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FMS > MSCT Week 3: Embryology Basic Body Plan > Flashcards

MSCT Week 3: Embryology Basic Body Plan Flashcards

1
Q

First Trimester AKA

A

Embryonic Period

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2
Q

2nd and 3rd Trimesters AKA

A

Fetal Period

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3
Q

Embryonic Period Timeline

A

Fertilization to 8 weeks

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4
Q

Organogenesis is?

A

Formation of Organs

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5
Q

The basic body plan is set up during _______________.

A

Weeks 1-3 of the embryonic period

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6
Q

Fetal Period Timeline

A

9 weeks until birth (38-weeks post-fertilization)

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7
Q

Clinicians describe pregnancy by trimesters, three-month periods starting with the date of the onset of? and ending with?

A

Onset of the last menstrual period and ending with birth

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8
Q

landmark events during the first week

4 listed

A
  • Fertilization
  • Cleavage
  • Blastocyst formation
  • Implantation
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9
Q

describe how oocytes are selected

4 steps

A
  • with each ovarian cycle, 5-15 ovarian follicles with surrounding epithelial cells begin to grow
  • only one reaches maturity (called an Ovum)
  • ovum is ovulated (released) from the follicle in response to a surge in luteinizing hormone from the pituitary gland
  • The fimbrae, (fingerlike projections of the uterine or oviduct sweep the ovum into the uterine tube or oviduct
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10
Q

Ovum are ovulated in response to?

A

A Surge of luteinizing hormone (LH) from the pituitary gland

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11
Q

Fimbrae are?

A

Finger-like projections of the uterine tube or oviduct that sweep the ovum into the uterine tube

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12
Q

uterine tube AKA

A

Oviduct

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13
Q

Oviduct AKA

A

Uterine Tube

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14
Q

How does fertilization occur?

4 steps

A
  • when sperm swim through the uterus and oviduct to meet the ovum in a wide part of the oviduct called the ampulla
  • As soon as a sperm enters the ovum, the ovum completes the second meiotic division and the female pronucleus forms
  • The head of the sperm swells and becomes the male pronucleus
  • This diploid cell is now called a zygote
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15
Q

Zygote is?

A

Diploid cell that is the progenitor of the embryo

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16
Q

Cleavage is characterized by?

A

Mitotic divisions without growth

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17
Q

Cleavage begins…

A

as the one-celled zygote moves through the oviduct toward the uterus

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18
Q

The cells of the cleaving embryo are called?

A

Blastomeres

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19
Q

Blastomere potency

A

Blastomeres are totipotent until the 4-8 cell stage

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20
Q

Blastomeres give rise to…

A

The embryo and the fetal part of the placenta

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21
Q

When an embryo has 16 cells it is called a…

A

Morula (mulberry)

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22
Q

Morula means?

A

Mulberry

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23
Q

As the cells of the morula divide, they _________ and ______________.

A

As the cells of the morula divide, they compact (move closer together) and secrete fluid to form a cavity (cavitate)

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24
Q

After the morula divides and cavitates it is now a?

A

Blastocyst

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25
Q

The blastocyst arrives in the uterine cavity by

A

4-5 days after fertilization

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26
Q

4-5 days after fertilization?

A

The blastocyst arrives in the uterine cavity

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27
Q

When does the blastocyst attach to the uterine wall (implant)?

A

By day 6

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28
Q

By day 6, the blastocyst…

A

begins to invade the uterine wall (Implantation)

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29
Q

Implantation in the uterus timeline

A

day 6 - first 2 weeks

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30
Q

Identify

+

What time in development is pictured?

A

Week 1 of embryonic development

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31
Q

blastomere cell types

A

blastomeres of the 6-day embryo segregate into two distinct cell types

Inner cell mass (embryoblast)

Outer Cell Mass (Trophoblast)

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32
Q

Inner cell mass AKA

A

Embryoblast

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33
Q

Outer Cell Mass AKA

A

Trophoblast

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34
Q

Identify

A
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35
Q

Embryoblast gives rise to?

A

these cells form the embryo and are pluripotent stem cells

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36
Q

The Trophoblast gives rise to?

A

These cells surround the embryoblast and blastocyst cavity and will form the fetal part of the placenta

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37
Q

During week 2, the embryoblast and trophoblast each differentiate into?

