Embryology Flashcards

1
Q

which steps occur during the first week of pregnancy

A

ovulation
fertilisation
implantation

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2
Q

what is a zygote

A

fertilised ovum

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3
Q

what is a morula

A

what the zygote becomes once it has completed its first cell divisions - a solid mass of cells

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4
Q

after how many days does the morula form

A

4-6

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5
Q

what is a blastocyst

A

this is what the morula develops into during days 6-10 of pregnancy and is a hollow ball of cells

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6
Q

what is contained within the blastocyst

A

inner cell mass and trophoblast

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7
Q

what replenishes the baby’s blood

A

the mother’s blood

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8
Q

do the circulations of the embryo and mother mix

A

no

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9
Q

what separates the circulations of the embryo and mother

A

a thin barrier, permeable to most molecules but not cells

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10
Q

what occurs at 10-12 days of pregnancy

A

the implanted trophoblast contains an embryo with two cell layers

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11
Q

what are the two layers to the bilaminar embryo

A

epiblast and hypoblast

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12
Q

what is the function of the epiblast

A

gives rise to the embryonic ectoderm, mesoderm and endoderm

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13
Q

what does the hypoblast layer of the bilaminar embryo do

A

participates in the formation of the endoderm and the extraembryonic mesoderm

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14
Q

describe the shape of the bilaminer embryo

A

a disc with no distinct orientation or axis

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15
Q

what happens during gastrulation

A

the embryo develops an axis and the three embrionic cell layer

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16
Q

what is the key stage of gastrulation

A

the formation of a groove called the primitive streak

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17
Q

why does the bilaminar embryo develop an axis during gastrulation

A

to become bilaterally symmetrical

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18
Q

what are the mesoderm

A

the ectodermal cells that are induced to differentiate and migrate through the primitive streak toward the hypoblast

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19
Q

what forms the endoderm

A

interaction between the newly formed mesoderm and the hypoblast

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20
Q

how do the mesodermal cells form a third layer

A

by pushing through the primitive streak and spreading out

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21
Q

what occurs during weeks 3-8

A

organogenesis

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22
Q

what is organogenesis

A

formation of major organs from the three basic germ cell layers

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23
Q

what is the one of the first organs to be developed

A

the central nervous system

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24
Q

what is the neural tube

A

forerunner of the central nervous system

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25
Q

what is spina bifida

A

defect of the neural tube where it persists

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26
Q

what is the ectomesenchyme

A

a population of cells produced from the neural crest

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27
Q

what is the neural crest derived from

A

the ectoderm

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28
Q

what happens at around 25 days of pregnancy

A

the embryo folds around the yolk sac and some important organs appear like the heart, liver and lungs

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29
Q

what are stem cells

A

unspecialised cells that can develop into more specialised cells

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30
Q

what are the types of stem cells

A

embryonic and adult stem cells

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31
Q

describe embryonic stem cells

A

the inner cell mass is totipotent and has potential to differentiate into many cell types. stem cells found in the three germ layers are pluripotent as they are more restricted in potential

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32
Q

describe adult stem cells

A

generally committed cell lines like bone marrow stem cells

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33
Q

what does stem cell development involve

A

genes and various signalling molecules

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34
Q

what are all body tissues developed from

A

the three primary embryonic layers

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35
Q

what are the three primary embryonic layers

A

ectoderm
mesoderm
endoderm

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36
Q

what is the ectoderm

A

the outer covering

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37
Q

what is the mesoderm

A

the middle

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38
Q

what is the endoderm

A

the inner lining

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39
Q

what does the ectoderm develop into

A

skin
mucous membranes of the mouth and anus
brain
spinal cord
tooth enamel

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40
Q

what does the mesoderm develop into

A

most connective tissues
most muscle
blood vessels
kidney and urinary system
reproductive system
serous membranes

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41
Q

what does the endoderm develop into

A

the alimentary canal
respiratory system
parts of the urogenital system

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42
Q

what is the ectomesenchyme

A

the fourth germ layer

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43
Q

what does the ectomesenchyme develop into

A
  • sensory and autonomic nerves
  • melanocytes
  • adrenal medulla
  • most of the head mesenchyme
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44
Q

