embryo 2 (wk8) Flashcards

(62 cards)

1
Q

what axis does the notochord develop

A

longitudinal axisw

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2
Q

what structure does notochord contribute to

A

intervertebral discs

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3
Q

what does the notochord provide signals for

A

Providessignalsfor the development of axial MSK structures and the CNS

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4
Q

how is the notochordal process formed

A

mesenchymal cells dive
into the primitive pit and migrate cephalad

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5
Q

what is the lumen in the notochordal process called

A

Notochordal canal

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6
Q

how does the notochordal process become the notochordal plate

A

notochordal process approaches the prechordal plate, the floor of the process “fuses” with the endoderm

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7
Q

how can the amniotic cavity and umbilical vesicle communicate through

A

an opening (the neurenteric canal)

– this opening is where the primitive pit opened into the notochordal canal

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8
Q

what happens to the notochordal plate to form the notochord

A

cells proliferate and fold inwards

-no canal present

▪ Notochordal plate! notochord transition starts cranially (cephally) and progresses caudally

  • After the notochord is fully-developed, the neurenteric canal is obliterated
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9
Q

what layer is absent in the floor of the plate where the neurocentric canal is

A

endoderm

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10
Q

what do the notochord and its preceding structures (process, plate) help organize?

A

-induce overlying ectoderm to develop into neural plate
-acts as central axis (divide left and right)

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11
Q

what thing does the notochord structures approach but not go beyond

A

the prechordal plate

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12
Q

what does the prechrodal plate organzie

A

cranial structures

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13
Q

what does the prechordal plate act as a stop signal for

A

notochord; prevent it from going to far anteriorly

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14
Q

what does the prechordal plate develop into

A

the oropharyngeal membrane

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15
Q

oropharyngeal membrane; how many layers and where is it found

A

2 layers; ecto and endoderm

cardiogenic mesoderm found anteriroly

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16
Q

where does the cloacal membrane form

A

caudal to the primitive streak

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17
Q

how many layers in cloacal membrane and what does it become

A

2; ecto and endoderm

future site of anus

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18
Q

what is the allantois

A

Small, vascularized diverticulum (outpouching) from the caudal wall of umbilical vesicle, extending into connecting stalk

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19
Q

what does the allantois function in

A

early blood formation and bladder development

▪ Blood vessels become umbilical arteries

▪ Small portion persists as urachus that extends from bladder to umbilical region

  • Becomes median umbilical ligament in adults
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20
Q

how does neuroectoderm form

A

Notochord induces overlying ectoderm to form the neural plate

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21
Q

what does neuroectoderm give rise to

A

Gives rise to the CNS, retina, and the tissues that arise
from the neural crest

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22
Q

on day 18, what does neural plate invagination cause formation of

A

On day 18, the neural plate invaginates to form the neural groove – neural folds are found on either side of the groove