A

2 layers and 2 cavities form giving rise to the bilaminar embryo

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38
Q

Bilaminar Embryo is?

A

embryoblast with 2 layers and 2 cavities formed by the embryoblast and trophoblast

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39
Q

Name the layers of the embryoblast

A
  • Epiblast
  • Hypoblast
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40
Q

The trophoblast differentiates into the?

A
  • Syncytiotrophoblast
  • Cytotrophoblast
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41
Q

The Epiblast is?

A

Columnar cells that secrete fluid to form the amniotic cavity above them

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42
Q

The Hypoblast is?

A

Cuboidal cells below the epiblast that migrate to line the blastocyst cavity converting it to the primitive yolk sac

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43
Q

Identify

A
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44
Q

Syncytiotrophoblast

A
  • Outer layer
  • one cytoplasm with many nuclei; a syncytium
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45
Q

Cytotrophoblast

A
  • Inner Layer
  • Actively proliferating cells
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46
Q

describe embryoblast development

A
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47
Q

By 12 days, the blastocyst is?

A

Completely embedded in the uterine wall

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48
Q

Lacunae means

A

Lakes

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49
Q

spaces in the syncytiotrophoblast called Lacunae serve what function?

A

Connect to capillaries in the uterine wall to establish the placental blood supply

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50
Q

The hypoblast cells lining the primitive yolk sac proliferate to form?

A

Loose connective tissue called extraembryonic mesoderm

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51
Q

Extraembryonic mesoderm arises from

A

The hypoblast cells lining the primitive yolk sac

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52
Q

How is the chorionic cavity formed?

A

spaces appear in the extraembryonic mesoderm and coalesce to form the chorionic cavity by 13 days

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53
Q

The connecting stalk function

A

suspends the bilaminar embryo within the chorionic cavity

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54
Q

The connecting stalk is composed of?

A

Extraembryonic mesoderm

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55
Q

The secondary or definitive yolk sac is characterized by?

A

The suspension of the bilaminar embryo in the chorionic cavity by the connecting stalk

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56
Q

Identify

+

what is this called?

A

Primary Yolk Sac 12 days

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57
Q

Identify

+

What is this called?

+

When does this occur?

A

13 days Secondary Yolk Sac

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58
Q

Explain the primary to secondary yolk sac transition

A
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59
Q

Dizygotic or Fraternal Twins arise from?

+

Dizogitic twins represent what percentage of twins?

A
  • Two oocytes fertilized by two sperm and represent
  • 70% of all twins
60
Q

The zygotes in dizygotic twins are genetically?

A

Distinct

61
Q

Implantation of dizygotic twins?

A

Implant separately

62
Q

Dizygotic twins fetal structures

A

Have separate

  • fetal membranes
  • placentas
  • amnions
  • chorions
63
Q

% of twins that are monozygotic?

A

30% of twins

64
Q

Monozygotic twins develop from?

A

One oocyte fertilized by one sperm

65
Q

Monozygotic twins mechanism

A

the zygote splitting at different stages of development so the twins are genetically identical

66
Q

Monozygotic twins are genetically?

A

Identical

67
Q

Fetal structures of monozygotic twins

A

Depending on when the splitting occurs, the placentas, amnions and chorions can be separate or shared

68
Q

If the zygote splits at the two-cell stage…

A

The embryos implant separately and develop similarly to dizygotic twins, each with its own placenta, amnion and chorion

69
Q

If the inner cell mass splits at the early blastocyst stage…

A

The embryos occupy the same chorion, but have separate amnions and one placenta

70
Q

If splitting occurs in the bilaminar embryo…

A

The embryos share an amnion, chorion and placenta

71
Q

Conjoined twins result from?

A

Very rarely when the embryos do not separate fully

72
Q

Describe monozygotic and dizygotic twinning and structures shared, splitting stages…

A
73
Q

Hydatidiform mole properties and prevalence

A
  • In 0.1% to 0.5% of pregnancies the fetal part of the placenta forms but the embryo does not.
  • This is called a molar pregnancy or hydatidiform mole
  • Hydatidiform moles can be complete or partial
74
Q

Hydatidiform mole means

A
  • Greek
  • hydatidos meaning water
  • mole means spot
75
Q

A complete mole characterization

A
  • complete lack of an embryo
  • the placental or chorionic villi become swollen as fluid is taken up from the maternal circulation and has nowhere to go and become swollen and resemble bunches of grapes or drops of water
76
Q

Do Complete moles abort?

