Embryology Flashcards
1
Q
which steps occur during the first week of pregnancy
A
ovulation
fertilisation
implantation
2
Q
what is a zygote
A
fertilised ovum
3
Q
what is a morula
A
what the zygote becomes once it has completed its first cell divisions - a solid mass of cells
4
Q
after how many days does the morula form
A
4-6
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
6
Q
what is contained within the blastocyst
A
inner cell mass and trophoblast
7
Q
what replenishes the baby’s blood
A
the mother’s blood
8
Q
do the circulations of the embryo and mother mix
A
no
9
Q
what separates the circulations of the embryo and mother
A
a thin barrier, permeable to most molecules but not cells
10
Q
what occurs at 10-12 days of pregnancy
A
the implanted trophoblast contains an embryo with two cell layers
11
Q
what are the two layers to the bilaminar embryo
A
epiblast and hypoblast
12
Q
what is the function of the epiblast
A
gives rise to the embryonic ectoderm, mesoderm and endoderm
13
Q
what does the hypoblast layer of the bilaminar embryo do
A
participates in the formation of the endoderm and the extraembryonic mesoderm
14
Q
describe the shape of the bilaminer embryo
A
a disc with no distinct orientation or axis
15
Q
what happens during gastrulation
A
the embryo develops an axis and the three embrionic cell layer
16
Q
what is the key stage of gastrulation
A
the formation of a groove called the primitive streak
17
Q
why does the bilaminar embryo develop an axis during gastrulation
A
to become bilaterally symmetrical
18
Q
what are the mesoderm
A
the ectodermal cells that are induced to differentiate and migrate through the primitive streak toward the hypoblast
19
Q
what forms the endoderm
A
interaction between the newly formed mesoderm and the hypoblast
20
Q
how do the mesodermal cells form a third layer
A
by pushing through the primitive streak and spreading out
21
Q
what occurs during weeks 3-8
A
organogenesis
22
Q
what is organogenesis
A
formation of major organs from the three basic germ cell layers
23
Q
what is the one of the first organs to be developed
A
the central nervous system
24
Q
what is the neural tube
A
forerunner of the central nervous system
25
what is spina bifida
defect of the neural tube where it persists
26
what is the ectomesenchyme
a population of cells produced from the neural crest
27
what is the neural crest derived from
the ectoderm
28
what happens at around 25 days of pregnancy
the embryo folds around the yolk sac and some important organs appear like the heart, liver and lungs
29
what are stem cells
unspecialised cells that can develop into more specialised cells
30
what are the types of stem cells
embryonic and adult stem cells
31
describe embryonic stem cells
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
32
describe adult stem cells
generally committed cell lines like bone marrow stem cells
33
what does stem cell development involve
genes and various signalling molecules
34
what are all body tissues developed from
the three primary embryonic layers
35
what are the three primary embryonic layers
ectoderm
mesoderm
endoderm
36
what is the ectoderm
the outer covering
37
what is the mesoderm
the middle
38
what is the endoderm
the inner lining
39
what does the ectoderm develop into
skin
mucous membranes of the mouth and anus
brain
spinal cord
tooth enamel
40
what does the mesoderm develop into
most connective tissues
most muscle
blood vessels
kidney and urinary system
reproductive system
serous membranes
41
what does the endoderm develop into
the alimentary canal
respiratory system
parts of the urogenital system
42
what is the ectomesenchyme
the fourth germ layer
43
what does the ectomesenchyme develop into
- sensory and autonomic nerves
- melanocytes
- adrenal medulla
- most of the head mesenchyme
44
what are the connective tissues formed from the mesoderm
dermis
tendons
cartilage
bone
45
what parts of the mesenchyme of the head are developed from the ectomesenchyme
muscles
connective tissues
dentine
cementum
pulp
periodontal ligament
jaw bones
46
when do developmental abnormalities occur
during critical or sensitive periods of development
47
what can occur during the first two weeks of pregnancy
spontaneous abortion
48
what can occur during weeks 3-12
this is the period of greatest sensitivity ie likelihood of miscarriage
49
what is the first trimester
3-12 weeks
50
whane do most developmental defects occur
during the first trimester
51
what is the period of functional maturity of the foetus
weeks 13-39
52
when does the central nervous system first develop
week 3
53
what happens in week one of pregnancy
the zygote becomes the morula becomes the blastocyst which is implanted
54
in which weeks of pregnancy can spontaneous abortion occur
1-2
55
do ears develop before or after the eyes
before
56
which limbs form first
upper
57
when does the heart form
mid way through week 3
58
when do teeth form
mid way through week 6
59
when do external genitalia form
week 7
60
what is ovulation
release of the egg
61
what is the endometrium
innermost layer of the uterus composed of epithelial layer and lamina propria. has two layers
62
what are the two layers of the endometrium
basal and functional
63
describe the basal layer of the endometrium
composed of stem cells that serve to regenerate the functional layer
64
describe the functional layer
adjacent to the uterine cavity, lined by a single layer of columnar epithelium . hosts the embryo during pregnancy or is shed during menstruation.
65
what happens to the endometrium when pregnancy occurs
it becomes a thick blood vessel rich glandular tissue layer
66
what is the function of the endometrium
provide the optimal environment for the implementation of the embryo and maintain the patency of the uterus
67
what is the menstrual cycle
loss of the endometrial tissue
68
what is the placenta
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
what is responsible for the embryo's life support
the placenta
70
why can the circulatory systems of the foetus and the mother be described as closed
becuse they do not interact
71
what is rhesus factor
a protein found on the surface of red blood cells
72
what is Rh compatibility
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
what can happen if the circulations of the baby and mother mix
Rh incompatibility can occur
74
why can medication have an impact on the baby
it can pass through the placenta into the circulation of the child
75
what does the epiblast layer of the bilaminar embryo give rise to
embryonic cells to form the embryp
76
when is left and right handedness established
week three
77
what happens to the bilaminar embryo in gastrulation
it acquires a third layer to become the trilaminar disc, and it develops axial inclination.
