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COT 1 (WPH) > 1.3 embryology - zygote to primitive epithelia > Flashcards

1.3 embryology - zygote to primitive epithelia Flashcards

1
Q

embryonic stage of development

A

fertilization - week 8 (day 56) when all major structures are present

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2
Q

fetal stage of development

A

day 57 - birth

period of growth and differentiation of tissues and organs formed in embryonic period

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3
Q

fertilization - beginning and end

A

sperm/oocyte contact to mixing chromosomes

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4
Q

cleavage divisions

A

mitotic divisions of zygote resulting in collection of blastomeres

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5
Q

blastomere

A

cell produced by zygotic cleavage. collection forms 12 cell morula

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6
Q

morula enters uterus, develops fluid filled cavity, becomes this

A

blastocyst

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7
Q

embryoblast

A

inner cell mass of blastocyst gives rise to embryo

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8
Q

trophoblast

A

outer cell mass of blastocyst gives rise to placenta

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9
Q

endometrium

A

luminal layer of uterus, simple columnar epithelium with connective tissue stroma

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10
Q

stroma

A

connective tissue framework

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11
Q

2 layers of endometrium

A

functionalis

basalis

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12
Q

decidua

A

functionalis becomes the decidua during pregnancy

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13
Q

cytotrophoblast

A

thin, mitotically active layer that develops from the trophoblast after implantation

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14
Q

what happens to the trophoblast after implantation?

A

proliferates rapidly and becomes the cytotrophoblast and the syncytiotrophoblast

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15
Q

trophoblast turns develops into what 2 layers after implantation?

A

cytotrophoblast

syncytiotrophoblast

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16
Q

syncytiotrophoblast

A

outer mass of the trophoblast consisting of a multinucleated mass with no cell boundaries

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17
Q

what is the chorion formed by?

A

extraembryonic mesoderm, syncytiotrophoblast, and cytotrophoblast

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18
Q

what does the chorion do?

A

contributes to fetal portion of placenta

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19
Q

ectopic pregnancy

A

implantation of blastocyst outside of uterus, usually in ampulla of oviduct

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20
Q

bilaminar disc - what does it arise from and when?

A

arises from changes in the embryoblast in the second week of development

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21
Q

epiblast

A

thick, dorsal aspect of the bilaminar disc consisting of high columnar cells related to the amniotic cavity

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22
Q

hypoblast

A

ventral layer of the bilaminar disc located below the epiblast, consisting of small cuboidal cells related to yolk sac formation and extraembryonic mesoderm

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23
Q

what is another name for the hypoblast?

A

primitive endoderm

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24
Q

does the hypoblast contribute to the tissues of the embryo?

A

no

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25
Q

yolk sac

A

ventral structure lined by hypoblast cells, below hypoblast layer

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26
Q

function of the yolk sac?

A
  • origin of primordial germ cells
  • early blood cell development
  • regulation of nutrients to embryo
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27
Q

how is the amnion formed?

A

from cells that separate from the epiblast

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28
Q

what does the amnion do?

A

encloses the amnionic cavity

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29
Q

amnionic cavity

A

surrounds embryo and fetus with amnionic fluid - critical to health of embryo

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30
Q

primitive streak

A

thickened band of epiblast cells appearing at the beginning of week 3 in the caudal, dorsal aspect of the bilaminar disc. epiblast cells migrate down through streak to form endoderm and mesoderm during gastrulation

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31
Q

where does the primitive streak first appear?

A

caudal, dorsal aspect of the bilaminar disc
-aka-
caudal aspect of the epiblast

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32
Q

when does the primitive streak first appear?

A

beginning of week 3

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33
Q

epiblast cells migrate through the primitive streak to form what 2 layers during gastrulation?

A

endoderm

mesoderm

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34
Q

gastrulation

A

period of epiblast proliferation, migration, and differentiation through which the 3 germ layers form

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35
Q

what are the 3 germ layers formed during gastrulation?

A

ectoderm
mesoderm
endoderm

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36
Q

what do the ectoderm, endoderm, and mesoderm give rise to?

