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Anatomy Week 2 > Embryology 1 > Flashcards

Embryology 1 Flashcards

1
Q

Primordial Germ Cells (PGC)

A

precursors to the developement of gametes in males and females

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2
Q

Epiblast

A

where primordial germ cells arise from

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3
Q

Where do PGCs migrate in the fourth week of development?

A

yolk sac

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4
Q

T or F yolk sac serves as nutritional support in development?

A

false

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5
Q

What happens to PGCs during the 4th and 6th weeks of developement?

A

migration of PGCs from yolk sac to populate gonads

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6
Q

Where do gonads develope weeks 4-6?

A

urogenital ridge on posterior abd. wall

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7
Q

What happens to PGCs on their way to gonads?

A

rapid MITOSIS

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8
Q

When do PGCs begin gametogenesis?

A

when they enter testis/ovary and begin meiosis

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9
Q

If primordial germ cells fail to migrate to urogenital crest what will happen?

A

No gonad will develop at that site

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10
Q

what two major events occcur in meiosis 1 but not in meiosis 2?

A

crossover and synapsis

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11
Q

What is the foundation for most genetic variability from person to person?

A

crossover

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12
Q

Crossover

A

segmental exchange of DNA from part of one chromosome to another

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13
Q

What happens to male primordial cells when they populate the future testis?

A

they go dormant until puberty

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14
Q

When does male spermatogensis begin?

A

puberty

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15
Q

What happens to male PGCs at puberty?

A

they diffentiate into type A and B spermatogonia

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16
Q

What do type A spermatogonia do?

A

remain in seminiferous tubules for life and go through mitotic divisions to keep a constant supply of type B. (funct. as stem cells)

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17
Q

What do type B spermatogonia do?

A

undergo meiosis 1 and 2 to from haploid spermatozoa (birth to death)

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18
Q

Primary spermatocyte

A

cells in meiosis I

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19
Q

secondary spermatocyte

A

cells in meiosis II

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20
Q

In males is there interphase between meiosis I and II?

A

NO

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21
Q

what does a secondary spermatocyte split to form?

A

spermatids

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22
Q

What happens when PGC’s in females migrate to the urogenital region from the yolk sac?

A

immediate differentiation to primary oocyte

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23
Q

When does Oogenesis and meiosis one begin in females?

A

5th month of development

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24
Q

What happens in females at puberty to oocytes?

A

exit the arrest of prophase of meiosis 1

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25
Q

How many gametes are produced from one spermatogonia?

A

4

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26
Q

How many gametes from one oogonia

A

1 and 2 polar bodies

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27
Q

Where does fertilization generally take place?

A

ampulla (distal in of fallopian)

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28
Q

capacitation reaction

A

takes 7-8 hours, rearrangement of proteins in acrosome to allow it to drill a hole through the zona pellucida

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29
Q

acrosome reaction

A

initiates on sperm contact with zona pellucida, pore in head opens up and releases proteolytic enzymes to bore through zona pellucida (much faster than capacitation)

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30
Q

What part of sperm actually enters the oocyte?

A

head- mitochondria left behind

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31
Q

cortical/zonal reaction

A

makes oocyte impermeable to other sperm

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32
Q

Male pronucleus

A

induces oocyte to unarrest

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33
Q

zygote

A

single cell resulting from fertilization

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34
Q

Graffin follicle

A

develops ~day14

oocyte becomes unarrested and quickly forms secondary oocyte (before arresting again)

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35
Q

Event after zygote formation is…

A

cleavage

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36
Q

When does cleavage take place?

A

days 1-4 initiated by fusion of male and female pronuclei

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37
Q

What happens during cleavage

A

cell divisions (1,4,8,16, 32)

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38
Q

What prevents the mass of cells from growing during cleavage?

A

zona pellucida encapsulates cells and prevents growth

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39
Q

When does morula form?

A

Day 5 (16-32 cell) when zona pellucida breaks down

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40
Q

when the morula undergoes reorganization it becomes the…

A

blastocyst

41
Q

3 parts of the blastocyst

A

embryoblast (embryo), trophoblast (placenta), Blastocyst cavity

42
Q

Where does implantation normally take place?

A

inner wall of the uterine cavity

43
Q

What does the trophoblast layer do to aid in implanation?

A

differentiates into two cells lines cytotrophoblasts and syncyiotrophoblasts

44
Q

What is the cytotrophoblast?

A

layer that remains in the postion of the trophoblast after trophoblast differentiation

45
Q

What is the syncyiotrophoblast?

A

portion of trophoblast that differntiates into projections that release enzymes that erode uterine lining (allow adherance of embryo)

46
Q

where is morula found?

A

in ampulla

47
Q

how is morula moved?

A

moved to uterine cavity using cilia, fluid movement, and muscular contraction

48
Q

What marks the beginning of week 2?

A

completion of implantation and uteroplacental blood flow

w2

49
Q

What happens to the embryoblast at the beginning of week 2?

A

it has reorganized into a bilaminar disc

w2

50
Q

What composes the bilaminar disc?

A 
epiblast cells (dorsal surface), hypoblast cells (ventral surface)
w2
51
Q

Which tissue is more important between epiblast and hypoblast?

A

all tissues making up humans derived from epiblast

w2

52
Q

What is the role of the hypoblast?

A

lays extraembryonic mesoderm (plays role in placenta and umbilical cord developement)
w2

53
Q

how long does the hypoblast persist?

