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BMS150 test 2 > embryo 1 (wk8) > Flashcards

embryo 1 (wk8) Flashcards

1
Q

what type of cell do we start off as

A

totipotent cell

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2
Q

fetus vs newborn

A
  • Fetus - an organism that breathes no air, does not use the
    digestive tract and lives in a sterile environment
  • Newborn - an air-breathing organism with a functional GI tract that quickly becomes colonized by microbial flora
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3
Q

what is produced in the ovaries

A

oocytes (female haploid gametes)

estrogen and progesterone

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4
Q

what happens in the uterine tube (fallopian tube)

A

§ Receives oocyte from ovaries

§ Site where sperm fertilizes the oocyte

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5
Q

where does the embryo develop

its also the same place where the placenta and membrane develop

A

uterus

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6
Q

placenta

A

site where the maternal and embryonic vasculature exchange substances

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7
Q

what is meosis

A

diploid (germ cell) –> haploid gamete

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8
Q

meiosis

A

§ A diploid cell (germ cell) undergoes meiosis to produce a
unique haploid gamete

  • Unique–>crossing-over between maternal and paternal chromatids during prophase I to end up with “mixed” chromatids
  • “mixed” = some paternal, some maternal genes
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9
Q

what is needed to complete meiosis

A

sperm

  • Meiosis is not completed in an oocyte until the sperm penetrates
    the oocyte

§ Spermatic pronucleus and the oocyte pronucleus fuse, thus completing fertilization

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10
Q

how is fertilization completed

A
  • Combination of spermatic and oocyte genetic material–>diploid cell
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11
Q

zygote

A

single diploid cell

combine sperm and oocyte

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12
Q

simple meiosis

A

meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes. In humans, the haploid cells made in meiosis are sperm and eggs.

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13
Q

prepuberty in ovaries

A

stop at meiosis I

  • A person with ovaries is born with a certain number of diploid oocytes that have been “paused” during the first stage of meiosis – do not continue meiosis until after puberty
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14
Q

post puberty in ovaries

fertilize vs non fertilize

A

do meiosis II if fertilized

  • After puberty, the ovaries release an ovum each cycle into the uterine tubes

§ The oocyte will not complete meiosis II unless fertilization occurs

§ Fertilization typically occurs in the ampulla of the uterine tube

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15
Q

where does fertilization occur

A

in the ampulla of the uterine tube

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16
Q

what is ovulation

A

release of a secondary oocyte from ovarian follicle

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17
Q

what is cumulus oophorus

A

Ovulated secondary oocyte together with zona pellucida, is externally covered with granulosa cells – cumulus oophorus

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18
Q

how is corona radiata formed?

A

Cumulus oophorus will rearrange and form corona radiata

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19
Q

where does the sperm cell penetrate into>

A

zona pellucida

  • Sperm cell penetrates the zona pellucida and “injects” its genetic material into the oocyte

§ Afterwards, the zona pellucida becomes impenetrable to other sperm cells (can’t have “double fertilization”)

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20
Q

how long for meiosis II to occur when sperm enters oocyte

A

§ After approximately 24 hours, the oocyte completes meiosis II and the zygote completes the first cell division
* This is the end of day 1, week 1

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21
Q

what is the corona radiata

A

cells that surround the oocyte, found outside of the zona pellucida

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22
Q

how do sperm get into the oocyte

A
  1. attracted to corona radiata and then break barrier to get to zone pellucida
  2. when get to zone pellucid, trigger acrosome reaction. sperm secrete digestive enzymes to break down glycoprotein membrane of zone pellucid to get into plasma membrane
  3. get into plsama membrane and fuse with oocyte. sperm releases its nucleus into the cytoplasm of the oocyte
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23
Q

what are the 2 gametes

A

oocyte and sperm

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24
Q

gamete

A
  • Gamete – a haploid germ cell
    § Oocyte – gamete from ovaries
    § Sperm – gamete from testes
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25
Q

fertilization

A

fusion of the pronucleus of the two gametes (oocyte and sperm)

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26
Q

zona pellucida

A

protein coat that surrounds an oocyte as well as the
early embryo

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27
Q

zygote

A

a fertilized, diploid oocyte – has not yet divided

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28
Q

embyro

A

– multicellular organism, prior to fetal stage
§ Arbitrarily defined as period from fertilization – end of week 7

