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Human Development (BSC5314) > Week 1 Development > Flashcards

Week 1 Development Flashcards

0
Q

How does the sperm find the oocyte?

A

chemotaxis toward oocyte attractants help guide sperm to the secondary oocyte

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1
Q

Where does fertilization usually occur?

A

occurs in the ampulla of the oviduct

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2
Q

What is the length of the window of opportunity for fertilization?

A

up to 24hrs

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3
Q

Penetration of corona radiata is facilitated by what enzyme?

A

Hyaluronidase released from acrosome

-capacitated sperm readily move through corona radiata cells

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4
Q

Penetration of zona pellucida is facilitated by what enzyme?

A

Acrosin causes lysis of thee zona pellucida to create a path

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5
Q

What is the zona reaction?

- What is the outcome

A

Zona reaction are the changes in the zona pellucida after the first sperm penetrates
- makes zona pellucida impenetrable by additional sperm

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6
Q

What of sperm enters oocyte during the fusion of sperm and secondary oocyte plasma membranes?

A

sperm contents

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7
Q

What happens when secondary oocyte completes meiosis II?

A
  • mature ovum and secondary polar body form

- ovum nuclear material decondenses somewhat to become the female pronucleus

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8
Q

How does the male pronucleus form?

A

forms as the sperm nucleus enlarges somewhat

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9
Q

How is the male pronucleus distinguishable from the female pronucleus?

A

They are morphologically indistinguishable

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10
Q

After the formation of the male pronucleus, what happens to thee rest of the sperm?

A

the other sperm contents degenerate

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11
Q

What is an Ootid?

A

An Ootid is the cell at the point containing the 2 pronuclei

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12
Q

What happens to the DNA in both pronuclei?

A

It is duplicated to form double-strand chromosomes

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13
Q

What happens when the male and female pronuclei fuse?

A

creation of a zygote

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14
Q

what is the ploidy number of the zygote?

A

4N

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15
Q

What is the chromosomal content of the zygote?

A

Genotypical sex is established as 46 XX, or 46XY

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16
Q

How are the follicles stimulated to grow in In Vitro fertilization?

A

development of multiple mature ovarian follicles is stimulated chemically

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17
Q

How are the oocytes harvested in in vitro fert.?

A

Mature secondary oocytes are harvested laparoscopically just prior to ovulation
- Or by ultrasound guided needle aspiration via the vaginal canal

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18
Q

Mature secondary oocytes are mixed with what after being harvested?

A

They are mixed with capacitated sperm in a Petri dish

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19
Q

How long does the development progress in vitro?

A

fertilization and early zygote cleavage are monitored microscopically for 3-5 days

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20
Q

How many embryos are typically transferred?

A

1-2 embryos are transferred by catheter into uterine lumen

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21
Q

In what position is the patient told to remain in to allow for implantation?

A

Supine for several hours

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22
Q

What happens to the rest of the embryos in in vitro fert.?

A

remaining viable embryos are cryopreserved in liquid nitrogen for later use

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23
Q

Gamete intrafallopian transfer involves what?

A

Placing harvested oocytes and capacitated sperm in the ampulla of the oviduct

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24
Q

What is done in surrogacy?

A

Placing in vitro fertilized oocytes of one woman into uterus of a different woman

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25
Q

What occurs in intracytoplasmic sperm injection?

A

single sperm injected directly into cytoplasm of mature oocyte
- used if male sperm count is low

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26
Q

When does the first division of the zygote occur?

A

30hrs after fertilization

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27
Q

Where is the zygote during the repeated mitotic divisions?

A

occurs as zygote is moving through oviduct towards uterus

- still surrounded by thick zona pellucida

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28
Q

What are blastomeres?

A

embryonic cells formed by zygote cleavage

- get progressively smaller with each mitotic division

29
Q

How does the zygote change in size?

A

Gets progressively smaller with each mitotic division (forming blastomeres)

30
Q

What is the process of compaction?

A
  • occurs after the 8-cell stage

- Increases cell contact and is mediated by cell surface adhesion glycoproteins

31
Q

Why is compaction a necessary step?

A

its a necessary step prior to forming certain cells that will become embyro

32
Q

What is the composition and appearance of a morula?