A

All cells, tissues, and structures of the embryo

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37
Q

brain growth, tooth development, secondary sex characteristics, and ossification of bones are all examples of development that occurs

A

postnatally

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38
Q

what are the two phases of prenatal development?

A

embryonic period

fetal period

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39
Q

4 significant developmental processes of the embryonic stage include:

A

cellular proliferation, migration, differentiation, formation of all major internal and external structures

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40
Q

what is another name for the embryonic period?

A

the period of organogenesis

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41
Q

what does the “period of organogenesis” refer to?

A

the embryonic period, in which all the major events of organ formation occur

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42
Q

why is the embryonic period also called the period of organogenesis?

A

all major events of organ formation occur

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43
Q

time frame of the embryonic period

A

fertilization to day 56 (week 8)

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44
Q

time frame of fetal period

A

day 57 (9th week) to birth

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45
Q

what is the fetal period significant for?

A

growth and maturation of the organ systems developed in the embryonic period

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46
Q

how many chromosomes are typical of a human somatic cell?

A

46

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47
Q

daughter cells of zygotic cleavage divisions are called

A

blastomeres

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48
Q

the 12-32 blastomere stage is called the

A

morula

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49
Q

how many cells in the morula

A

12-32 cells

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50
Q

the morula turns into the ___ by ____

A

the morula turns into the blastocyst by absorbing fluid and forming a large central cavity – the blastocyst cavity

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51
Q

what are 3 components of the blastocyst

A

embryoblast
trophoblast
blastocyst cavity

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52
Q

cells that migrate to the interior of the blastocyst become the

A

embryoblast (inner cell mass)

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53
Q

cells that migrate to the periphery of the blastocyst become the

A

trophoblast

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54
Q

why does the zona pellucida degenerate?

A

to allow for implantation and growth

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55
Q

when does implantation occur?

A

~day 6

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56
Q

what causes the endometrial layer to to increase in thickness and and provide nourishment for the embryo?

A

hormonal control

57
Q

when does the trophoblast begin to proliferate and divide into two layers?

A

as it contacts the endometrium

58
Q

teratogen

A

environmental agents that cause congenital abnormalities (i.e. alcohol, drugs, radiation)

59
Q

name 3 teratogens

A

alcohol, drugs, radiation

60
Q

what is the critical period of susceptibility to teratogens? why?

A

the embryonic period between weeks 2 and 8. critical period of tissue and organ system development

61
Q

when in the embyronic period is the embryo apparently not as susceptible to teratogens? why?

A

first 2 weeks. because death of the embryo (spontaneous abortion) is more likely to occur

62
Q

when do embryonic cells apparently transition from totipotent to pluripotent?

A

when the morula becomes the blastocyst

63
Q

fertilization age vs gestational age

A

age from fertilization vs age since last normal menstrual period (LNMP)

64
Q

typical menstrual cycle length

A

28 days

65
Q

typical time of fertilization

A

day 14-15 of menstrual cycle

66
Q

approximate difference between gestational and fertilization age

A

14 days (2 weeks)

67
Q

another name for fertilization age

A

conception age

68
Q

which is older, gestational age or fertilization age? by how much?

A

gestational age is 14 days older

69
Q

normal gestational age at birth (days)

A

280 days

70
Q

normal fertilization age at birth (days)

A

266 days

71
Q

how do you calculate estimated due date from date of last menstrual period?

A

subtract 3 months, add 7 days
-or-
add 9 months and 7 days (280 days)

72
Q

mom’s last period was Sept 5th, what is the estimated due date (EDD) of her baby?

A

June 12th

73
Q

what region of the blastocyst gives rise to only extraembryonic cells?

A

trophoblast - outer cell mass

74
Q

what region of blastocyst gives rise to intraembryonic cells?

A

embryoblast - inner cell mass

75
Q

what is the function of extraembryonic tissues?

A

allow embryo to survive in female uterus

76
Q

implantation induces the trophoblast to do what?