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29
Q

fetus

A

(multicellular organism, from end of embryonic stage (wk 8) to birth

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30
Q

neonate

A

newbron

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31
Q

extraembroynic

A

cells formed during development that do not become part of the neonatal organism, but involute or contribute to the fetal membranes

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32
Q

embryo vs fetus week timeline

A

embryo; week 0-7
fetus; week 8-brith

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33
Q

blastocoel

A

fluid cavity

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34
Q

morula

A

approximately 16-cell stage (12 – 32 cells) of an embryo

§ No blastocoel

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35
Q

blastocyst

A

a spherical mass of cells that is composed of a trophoblast that surrounds a fluid cavity (blastocoel) and an inner cell mass (embryoblast)

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36
Q

blastocyst 2 parts

A

trophoblast and embryoblast

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37
Q

cleavage

A

cell division in the early embryo–> each division does not increase the size of the embryo, instead each division results in smaller and smaller cells

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38
Q

blastomere

A

a cell that is totipotential and is present during very early development (first week)

§ Product of cleavage

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39
Q

totipotential

A

a cell that can become any cell

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40
Q

implantation

A

occurs when an embryo contacts and then becomes surrounded by the endometrium of the uterus

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41
Q

what gets implanted in the uterine wall/ cavity

A

blastocyst (after it sheds zone pellucida)

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42
Q

what is the 3 main steps in week 1

A
  1. fertilization
  2. zygote –> blastocyst
  3. adhere to endometrium (uterus) for implantation
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43
Q

what is cell division AKA and what does it form

A

cleavage; blastomeres

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44
Q

what is the trophoblast develop into

A

Manyofthesecellsdevelopintothe membranes of placenta

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45
Q

what does the embryoblast develop into

A

these cells develop into the embryo

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46
Q

embryoblast vs trophoblast; which is inner layer and which is outer

A

embryoblast aka inner cell mass

trophoblast is outer layer; but still covered by zone pellucida

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47
Q

where does fertilization of the oocyte occur

A

ampulla of uterine tube

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48
Q

how does the blastocyst get to the fundus of the uterus from the ampulla of there uterine tube

A

from increased in progesterone after ovulation and from cilliary movement in “wave”

49
Q

zona pellucida roles

A

barrier, communication, immunologic defense, signal

§ Barrier that ensures that only one sperm fertilizes an oocyte
§ Porous – allows communication between the embryo and the maternal reproductive structures
§ Protects the embryo from immunologic defences
§ Acts as a signal to help with differentiation of
trophoblast cells
§ Prevents premature implantation of the embryo
§ Prevents the blastomeres from dissociating

50
Q

what does the zone pellucida help prevent

A

early implantation of the embryo which leads to ectopic pregnancy

51
Q

when does embryo hatch out of zone pellucida

A

day 6

52
Q

how does the zone pellucida get broken down so that the blastocyst can hatch through

A

§ The trophoblastic cells just over the embryoblast seem to secrete/produce particular proteinases that weaken the wall of the ZP
§ The blastocyst “hatches” through this defect in the ZP and is ready to contact the endometrium and implant itself within it

53
Q

how does blastrocyst where to endometrial epithelium (2 parts)

A

endometrial epithelium has mucin and pinopods

trophoblast binds pinopods

adhesion via selectin (binds mucins) and integral binding

54
Q

when trophoblast contacts endometrial epithelium which 2 layers are formed; and which is inner and outer

A

cytotrophoblast- inner layer
syncytiotrophoblast- outer layer

55
Q

at which day does blastocyst contact endometrial epithelium

A

day 6

56
Q

how blastocyst gets implanted

A

synctiotrophoblast becomes multinuclear cell and invades endometrial stroma

  • Syncytiotrophoblast develops into a multinuclear cell “mass” where the borders between individual cells are indistinct
  • The syncytiotrophoblast invades quickly and deeply into the endometrial stroma (area under the epithelial cell)
57
Q

what happens when synctiotrophoblast invade endometrial stoma (2 functions)

A
  1. form villi via proteinases and adhesion molecules (later becomes placenta)
  2. secret human chorionic gonadotropin (hCG) to prevent shedding of endometrium

§ Invasion into the endometrial stroma and induction/formation of villi (later becomes the placenta)
* Proteinases and adhesion molecules perform this role §

