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Human Structure - Block 1 > Embryology 2 > Flashcards

Embryology 2 Flashcards

1
Q

Define ploidy.

A

number of copies of each chromosome in a nucleus

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2
Q

What is the ploidy of somatic cells?

A

2n

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3
Q

What is the ploidy of germ cells/gametes?

A

1n

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4
Q

What does the letter “c” refer to?

A

total number of copies of each unique DNA molecule

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5
Q

What is the “c” of resting somatic cells?

A

2c

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6
Q

What is the “c” of definitive gametes?

A

1c

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7
Q

What is the (#,n,c) of gamete precursor cells?

A

46, 2n, 2c

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8
Q

What is the name of the diploid precursor cells?

A

spermatogonium/oogonium

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9
Q

How does the name of the gamete precursor cells change through meiosis?

A
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10
Q

What is the (#,n,c) configuration for cells immediately prior to meiosis?

A

46, 2n, 4c

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11
Q

What is the (#,n,c) result of meiosis I?

A

(23, 1n, 2c) = secondary spermatocytes/oocytes

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12
Q

What is the (#,n,c) result of meiosis II?

A

(23, 1n, 1c) = spermatozoon/oocyte

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13
Q

Where does spermatogenesis take place?

A

seminiferous tubules of testes

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14
Q

Which cells support spermatogenesis?

A

Sertoli cells

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15
Q

Describe the movement of developing sperm cells in the seminiferous tubules.

A

developing cells gradually move from basal compartment to lumen via adluminal compartment

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16
Q

How are the terms “primary spermatocyte,” “spermatid” and “spermatozoa” related?

A

a primary spermatocyte undergoes two rounds of meiosis to become 4 spermatids; these 4 spermatids mature (i.e. tail growth) into spermatozoa

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17
Q

Where are spermatozoa released?

A

released into lumen of seminiferous tubules

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18
Q

In humans, how long does the production of spermatozoa take?

A

spermatogonium to spermatozoon takes 65 days

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19
Q

When does oogenesis begin in females?

A

prenatally

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20
Q

When exactly do oogonia, the female gamete precursor cells, start to undergo meiosis prenatally?

A

start to undergo meiosis I in 5th month of fetal life, but become arrested in meiosis I until girl reaches puberty

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21
Q

Describe what happens in the uterus on a monthly basis in terms of female definite oocyte production. (3)

A

1 primary oocyte made available for fertilization each month; developing oocyte embedded in follicle of uterus and produces estrogen; estrogen stimulates growth of endometrium

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22
Q

What happens to a primary oocyte right before ovulation?

A

primary oocyte, which until now was arrested in meiosis I, completes meiosis I and enters meiosis II

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23
Q

In females, meiosis I is completed right before ovulation. When is meiosis II completed?

A

only after fertilization

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24
Q

How is cell division different between spermatogenesis and oogenesis?

A

in oogenesis, cytoplasm division is unequal — only one secondary oocyte receives all cytoplasm whereas other is called a polar body and degenerates

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25
Q

What happens to the oocyte upon ovulation?

A

follicle ruptures and releases oocyte + surrounding cells

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26
Q

Define corona radiata.

A

structure composed of oocyte + surrounding cells released upon ovulation

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27
Q

Define corpus luteum.

A

residual tissue of follicle after ovulation that secretes progesterone

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28
Q

What is the function of the progesterone secreted by the corpus luteum?

A

prepares endometrium for implantation by increasing vascularization and stimulating glands to produce nutrients

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29
Q

Where does fertilization take place?

A

the ampulla, which is the intermediate part of the uterine tube

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30
Q

Describe how sperm interact with the corona radiata and zona pellucida.

A

several sperm can penetrate the corona radiata, but only one sperm can penetrate the zona pellucida, and once it does, chemical processes prevent other sperm from interacting with the zona pellucida

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31
Q

What is the sequence of events in fertilization?

A

sperm penetrates zona pellucida; plamsa membranes of oocyte and sperm fuse and sperm enters cytoplasm of oocyte; oocyte completes meiosis II; (23, 1n) sperm and (23, 1n) oocyte form diploid (46, 2n) zygote

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32
Q

Cleavage occurs how many days after fertilization?

A

1-3 days after fertilization

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33
Q

Define blastomeres.

A

The new cells that result from rapid mitotic division of the zygote as it travels along the uterine tube towards the uterus

34
Q

What is notable about the size of the zygote during cleavage?

A

the size of the zygote remains the same because the blastomeres formed by mitotic division do not grow, meaning the cells become smaller with each division to maintain the same size

35
Q

After undergoing several mitotic divisions, the zygote is now called

A

a morula

36
Q

When does the morula enter the uterus?

A

4 days after fertilization

37
Q

Describe the toti/pluri/multipotency of the zygote.

