1.3 embryology - zygote to primitive epithelia Flashcards Preview

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Flashcards in 1.3 embryology - zygote to primitive epithelia Deck (139)
1

embryonic stage of development

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

2

fetal stage of development

day 57 - birth
period of growth and differentiation of tissues and organs formed in embryonic period

3

fertilization - beginning and end

sperm/oocyte contact to mixing chromosomes

4

cleavage divisions

mitotic divisions of zygote resulting in collection of blastomeres

5

blastomere

cell produced by zygotic cleavage. collection forms 12 cell morula

6

morula enters uterus, develops fluid filled cavity, becomes this

blastocyst

7

embryoblast

inner cell mass of blastocyst gives rise to embryo

8

trophoblast

outer cell mass of blastocyst gives rise to placenta

9

endometrium

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

10

stroma

connective tissue framework

11

2 layers of endometrium

functionalis
basalis

12

decidua

functionalis becomes the decidua during pregnancy

13

cytotrophoblast

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

14

what happens to the trophoblast after implantation?

proliferates rapidly and becomes the cytotrophoblast and the syncytiotrophoblast

15

trophoblast turns develops into what 2 layers after implantation?

cytotrophoblast
syncytiotrophoblast

16

syncytiotrophoblast

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

17

what is the chorion formed by?

extraembryonic mesoderm, syncytiotrophoblast, and cytotrophoblast

18

what does the chorion do?

contributes to fetal portion of placenta

19

ectopic pregnancy

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

20

bilaminar disc - what does it arise from and when?

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

21

epiblast

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

22

hypoblast

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

23

what is another name for the hypoblast?

primitive endoderm

24

does the hypoblast contribute to the tissues of the embryo?

no

25

yolk sac

ventral structure lined by hypoblast cells, below hypoblast layer

26

function of the yolk sac?

-origin of primordial germ cells
-early blood cell development
-regulation of nutrients to embryo

27

how is the amnion formed?

from cells that separate from the epiblast

28

what does the amnion do?

encloses the amnionic cavity

29

amnionic cavity

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

30

primitive streak

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

31

where does the primitive streak first appear?

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

32

when does the primitive streak first appear?

beginning of week 3

33

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

endoderm
mesoderm

34

gastrulation

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

35

what are the 3 germ layers formed during gastrulation?

ectoderm
mesoderm
endoderm

36

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

All cells, tissues, and structures of the embryo

37

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

postnatally

38

what are the two phases of prenatal development?

embryonic period
fetal period

39

4 significant developmental processes of the embryonic stage include:

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

40

what is another name for the embryonic period?

the period of organogenesis

41

what does the "period of organogenesis" refer to?

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

42

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

all major events of organ formation occur

43

time frame of the embryonic period

fertilization to day 56 (week 8)

44

time frame of fetal period

day 57 (9th week) to birth

45

what is the fetal period significant for?

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

46

how many chromosomes are typical of a human somatic cell?

46

47

daughter cells of zygotic cleavage divisions are called

blastomeres

48

the 12-32 blastomere stage is called the

morula

49

how many cells in the morula

12-32 cells

50

the morula turns into the ___ by ____

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

51

what are 3 components of the blastocyst

embryoblast
trophoblast
blastocyst cavity

52

cells that migrate to the interior of the blastocyst become the

embryoblast (inner cell mass)

53

cells that migrate to the periphery of the blastocyst become the

trophoblast

54

why does the zona pellucida degenerate?

to allow for implantation and growth

55

when does implantation occur?