Secretion of human chorionic gonadotropin (hCG)
* hCG prevents the shedding of the endometrium (and loss of the embryo) by maintaining ovarian secretion of steroid hormones (i.e. progesterone)
* hCG is the hormone detected in pregnancy tests

58
Q

what 2 layers does the embryoblast divide into when synctiotrophoblast invades into the stroma

A

epiblast and hypoblast

§ Epiblast
* This layer will become embryo
proper

§ Hypoblast
* It will line the blastocystic cavity (coelom) and form the primary yolk sac
* Also known as the primary endoderm

59
Q

what does epiblast becomes

A

embryo proper

60
Q

what does hypoblast become

A

primary yolk sac

61
Q

cephalad

A

towards the head region (anatomical term)

62
Q

caudad

A

towards the “tail” region (anatomical term)

63
Q

coelom

A

a fluid-filled cavity

64
Q

gastrulation

A

the process of forming three embryonic germ layers; ectoderm, endoderm, mesoderm

65
Q

ectoderm

A

outer

a layer that is typically found on the “exterior” of the organism

66
Q

endoderm

A

inner

a layer that is typically found on the “interior” of the organism

67
Q

mesoderm

A

middle

(intraembryonic mesoderm) – a layer found between the ectoderm and mesoderm

68
Q

which 2 layers that are formed in gastrulation be formed in the later weeks and be extra embyronic

A

endoderm and mesoderm

endoderm and mesoderm can also be extra- embryonic (formation of extra-embryonic endoderm and mesoderm is not classified as gastrulation)

69
Q

which day is implantation complete by and what does it look like

A

day 10

§ The embryo is completely embedded within the endometrium § Surrounded by syncytiotrophoblast cells

70
Q

which cells undergo decidulatization and what do they become

A

stomal cells –> decidual cells

71
Q

decidual cells purpose

A

get glycogen and lipids. contact syncytiotrophoblast= apoptosis and release nutrients needed for embryonic growth

  • The stromal cells (below the epithelium) undergo decidualization
    § Now known as decidual cells
    § Decidual cells accumulate glycogen and lipids throughout the uterus
    § The decidual cells that the syncytiotrophoblast contact undergo apoptosis, releasing stored nutrients needed for embryonic growth (until the placenta is better established)
72
Q

amnioblast

A

cells that surround the developing
amniotic cavity

73
Q

what enlarges and gives rise to the amnioblast

A

epiblast

74
Q

how is extra embryonic mesoderm formed

A

The hypoblast extends around the entire interior surface of the blastocoel

§ New class of cells begin to form and migrate between the hypoblast-derived cells (yolk sac or extraembryonic endoderm) and the cytotrophoblast. These cells form extraembryonic mesoderm

75
Q

what does blastocoel turn into after hypoblast makes extra embryonic mesoderm

A

primary umbilical vesicle / primary yolk sac

76
Q

what makes the bilmainar disk

A

hypoblast and epiblast

77
Q

where does extra embryonic mesoderm develop

A

between the cytotrophoblast and the cells derived from the hypoblast

78
Q

where is the extra embryonic coelom formed

A

between extra embryonic mesodermal cells

Fluid begins to accumulate between the extra- embryonic mesodermal cells to form another cavity that is known as the extraembryonic coelom

79
Q

3 fluid filled cavities in week 2/3

A
  1. umbilical vesicles/ yolk sac
  2. amniotic cavity
  3. extra embryonic coelom

§ Umbilical vesicle – as the embryo develops the primary umbilical vesicle becomes the smaller secondary umbilical vesicle
§ The amniotic cavity – found above the epiblast
§ Extraembryonic coelom – as this enlarges and develops, it will develop into the chorionic cavity

80
Q

what day does fluid in extra-embryonic mesoderm become extra-embryonic coelom

A

day 13

81
Q

where is the extraembyronic coelom form

A

in extraembryonci mesoderm

Extraembryonic coelom completely surrounds the rest of the embryo everywhere except for at the junction of the amniotic cavity and the rest of the chorionic sac

82
Q

the connecting stalk forms from what and will become what

A

derived from the extraembryonic mesoderm.

junction of the amniotic cavity and the rest of the chorionic sac

  • This junction will become the connecting stalkàthis develops later into the umbilical cord
83
Q