A

The zygote, up until the division that creates 16 cells, is totipotent, meaning it can differentiate into any embryonic or extraembryonic cell

38
Q

When does formation of the blastocyst occur?

A

4-6 days after fertilization

39
Q

As the morula hollows out, it is called

A

a blastocyst

40
Q

What are the components of the blastocyst?

A

outer layer - trophoblast; inner cell mass - embryoblast; blastocystic cavity

41
Q

The trophoblast develops into

A

part of the placenta

42
Q

The embryoblast develops into

A

the embryo

43
Q

The blastocystic cavity develops into

A

the yolk sac

44
Q

What is the significance of the blastocyst’s development in relation to the dorsal-ventral axis?

A

the side of the inner cell mass facing the blastocystic cavity will become the ventral surface of the embryo

45
Q

When does implantation in the uterus occur?

A

7-12 days after fertilization (begins 7 days after, complete 12 days after)

46
Q

What two hormones are critical for implantation?

A

estrogen, which thickens the endometrium, and progesterone, which stimulates production of nutrients

47
Q

What happens to the trophoblast upon implantation?

A

proliferates significantly and differentiates into two portions: inner cytotrophoblast and outer syncytiotrophoblast

48
Q

The trophoblast differentiates into

A

inner cytotrophoblast and outer syncytiotrophoblast

49
Q

Define syncytium.

A

large, multinucleated mass of cytoplasm

50
Q

Describe how the cytotrophoblast and syncytiotrophoblast develop.

A

as cytotrophoblast proliferates, its outer layer cells fuse to form syncytiotrophoblast

51
Q

What is the purpose of the syncytiotrophoblast?

A

to invade endometrium and erode maternal blood vessels, which forms in blood-filled lacunae that provides embryo access to O2 and nutrients

52
Q

What structure produces hCG?

A

syncytiotrophoblast

53
Q

What is the function of hCG?

A

maintain progesterone production in corpus luteum

54
Q

When can hCG levels be reliably detected in maternal blood or urine?

A

maternal blood - 2-3 days after implantation; maternal urine - 6-8 days after implantation

55
Q

Why are the first two weeks after conception referred to as the “all or nothing” period?

A

because only healthy morulas and blastocysts will survive — all others will spontaneously abort

56
Q

What percentage of pregnancies result in early, spontaneous abortion?

A

10-15%

57
Q

Where do most ectopic implantations occur?

A

uterine tube

58
Q

Describe the hypoblast.

A

forms on ventral surface of embryoblast

59
Q

Describe the amniotic cavity.

A

forms between dorsal trophoblast and embryoblast

60
Q

Describe how the amnion forms.

A

result of some embryoblast cells differentiating

61
Q

The epiblast layer originates from

A

the upper layer of the embryoblast

62
Q

The epiblast layer consists of

A

columnar cells

63
Q

The hypoblast layer consists of

A

cuboid cells

64
Q

The embryonic disc results from

A

the hypoblast and epiblast layers forming a bilaminar plate of cells

65
Q

The exocoelomic membrane results from

A

cells from the hypoblast surrounding the blastocytic cavity

66
Q

Following formation of the exocoelomic membrane, the blastocytic cavity is now called

A

the exocoelomic cavity a.k.a. primary yolk sac

67
Q

What are the two associated cavities of the embryonic disc?

A

amniotic cavity and primary yolk sac

68
Q

When hypoblast cells surround the embryonic disc and proliferate, what tissue forms?

A

extraembryonic mesoderm

69
Q

The extraembryonic mesoderm, as a result of gaps appearing, becomes

A

the extraembryonic coelom

70
Q

The extraembryonic mesoderm splits into

A

extraembryonic splanchic mesoderm; outer extraembryonic somatic mesoderm

71
Q

What makes up the chorion?

A

extraembryonic somatic mesoderm + cytotrophoblast + syncytiotrophoblast

72
Q

What makes up the placenta?

A

chorion + parts of maternal endometrium

73
Q

The secondary yolk sac originates from

A

the primary yolk sac

74
Q

What is the function of the secondary yolk sac?

A

its blood vessels form vitelline arteries/veins; portions of secondary yolk sac contribute to gut tube

75
Q

What is the fate of the primary yolk sac?

A

disintegrates within a few days

76
Q

What connects the developing embryo to the developing placenta?

A

connecting stalk

77
Q

What is the significance of the prechordal plate?

A

primordium of the mouth; defines the cranial pole of the embryo

78
Q

What gives rise to the prechordal plate?

A

hypoblast cells in the embryonic disc becoming more columnar in a specific circular area gives rise to prechordal plate

79
Q

Draw out a diagram illustrating gamete cell naming conventions.

A
80
Q

Draw out a diagram showing how a zygote differentiates.

A

Human Structure - Block 1 (14 decks)

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