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Embryo > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

3 week embryonic development (5 weeks after LMP)

A

appearance of primitive streak, notochord development, differentiaion of germ layers

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2
Q

first morphologic sign of gastrulation

A

primitive streak formation on surface of epiblast (caudally)

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3
Q

embryonic ectoderm derivatives

A

epidermis, central/peripheral nervous systems, eye, inner ear, neural crest cells

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4
Q

embryonic endoderm derivatives

A

epithelial linings of respiratory/alimentary tracts, glands opening into GI tract, glandular cells of associated organs (liver and pancreas)

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5
Q

embryonic mesoderm derivatives

A

Skeletal muscle, blood cells, lining of blood vessels, visceral smooth muscle, serosal linings of body cavities, ducts and organs of reproductive/excretory systems, most cardiovascular system, connective tissue/cartilage/bones/tendons/ligaments/dermis in trunk, stroma of internal organs

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6
Q

what forms primitive streak

A

proliferation and movement of epiblast cells to the median plane of embryonic disc

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7
Q

cranial end of primitive streak forms

A

primitive node

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8
Q

primitive pit

A

small depression in primitive node

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9
Q

primitive groove

A

narrow groove in primitve streak continuous with primitive pit

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10
Q

what causes primitive pit/groove formation

A

evagination of epiblastic cells

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11
Q

mesenchyme

A

loosely arranged cells suspended in gelatinous matrix; cells are ameboid and actively phagocytic

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12
Q

what induces formation of mesoderm

A

signaling molecules of the transforming growth factor B superfamily

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13
Q

what gives rise to all 3 germ layers

A

cells of the epiblast

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14
Q

when does mesoderm production slow down

A

early part of 4th week

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15
Q

when does the primitive streak dissappear

A

end of 4th week

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16
Q

notochordal process origin

A

mesenchymal cells ingress through streak, migrate cranially from primitive node and pit - form median cellular cord

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17
Q

notochoral growth

A

grows cranially between ectoderm and endoderm until it reaches prechordal plate

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18
Q

prechordal plate

A

small circular area of columnar endodermal cells where endoderm and ectoderm are in contact; premordium of oropharyngeal membrane

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19
Q

prechoral mesoderm inducts formation of…

A

forebrain and eye

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20
Q

heart primordium begins to develop when

A

end of 3rd week

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21
Q

cloacal membrane

A

caudal to primitive streak; indicates future site of anus

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22
Q

2 sites where embryonic disc remains bilaminar

A

cloacal and oropharyngeal membrane

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23
Q

what induces notochord formation

A

signals from primitive streak region induce notochordal precursor cells (involves Shh from floor of neural tube)

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24
Q

Notochord properties

A

1)defines primordial longitudinal axis and gives rigitity 2)provides signals necessary for dvlpmnt of axial musculoskeletal structures and CNS 3) contributes to intervertebral discs