A

many mitotically divided cells (12-32 blastomeres) in the inside and zona pellucida on the outside

33
Q

When does a morula form?

A

Forms ~3 days after fertilization

34
Q

Which blastomeres of the morula will form the:

1) embryo
2) embryonic part of the placenta
A

1) internal cells will become the embryo

2) outer cells will become the embryonic part of the placenta

35
Q

What is the chromosomal condition referred to as mosaic?

A

results from nondisjunction in early mitotic cleavage of zygote

36
Q

What are the results of mosaic?

A

results in 2+ cell lines with different chromosomal complements

37
Q

Is Mosaic a permanent condition?

A

These may be a lost or persist as development continues

38
Q

Where is the morula on day 4?

A

enters the uterine cavity

39
Q

How does the blastocyst differ from the morula?

A

Blastocyst is the next stage of development in which the morula has developed a fluid-filled cavity

40
Q

What is the blastocoele?

A

The fluid filled cavity of the blastocyst

41
Q

Where does the fluid in the blastocyst come from?

A

Fluid diffuses through the zona pellucida into the blastocoele from the uterine cavity

42
Q

What is the trophoblast?

A

thin outershell of blastomeres

43
Q

What are the 2 groups that the blastomeres are separated into?

A

1) Trophoblast

2) Embryoblast

44
Q

What will the Trophoblast develop into?

A

Develops into the embryonic portion of placenta

45
Q

What is the embryoblast? Embryonic pole?

A
  • Embryoblast is a cluster of cells located on inner surface in one region of trophoblast (will develop into embryo)
  • The region of blastocyst containing the embryoblast is the embryonic pole
46
Q

When does the zona pellucida disappear?

A

Day 5

47
Q

What happens to the zygote after Day 5

A

The blastocyst will finally start increasing in size

48
Q

Will the blastocyst implant immediately?

A

The blastocyst will float freely in the uterine cavity for up to 2 days

49
Q

How do monozygotic twins develop?

A

from one zygote

50
Q

how common are monozygotic twins?

A

~25% of all twins

51
Q

When does twinning like monozygotic occur?

A

twinning usually occurs in week 1 with division of the embryoblast in blastocyst

52
Q

What is the genotype and phenotype of the monozygotic twins?

A

same sex, genetically identical, very similar physical appearance

53
Q

How many physical differences in monozygotic twins occur?

A

Physical differences may result from varied placental blood supply

54
Q

How do dizygotic twins develop?

A

Develop from 2 ova fertilized by 2 sperm in the same cycle

55
Q

How common do dizygotic twins occur?

A

~75% of all twins

56
Q

When does twinning like dizygotic occur?

A

hereditary tendency - recurrence in families is approx 3x the general population

57
Q

What is the phenotype and genotype of dizygotic twins?

A

may be same sex or different sex (fraternal twins)

- no more genetically similar than other brothers/sisters

58
Q

How do Conjoined monozygotic twins develop?

A

due to incomplete separation of the embryonic disk

59
Q

What is craniopagus?

A

joined at the head

60
Q

What is thoracopagus?

A

joined at the anterior thorax

61
Q

How are the unions structured in conjoined monozygotic twins?

A

Unions may be skin only or involve other tissues as well

62
Q

How are embryonic stem cells harvested?

A

Derived from embryoblast cells

63
Q

What are embryonic stem cells potential?

A

pluripotent - can form virtually any cell or tissue type

64
Q

What are the ethical considerations for stem cells?

A

obtained from embryos produced by in vitro fertilization

- limit the availability of cells from these sources

65
Q

What are adult stem cells?

A

multipotent - restricted in their availability to form only certain cells or tissue types

66
Q

What are the disadvantages to working with adult stem cells?

A

difficult to isolate and they have a low mitotic index

67
Q

Therapeutic cloning is also known as?

A

somatic cell nuclear transfer

68
Q

How does therapeutic cloning work?

A
  • insert nucleus of adult skin cell into an enucleated oocyte
  • oocyte is stimulated to differentiate into a blastocyst to provide embryonic stem cells
69
Q

What are the advantages of therapeutic cloning?

A

stem cells are genetically identical to recipient and no fertilization is involved

Human Development (BSC5314) (34 decks)

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