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Embryology > Cleavage > Flashcards

Cleavage Flashcards

1
Q

Cleavage forms from_____ to _____

A

Day 1-5

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2
Q

Patterns of cleavage

A

1.) Poles
2.) Cleavage pattern divisions (1-5)
3.) Cleavage patterns yolk
4.) Timing of cleavage pattern

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3
Q

Cleavage humans

A

1.) Recap
2.) At 8-cell stage (morula)
3.) Morula by day 4
4.) Blastocyst by day 5

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4
Q

Principles of cleavage

A

1.) Now 1 cell: initial phase of cell division after fertilization (within 24 hours)
2.) New established combination of DNA, complete set of genetic information
3.) Rapid series of mitotic cell divisions and cells form daughter blastomeres
4.) Cell is “cleaved” or “cut up” into smaller cells (within Zona Pellucida)
5.) Cleavage produces cells of a geometric progression
6.) Morula (solid ball)

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5
Q

Cell is “cleaved” into smaller cells within the ________

A

Zona pellucida

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6
Q

Nucleocytoplasmic reaction (“cleaved”)

A
  • specific ratio of nucleus to cytoplasm
  • SAME overall size but the cell divides
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7
Q

Cleavage geometric progression

A
  • 2 cells
  • 4 cells
  • 8 cells
  • 16 cells
  • 32 cells
    (hard to follow 32 cells)
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8
Q

Morula

A
  • solid, ball-like structure
  • up to 32 cells “raspberry”
  • same size as original egg
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9
Q

Morula (16-32 cells) is also known as_______

A

“raspberry”

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10
Q

Timeline

A
  • Time 0: sperm + egg (zygote)
  • 24 hours: 2 cells
  • 40 hours: 4 cells
  • 3 days: 6-12 cells
  • 4 days: 16-32 cells (morula)
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11
Q

egg + sperm –> fertilization –> zygote

A

true

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12
Q

1st mitotic divisions are called_______ and results in _____ daughter cells

A

cleavage; 2 (2n)

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13
Q

Blastomeres

A

smaller than original cell, daughter cells

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14
Q

Morula

A

embryo at 16-32 cell stage

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15
Q

– blast

A

immature cell (actively making something)

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16
Q

– cyte

A

mature cell

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17
Q

– cyst

A

sac full of fluid

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18
Q

ESC

A

Embryonic Stem Cells from inner cell mass (ICM) of blastocyst

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19
Q

Pluripotent

A

ESC that can become any one of the 3 germ line cells

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20
Q

Differentiate

A

Cell than can alter into another specific cell

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21
Q

Embryo

A

After zygote and into 1st cell divisions, from implantation through 8th week pregnancy

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22
Q

Fetus

A

after 9 weeks of fertilization 11 weeks gestation

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23
Q

Holo

A

entire or complete

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24
Q

Mero

A

part

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25
Q

Meso

A

middle

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26
Q

Gestation age has a _______ lag time to fertilization time

A

2 week

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27
Q

3 “D” roles of cleavage

A

1.) Divison
2.) Distribution
3.) Differentiation

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28
Q

Divison

A

to pass on many identical copies of the genome to each cell (mitotic process to create diploid somatic cells)

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29
Q

Distribution

A

To produce a large number of cells that can relocate to one another and build a structure of the organism

“Blastomeres as bricks!”

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30
Q

Differentiation

A

To give themselves a molecular DNA determination, identify via touch

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31
Q

Cell division

A

1.) The nucleus divides by mitosis
2.) The cytoplasm divides by cytokinesis

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32
Q

Nucleus (mitosis)

A
  • Chromosomes are condensed, copied and pulled apart in the various stages of mitosis to create two genetically identical cells

-*the KEY organelles of mitosis of the mitotic spindle’s specialize microtubules, organized by pair of centrioles

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33
Q

Stages of mitosis

A

1.) Interphase
2.) Prophase
3.) Metaphase
4.) Anaphase
5.) Telophase

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34
Q

Cytoplasm (cytokinesis)

A

-*The KEY organelle and cytokinesis is a contract tile ring of ACTIN in MYOSIN filaments
- closing contractile ring create a CLEAVAGE FURROW that pinches through the cytoplasm

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35
Q

Cytokinesis

A

Creation of the cytoplasm into two new daughter cells (pinch into 2 new daughter cells)

36
Q

Cytokinesis and Mitosis are Separately regulated events

A

True
- complete mitosis before cytokinesis

37
Q

_______ signals often directed the first few cleavages

A

Maternal

38
Q

Walther Flemming

A
  • drawing of chromosomes during mitosis, circa 1880
  • “Cell substance, nucleus, and cell division”
  • Flemming repeatedly observed the different forms of chromosomes leading up to and during cytokinesis, the ultimate division of one cell into two during the last stage of mitosis
39
Q

Poles

A
  • Animal pole
  • Vegetal pole
40
Q

Animal pole

A

area of egg that has little or no Yolk

41
Q

Vegetal pole

A

concentration of Yolk

42
Q

Bilateral symmetry result of_______ ______

A

cytoplasmic segregation

43
Q

1st cleavage

A

(2) from animal to vegetal pole

44
Q

2nd cleavage

A

(4) occurs at right angle to the 1st again from animal to vegetal pole

45
Q

3rd cleavage

A

(8) HORIZONTAL cleavage, BETWEEN animal and vegetal poles

46
Q

4th cleavage

A

(16) from animal to vegetal pole DOUBLE cleavage plane

47
Q

5th cleavage

A

(32) HORIZONTAL cleavage, BETWEEN animal and vegetal poles DOUBLE plane II to cleavage III

48
Q

Morula

A

16 blastomere in animal pole + 16 blastomeres in vegetal pole

49
Q

Cleavage pattern is affected by____

A

Yolk
- how much and where is it located?

