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MSK Exam I > Lecture 9: Fertilization and Gastrulation > Flashcards

Lecture 9: Fertilization and Gastrulation Flashcards

1
Q

Gametes include oocytes and sperm, which are haploid cells that can undergo ______ (or fusion of nuclei of 2 sex cells)

A

Karyogamy

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2
Q

What is the difference in motility between oocytes and sperm?

A

Oocytes are immotile; sperm are highly motile

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3
Q

What is the sex chromosome constitution in sperm vs. oocytes?

A

Sperm: 23X or 23Y

Oocyte: 23X

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4
Q

In addition to their sex chromosome constitution, gamets have ____ autosomes

A

22

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5
Q

Primary oocytes remain dormant until when?

A

Puberty

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6
Q

During puberty, the ______ of the oocyte matures and completes meiosis I to form a _________ _________

A

Follicle

Secondary oocyte

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7
Q

Meiosis I of the primary oocyte at puberty produces a secondary oocyte.

The secondary oocyte begins the second meiotic division, but stops at what phase?

A

Metaphase

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8
Q

What happens to the ~2 million oocytes present in females at birth?

A

Most regress during childhood

No more than 40,000 remain at adolescence

~400 will form secondary oocytes and are ovulated

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9
Q

The oocyte is surrounded by __________ cells which are responsible for folliculogenesis

A

Granulosa

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10
Q

What 3 things are associated with the granulosa cells responsible for folliculogenesis?

A

Cumulous oophorus
Mural granulosa cells
Corona radiata

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11
Q

_________ __________ anchors the primary oocyte to the wall of the follicle

A

Cumulus oophorous

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12
Q

What lines the wall of the oocyte follicle?

A

Mural granulosa cells

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13
Q

What is firmly anchored to the zona pellucida of the oocyte?

A

Corona radiata

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14
Q

________ ________ is the thick layer of glycoproteins deep to the corona radiata of the oocyte

A

Zona pellucida

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15
Q

What are the 3 major components of a mature sperm?

A

Head - forms most of the bulk of the sperm and contains nucleus

Neck - junction of head and tail

Tail - provides motility to fertilization site

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16
Q

The head of the sperm is covered by the ________, a cap-like organell containing enzymes

A

Acrosome

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17
Q

What are the 2 major function of the acrosome of mature sperm?

A

Facilitates dispersion of follicular cells of corona radiata

Penetration of zona pellucida of oocyte

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18
Q

What is the cortical reaction and why is it so important?

A

Process initiated during fertilzation by the release of cortical granules from the egg

Prevents polyspermy, or the fusion of multiple sperm with one egg!

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19
Q

Meiosis I of the primary oocyte at puberty produces a secondary oocyte.

The secondary oocyte begins the second meiotic division, but stops at metaphase.

What stimulates the oocyte to complete meiosis II?

A

Fertilization

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20
Q

Fertilization stimulates the oocyte to complete meiosis II, resulting in fusion of ________ into a diploid aggregation of 46 chromosomes

At this point, the cell is referred to as a _________

A

Pronuclei

Zygote

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21
Q

What happens to the chromosomes once there is fusion of pronuclei and the cell becomes a zygote?

A

They arrange on the cleavage spindle and prepare for cleavage

There is metabolic activation and initiation of cleavage

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22
Q

One form of mosaicism is called _______, meaning failure of a chromosome pair to separate

A

Nondisjunction

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23
Q

When does nondisjunction occur and what does it produce?

A

Occurs during early cleavage

Produces an embryo with 2+ cell lines with different chromosome complements

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24
Q

Individuals with mosaicism are _______

A

Mosaics

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25
Q

What is the most common example of mosaicism?

A

Numerical mosaicism - such as trisomies

[typically trisomic mosaicism is less severe than nonmosaic condition]

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26
Q

Repeated mitotic divisions of the zygote produces _________

A

Bastomeres

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27
Q

How does cell number vs. cell size change during cleavage to produce blastomeres?

A

Increase in cell number, but decrease in blastomere size

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28
Q

When does production of blastomeres occur relative to fertilization?

A

About 30 hours after fertilization

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29
Q

At the 9-cell stage, the blastomeres undergo _________. At 12-32 cells, the developing human is called a ________

A

Compaction

Morula

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30
Q

During blastogenesis, after entering the uterus, the ________ _______ appears inside the morula.

A

Blastocystic cavity

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31
Q

Once the blastocystic cavity has formed inside the morula, the blastomeres make their first lineage decision to become what vs. what?

