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Human Development (BSC5314) > Week 2 Development > Flashcards

Week 2 Development Flashcards

0
Q

How many days after LNMP (last normal menstrual period) does implantation occur

A

Begins approximately 20 days after onset of LNMP

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1
Q

What day does implantation begin?

A

~6 days after fertilization and is completes by day 14

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2
Q

What is the uterine phase of implantation?

A

usually the embryonic pole of the blastocyst attaches to the uterine endometrium

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3
Q

Where does implantation occur?

A

superior in uterine body and more often posterior

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4
Q

What is placenta previa?

- What is the concern?

A

implantation inferior in uterus near internal os of endocervical canal

- may cover the internal os leading to severe, possibly life-threatening, bleeding
- may result in premature separation during pregnancy or delivery
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5
Q

What is the cytotrophoblast?

A

inner cellular layer (closest to embryoblast)

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6
Q

What is the syncytiotrophoblast?

A
  • outer multinucleated protoplasmic mass (noncellular, invasive)
  • erodes and invades the endometrial tissues and derives nourishment here
    • endometrial cells facilitate this invasion by undergoing apoptosis
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7
Q

What does the syncytiotrophoblast secrete?

A

human chorionic gonadotrophin (hCG)

- maintains the secretory activity of the corpus luteum in the ovary
- hCG detection is the basis for pregnancy tests
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8
Q

What is the hypoblast?

A

layer of original embryoblast blastomeres adjacent to blastocoele

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9
Q

What is the epiblast?

A

remaining blastomeres of the original embryoblast

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10
Q

What is the embryonic disc?

A

flat, circular bilaminar structure comprised of the combined epiblast and hypoblast

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11
Q

What is the most common location of extrauterine implantation?

A

95-98% implant in oviducts

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12
Q

What causes ectopic implantation in oviducts?

A

may be due to infection or scarring which reduces the transport rate
- primary cause of maternal death in the first trimester

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13
Q

What are the signs and symptoms of tubal pregnancy?

A
  • missed menstrual period
  • abdominal pain and tenderness
  • abnormal bleeding
  • peritonitis
  • hCG is produced at slower rate so may give false negative when tested
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14
Q

What does an ectopic pregnancy result in usually?

A

results in a ruptured oviduct and hemorrhage into peritoneal cavity

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15
Q

How are ectopic pregnancies addressed?

A

affected oviduct and conceptus must be surgically removed

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16
Q

Where might abdominal pregnancies occur?

A

implant in rectouterine pouch, mesentery or parietal peritoneum

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17
Q

Why are abdominal implantation dangerous?

A
  • Usually causes considerable intraperitoneal bleeding

- severe risk for maternal death

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18
Q

Could abdominal implantation develop to term?

A

exceptional cases may allow for full term delivery via abdominal incision

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19
Q

What is a stone fetus?

A

unusual case in which fetus dies and become calcified

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20
Q

What are the rare cases with abdominal pregnancy?

A

rare cases where simultaneous intrauterine and extrauterine pregnancies occur
- extrauterine would usually be terminated

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21
Q

What % of zygotes fail to implant?

A

30-50%

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22
Q

What is the explanation for inhibition of implantation?

1) Endometrium
2) Chromosome abnormalities
A

1) endometrium may not be sufficiently receptive

2) chromosomal abnormalities may be incompatible with life

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23
Q

How do morning after pills work?