A

divide into 2 layers: cytotrophoblast and syncytiotrophoblast

77
Q

of the two layers of the former trophoblast, which is inner and which is outer?

A

inner - cytotrophoblast

outer - syncytiotrophoblast

78
Q

of the two layers of the former trophoblast, which produces hCG?

A

syncytiotrophoblast

79
Q

the syncytiotrophoblast produces what hormone?

A

human chorionic gonadotropin, hCG

80
Q

what hormone can be used to detect pregnancy?

A

human chorionic gonadotropin, hCG

81
Q

how many days after implantation can hCG be detected by an early pregnancy detection kit?

A

6-12 days after implantation

82
Q

how many days after fertilization can hCG be detected by an early pregnancy detection kit?

A

12-18 days after fertilization

83
Q

“ectopic” =

A

“out of place”

84
Q

are ectopic pregnancies potentially life threatening? why?

A

Yes. Internal bleeding.

85
Q

decidua

A

the pregnant endometrium

86
Q

decidua reaction

A

stromal cells of the decidua become large rounded cells filled with glycogen and lipids

87
Q

____ penetrates deeper into the stroma of the decidua and erodes the cells and walls of blood vessels

A

syncytiotrophoblast

88
Q

what is the role of hCG?

A

induces the ovary to produce estrogen and progesterone to maintain the pregnancy

89
Q

hCG is secreted by ___

in order to ___

A

the uterus-syncytiotrophoblast

induce the ovary to produce estrogen and progesterone to maintain the pregnancy

90
Q

in what week does the bilaminar disk form?

A

week 2

91
Q

which layer of the bilaminar disk encloses the amnonic cavity?

A

the epiblast

92
Q

what kind of tissue forms all glands of the body?

A

epithelial tissue

93
Q

what kind of tissue covers the body surface and lines cavities?

A

epithelial tissue

94
Q

all ____ cells contact a basal lamina

A

epithelial

95
Q

what are the two cavities formed in week 2?

A

amniotic cavity

yolk sac

96
Q

cells from which part of the bilaminar disc form the amnion that lines the amnionic cavity?

A

cells from the epiblast

97
Q

cells from which part of the bilaminar disc form the membrane of the yolk sac?

A

cells from the hypoblast

98
Q

early networks that form in the uterine lining to supply blood to the embryo are called

A

lacunar networks

99
Q

trophoblastic lacunae and enlarged blood vessels of the uterus meet to form the

A

primordial uteroplacental circulation

100
Q

cells of the epiblast surrounding the amniotic cavity are called

A

amnioblasts

101
Q

the migration of cells from the hypoblast over the inner surface of the cytotrophoblast form

A

the primary yolk sac

102
Q

the secondary (definitive) yolk sac replaces the primary yolk sac through

A

a second migration of primordial endodermal cells from the hypoblast

103
Q

2 important functions of the yolk sac

A

hematopoiesis, primordial germ cells… formation? migration? unclear…

104
Q

hematopoiesis

A

blood cell formation

105
Q

the yolk sac is important during what time period

A

the first 4 weeks of development, then it regresses and typically vanishes by birth

106
Q

primordial germ cells are first recognized where

A

on the wall of the yolk sac prior to migration to gonads

107
Q

the development of the three layered embryo from the bilaminar disc is called

A

gastrulation

108
Q

the primitive streak moves from

A

caudal to rostral (cranial)

109
Q

the primitive pit is found on the __ end of the primitive groove

A

cranial

110
Q

T/F the primitive streak establishes major body axes

A

True

111
Q

4 body axes established by the primitive streak include:

A

caudal / cranial
medial / lateral
right / left
dorsal / ventral

112
Q

this structure appears to arise from the cranial end of the primitive streak, inserts into the endoderm, forms a thickening, contributes to the oropharyngeal membrane, forms an important signaling center involved in formation of the forebrain of the central nervous system, and contributes connective tissue to the head region

A

the prechordal plate

113
Q

what cells form the primitive endoderm?