A

Trophoblast layer vs. embryoblast

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32
Q

The term _______ refers to an embryo and its membranes

A

Blastocyst

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33
Q

2 days after fertilization, the _______ ________ degenerates, which is sometimes referred to as the “hatching” of the blastocyst

A

Zona pellucida

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34
Q

Describe cell stages from day 0 through day 5 after fertilization

A

Day 0: pronuclear stage

Day 1: 2-cell (24 hours)

Day 2: 4-cell (48 hours)

Day 3: 8-cell (72 hours)

Day 4: morula (96 hours)

Day 5: blastocyst (120 hours) - hatching

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35
Q

Describe the process of in vitro fertilization and embryo transfer

A

Hormonal stimulation of mature oocyte formation, resulting in several mature follicles

Collection of occytes from follicles with aspirator during laparoscopy

Placement of oocytes in petri dish with capacitated sperms; in vitro fertilization of oocytes

Cleavage of zygotes in culture medium until 4-8 cell stages are reached

Transfer of 1-2 cleavage embryos into uterine cavity by way of catheter inserted through vagina and cervical canal

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36
Q

Assisted Reproductive Technology, or ART, consists of what 3 major methods?

A

Cryopreservation of embryos

Intracytoplasmic sperm injection

Assisted IVF

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37
Q

Describe cryopreservation of embryos

A

Early embryos from IVF are preserved by freezing in liquid nitrogen

Transfer of 4-8 cell embryos and blastocysts into uterus

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38
Q

Describe intracytoplasmic sperm injection

A

Sperm injected into mature oocyte, commonly done when few sperms are available

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39
Q

Where does fertilization occur with assisted IVF? How does this compare to the usual location of fertilization?

A

In the ampulla, which is the usual location of fertilization

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40
Q

T/F: many zygotes, morulae, and blastocysts abort spontaneously; the overall early spontaneous abortion rate is thought to be approx. 45%

A

True

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41
Q

What are 2 potential causes for spontaneous abortion?

A

Inadequate production of progesterone and estrogen from corpus luteum

Chromosomal abnormalities (abnormal segregation, duplication, deletions, dispermy, etc.)

42
Q

How many chromosomes are present in dispermy?

A

69

43
Q

What procedure may be required in the event of a spontaneous abortion?

A

Dilation and curettage (D and C)

44
Q

What condition is characterized by implantation of the blastocyst outside the uterine cavity?

A

Ectopic pregnancy

45
Q

Where do ectopic pregnancies typically occur?

A

In the oviduct = tubal pregnancy (mainly in ampullary region)

46
Q

What are some signs of ectopic pregnancy?

A

Abdominal pain
Amenorrhea
Vaginal bleeding
Profuse bleeding and rupture of oviduct wall

47
Q

___________ differentiation occurs 6 days after fertilization

A

Trophoblast

48
Q

Trophoblasts differentiate into what 2 layers?

A

Syncytiotrophoblasts (outer layer)

Cytotrophoblasts (inner layer)

49
Q

Which layer of the trophoblast will invade to produce chorionic villi?

A

Cytotrophoblast

50
Q

__________ are a multinucleated protoplasmic mass without cell boundaries

A

Syncytiotrophobasts

51
Q

With syncytiotrophoblasts, cells expand within the embryonic _____ and produce digestive enzymes that erode the endometrium in a process called ___________

This enables the blastocyst to burrow into the endometrium

A

Pole

Decidualization

52
Q

Embryoblast reorganization occurs with formation of the _________ embryonic disc

A

Bilaminar

53
Q

What are the 2 layers of the bilaminar embryonic disc?

A

Hypoblast (primitive endoderm)

Epiblast

54
Q

Which layer of the bilaminar embryonic disc consists of a layer of columnar cells?

A

Epiblast (layer of columnar cells deep to hypoblast)

55
Q

The columnar cells of the epiblast will give rise to what?

A

Embryo proper

56
Q

The hypoblast, or primitive endoderm, is formed by an internal layer of _________ cells.

It is a result of the ________ of cells from the embryoblast and faces the ________ cavity.

A

Cuboidal

Delamination; blastocystic

57
Q

What forms the 4 extraembryonic membranes and what are they?

A

Membranes are produced by bilaminar germinal disc and trophoblast layer

Amnion
Yolk sac
Chorion
Allantois

58
Q

Which extraembryonic membrane gives rise to the embryonic portion of the placenta?

A

Chorion

59
Q

Which extraembryonic membrane serves as a site for early blood cell and vessel formation?

A

Yolk sac

60
Q

Which extraembryonic membrane consists of a thin layer of cells that encloses the epiblast and holds amniotic fluid?

A

Amnion

61
Q

When does the amniotic cavity appear?

A

In the 2nd week

62
Q

The amniotic cavity appears the 2nd week when fluid collects between the _____ and _____ cells

A

Epiblast; trophoblast

[the epiblast cells expand toward embryonic pole to form the amnion. The amniotic cavity will enclose the entire embryo]

63
Q

The development of the yolk sac occurs as a result of proliferation of the _______ (day 8)

A

Hypoblast

64
Q

Proliferation from the hypoblast occurs into the blastocyst cavity, forming the primary yolk sac. What is the term for the cells that line the yolk sac?

A

Heuser’s membrane

65
Q

After formation of the Heuser’s membrane, extraembryonic ________ forms and fills the remainder of the space

A

Mesoderm

66
Q

Extraembryonic mesoderm arises from what 2 components?