A

1 week

w2

54
Q

What happens to cytotrophoblast cells in week 2?

A

grow and push into syncytiotrophoblast until they lose membranes and become part of the mass
w2

55
Q

What second fluid filled space besides blastocyst arises in week 2?

A

amnion

w2

56
Q

Where does amnion arise?

A

in epiblast layer as a cleft

w2

57
Q

What are the epiblast cells that form the roof of the amnion?

A

amnioblasts

w2

58
Q

Polyhydramnios

A

amniotic fluid levels that are too high

59
Q

oligohydramnios

A

amniotic fluid levels are too low

60
Q

what is the primary yolk sac?

A

its what the blastocyst is referred to once Heuser’s (exocoelomic) membrane forms

w2

61
Q

What happens after after exocoelomic membrane?

A

extraembyonic mesoderm forms

w2

62
Q

How is chorionic space formed?

A

extraembyonic layer forms vacuoles that fuse

w2

63
Q

How is the definitive yolk sac different than the primary yolk sac?

A

definitive yolk sac is directly against the hypoblast, while cells off hypoblast push the primary yolk sac away

w2

64
Q

What is the purpose of the definitive yolk sac?

A

houses primordial germ cells early in development and hematopoiesis

w2

65
Q

What gives rise to the umbilical cord?

A

the connecting stalk - arises dorsal to amnion where chorionic cavity doesn’t separate the layers

w2

66
Q

The chorion is made of what 3 layers?

A

(int –> ext) extraembryonic somatic mesoderm, cytotrophoblast, and syncytiotrophoblast (THESE GIVE RISE TO FETUS)

w2

67
Q

T or F it is important to have rudimentary circulation in developing embryo by end of week 2?

A

T

w2

68
Q

What are lacunar networks?

A

Lakes of blood formed by syncytiotrophoblasts penetrating multiple vessels

w2

69
Q

What does the prechordal plate give rise to?

A

marks future mouth

w2

70
Q

What major 4 events occur in week 2 of development?

A

trophoblast divides into 2 layers (cytotrophoblast and syncytiotrophoblast)
embryoblast forms 2 layers (epiblast and hypoblast)
extraembryonic mesoderm splits to 2 layers (somatic and splanchnic)
two fluid filled spaces for (amnion and yolk sac)

71
Q

Syncytiotrophoblasts secrete which important hormone for maintaining pregnancy?

A

hCG-secretion begins in week 2

w2

72
Q

What important events occur during the first 3 and a half days of the third week?

A
  1. Formation of the primitive streak and node

2. Migration of epiblast cells through the primitive streak and subsequent development of 3 germ layers

73
Q

What begins in the second half of the third week of pregnancy?

A

organogenesis (continues through 8th week)

74
Q

What is the first step in gastrulation?

A

formation of primitive streak and primitive node

w3

75
Q

What covers the definitive yolk sac?

A

extraembryonic mesoderm

w3

76
Q

What axis is the primitive streak formed along?

A

cranial-caudal axis

w3

77
Q

What forms the future mouth?

A

prechordal plate - marks cranial end

w3

78
Q

What marks the caudal end during gastrulation?

A

cloacal membrane - future anus
marks caudal end

w3

79
Q

Where does the primative streak form?

A

in the caudal end during gastrulation

w3

80
Q

What is the elevated disc formed by thickening of epiblast cells?

A

Primitive groove (streak)

w3

81
Q

What happens after primitive groove formation?

A

epiblast cells migrate from all directions and fall into the streak (groove)

w3

82
Q

Define gastrulation?

A

migration of epiblast cells to the primitive streak

w3

83
Q

T or F: the primitive streak extends to the cranial end

A

False

w3

84
Q

What is located at the end of the primitive streak?

A

Primitive node

w3

85
Q

What is the center point of the primitive node called?

A

primitive pit

w3

86
Q

What happens to the first wave of epiblast cells to move through the primitive streak?

A
  1. They move ventrally to become adjacent to hypoblast cells
  2. They move hypoblast cells out
  3. These cells make up the endoderm

w3

87
Q

What happens to the second wave epiblast cells that move through the primitive streak?

A
  1. they move between 1st layer of epiblast cells and hypoblast
  2. they form the mesoderm

w3

88
Q

What happens to the third wave of epiblast cells that in gastrulation?

A
  1. They do not move through primitive streak
  2. they form the ectoderm

w3

89
Q

What is the trilaminar disc?

A

3 layered disc formed by gastrulation of epiblast cells to form endoderm, mesoderm, and ectoderm

w3

90
Q

What is sarcococcygeal teratoma?

A

Tumor made of tissue from all three germ layers (hair, bone, and nerve)

91
Q

T or F sarcococcygeal teratomas usually become malignant.

A

True

92
Q

What is the cause of sarcococcygeal teratoma?

A

failure of primative streak to fully regress after gastrulation

93
Q

T or F: sarcococcygeal teratoma is most common in males

A

False

94
Q

What is a mature male gamete called?

A

Spermatozoa

95
Q

What are three parts of a spermatozoa?

A

Head Piece (contains acrosome), Middle piece (mitochondria), Tail (microtubules)

96
Q

What is the zona pelluida?

A

Very dense PROTEIN coat surrounding the secondary oocyte

97
Q

What is the corona radiata?

A

A network of follicular cells outside of the corona radiata

98
Q

What are the zona pellucida and corona radiata derived from?

A

the graffian follicle

Anatomy Week 2 (12 decks)

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