A

hypoblast cells before the primitive streak develops and replaces with the definitive endoderm

114
Q

summarize the formation of the endoderm during gastrulation

A

early epiblast cells slip through the basal lamina in the primitive streak and displace the primitive endoderm (hypoblast cells) with the definitive endoderm

115
Q

summarize the formation of the mesoderm during gastrulation

A

later epiblast cells migrating through the primitive streak and past the endoderm form the mesoderm

116
Q

summarize the formation of the ectoderm during gastrulation

A

cells remaining in the epiblast layer (not migrating through the primitive streak) form the ectoderm

117
Q

this structure replaces the primitive pit

A

the notochord

118
Q

the notochord extends cranially to the

A

prechordal plate

119
Q

what is the fate of the hypoblast after gastrulation?

A

unclear. apparently estraembryonic structures and the cloacal membrane

120
Q

cloacal membrane

A

membrane over anus that breaks down early in development

121
Q

oropharyngeal membrane

A

membrane over the mouth that breaks down early in development

122
Q

the notochord is considered a derivative of which germ layer?

A

the mesoderm

123
Q

3 layers of the chorion

A
  • extraembryonic somatic mesoderm (and splanchnic mesoderm?) (line amnion & yolk sac)
  • cytotrophoblast layer
  • syncytiotrophoblast layer
124
Q

the chorionic cavity divides the extraembryonic mesoderm into the…

A

-extraembryonic somatic mesoderm (lines trophoblast and amnion)
-extraembryonic splanchnic
mesoderm- lines the yolk sac

125
Q

the fetal and maternal contributions to the placenta are

A

chorion (fetal)

decidua (maternal)

126
Q

can drugs, viruses, or alcohol cross the placental membrane?

A

Yes.

127
Q

draw the amnionic cavity, the secondary yolk sac, the chorionic cavity, and the remnant of the primitive yolk sac

A

draw it

128
Q

3rd week most significant for

A

conversion of bilaminar disc to trilaminar disc through gastrulation

129
Q

what day does the primitive streak appear?

A

15-16 days post fert

130
Q

in the bilaminar disc, high columnar cells form the __

A

epiblast

131
Q

function of the syncytiotrophoblast

A

secrete hCG along with the uterus

132
Q

in week 2 when the yolk sac forms, does the yolk sac contain yolk? what nourishes the embyro?

A

the yolk sac contains no yolk. the embryo is nourished by the lacunar networks

133
Q

in week 2, what new layer of cells forms between the yolk sac and the cytotrophoblast?

A

the extraembryonic mesoderm

134
Q

cavities form in the extramebryonic mesoderm and form a new space, the…

A

chorionic cavity

135
Q

the chorionic cavity divides the extraembryonic mesoderm into these 3 layers…

A
  • extraembryonic somatic mesoderm – lining trophoblast and amnion
  • extraembryonic splanchnic mesoderm – lines the yolk sac
  • chorion, lines the chorionic cavity
136
Q

does the extraembryonic splanchnic mesoderm line the primary or secondary (definitive) yolk sac?

A

the definitive yolk sac – the primary yolk sac is pinched off and regressing

137
Q

when the primary yolk sac is pinched off it becomes the….

A

exocoelemic cyst

138
Q

in what layer of embryonic cells are the lacunar networks formed?

A

syncytiotrophoblast

139
Q

when does the decidua reaction begin? how long does it last?

A

Amusingly, the decidual reaction in humans begins with ovulation. This doesn’t make too much intellectual sense, though, so I’ll forgive you if you want to believe it begins with implantation, as is true in many other animals. A major purpose of decidualization is to prepare the uterine mucosa for a “burrowing” conceptus. The decidualized cells limit the ability of the trophoblast to enzymatically dissolve the mucosa. (You want the conceptus to become encapsulated within the mucosa, but you don’t want it to reach the muscularis layer.) The mucosa remains decidualized for the duration of the pregnancy. (During a normal cycle, the decidualization is relatively insignificant, and any decidualized cells are lost at menstruation.)

COT 1 (WPH) (25 decks)

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