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Embryo > Chapter 4 > Flashcards

Chapter 4 Flashcards

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
Q

Notochord development step 1 of 9:

A

notochordal process elongates by invagination of cells from the primitive pit

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26
Q

Notochord development step 2 of 9:

A

primitive pit extends into notochordal process forming norochordal canal

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27
Q

Notochord development step 3 of 9:

A

notochordal process (now a cellular tube) extends cranially from the primitive node to the prechordal plate

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28
Q

Notochord development step 4 of 9:

A

floor of notochordal process fused with underlying embryonic endoderm

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29
Q

Notochord development step 5 of 9:

A

fused layers gradually undergo degeneration; openings in floor of notochordal process form; notochordal process is in communication with umbilical vesicle

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30
Q

Notochord development step 6 of 9:

A

openings become confluent and floor of notochordal canal disappears; remains of notochordal process form flattened, grooved notochordal plate

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31
Q

Notochord development step 7 of 9:

A

starting at cranial end of embryo, notochordal cells proliferate and notochordal plate infolds to form the notochord

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32
Q

Notochord development step 8 of 9:

A

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

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33
Q

Notochord development step 9 of 9:

A

notochord becomes detached from endoderm of umbilical vesicle; endoderm becomes continuous layer

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34
Q

notochord extends from where to where

A

oropharyngeal membrane o the primitive node

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35
Q

when does notochord degenerate

A

when bodies of the vertebrae form

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36
Q

The notochord induces overlying ectoderm to thicken and form…

A

neural plate (primordium of CNS)

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37
Q

Chordomas

A

remnants of notochordal tissue; generally at base of cranium

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38
Q

allantois

A

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

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39
Q

what does allantoic mesoderm form in humans

A

expands beneath thw chorion and forms blood vessels that will serve the placenta

40
Q

urachus

A

proximal part of allantoic diverticulum that extends from bladder to umbilical region; median umbilical ligament in adults

41
Q

neurulation

A

process involved in formation of neural plate and neural folds and closure of folds to form neural tube

42
Q

when is neurulation complete

A

by the end of the 4th week (when closure of neuropore also closes)

43
Q

where is neural plate located initially

A

rostral to primitive node and dorsal to underlying notochord and mesoderm adjacent; eventually it extends beyond notochord

44
Q

What occurs to neural plate day 18

A

invaginates along central axis to form longitudinal median neural groove with neural folds on each side

45
Q

what is the first sign of brain development

A

prominent neural folds at cranial end of embryo

46
Q

when is neural tube formed

A

by end of 3rd week when neural folds move together and fuse

47
Q

what occurs to neural crest cells as neural folds meet to form tube

A

undergo epithelial to mesenchymal transition and migrate away

48
Q

what ganglia do neural crest cells give rise to

A

spinal ganglia (dorsal root ganglia) and ganglia of ANS (CN ganglia V, VII, IX, and X partly derived from neural crest cells)

49
Q

leptomeninges

A

pia and arachnoid mater; neural crest cells contribute to formation

50
Q

other areas neural crest cells contribute to

A

neurolemma sheath of peripheral nerves; pigment cells, adrenal medulla; connective tissue components in head

51
Q

most common anamaly affecting the CNS

A

Meroencephaly (partial absence of the brain)

52
Q

What do teratogenic drugs affect

A

cell fates, adhesion, and mechanism of neural tube closure

53
Q

What do primitive node derived cells form

A

notochord and paraxial mesoderm

54
Q

paraxial membrane location/description

A

thick, longitudinal column of cells continuous laterally with intermediate mesoderm

55
Q

what happens to paraxial membrane at the end of week 3

A

differenciates, condenses, and begins to divide into paired cuboidal bodies called somites

56
Q

what is lateral mesoderm continuous with

A

extraembryonic mesoderm covering the umbilical vesicle and amnion

57
Q

what order do somites form

A

cranial to caudal

58
Q

how many pairs of somites develop during the somite period of human development

A

38 pairs

59
Q

how many somites are present at the end of week 5

A

42-44 pairs (used to determine embryo ago in 4th-5th weeks)

