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APBI 411 Reproductive physiology and technology > Fertility and Early Development > Flashcards

Fertility and Early Development Flashcards

1
Q

What are the two sites of sperm deposition?

A
  • fornix

- Cervix

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2
Q

What is seminal plasma used for?

A
  • Vehicle for transport

- Energy, motility and pH

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3
Q

What do vaginal secretions do to sperm?

A

they immobilize sperm within 1-2 hours

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4
Q

How do sperm achieve rapid transport?

A

Through contractile activity of the myometrium

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5
Q

How long does it take sperm to reach the site of fertilization?

A

About 15 minutes

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6
Q

Where are sperm reservoirs?

A
  • In the cervical crypts

- In the utero-tubal junction

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7
Q

What happens in sperm reservoirs over time?

A
  • Phagocytosis and loss of sperm cells

- Slow release of sperm cells

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8
Q

What prevents excessive numbers of sperm from descending on the site of fertilization?

A

Anatomic and Physiologic barriers

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9
Q

What increases the chances of fertilization?

A

The slow release of sperm from the reservoirs

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10
Q

What causes opposite direction transport of sperm?

A
  • Peristalsis and anti-peristalsis

- Complex nervous control

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11
Q

How long do sperm survive?

A

normally a maximum of 24 hours

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12
Q

How are sperm killed off?

A
  • Loss by phagocytosis and physical barriers
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13
Q

Where do sperm cells mature?

A

epididymis

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14
Q

How do sperm mature in the epididymis?

A
  • Gain motility

- Loose cytoplasmic droplet

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15
Q

When does capacitation start?

A

In the uterus, but mainly in the isthmus

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16
Q

Where does the acrosome reaction occur?

A

in the oviduct before fertilization

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17
Q

What is Capacitation?

A

sperm surface components are modified or removed by genital tract secretions causing the phospholipid bilayer to become destabilized, permitting acrosomal activation
- makes the sperm capable of attaching to and penetrating the ovum

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18
Q

What does capacitation function to prevent?

A

premature acrosome activation until the sperm reach the site of fertilization and come in contact with the ovum.

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19
Q

What changes do the sperm undergo during capacitation?

A
  • depletion of sperm cholesterol at sperm surface
  • alteration in glycosaminoglycans
  • changes in ions as sperm traverse the genital tract
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20
Q

What modifications happen on the surface of the spermatozoa?

A
  • Cholesterol efflux along with PKA-dependent phosphorylation
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21
Q

What modifications happen to the surface of the mitochondria?

A
  • loosely wraped around the axoneme or distended
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22
Q

What does looser wrapping of the mitochondria allow?

A

Faster moving sperm –> the sprint before the finish

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23
Q

What surface components are modified or removed (not including mitochondria or spermatozoa)

A
  • Secretions and accessory gland fluids
  • Phospholipid layer destabilized
  • Acrosome activation
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24
Q

Where does capacitation usually occur and why?

A

in the lower segment of the isthmus where fertilizing sperm are stored

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25
Q

What is capacitation facillitated by?

A

rubbing off of sperm surface-absorbed materials against the cervical mucus

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26
Q

What happens during the acrosome reaction?

A
  • Sperm plasma membrane fuses with outer acrosomal membrane
  • Vesiculation of acrosome
  • Release of hydrolytic enzymes
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27
Q

What are the functions of the acrosome reaction?

A
  • Eggs are surrounded by glycoprotein coats which the sperm have to travel through.
  • Acrosome-reacted sperm dissolve coat locally to produce a hole through which the sperm swim
  • outer acrosomal membrane overlying plasma membrane destroyed or becomes detached from the main body of the sperm.
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28
Q

What is required for freshly ovulated eggs to be picked up into the oviduct?

A
  • characteristics of fimbriae of infundibulum and relationship to the surface of the ovary at the time of ovulation
  • Pattern of release of cumulus cells and egg
  • Biophysical properties of follicular fluid released
  • coordinated contraction of the fimbriae and the utero-ovarian ligaments
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29
Q

What is the average transport time of the ova?

A

72-96 hours in cattle swine and sheep

- months in mares

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30
Q

what is the fertile life of the egg?

A

12-24 hours after ovulation

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31
Q

What happens if the egg is delayed?

A

increased chance for polyspermy

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32
Q

At ovulation, what phase in the ovum in?

A

metaphase 2

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33
Q

When is maturation of the ovum completed?

A

after fertilization and zygote formation

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34
Q

what happens when the male and female pronuclei fuse?