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23
Q

how is neural tube made

A

The neural folds eventually fuse together, and form the neural tube

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24
Q

what is the structure the neural tube makes

A

is the primordium of the CNS

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25
when is neuralation complete
end of week 4
26
derivative of neural crest cells...
▪ Ganglia of CN V, VII, IX, X ▪ Spinal ganglia (i.e. dorsal root ganglia) ▪ Autonomic nervous system ganglia ▪ Neurolemma sheaths of peripheral nerves ▪ Contribute to the arachnoid and pia ▪ Adrenal medulla ▪ Melanocytes ▪ Craniofacial bone and cartilage ▪ Portions of the heart
27
what are the 3 structures that the intraembryonic mesoderm proliferates to from a thick column of mesoderm on the sides of the notochord
During the 3rd week: ▪ Intraembryonic mesoderm proliferates to form a thick column of mesoderm on either side of the notochord * Beside the axis of the organism (as defined by the notochord) = paraxial mesoderm ▪ The intermediate mesoderm is found just lateral to the paraxial mesoderm ▪ The lateral mesoderm is lateral to the intermediate mesoderm
28
what are somites
During the 3rd – 5th week, somites develop adjacent to the neural tube * Somite = cuboidal masses of mesoderm on either side of the notochord, visible along the dorso-lateral surface of the embryo on each side of the neural tube
29
what are the somites formed from
* Formed from the paraxial mesoderm
30
what do somites give rise to
Somites give rise to most of the axial skeleton and associated musculature, as well as the dermis in those areas
31
how is primordial heart formed
* During the 3rd week mesenchymal cells migrate anteriorly, lateral to the notochordal process to eventually form cardiogenic mesoderm ▪ Found anterior to the prechordal plate, eventually gives rise to the embryonic heart primordia ▪ The heart begins as a pair of tubes that are brought together by folding of the embryo
32
intraembrionic coelom is found in?
appears as isolated spaces in the lateral mesoderm and cardiogenic mesoderm ▪ These spaces soon coalesce (join together) and form a single horseshoe-shaped intraembryonic coelom
33
which 2 layers does the intra-embryonic coelom divide the lateral mesoderm into
▪ A somatic or parietal layer of lateral mesoderm located beneath the ectodermal epithelium and continuous with the extraembryonic mesoderm covering the amnion ▪ of lateral mesoderm next to the endoderm and continuA splanchnic or visceral layer ous with the extraembryonic mesoderm covering the umbilical vesicle
34
3 regions that are in the lateral mesoderm on day 19-21that come from the intraembryonic coelom
Somatopleure – the somatic mesoderm and the overlying ectoderm * Forms the body wall ▪ Splanchnopleure – the splanchnic mesoderm and the underlying intraembryonic endoderm * Forms the embryonic gut ▪ Intraembryonic coelom in between the somatopleure and splanchnopleure
35
what does the somatopleure form?
body wall
36
what does the splanchnopleure form?
embryonic gut
37
where in the intraembryonic coelom
in between the somatopleure and splanchnopleure
38
during the 2nd month what does the intraemnyronic coelom develop into? hint 3 cavities
▪ Pericardial cavity ▪ Pleural cavity ▪ Peritoneal cavity
39
2 types of folding
median plane= cranial-caudal folding --> brain vesicles and somites horizontal plane= lateral folding --> body wall
40
stomodeum
primordial of the mouth
41
foregut
Part of the endoderm of the umbilical vesicle is incorporated into the embryo as the foregut ▪ The foregut lies between the brain and heart ▪ Oropharyngeal membrane separates the foregut from the stomodeum
42
septum transversum
Septum transversum lies caudal to the heart ▪ develops into the central tendon of the diaphragm and separates the abdominal cavity from the thoracic cavity
43
tail folding
caudal eminence (tail region) projects over the cloacal membrane (future site of anus) Part of the endodermal germ layer is incorporated into the embryo as the hindgut connecting stalk (primordium of umbilical cord)
44
which folding makes foregut, hindgut and midgut
cranial folding= foregut lateral folding= midgut tail folding= hindgut
45
what does lateral folding make
mid gut omphaloenteric duct (decrease connection between midgut and umbilical vesicle)
46
when does neural plate begin
day 19
47
when does neurulation end
day 27
48
what happens to end neuraltion
closure of neuropores at this point the neural tube no longer communicates with the amniotic cavity
49
when neuropore close what happens to circulation
After neuropore closure, a basic blood circulation has been established
50
what makes the brain and spine
* At day 22, the cranial 2/3 of the neural tube forms the brain, caudal 1/3 of the neural tube will form the spinal cord
51
what are the 3 zones that are in the spinal cord and which one is developed first
ventricular zone (inner) - developed 1st intermediate zone outer marginal zone
52
what do the 3 zones of the spinal cord become
ventricular zone (inner) - neurons and microglia intermediate zone- primordial neuroblasts outer marginal zone- white matter tracts
53
what cells line the central canal of the spinal cord
ependymal cells
54
what are the 3 primary brain vesicles
forebrain (prosencephalon) midbrain (mesencephalon) hindbrain (rhombenceophalon)
55
what does the forebrain (prosencephalon) divide into during week 5
telencephalon and diencephalon
56
what does the hindbrain (rhombenceophalon) divide into during week 5
metencephalon and myencephalon
57
on day 25 what forms on the forebrain
2 lateral outgrowuth- optic vesicles
58
what do the 2 lateral outgrowths on the forebrain turn into
primordia of the retinae and optic nerves
59
what are the telencephalon vesicles the primordial of
cereberal hemisphere and lateral ventricles
60
what do the three swellings of the third ventricle become
thalamus, hypothalamus and epithalamus
61
what are the alar plate of the spinal cord
dorsal gray horns
62
what are the basal plates of the spinal cord
ventral and lateral gray horns