60
Q

somite description

A

form distinct elevations on embryo, somewhat triangular in transverse section

61
Q

what do somites give rise to

A

axial skeleton and associated musculature as well as ajacent dermis of skin

62
Q

when do the first pair of somites appear

A

end of 3rd week caudal to otic placode formation site

63
Q

ordered progrssion of segmentation involes what

A

clock mechanism/oscillator of gene expression

64
Q

somite formation is preceded by expression of what

A

forkhead transcription factors Fox C1 and C2

65
Q

cranialcaudal segmental pattern of somites is regulated by

A

Delta-Notch signaling system

66
Q

primordium of intraembryonic coelom (body cavity)

A

appears as isolated coelomic spaces in lateral mesoderm and cardiogenic mesoderm

67
Q

intraembryonic coelom divides lateral mesoderm into what two layers

A

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
Q

somatopleure

A

embryonic body wall formed by somati mesoderm and overlying embryonic ectoderm

69
Q

splanchnopleure

A

embryonic gut formed by splanchnic mesoderm and underlying embryonic endoderm

70
Q

Body cavities of intraembryonic coelom during second month

A

pericardial, pleural, and peritoneal

71
Q

how is embryonic nutrition obtained at end of week 2

A

from maternal blood by diffusion through extraembryonic coelom and umbilical vesicle

72
Q

when does vasculogensis and angiogenesis begin

A

beginning of week 3 in extraembryonic mesoderm of umbilcal vesicle, connecting stalk, and chorion

73
Q

vasculogenesis

A

formation of new vascular channels by assembly of individual cell precursors (angioblasts)

74
Q

Angiogenesis

A

formation of new vessels by budding and branching from preexisting vessels

75
Q

Step 1 of 5 vasculogenesis

A

mesenchymal cells differentiate into endothelial cell precursors (angioblasts) which aggregate to form blood islands

76
Q

Step 2 of 5 vasculogenesis

A

small cavities appear within blood islands and endothelial cells by confluence of intercellular clefts

77
Q

Step 3 of 5 vasculogenesis

A

angioblasts flatten to form endothelial cells and arrange themselves around cavities

78
Q

Step 4 of 5 vasculogenesis

A

endothelium-lined cavities fuse to form networks of endothelial channels

79
Q

Step 5 of 5 vasculogenesis

A

vessels sprout into adjacent areas by endothelial budding and fuse with other vessels

80
Q

where are blood cells formed at the end of week 3

A

endothelial cells of vessels on umbilical vesicle and allantois

81
Q

when does blood formation begin

A

hematogenesis begins week 5

82
Q

progression of blood formation through development

A

1) aorta 2)various parts of embryonic mesenchyme (mainly liver) 3)spleen, bone marrow, and lymph nodes

83
Q

what do the mesenchymal cells surrounding primordial endothelial vessels differentiate into

A

muscular and connective tissue elements of vessels

84
Q

when do endocardial heart tubes fuse to form primordial heart

A

week 3

85
Q

when does heart begin to beat

A

21st or 22nd day (first organ to reach functional state)

86
Q

when can heartbeaat be detected using Doppler ultracsound

A

during 5th week (7 weeks from LMP)

87
Q

hydatidiform moles

A

chorionic villi that do not complete development; resemble bunch of grapes; produce human chorioic gonadotropin; paternal origin

88
Q

choriocarcinomas

A

malignant trophoblastic lesions

89
Q

primary chorionic villi

A

appear end week 2

90
Q

secondary chorionic villi

A

mesenchyme tissue in core; early week 3; coversurface of chorionic sac

91
Q

tertiary chorionic villi

A

capillaries and blood cells visible

92
Q

arteriocapillary networks

A

capillaries and chorionic villi fuse

93
Q

cytotrophoblastic shell

A

surrounds chorionic sac and attaches it to endometrium

94
Q

stem chorionic villi

A

villi that attach to maternal tissues through cytotrophoblastic shell

95
Q

branch chorionic villi

A

villi that grow from sides of stem villi

96
Q

where does main exchange of material between mom/embryo occur

A

branch villi

Embryo (5 decks)

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