudinally
trapezius and sternocleidomastoid muscles
59
skeletal muscle myogenesis
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
why are skeletal muscle multinucleate?
b/c multiple myoblasts fuse
61
Poland syndrome
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
somatic layer of LATERAL PLATE mesoderm will give rise to what?
connective tissues of limbs ``` -bones tendons ligaments dermis blood blood vessels ```
63
axial skeletal comes from
paraxial mesoderm
64
surface ectoderm gives rise to
epidermis
65
myotome of somites gives rise to
all skeletal muscle of limbs
66
upper limb limb buds show up when?
Day 25-26
67
lower limb limb buds show up when?
day 27-28 later than upper limb CRANIAL TO CAUDAL SEQUENCING
68
what is the AER and where is it?
apical ectodermal ridge signals limb growth located at the apex of the limb bud
69
hand and foot plates
form at week 5 distal ends of limb buds flatten to become paddle like separated from limb bud by circular constriction
70
what are digital rays
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
ectrodactyly
one missing digit or multiple missing digit
72
brachydactyly
shortened digits AER fail to lay down enough mesoderm
73
polydactyly
too many digits one extra apoptotic zone
74
syndactyly
fusion of digits not enough apoptotic cell death osseous or dermal fusion of phalanges
75
amelia
lack of limb formation | no AER formed or it doesn't signal properly
76
meromelia
partial limb formation (phocomelia)
77
what is the main signal for proximal and distal growth in limbs?
AER shoulder (proximal) to wrist (distal)
78
what is the main signal for dorsal and ventral
dorsal (elbow and knee) ventral (palm of hand, plantar surface of foot)
79
anterior posterior axis of limb
defines thumb and great toe as anterior little toe and little finger posterior ZPA responsible for signalling this
80
ZPA
zone of polarizing activity releases retinoic acid which forms gradient that establishes anterior and posterior axis
81
limb ossification
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
joint formation
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
when do secondary ossification centers form?
mostly after birth important for growth
84
muscle formation in the limb
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
myotomes that migrate into the upper limb
C5- T1
86
myotomes that migrate into the lower limb
L2-S3
87
limb rotation
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
Sensory limb innervation
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
how is sensory innervation distributed in limbs?
Radially spiral effect in lower limb-b/c of limb rotation
90
what is different about how dermatomes and myotomes form?
dermatomes are already established before limbs form myotomes migrate in after limb has been established
91
limb motor innervation
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
phocomelia
absence of long bones
93
congenital clubfoot
abnormal position of foot: sole inverted, foot adducted and plantar flexed common cause is oligohydramnios (too little amniotic fluid)
94
amniotic bands do what?
act as truncates can circle and entrap portions of the fetus cutting off circulation as fetus develops and may cause amputations
95
congenital hip dislocation
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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