what are the connective tissues formed from the mesoderm

A

dermis
tendons
cartilage
bone

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45
Q

what parts of the mesenchyme of the head are developed from the ectomesenchyme

A

muscles
connective tissues
dentine
cementum
pulp
periodontal ligament
jaw bones

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46
Q

when do developmental abnormalities occur

A

during critical or sensitive periods of development

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47
Q

what can occur during the first two weeks of pregnancy

A

spontaneous abortion

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48
Q

what can occur during weeks 3-12

A

this is the period of greatest sensitivity ie likelihood of miscarriage

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49
Q

what is the first trimester

A

3-12 weeks

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50
Q

whane do most developmental defects occur

A

during the first trimester

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51
Q

what is the period of functional maturity of the foetus

A

weeks 13-39

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52
Q

when does the central nervous system first develop

A

week 3

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53
Q

what happens in week one of pregnancy

A

the zygote becomes the morula becomes the blastocyst which is implanted

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54
Q

in which weeks of pregnancy can spontaneous abortion occur

A

1-2

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55
Q

do ears develop before or after the eyes

A

before

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56
Q

which limbs form first

A

upper

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57
Q

when does the heart form

A

mid way through week 3

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58
Q

when do teeth form

A

mid way through week 6

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59
Q

when do external genitalia form

A

week 7

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60
Q

what is ovulation

A

release of the egg

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61
Q

what is the endometrium

A

innermost layer of the uterus composed of epithelial layer and lamina propria. has two layers

62
Q

what are the two layers of the endometrium

A

basal and functional

63
Q

describe the basal layer of the endometrium

A

composed of stem cells that serve to regenerate the functional layer

64
Q

describe the functional layer

A

adjacent to the uterine cavity, lined by a single layer of columnar epithelium . hosts the embryo during pregnancy or is shed during menstruation.

65
Q

what happens to the endometrium when pregnancy occurs

A

it becomes a thick blood vessel rich glandular tissue layer

66
Q

what is the function of the endometrium

A

provide the optimal environment for the implementation of the embryo and maintain the patency of the uterus

67
Q

what is the menstrual cycle

A

loss of the endometrial tissue

68
Q

what is the placenta

A

temporary organ of pregnancy found in the uterus. functions to interchange between the mother and uterus - supply of oxygen and nutrients and removal of waste material and carbon dioxide

69
Q

what is responsible for the embryo’s life support

A

the placenta

70
Q

why can the circulatory systems of the foetus and the mother be described as closed

A

becuse they do not interact

71
Q

what is rhesus factor

A

a protein found on the surface of red blood cells

72
Q

what is Rh compatibility

A

this is when the pregnant woman is Rh negative and the baby is Rh positive, causing the mother’s immune system to produce antibodies that attack the baby’s blood cells, leading to anaemia and jaudince in the baby of the next pregnancy

73
Q

what can happen if the circulations of the baby and mother mix

A

Rh incompatibility can occur

74
Q

why can medication have an impact on the baby

A

it can pass through the placenta into the circulation of the child

75
Q

what does the epiblast layer of the bilaminar embryo give rise to

A

embryonic cells to form the embryp

76
Q

when is left and right handedness established

A

week three

77
Q

what happens to the bilaminar embryo in gastrulation

A

it acquires a third layer to become the trilaminar disc, and it develops axial inclination.

78
Q

how does gastrulation begin

A

linear region of cells of the epiblast layer becomes thicker at the caudal (posterior) aspect of the embryo. this becomes the primitive streak, and it develops as the epiblast cells replicate and migrate to the midline of the bilaminar disc

79
Q

what is nodal

A

transformation growth factor protein that initiates and maintains the primitive streak

80
Q

what comprises the primitive streak

A

totipotent stem cells from the epiblast

81
Q

what forms the primitive node

A

when cells are added to the posterior end of the primitive streak, the cranial end begins to englarge and form the primitive node