A
  • upset the balance of progesterone and estrogen
  • reduces the receptivity of the endometrium
  • speeds the transport of the cleavage zygote through the oviduct
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24
How do intrauterine devices work?
reduces receptivity of the endometrium by causing local inflammatory response
25
Where do amnioblasts come from?
as the embryonic disc forms, amnioblasts separate from the epiblast leaving a cavity
26
Where is the amniotic cavity located?
space created between the epiblast and the amnioblasts
27
What is the amnion?
layer of amnioblasts that separated from epiblast
28
What forms the exocoelomic membrane?
hypoblasst cells migrate around blastocoele to line inner surface of cytotrophoblast
29
What is the umbilical vesicle?
space defined by the boundaries of the exoceolomic membrane and the hypoblast
30
What are alternative names for the umbilical vesicle?
exocoelomic cavity or the yolk sac
31
What and where are the lacunae?
- begin to form within the syncytiotrophoblast - lacunae fill with aternal blood and cellular debris from ruptured uterine glands - this fluid diffuses to embryonic disc and is nutritive
32
What are lacunar networks?
over time the lacunae of the syncytiotrophoblast fuse and swell
33
What and where are sinusoids?
dilations of endometrial capillaries | - as syncytiotrophoblast invades the endometrium, sinusoids and lacunar networks communicate freely with each other
34
How is material exchanged at this point in development?
diffusion through the cytotrophoblast supports embryonic development at this time
35
What forms the extraembryonic mesoderm?
the primitive connective tissue secreted by the exocoelomic membrane
36
Where is the extraembryonic mesoderm located?
spread to surround the umbilical vesicle and the amnion
37
How does the extraembryonic coelom form?
cavity that forms as the spaces in the extraembryonic mesoderm fuse together
38
Where is the extraembryonic coelom located?
surrounds the amnion and the primary umbilical vesicle
39
What is the connecting stalk?
persistent extraembryonic mesoderm spanning from amnion to cytotrophoblast
40
What will the connecting stalk become?
will eventually become the umbilical cord
41
What happens to the umbilical vesicle?
as the extraembryonic coelom enlarges, the umbilical vesicle shrinks
42
Where is extraembryonic splanchnic mesoderm?
surrounds the umbilical vesicle
43
Where is the extraembryonic somatic mesoderm
lines the cytotrophoblast and covers the amnion
44
What are the 3 components of the chorion?
extraembryonic somatic mesoderm + cytotrophoblast + syncytiotrophoblast
45
What does the chorion surround?
- amniotic cavity - embryonic disc - umbilical vesicle
46
What was the previous name for the chorionic cavity?
the extraembryonic coelom
47
What are the chorion functions?
- embeds conceptus in uterine endometrium - enables nutrient, gas and waste exchange between embryo and maternal blood - secretes hCG and progesterone
48
Primary chorionic villi appear when?
appear at the end of week 2
49
How do primary chorionic villi form?
these are extensions of cytotrophoblast cells into the syncytiotrophoblast
50
Do primary chorionic villi branch?
shortly after forming they also branch
51
How do secondary chorionic villi differ from primary chorionic villi?
secondary chorionic villi form as mesenchyme grows into the primary villi
52
Where are secondary chorionic villi located?
these completely surround the chorionic sac at this point
53
How do tertiary chorionic villi differ from secondary chorionic villi?
Form as blood vessels from in the mesenchyme core of the secondary villi
54
Where are tertiary chorionic villi located?
these blood vessels connect into the primitive embryonic cardiovascular system
55
maternal blood circulates where?
maternal blood fills the intervillous spaces
56
Bidirectional diffusion occurs where?
bidirectional diffusion through the wall of the tertiary chorionic villus occurs - facilitates gas, nutrient & waste exchange between embryonic and maternal circulation
57
Where is the cytotrophoblastic shell?
cytotrophoblast cells continue proliferating to form a cytotrophoblastic shell - surrounds the chorionic sac and the associated tertiary villi
58
What are stem chorionic villi?
- span from the chorion to the cytotrophoblastic shell | - anchor the developing placenta in the endometrium
59
What are branch chorionic villi?
- grow from the sides of the stem chorionic villi - continually bathed by maternal blood in the intervillous spaces - primary location for material exchange between embryonic and maternal circulation
60
What is the fetal contribution of the placenta?
fetal contribution is the chorion (chorionic villi)
61
What is the maternal contribution of the placenta?
maternal contribution is the decidua - shed at partuition - endometrial derivative that controls the invasion by the syncytiotrophoblast - cells here contain large amounts of glycogen and lipid
62
What kind of blood is in the umbilical arteries?
carry deoxy blood rich in wastes from embryo/fetus to placenta
63
Where does this fetal-placental blood circulate?
circulates through capillaries in branch chorionic villi
64
What surrounds the branch chorionic villi?
bathed in maternal blood in surrounding intervillous spaces
65
What activity occurs in the branch villi capillaries?
material exchange occurs here
66
Are blood cells exchanged in capillaries in villi?
little, if any, fetal blood escapes through defects into maternal circulation
67
What kind of blood is in the umbilical vein?
carries oxygenated blood rich in nutrients
68
Where does the blood from the umbilical vein circulate to?
from placenta to embryo/fetus
69
What kind of blood is in the spiral arteries?
endometrial arteries that supply the intervillous spaces
70
Where do spiral artery blood circulate to?
intervillous spaces - extravascular spaces located between the chorionic villi
71
How often is the intervillous space blood exchanged?
In mature placenta, contain about 150ml of blood which is exchanged 3-4 times/min.
72
Cholesterol, glycogen, fatty acid synthesized in the placenta are used for?
nutrient and energy source for developing embryo/fetus
73
What is placental synthesized hormone hCG do?
maintains the corpus luteum (supports early pregnancy & prevents menstruation)
74
What does placental synthesized hormone progesterone do?
progesterone maintains the later pregnancy after corpus luteum involutes
75
What does placental synthesized hormone estrogen do?
relaxes the pelvic ligaments and cervix during delivery
76
What affects placental gas exchange?
blood flow rates affect this dramatically
77
By what mechanisms is nutrient exchange done in the placenta?
(by diffusion and active transport) - water, electrolytes, glucose, amino acids, water soluble vitamins cross readily - cholesterol, triglycerides, FAs and phospholipids cross poorly
78
By what mechanism is waste exchange done in the placenta?
Urea and conjugated bilirubin cross readily to maternal circulation
79
How is passive immunity mediated in the placenta?
(by pinocytes) | cross in low numbers and provide some passive immunity to certain diseases
80
What is the concern for drug exchange in the placenta?
(by diffusion) | most cross readily and cause addiction
81
Infectious agent exchange in the placenta: 1) do viruses pass through? 2) do bacteria pass through?
1) viruses cross | 2) most bacteria do not cross

Human Development (BSC5314) (34 decks)

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