On day 13/14 what 2 layers are formed by the extraembyronic mesoderm

A

extra embryonic splanchnic mesoderm and extra embryonic somatic mesoderm

84
Q

what separates the 2 layers of the extraembyronic mesoderm

A

fluid in the extraembryonic coelom

85
Q

extra embryonic splanchnic mesoderm vs extra embryonic somatic mesoderm location

A

§ Extraembryonic splanchnic mesoderm – surrounds the umbilical vesicle(s) (yolk sac)

§ Extraembryonic somatic mesoderm – found just underneath the cytotrophoblast, inner lining of the chorionic sac

86
Q

what is the chorion made of

A

extraembryonic somatic mesoderm + trophoblast

87
Q

what is inside and outside of the chorionic sac

A

Chorionic sac encloses the embryo and its cavities, and is surrounded by the syncytiotrophoblast

88
Q

when does extra embryonic coelom become chorionic cavity

A

day 14

89
Q

how are the amniotic cavity, secondary umbilical vesicle, and bilaminar disk “attached” to the chorion

A

connecting stalk

90
Q

What is formed when syncytiotrophoblast contact endometrial blood vessels

A

they deteriorate and blood pools = lacunar netowkrs

91
Q

how is the embryo nourished

A

by oxygenated maternal blood via simple diffusion from lacunar networks and glycogen/ lipids from deteriorating decidual cells

-no circulation yet

92
Q

how are primary villi formed and when

A

day13/14 cytotrophoblasts send extension to lacuna

precurors of functional placental villi

93
Q

prechordal plate

A

§ Thickened area of columnar cells that acts as an organization
area, found in the cephalad region of the hypoblast

93
Q

what are is prechordal plate at

A

cephlad region of hypoblast

94
Q

role of prechordal plate

A

organizing center

95
Q

induction

A

signaling “episodes” by key areas of the embryo that stimulate differentiation and development of local structures

96
Q

what is the organizer for head and mouth region and induces formations of structures at cephalad pole

A

hypoblast

97
Q

hypoblasts induce cephalad pole structure formation and what else do they do in conjunction with this

A

§ It also prevents the formation of structures that belong at the caudal aspect of the embryo

98
Q

thickening of hypoblast forms

A

prechordal plate

99
Q

main event in week 3

A

gastrulation
3 layers
* Ectoderm
* Mesoderm
* Endoderm

100
Q

in week 3 what is the embryo now referred to as

A

gastrula

101
Q

in week 3 what does the bilaminar embryonic disc become

A

trilaminar embryonic disc

102
Q

when does gastrulation take place

A

week 3

103
Q

when does the primitive streak appear

A

beginning of week 2

104
Q

what is the primitive streak

A

thickened linear band in the median plane of the dorsal aspect of the embryonic disc

105
Q

what region does the primitive streak initiate

A

caudal region of epiblast

106
Q

how is the primitive streak formed

A

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

107
Q

where does the primitive node form

A

Cells at the cephalad end of the primative streak proliferate to form a primitive node

108
Q

where do the cells that form the mesenchyme come from

A

from deep surface of primitive streak

109
Q

mesenchyme

A

embryonic connective tissue which forms the supporting tissues of the embryo (i.e. embryonic connective tissue)

110
Q

what does some of the mesenchyme form

A
  • Some mesenchyme forms mesoblastic cells (undifferentiated mesoderm)

§ The mesoblasts form the intraembryonic, or embryonic, mesoderm

111
Q

where is embryonic mesoderm from (intraembryonic)

A

mesoblastic cells from mesenchyme

112
Q

SIMPLE
ecto
endo
mesoderm

from what?

A

mesoderm from mesoblasts

endoderm from epiblast and primitive node/streak

ectoderm from remaining epiblast cells

113
Q

what type of cells are mesenchymal cells? where do they migrate to? and what do they turn into>

A

pluripotent

Mesenchymal cells derived from the primitive streak migrate widely

differentiate to ie. Fibroblasts, chondroblasts, osteoblasts

114
Q

embryonic endoderm in the roof of the umbilical vesicle is formed by?

A

Cells from the epiblast, as well as from the primitive node and other parts of the primitive streak, displace the hypoblast

115
Q

embryonic ectoderm is formed by?

A

The cells remaining in the epiblastw

116
Q

what gives rise to all 3 layers in gastrulation

A

epiblast

117
Q

when does the primitive streak diminish in size and become insignificant structure in sacrococcugeal region

A

end of 4th week

BMS150 test 2 (18 decks)

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