82
Q

what maintains the primitive node and streak

A

hepatocyte nuclear factor

83
Q

what is FGF8

A

fibroblast growth factor 8

84
Q

what is produced by the cells of the primitve streak

A

FGF*

85
Q

where is the ectoderm located on the embryo

A

dorsal surface

86
Q

what can the ectoderm be divided into

A

the neural ectoderm and the surface ectoderm

87
Q

what does the neural ectoderm give rise to

A

the sensory organs like the eyes and the internal ears

88
Q

what does the neural ectoderm subdivide into

A

the neural tube and the neural crest

89
Q

what does the neural tube develop into

A

brain and spinal cord

90
Q

what does the neural crest develop into

A

head mesenchyme and the peripheral nervous system

91
Q

what are the three divisions of the mesoderm

A

paraxial
intermediate
lateral plate

92
Q

what does the lateral plate mesoderm develop into

A

spleen
lymphatics
adipose tissue

93
Q

what does the intermediate mesoderm develop into

A

urinary tract
kidneys
reproductive system

94
Q

what does the paraxial mesoderm develop into

A

bone
ligaments
tendons
cartilage
skeletal muscle
dermis

95
Q

what does the zygote develop into

A

inner cell mass and trophoblast

96
Q

what does the inner cell mass contain

A

the epiblast and hypoblast

97
Q

what does the epiblast develop into

A

the primitive streak and the ectoderm

98
Q

what does the primitive streak become

A

the mesoderm and endoderm

99
Q

what does the surface ectoderm develop into

A

epidermis

100
Q

what does the endoderm develop into

A

the gut tube

101
Q

what develops from the gut tube

A

thyroid
liver
gi tract
prostate
pancreas
lung
thymus

102
Q

what is the function of the hypoblast

A

formation of the endoderm

103
Q

when does division of the embryo occur for identical twins

A

after fertilisation

104
Q

when does division of the embryo occur for fraternal twins

A

there is no division as two separate eggs are fertilised by different sperms

105
Q

how many placentas do identical twins have

A

one

106
Q

how many placentas do fraternal twins have

A

two

107
Q

what happens at 16-18 days of pregnancy

A

rearrangement of the primitive streak to organise itself to the neural tube

108
Q

what are somites

A

cells responsible for the formation of muscle

109
Q

when do muscles form in relation to nerves

A

at the same time

110
Q

what forms the dorsal root ganglia

A

the neural crest

111
Q

what causes spina difida

A

persistence of the neural groove - it is associated with the non closure of the neural groove that usually forms the neural tube

112
Q

what is the cardiac structure formed through

A

the heart tube

113
Q

what are the areas of the trilaminar embryo

A

head and tail

114
Q

what happens to the neural tube at 4 weeks

A

parts of tissue from the sides of the tube move forward to form the face

115
Q

what forms the face at 4 weeks of pregnancy

A

migration of cells from posterior region to anterior region

116
Q

what happens between 4-7 weeks to the face

A

migration of cells from the posterior region to the anterior region occurs which begins to resemble the face

117
Q

when do legs begin to form

A

week 9

118
Q

what happens between 9 and 14 weeks of pregnancy

A

maturation of organs

119
Q

when does formation of organs begin

A

week 7

120
Q

when does the embryo become the foetus

A

week 9

121
Q

what is found within the embryonic stem cells

A

the inner cell mass for forming the three germs

122
Q

what are totipotent cells

A

cells that differentiate into anything

123
Q

why are the three germ layers described as pluripotent

A

more restricted in potential

124
Q

which stem cells have the most limited potential

A

adult stem cells

125
Q

what do all body tissues come from

A

primary embryonic cell layers

126
Q

which germ layer develops into tooth enamel

A

ectoderm

127
Q

what is the ectomesenchyme

A

the fourth layer that gives rise to sensory and autonomic nerves

128
Q

which teeth finish developing first

A

the permanent teeth

129
Q

which teeth finish maturing first

A

deciduous

130
Q

what is gastrulation characterised by

A

extensive movements of the cells

131
Q

what forms the three primary germ layers

A

morphogenic movements of the embryo cells

132
Q

what is gastrulation centred around

A

the primitive streak - transient midline that serves as conduit through which epiblast cells fated to become mesoderm and endoderm ingress to establish the germ layers

133
Q

what specifies cell fate

A

the primitive streak

134
Q

what are the sources of the endoderm

A

epiblast
caudolateral region of the blastoderm
yolky cells

135
Q

what is the yolk sac

A

this is the umbilical vesicle that is a small membranous structure outside the embryo.

136
Q

what is the innermost tissue found in the embryo

A

the endoderm

137
Q

what gives rise to epithelial cells that line the respiratory and digestive systems

A

endoderm

138
Q

what do endodermally derived organs in the human body include

A

thyroid
thymus
liver
lungs
biliary system
pancreas

139
Q

what are the functions of the endodermally derived organs

A

gas exchange
digestion
nutrient absorption
glucose homeostasis
detoxification
blood clotting

140
Q

what does the mesoderm surround

A

the gut tube

141
Q

which pregnancy period is the least prone to having defects of development

A

weeks 13-9

142
Q

what is the pre embryonic period

A

1-2 weeks

143
Q

when are the regions of the gut tube

A

foregut midgut and hindgut

144
Q

how can the domains of the gut tube be observed at a molecular level

A

restricted gene expression patterns

145
Q

what does the foregut give rise to

A

esophagus, trachea, stomach, lungs, thyroid, liver, biliary system and the pancreas

146
Q

what does the midgut form

A

the small intestine

147
Q

what does the hindgut form

A

the large intestine

148
Q

in what process are the germ layers generated

A

gastrulation

149
Q

what is the timeline of organ formation

A

endoderm formation
endoderm patterning
organ specification
organ buds
proliferation
differentiation

150
Q

what is mesenchyme

A

loosely organised embryonic connective tissue of undifferentiated cells that gives rise to most tissues, like skin blood and bone. the interactions between mesenchyme and epithelium help to form nearly every organ in the developing embryo