~day 6

56

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

hormonal control

57

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

as it contacts the endometrium

58

teratogen

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

59

name 3 teratogens

alcohol, drugs, radiation

60

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

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

61

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

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

62

when do embryonic cells apparently transition from totipotent to pluripotent?

when the morula becomes the blastocyst

63

fertilization age vs gestational age

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

64

typical menstrual cycle length

28 days

65

typical time of fertilization

day 14-15 of menstrual cycle

66

approximate difference between gestational and fertilization age

14 days (2 weeks)

67

another name for fertilization age

conception age

68

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

gestational age is 14 days older

69

normal gestational age at birth (days)

280 days

70

normal fertilization age at birth (days)

266 days

71

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

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

72

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

June 12th

73

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

trophoblast - outer cell mass

74

what region of blastocyst gives rise to intraembryonic cells?

embryoblast - inner cell mass

75

what is the function of extraembryonic tissues?

allow embryo to survive in female uterus

76

implantation induces the trophoblast to do what?

divide into 2 layers: cytotrophoblast and syncytiotrophoblast

77

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

inner - cytotrophoblast
outer - syncytiotrophoblast

78

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

syncytiotrophoblast

79

the syncytiotrophoblast produces what hormone?

human chorionic gonadotropin, hCG

80

what hormone can be used to detect pregnancy?

human chorionic gonadotropin, hCG

81

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

6-12 days after implantation

82

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

12-18 days after fertilization

83

"ectopic" =

"out of place"

84

are ectopic pregnancies potentially life threatening? why?

Yes. Internal bleeding.

85

decidua

the pregnant endometrium

86

decidua reaction

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

87

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

syncytiotrophoblast

88

what is the role of hCG?

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

89

hCG is secreted by ___
in order to ___

the uterus-syncytiotrophoblast
induce the ovary to produce estrogen and progesterone to maintain the pregnancy

90

in what week does the bilaminar disk form?

week 2

91

which layer of the bilaminar disk encloses the amnonic cavity?

the epiblast

92

what kind of tissue forms all glands of the body?

epithelial tissue

93

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

epithelial tissue

94

all ____ cells contact a basal lamina

epithelial

95

what are the two cavities formed in week 2?

amniotic cavity
yolk sac

96

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

cells from the epiblast

97

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

cells from the hypoblast

98

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

lacunar networks

99

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

primordial uteroplacental circulation

100

cells of the epiblast surrounding the amniotic cavity are called

amnioblasts

101

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

the primary yolk sac

102

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

a second migration of primordial endodermal cells from the hypoblast

103

2 important functions of the yolk sac

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

104

hematopoiesis

blood cell formation

105

the yolk sac is important during what time period

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

106

primordial germ cells are first recognized where

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

107

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

gastrulation

108

the primitive streak moves from

caudal to rostral (cranial)

109

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

cranial

110

T/F the primitive streak establishes major body axes

True

111

4 body axes established by the primitive streak include:

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

112

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

the prechordal plate

113

what cells form the primitive endoderm?

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

114

summarize the formation of the endoderm during gastrulation

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

115

summarize the formation of the mesoderm during gastrulation

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

116

summarize the formation of the ectoderm during gastrulation

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

117

this structure replaces the primitive pit

the notochord

118

the notochord extends cranially to the

prechordal plate

119

what is the fate of the hypoblast after gastrulation?

unclear. apparently estraembryonic structures and the cloacal membrane

120

cloacal membrane

membrane over anus that breaks down early in development

121

oropharyngeal membrane

membrane over the mouth that breaks down early in development

122

the notochord is considered a derivative of which germ layer?

the mesoderm

123

3 layers of the chorion

-extraembryonic somatic mesoderm (and splanchnic mesoderm?) (line amnion & yolk sac)
-cytotrophoblast layer
-syncytiotrophoblast layer

124

the chorionic cavity divides the extraembryonic mesoderm into the...

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

125

the fetal and maternal contributions to the placenta are

chorion (fetal)
decidua (maternal)

126

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

Yes.

127

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

draw it

128

3rd week most significant for

conversion of bilaminar disc to trilaminar disc through gastrulation

129

what day does the primitive streak appear?

15-16 days post fert

130

in the bilaminar disc, high columnar cells form the __

epiblast

131

function of the syncytiotrophoblast

secrete hCG along with the uterus

132

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

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

133

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

the extraembryonic mesoderm

134

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

chorionic cavity

135

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

-extraembryonic somatic mesoderm -- lining trophoblast and amnion
-extraembryonic splanchnic mesoderm -- lines the yolk sac
-chorion, lines the chorionic cavity

136

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

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

137

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

exocoelemic cyst

138

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

syncytiotrophoblast

139

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

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.)