78
how does gastrulation begin
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
what is nodal
transformation growth factor protein that initiates and maintains the primitive streak
80
what comprises the primitive streak
totipotent stem cells from the epiblast
81
what forms the primitive node
when cells are added to the posterior end of the primitive streak, the cranial end begins to englarge and form the primitive node
82
what maintains the primitive node and streak
hepatocyte nuclear factor
83
what is FGF8
fibroblast growth factor 8
84
what is produced by the cells of the primitve streak
FGF*
85
where is the ectoderm located on the embryo
dorsal surface
86
what can the ectoderm be divided into
the neural ectoderm and the surface ectoderm
87
what does the neural ectoderm give rise to
the sensory organs like the eyes and the internal ears
88
what does the neural ectoderm subdivide into
the neural tube and the neural crest
89
what does the neural tube develop into
brain and spinal cord
90
what does the neural crest develop into
head mesenchyme and the peripheral nervous system
91
what are the three divisions of the mesoderm
paraxial
intermediate
lateral plate
92
what does the lateral plate mesoderm develop into
spleen
lymphatics
adipose tissue
93
what does the intermediate mesoderm develop into
urinary tract
kidneys
reproductive system
94
what does the paraxial mesoderm develop into
bone
ligaments
tendons
cartilage
skeletal muscle
dermis
95
what does the zygote develop into
inner cell mass and trophoblast
96
what does the inner cell mass contain
the epiblast and hypoblast
97
what does the epiblast develop into
the primitive streak and the ectoderm
98
what does the primitive streak become
the mesoderm and endoderm
99
what does the surface ectoderm develop into
epidermis
100
what does the endoderm develop into
the gut tube
101
what develops from the gut tube
thyroid
liver
gi tract
prostate
pancreas
lung
thymus
102
what is the function of the hypoblast
formation of the endoderm
103
when does division of the embryo occur for identical twins
after fertilisation
104
when does division of the embryo occur for fraternal twins
there is no division as two separate eggs are fertilised by different sperms
105
how many placentas do identical twins have
one
106
how many placentas do fraternal twins have
two
107
what happens at 16-18 days of pregnancy
rearrangement of the primitive streak to organise itself to the neural tube
108
what are somites
cells responsible for the formation of muscle
109
when do muscles form in relation to nerves
at the same time
110
what forms the dorsal root ganglia
the neural crest
111
what causes spina difida
persistence of the neural groove - it is associated with the non closure of the neural groove that usually forms the neural tube
112
what is the cardiac structure formed through
the heart tube
113
what are the areas of the trilaminar embryo
head and tail
114
what happens to the neural tube at 4 weeks
parts of tissue from the sides of the tube move forward to form the face
115
what forms the face at 4 weeks of pregnancy
migration of cells from posterior region to anterior region
116
what happens between 4-7 weeks to the face
migration of cells from the posterior region to the anterior region occurs which begins to resemble the face
117
when do legs begin to form
week 9
118
what happens between 9 and 14 weeks of pregnancy
maturation of organs
119
when does formation of organs begin
week 7
120
when does the embryo become the foetus
week 9
121
what is found within the embryonic stem cells
the inner cell mass for forming the three germs
122
what are totipotent cells
cells that differentiate into anything
123
why are the three germ layers described as pluripotent
more restricted in potential
124
which stem cells have the most limited potential
adult stem cells
125
what do all body tissues come from
primary embryonic cell layers
126
which germ layer develops into tooth enamel
ectoderm
127
what is the ectomesenchyme
the fourth layer that gives rise to sensory and autonomic nerves
128
which teeth finish developing first
the permanent teeth
129
which teeth finish maturing first
deciduous
130
what is gastrulation characterised by
extensive movements of the cells
131
what forms the three primary germ layers
morphogenic movements of the embryo cells
132
what is gastrulation centred around
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
what specifies cell fate
the primitive streak
134
what are the sources of the endoderm
epiblast
caudolateral region of the blastoderm
yolky cells
135
what is the yolk sac
this is the umbilical vesicle that is a small membranous structure outside the embryo.
136
what is the innermost tissue found in the embryo
the endoderm
137
what gives rise to epithelial cells that line the respiratory and digestive systems
endoderm
138
what do endodermally derived organs in the human body include
thyroid
thymus
liver
lungs
biliary system
pancreas
139
what are the functions of the endodermally derived organs
gas exchange
digestion
nutrient absorption
glucose homeostasis
detoxification
blood clotting
140
what does the mesoderm surround
the gut tube
141
which pregnancy period is the least prone to having defects of development
weeks 13-9
142
what is the pre embryonic period
1-2 weeks
143
when are the regions of the gut tube
foregut midgut and hindgut
144
how can the domains of the gut tube be observed at a molecular level
restricted gene expression patterns
145
what does the foregut give rise to
esophagus, trachea, stomach, lungs, thyroid, liver, biliary system and the pancreas
146
what does the midgut form
the small intestine
147
what does the hindgut form
the large intestine
148
in what process are the germ layers generated
gastrulation
149
what is the timeline of organ formation
endoderm formation
endoderm patterning
organ specification
organ buds
proliferation
differentiation
150
what is mesenchyme
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