A

Hypoblast

Primary yolk sac

67
Q

By day 12, the primary yolk sac is displaced (will degenerate) by migrating ________ cells, which form the secondary yolk sac

A

Hypoblast

68
Q

A new space, called the _______ ______ is formed by splitting of the extraembryonic mesoderm into 2 layers

A

Chorionic cavity

69
Q

The chorionic cavity separates the embryo with its attached amnion and yolk sac frmo the outer wall of the blastocyst = ___________

A

Chorion

70
Q

What 2 extraembryonic germ layers are associated with the amnion?

A

Ectoderm

Mesoderm

71
Q

What 2 extraembryonic germ layers are associated with the yolk sac?

A

Endoderm

Mesoderm

72
Q

What extraembryonic germ layer is associated with the chorion?

A

Mesoderm

73
Q

By day 13, the embryo proper is suspended in the chorionic cavity by the ______ _____, made up of extraembryonic mesoderm

A

Connecting stalk

74
Q

What condition is characterized as an abnormal blastocyst with continued trophoblast development?

A

Hydatiform mole

75
Q

What type of hydatiform mole shows some evidence of embryonic development and may appear triploid (69, XXX; 69, XXY; 69, XYY)?

A

Partial

76
Q

With complete hydatiform mole, the oocyte lacks a female ________, and there is dispermy. No embryonic development occurs

A

Pronucleus

[note: dispermy = duplication of male pronucleus]

77
Q

Hydatiform moles produce high levels of _____ and may produce benign or malignant tumors called _________

The placental villi will be swollen and ________

A

hCG; choriocarcinoma

Vesicular

78
Q

The bilayer embryonic disc consists of epiblast and hypoblast.

Epiblast differentiates into what 3 structures?

A

Ectoderm of amnion
Embyronic ectoderm
Primitive streak

79
Q

The bilayer embryonic disc consists of epiblast and hypoblast.

The hypoblast becomes the ______ of umbilical vesicle, which then differentiates into extraembryonic mesoderm

A

Endoderm

80
Q

Extraembryonic mesoderm, embryonic mesoderm, notochordal process, and embryonic endoderm arise from what structure derived from the epiblast?

A

Primitive streak

81
Q

________ is the process by which cells from the epiblast migrate to form the primary germ layers

A

Gastrulation

[primary germ layers give rise to all adult structures and establish tube-within-a-tube body plan]

82
Q

Gastrulation begins during week 3 with formation of the ________ _______, which is a thin depression on the surface of the epiblast

A

Primitive streak

83
Q

What is established once all germ layers are present in gastrulation?

A

Trilaminar embryonic disc

84
Q

At the beginning of morphogenesis, epiblast cells move through the primitive streak to relocate between the epiblast and hypoblast layers in a process called _______

A

Ingression

85
Q

Describe the ingression of epiblast cell relocation

A

Lateral –> midline –> through primitive streak –> move back to lateral

86
Q

Epiblast cells displace the hypoblast, forming what germ layer?

A

Embryonic endoderm

87
Q

Epiblast cells displace the hypoblast, forming embryonic endoderm. The cells remaining in the epiblast form what germ layer?

A

Embryonic ectoderm

88
Q

Epiblast cells displace the hypoblast, forming embryonic endoderm. The cells remaining in between epiblast and hypoblast become what germ layer?

A

Embryonic mesoderm

89
Q

_________ are tumors that arise from primordial germ cells (PGCs), which are migratory cells that normally populate the gonads

A

Teratomas

90
Q

Are teratomas more common in males or females?

A

4x more frequent in females

[represents 3% of childhood malignancies overall]

91
Q

Which germ layers are teratomas derived from?

A

May be derived from any one to all germ layers

Contain a range of cell types: hair, teeth, pituitary tissue, etc.

92
Q

Formation of the notochordal process begins with cranial extension from the _______ ________

A

Primitive node

93
Q

The notochordal process extends cranially from the primitive node between ectoderm and endoderm until reaching the _____ ______

A

Prechordal plate

94
Q

T/F: by day 20, the notochordal process is complete

A

True

95
Q

The notochordal process will form the notochord as it progresses from hollow tube –> flattened plate –> solid rod.

The notochord is a _______ derivative

A

Mesodermal

96
Q

What is the primary inductor in the early embryo, providing the signaling required for development of axial musculoskeleton and CNS?

A

Notochord

97
Q

The notochord contributes to the nucleus ______ in infants and children

A

Pulposus

98
Q

The endoderm is the source of what body structures?

A

Epithelial linings of the respiratory and digestive tracts

Glands opening into the GI tract, glandular cells of associated organs such as the liver and pancreas

99
Q

The ectoderm is the source of what body structures?

A

Epidermis of skin, and epidermal derivatives

CNS and PNS

Neural crest cells, eyes, and internal ears

100
Q

The mesoderm is the source of what body structures?

A

All skeletal muscles, blood cells, the lining of blood vessels

All visceral smooth muscular coats, serial linings of all body cavities, urogenital ducts and organs

Most of the cardiovascular system

All trunk CT (including cartilage, bones, tendons, ligaments, dermis, and storm of internal organs)

MSK Exam I (18 decks)

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