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25
Notochord development step 1 of 9:
notochordal process elongates by invagination of cells from the primitive pit
26
Notochord development step 2 of 9:
primitive pit extends into notochordal process forming norochordal canal
27
Notochord development step 3 of 9:
notochordal process (now a cellular tube) extends cranially from the primitive node to the prechordal plate
28
Notochord development step 4 of 9:
floor of notochordal process fused with underlying embryonic endoderm
29
Notochord development step 5 of 9:
fused layers gradually undergo degeneration; openings in floor of notochordal process form; notochordal process is in communication with umbilical vesicle
30
Notochord development step 6 of 9:
openings become confluent and floor of notochordal canal disappears; remains of notochordal process form flattened, grooved notochordal plate
31
Notochord development step 7 of 9:
starting at cranial end of embryo, notochordal cells proliferate and notochordal plate infolds to form the notochord
32
Notochord development step 8 of 9:
proximal part of notochordal canal persists temporarily as neurenteric canal which forms transitory communication between amniotic and umbilical vesicle cavities; eventually obliterates when notochord is complete
33
Notochord development step 9 of 9:
notochord becomes detached from endoderm of umbilical vesicle; endoderm becomes continuous layer
34
notochord extends from where to where
oropharyngeal membrane o the primitive node
35
when does notochord degenerate
when bodies of the vertebrae form
36
The notochord induces overlying ectoderm to thicken and form…
neural plate (primordium of CNS)
37
Chordomas
remnants of notochordal tissue; generally at base of cranium
38
allantois
appears day 16 as diverticulum from caudal wall of umbilical vesicle that extends into the connecting stalk; has respiratory/urinary resevoir fxn in some species
39
what does allantoic mesoderm form in humans
expands beneath thw chorion and forms blood vessels that will serve the placenta
40
urachus
proximal part of allantoic diverticulum that extends from bladder to umbilical region; median umbilical ligament in adults
41
neurulation
process involved in formation of neural plate and neural folds and closure of folds to form neural tube
42
when is neurulation complete
by the end of the 4th week (when closure of neuropore also closes)
43
where is neural plate located initially
rostral to primitive node and dorsal to underlying notochord and mesoderm adjacent; eventually it extends beyond notochord
44
What occurs to neural plate day 18
invaginates along central axis to form longitudinal median neural groove with neural folds on each side
45
what is the first sign of brain development
prominent neural folds at cranial end of embryo
46
when is neural tube formed
by end of 3rd week when neural folds move together and fuse
47
what occurs to neural crest cells as neural folds meet to form tube
undergo epithelial to mesenchymal transition and migrate away
48
what ganglia do neural crest cells give rise to
spinal ganglia (dorsal root ganglia) and ganglia of ANS (CN ganglia V, VII, IX, and X partly derived from neural crest cells)
49
leptomeninges
pia and arachnoid mater; neural crest cells contribute to formation
50
other areas neural crest cells contribute to
neurolemma sheath of peripheral nerves; pigment cells, adrenal medulla; connective tissue components in head
51
most common anamaly affecting the CNS
Meroencephaly (partial absence of the brain)
52
What do teratogenic drugs affect
cell fates, adhesion, and mechanism of neural tube closure
53
What do primitive node derived cells form
notochord and paraxial mesoderm
54
paraxial membrane location/description
thick, longitudinal column of cells continuous laterally with intermediate mesoderm
55
what happens to paraxial membrane at the end of week 3
differenciates, condenses, and begins to divide into paired cuboidal bodies called somites
56
what is lateral mesoderm continuous with
extraembryonic mesoderm covering the umbilical vesicle and amnion
57
what order do somites form
cranial to caudal
58
how many pairs of somites develop during the somite period of human development
38 pairs
59
how many somites are present at the end of week 5
42-44 pairs (used to determine embryo ago in 4th-5th weeks)
60
somite description
form distinct elevations on embryo, somewhat triangular in transverse section
61
what do somites give rise to
axial skeleton and associated musculature as well as ajacent dermis of skin
62
when do the first pair of somites appear
end of 3rd week caudal to otic placode formation site
63
ordered progrssion of segmentation involes what
clock mechanism/oscillator of gene expression
64
somite formation is preceded by expression of what
forkhead transcription factors Fox C1 and C2
65
cranialcaudal segmental pattern of somites is regulated by
Delta-Notch signaling system
66
primordium of intraembryonic coelom (body cavity)
appears as isolated coelomic spaces in lateral mesoderm and cardiogenic mesoderm
67
intraembryonic coelom divides lateral mesoderm into what two layers
1) somatic/parietal layer beneath ectodermal epithelium (continuous with extraembryonic mesoderm covering amnion) 2)splanchnic/visceral layer of lateral mesoderm adjacent to endoderm (continuous with extraembryonic mesoderm covering umbilical vesicle)
68
somatopleure
embryonic body wall formed by somati mesoderm and overlying embryonic ectoderm
69
splanchnopleure
embryonic gut formed by splanchnic mesoderm and underlying embryonic endoderm
70
Body cavities of intraembryonic coelom during second month
pericardial, pleural, and peritoneal
71
how is embryonic nutrition obtained at end of week 2
from maternal blood by diffusion through extraembryonic coelom and umbilical vesicle
72
when does vasculogensis and angiogenesis begin
beginning of week 3 in extraembryonic mesoderm of umbilcal vesicle, connecting stalk, and chorion
73
vasculogenesis
formation of new vascular channels by assembly of individual cell precursors (angioblasts)
74
Angiogenesis
formation of new vessels by budding and branching from preexisting vessels
75
Step 1 of 5 vasculogenesis
mesenchymal cells differentiate into endothelial cell precursors (angioblasts) which aggregate to form blood islands
76
Step 2 of 5 vasculogenesis
small cavities appear within blood islands and endothelial cells by confluence of intercellular clefts
77
Step 3 of 5 vasculogenesis
angioblasts flatten to form endothelial cells and arrange themselves around cavities
78
Step 4 of 5 vasculogenesis
endothelium-lined cavities fuse to form networks of endothelial channels
79
Step 5 of 5 vasculogenesis
vessels sprout into adjacent areas by endothelial budding and fuse with other vessels
80
where are blood cells formed at the end of week 3
endothelial cells of vessels on umbilical vesicle and allantois
81
when does blood formation begin
hematogenesis begins week 5
82
progression of blood formation through development
1) aorta 2)various parts of embryonic mesenchyme (mainly liver) 3)spleen, bone marrow, and lymph nodes
83
what do the mesenchymal cells surrounding primordial endothelial vessels differentiate into
muscular and connective tissue elements of vessels
84
when do endocardial heart tubes fuse to form primordial heart
week 3
85
when does heart begin to beat
21st or 22nd day (first organ to reach functional state)
86
when can heartbeaat be detected using Doppler ultracsound
during 5th week (7 weeks from LMP)
87
hydatidiform moles
chorionic villi that do not complete development; resemble bunch of grapes; produce human chorioic gonadotropin; paternal origin
88
choriocarcinomas
malignant trophoblastic lesions
89
primary chorionic villi
appear end week 2
90
secondary chorionic villi
mesenchyme tissue in core; early week 3; coversurface of chorionic sac
91
tertiary chorionic villi
capillaries and blood cells visible
92
arteriocapillary networks
capillaries and chorionic villi fuse
93
cytotrophoblastic shell
surrounds chorionic sac and attaches it to endometrium
94
stem chorionic villi
villi that attach to maternal tissues through cytotrophoblastic shell
95
branch chorionic villi
villi that grow from sides of stem villi
96
where does main exchange of material between mom/embryo occur
branch villi

Embryo (5 decks)

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