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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
Q

How do intrauterine devices work?

A

reduces receptivity of the endometrium by causing local inflammatory response

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25
Q

Where do amnioblasts come from?

A

as the embryonic disc forms, amnioblasts separate from the epiblast leaving a cavity

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26
Q

Where is the amniotic cavity located?

A

space created between the epiblast and the amnioblasts

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27
Q

What is the amnion?

A

layer of amnioblasts that separated from epiblast

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28
Q

What forms the exocoelomic membrane?

A

hypoblasst cells migrate around blastocoele to line inner surface of cytotrophoblast

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29
Q

What is the umbilical vesicle?

A

space defined by the boundaries of the exoceolomic membrane and the hypoblast

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30
Q

What are alternative names for the umbilical vesicle?

A

exocoelomic cavity or the yolk sac

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31
Q

What and where are the lacunae?

A
  • 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
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32
Q

What are lacunar networks?

A

over time the lacunae of the syncytiotrophoblast fuse and swell

33
Q

What and where are sinusoids?

A

dilations of endometrial capillaries

- as syncytiotrophoblast invades the endometrium, sinusoids and lacunar networks communicate freely with each other

34
Q

How is material exchanged at this point in development?

A

diffusion through the cytotrophoblast supports embryonic development at this time

35
Q

What forms the extraembryonic mesoderm?

A

the primitive connective tissue secreted by the exocoelomic membrane

36
Q

Where is the extraembryonic mesoderm located?

A

spread to surround the umbilical vesicle and the amnion

37
Q

How does the extraembryonic coelom form?

A

cavity that forms as the spaces in the extraembryonic mesoderm fuse together

38
Q

Where is the extraembryonic coelom located?

A

surrounds the amnion and the primary umbilical vesicle

39
Q

What is the connecting stalk?

A

persistent extraembryonic mesoderm spanning from amnion to cytotrophoblast

40
Q

What will the connecting stalk become?

A

will eventually become the umbilical cord

41
Q

What happens to the umbilical vesicle?

A

as the extraembryonic coelom enlarges, the umbilical vesicle shrinks

42
Q

Where is extraembryonic splanchnic mesoderm?

A

surrounds the umbilical vesicle

43
Q

Where is the extraembryonic somatic mesoderm

A

lines the cytotrophoblast and covers the amnion

44
Q

What are the 3 components of the chorion?

A

extraembryonic somatic mesoderm + cytotrophoblast + syncytiotrophoblast

45
Q

What does the chorion surround?

A
  • amniotic cavity
  • embryonic disc
  • umbilical vesicle
46
Q

What was the previous name for the chorionic cavity?

A

the extraembryonic coelom

47
Q

What are the chorion functions?

A
  • embeds conceptus in uterine endometrium
  • enables nutrient, gas and waste exchange between embryo and maternal blood
  • secretes hCG and progesterone
48
Q

Primary chorionic villi appear when?

A

appear at the end of week 2

49
Q

How do primary chorionic villi form?

A

these are extensions of cytotrophoblast cells into the syncytiotrophoblast

50
Q

Do primary chorionic villi branch?

A

shortly after forming they also branch

51
Q

How do secondary chorionic villi differ from primary chorionic villi?

A

secondary chorionic villi form as mesenchyme grows into the primary villi

52
Q

Where are secondary chorionic villi located?

A

these completely surround the chorionic sac at this point

53
Q

How do tertiary chorionic villi differ from secondary chorionic villi?

A

Form as blood vessels from in the mesenchyme core of the secondary villi

54
Q

Where are tertiary chorionic villi located?

A

these blood vessels connect into the primitive embryonic cardiovascular system

55
Q

maternal blood circulates where?

A

maternal blood fills the intervillous spaces

56
Q

Bidirectional diffusion occurs where?

A

bidirectional diffusion through the wall of the tertiary chorionic villus occurs
- facilitates gas, nutrient & waste exchange between embryonic and maternal circulation

57
Q

Where is the cytotrophoblastic shell?

A

cytotrophoblast cells continue proliferating to form a cytotrophoblastic shell
- surrounds the chorionic sac and the associated tertiary villi

58
Q

What are stem chorionic villi?

A
  • span from the chorion to the cytotrophoblastic shell

- anchor the developing placenta in the endometrium

59
Q

What are branch chorionic villi?

A
  • 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
Q

What is the fetal contribution of the placenta?

A

fetal contribution is the chorion (chorionic villi)

61
Q

What is the maternal contribution of the placenta?

A

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
Q

What kind of blood is in the umbilical arteries?

A

carry deoxy blood rich in wastes from embryo/fetus to placenta

63
Q

Where does this fetal-placental blood circulate?

A

circulates through capillaries in branch chorionic villi

64
Q

What surrounds the branch chorionic villi?

A

bathed in maternal blood in surrounding intervillous spaces

65
Q

What activity occurs in the branch villi capillaries?

A

material exchange occurs here

66
Q

Are blood cells exchanged in capillaries in villi?

A

little, if any, fetal blood escapes through defects into maternal circulation

67
Q

What kind of blood is in the umbilical vein?

A

carries oxygenated blood rich in nutrients

68
Q

Where does the blood from the umbilical vein circulate to?

A

from placenta to embryo/fetus

69
Q

What kind of blood is in the spiral arteries?

A

endometrial arteries that supply the intervillous spaces

70
Q

Where do spiral artery blood circulate to?

A

intervillous spaces - extravascular spaces located between the chorionic villi

71
Q

How often is the intervillous space blood exchanged?

A

In mature placenta, contain about 150ml of blood which is exchanged 3-4 times/min.

72
Q

Cholesterol, glycogen, fatty acid synthesized in the placenta are used for?

A

nutrient and energy source for developing embryo/fetus

73
Q

What is placental synthesized hormone hCG do?

A

maintains the corpus luteum (supports early pregnancy & prevents menstruation)

74
Q

What does placental synthesized hormone progesterone do?

A

progesterone maintains the later pregnancy after corpus luteum involutes

75
Q

What does placental synthesized hormone estrogen do?

A

relaxes the pelvic ligaments and cervix during delivery

76
Q

What affects placental gas exchange?

A

blood flow rates affect this dramatically

77
Q

By what mechanisms is nutrient exchange done in the placenta?

A

(by diffusion and active transport)

  • water, electrolytes, glucose, amino acids, water soluble vitamins cross readily
  • cholesterol, triglycerides, FAs and phospholipids cross poorly
78
Q

By what mechanism is waste exchange done in the placenta?

A

Urea and conjugated bilirubin cross readily to maternal circulation

79
Q

How is passive immunity mediated in the placenta?

A

(by pinocytes)

cross in low numbers and provide some passive immunity to certain diseases

80
Q

What is the concern for drug exchange in the placenta?

A

(by diffusion)

most cross readily and cause addiction

81
Q

Infectious agent exchange in the placenta:

1) do viruses pass through?
2) do bacteria pass through?
A

1) viruses cross

2) most bacteria do not cross

Human Development (BSC5314) (34 decks)

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