A

Yes, usually early

77
Q

Clinical signs of a complete mole

5 listed

A
  • preeclampsia (maternal high-blood pressure) during the 1st trimester
  • vaginal bleeding
  • elevated chorionic gonadotropin (hCG)
  • High hCG secreted by the trophoblast result in excessive nausea and vomiting
  • 3-5% of complete moles develop into malingnat disease called gestational trophoblastic neoplasia, a malignant tumor of the trophoblast (one histologic type is carcinoma)
78
Q

Gestational Trophoblastic Neoplasia

A
  • A malignant tumor of the trophoblast (one histologic type is choriocarcinoma)
  • 3-5% of complete moles develop into gestational trophoblastic neoplasia
79
Q

High levels of hCG result in?

A

Excessive Nausea and vomiting

80
Q

Preeclampsia during the first trimester, vaginal bleeding and elevated human chorionic gonadotropin indicate what?

A

Complete mole

81
Q

Diagnosis method of a complete molar pregnancy

A

Cytogenetic analysis

82
Q

A cytogenetic analysis of a complete molar pregnancy will show?

A

normal diploid karyotype but all chromosomes are parentally derived

83
Q

Possible karyotypes of a complete molar pregnancy

3 listed

A
  • 46 XX
  • 46 XY
  • 46 YY
84
Q

Dispermic fertilization mechanism and possible karyotypes

A

two sperm fertilizing an oocyte that lacks or loses its own nucleus with a karyotype of…

  • 46 XX
  • 46 XY
85
Q

Monospermic Fertilization mechanism and possible karyotypes

A

One sperm that fertilizes an oocyte lacking a nucleus, the sperm undergoes mitosis without cytokinesis, doubling its DNA with a karyotype of…

46 XX

86
Q

46 YY Zygote

A

doesn’t develop as it lacks X chromosome genes essential for development

87
Q

Partial moles result from?

A

dispermic fertilization of a normal oocyte or fertilization by a single abnormal diploid sperm

88
Q

PArtial moles result in?

A

fetal tissue is present and spontaneous abortion usually occurs in the second trimester

89
Q

Possible karyotypes of partial moles

A

Usually triploid

  • 69, XXX
  • 69, XXY
  • 69, XYY
90
Q

Week 3 of development

A

The major event of the third week is converting the 2-layer embryo into a 3-layer embryo (trilaminar embryo)

91
Q

blastomeres are totipotent until the?

A

4-8 cell stage

92
Q

Trilaminar Embryo AKA

A

3-layer embryo

93
Q

Gastrulation establishes

A

the 3 layers that will give rise to all adult tissues and organs

94
Q

When is the primitive streak developed?

A

15 days

95
Q

Where is the primitive groove?

A

In the center of the primitive streak

96
Q

Where is the primitive node?

A

along the cranial end of the primitive groove

97
Q

Where is the primitive pit?

A

In the center of the primitive node

98
Q

What defines the major body axes?

A

Formation of the primitive streak (cranial-caudal, medial-lateral) (primitive streak is the median or midline

99
Q

During gastrulation, TGFβ and Wnt signaling causes?

A

FGF8 production

100
Q

FGF8 stimulates

A

epiblast cell migration (epithelial to mesenchymal transition)

101
Q

During gastrulation, epiblast cells migrate where?

A

Toward the center of the bilaminar disc-shaped embryo forming the primitive streak and dive down or invaginate through the primitive groove to replace hypoblast cells beneath them

102
Q

When the hypoblast is replaced by epiblast cells this layer is now called?

A

Endoderm (inside layer)

103
Q

Epiblast cells then migrate between the newly formed endoderm and epiblast layers form the?

A

Intra-embryonic mesoderm (middle layer)

104
Q

The remaining epiblast cells that did not migrate from the upper layer become the?

A

Ectoderm (outside layer)

105
Q

Identify structures and stage

A

Trilaminar Embryo

106
Q

Cells migrate which direction first in gastrulation?

A

Cranially first and then caudally last so that cranial or head mesoderm forms first

107
Q

Ectoderm forms?

A
  • Central and Peripheral Nervous Systems
  • Some head skeletal and connective tissue
  • Epidermis, hair, nails
  • Sensory epithelium of nose, ear and eye
108
Q

Mesoderm forms?