50
Q

Alecithal (humans)

A
  • negligible or no Yolk (all placentals)
51
Q

Microlecithal

A
  • small yolk (urchins)
52
Q

Mesolecithal

A
  • 1/2 yolk (amphibians)
53
Q

Macrolecithal

A
  • Max yolk (insects, fish, reptiles, birds, monotremes)
54
Q

Lecithal

A

having yolk

55
Q

Isolecithal (humans)

A

eggs have yolk evenly distributed in the cytoplasm (sea urchins, mammals)

56
Q

Telolecithal

A

eggs have yolk concentrated at one end (amphibians and birds)
- polarity

57
Q

Centrolecithal

A

eggs have the yolk in the center, surrounded by “skin of cytoplasm” (drosophila)
- ex. insect

58
Q

Holoblastic (humans)

A

if yolk is sparse and evenly distributed, there is complete cytokinesis

59
Q

Meroblastic

A

if yolk is dense and unevenly distributed, division is partial or incomplete

60
Q

The more yolk, the _____ divisions

A

harder

61
Q

What cell pattern of motion do humans have?

A

Rotational

62
Q

Timing of cleavage pattern

A
  • synchronous (same time division)
  • asynchronous (NOT same time division)
63
Q

We have a __________ timing of cleavage pattern

A

asynchronous

64
Q

Cleavage pattern in humans

A
  • Microlecithal relies on maternal body for nutrients
  • holoblastic (has complete cytokinesis)
  • Cleavage rate is slower (divisions every 24 hours)
  • rotational divisions
  • asynchronous cell divisions
  • Days 1 thru 3, fertilization –> cleavage 2, 4, 6, 8 cells
65
Q

Day 4: At 8 cell stage to Morula (16-32 cells)

A
  • cell divisions continue
  • up to 16-32 cells is called morula
  • compact ball of cells
  • next phase: becoming Blastocyst
66
Q

Opening

A

antrum

67
Q

Morula will give rise to

A
  • embryo proper
  • extraembryonic membranes
  • contribute to placenta
68
Q

Day 4 morula (16-32) then Day 5___________

A

Blastocyst (100-200 cells)

69
Q

Day 5: Cells tightly adhere=

A

compaction

70
Q

Day 5: Cells begin to______

A

flatten

71
Q

Day 5: Cells-to-cell

A

contact

72
Q

Day 5: Blastocyst

A
  • compaction
  • flatten
  • contact
  • outer cell surface Convex
  • Inner cell surface Concave
  • Some cells migrate to surface and others migrate to center
  • Oviduct
  • 30 or so cells
  • absorbs fluid
  • Trophoblast becomes epithelium with Tight Junctions
  • Blastocoel forms within morula
  • ICM form a compact mass at one side of the cavity
  • Now called a BLASTOCYST (after 7-8 rounds of cell divisions)
73
Q

Outer Cell Mass (OCM)

A

Some cells migrate to surface
- Trophoblast (placenta)

74
Q

Inner Cell Mass (ICM)

A

Some cells migrate to center
- Embryo

75
Q

Blastocyst will give rise to

A
  • embryo proper
  • extraembryonic membranes
  • contribute to placenta
76
Q

Trophoblast Tight Junctions

A
  • E-cadherin (within membrane)
  • gap junctions (channel)
  • adherens junctions (“velcro”)
  • desmosomes (embedding membranes together)
77
Q

Blastocoel

A

Blastocyst cavity forms within morula

78
Q

Inner cell mass also known as________

A

embryoblasts (form a compact mass at one side of the cavity)

79
Q

Timeline

A

Pronuclear
- Day 0

Cleavage stage
- Day 1
- Day 2
- Day 3

Morula
- Day 4

Blastocyst
- Day 5+

80
Q

Tight junction

A

interlocking junctional proteins

81
Q

Anchoring/Adhering junctions

A

protein filaments

82
Q

Desmosome junction

A

linker protein (ex. Cadherin)

83
Q

Gap junctions

A

Channel between cells formed by connexons
- allows for communication between cells

84
Q

Blastocyst (by Day 5)

A
  • arriving at uterus
  • enzymatically bores a hole in Zona Pellucida and hatches out
  • Naked and can interact with endometrium and binds
  • Endometrium and uterine wall responds– more vascularization
  • Trophoblast produces hCG
  • By week 11-12, the placenta takes over Progesterone production and corpus luteum becomes corpus albicans
  • TWINS
85
Q

Trophoblast produces hCG

A
  • Human Chorionic Gonadotropin
  • supports Corpus Luteum which continues to supply PROGESTERONE to maintain pregnancy and grow lining
86
Q

Placenta

A

Progesterone production in pregnancy

Embryology (12 decks)

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