A
  • Skeletal, smooth, and cardiac muscle
  • cartilage, bone, connective tissue, blood
  • components of the kidneys and gonads (urogenital system)
109
Q

Endoderm forms?

A
  • Epithelium of gut and its derivatives (live, gallbladder, pancreas)
  • Epithelium of the respiratory system
110
Q

gastrulation 17-22 days

A
111
Q

Tube-within-a-tube body plan

A

The neural tube is not considered one of the tubes because it is not formed by body folding

112
Q

Caudal Regression Syndrome AKA

A

Caudal Dysplasia

113
Q

Caudal Regression Syndrome is?

A
  • A disorder that impairs the development of the lower (caudal) half of the body
  • this can include the lower limbs, lower back, and the lower gastrointestinal (gut) and urogenital (urinary and genital) tracts
114
Q

The underlying mechanism of Caudal Regression Syndrome

A
  • abnormal growth and migration during gastrulation resulting in abnormal development of the caudal mesoderm
  • Which is the last mesoderm to form
115
Q

The last mesoderm to form is?

A

Caudal Mesoderm

116
Q

Caudal Dysplasia Risk Factors

A

Multiple genetic and environmental factors are implicated in caudal dysplasia including:

  • maternal diabetes
  • Wnt gene defects
  • Vascular Abnormalities
  • Teratogens
117
Q

Sirenomelia AKA

A

Mermaid Syndrome

118
Q

Sirenomelia is?

A

an extreme and rare form of caudal dysplasia but it may be a distinct disorder

119
Q

Sirenomelia example

A
120
Q

Embryonic Induction

A
  • the stimulation of a specific developmental pathway in one group of cells (the responding tissue) by a closely approximated second group of cells (the inducing tissue).
  • It is also referred to as instructive interactions
  • In other words, a signal passes from the inducing to responding tissue, changing the fate of the responding tissue
121
Q

Embryonic Induction AKA

A

Instructive Interactions

122
Q

Embryonic Induction mechanisms

3 listed

A
  • Diffusion of the inducing molecule from one cell to another
  • Contact between the extracellular matrix of one cell to another
  • Direct contact between the inducing and responding cells
123
Q

Examples of embryonic Induction

4 listed

A
124
Q

Primitive Streak Formation Embryonic induction

A
125
Q

Mesoderm Formation Embryonic induction

A
126
Q

Neural Induction Embryonic induction

A
127
Q

Lens Induction Embryonic induction

A
128
Q

Ectopic Induction

A
129
Q

The period of susceptibility AKA

A

period of maximal sensitivity

130
Q

The period of susceptibility

A
  • is when the embryo is especially vulnerable to environmental factors causing abnormal development
  • this occurs during weeks 4-8 of the embryonic period when organs are forming during organogenesis
  • Insults during the first 3 weeks generally result in death of the embryo and spontaneous abortion
131
Q

Congenital Anomaly

A
  • something that is different or unusual at birth
  • AKA birth defect
    *
132
Q

Congenital anomalies account for more than _____ of infant deaths

A

20%

133
Q

Etiology of congenital anomailes

A
  • 50% of etiology of congenital anomalies is unknown
  • the other 50% is due to environmental factors, chromosomal defects, mutant genes, or are multifactorial
134
Q
A
135
Q

Possible mechanisms of congenital anomalies

4 listed

A
  • Faulty embryonic induction (mutant signaling molecule genes)
  • defects in apoptosis
  • defects in migration
  • developmental arrest
136
Q

Period of susceptibility timeline

A
137
Q

Causes of Congenital Anomalies

5 listed

A
138
Q

Anomaly definition

A

means a marked deviation from normal

139
Q

Association definition

A

nonrandom appearance of 2 or more anomalies together; cause is not known

140
Q

Congenital definition

A

Present at birth

141
Q
A
142
Q

Deformations definition

A

result from mechanical forces that mold a part of the fetus over a prolonged period

143
Q

Malformation definition

A

a structural defect in the body due to abnormal embryonic or fetal development

144
Q

Syndrome Definition

A

Is a group of anomalies occurring together that have a common cause

145
Q

Sequence Definition

A

is when a primary anomaly itself determines additional defects

146
Q

Teratogen Definition

A

Is any agent or factor that can disturb the development of an embryo

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