A
  • happens in the center of the ovum
  • nuclear envelope disperses
  • Intermixing of chromosome
  • 1st cleavage division
  • Zygote is formed
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35
Q

What is parthenogenesis?

A

the development of a zygote without a sperm

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36
Q

What are two types of twinning?

A
  • monozygotic

- dizygotic

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37
Q

What is monozygotic?

A

Zygote division

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38
Q

What is dizygotic?

A

double ovulation

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39
Q

What changes in the egg immediately after fertilization?

A

The surface of the ova

40
Q

What happens if blocking polyspermy fails?

A
  • Polispermic fertilization occurs which then results in polyploid embryos that undergo embryonic death or abnormal development
41
Q

Where is the polyspermic block performed?

A

at the zona

42
Q

How is the block performed?

A
  • sperm are allowed to penetrate but corticle granules released into peri-vitelline space (Ca++) causing a reorganization of zona or vitelline surface
43
Q

What is a zygote?

A

the cell produced by the union of two gametes (egg and sperm), before it undergoes cleavage.

44
Q

What do sperm maturational changes depend on?

A

epididymal secretions and transport time

45
Q

What roles do hyaluronidase and acrosin play?

A

Aid in the penetration of the ovum during the acrosome reaction

46
Q

What does the true acrosome reaction involve?

A

The fusion of the sperm plasma membrane with the outer acrosomal membrane followed by extensive vesiculation over the anterior segment of the acrosome

47
Q

When do high conception rates occur?

A

when sperm are present in the oviduct shortly before ovulation

48
Q

How is sperm fertilizability evaluated?

A
  • sperm’s ability to fertilize zona-free hampster eggs
  • motility patterns
  • surface characteristics
  • structural stability of head/tail
49
Q

What is capacitation controlled by?

A

autonomic nerve and hormonal controls

50
Q

How is capacitation achieved?

A

sperm-surface absorbed materials are rubbed off by the cervical mucus of the isthmus

51
Q

Low numbers of sperm in the oviduct are the result of what?

A
  • controlled movement into the ampulla by the utero-tubal junction and lower isthmus (Pigs) as well as from their movement from the vagina and cervix into the uterus (Ruminants)
52
Q

What does the low numbers of sperm in the oviduct prevent/allow/regulate?

A
  • regulates the number of sperm at the fertilization site (preventing polyspermy)
  • providing a sperm reservoir to ensure that capacitated sperm are present until ovulation
53
Q

What may assist in maintaining adequate numbers of sperm at the site of fertilization?

A

The ability of the sperm to adhere and release from the epithelial lining of the ampulla

54
Q

When do sperm become hyperactivated?

A

In the ampulla

55
Q

What does hyperactivation of sperm increase the probability of?

A

increases the probability that they will make contact with the ovum

56
Q

What three critical events are required for fertilization in mammals?

A
  1. Sperm migration between cumulus cells (if present)
  2. Sperm attachment and migration through the zona pellucida
  3. Fusion of sperm and the ovum plasma membranes
57
Q

What do peristalic contractions in the ampulla increase?

A

chance of ovum-sperm contact

58
Q

What is the attachment of the sperm head to the zona pellucida regulated by?

A

receptor sites on the suface of the zona pellucida

59
Q

What do antibodies to sperm or the zona pellucida do?

A

block or mask sperm receptor sites on sperm and zona surfaces

60
Q

What is acrosome organization required for?

A

to insure release of acrosome components in precise order to sperm traverse the egg vestments

61
Q

Why is the acrosome reaction an indicator of capacitation?

A

cause sperm do not undergo AR either spontaneously or mediated by ligands unless they become capacitated

62
Q

What happens chemically during the acrosome reaction? (what is massively influxed?)

A

Massive influx of Ca2+

63
Q

What does the glycoprotein layer of the inner surface of the outer acrosomal membrane do?

A

holds vesiculated plasma/outer acrosomal membranes together during AR

64
Q

What is essential for sperm attachment to the zona pellucida?

A

An intact acrosome

65
Q

What is required for the passage of sperm through the zona?

A
  • enzymes exposed during the AR

- Sperm motility

66
Q

What does binding with the ZP3 allow?

A

interactions with other zona components that stimulate acrosome activation

67
Q

What does the ZP2 serve as?

A

may serve as a secondary sperm receptor to maintain sperm attachment during passage through the zona

68
Q

What is the acrosome reaction a prerequisite for?

A

fusion between the ova and spermatozoa plasma membranes

69
Q

What is the ZP3?

A

sperm receptor to which only sperm with an intact acrosome can bind

70
Q

What happens once sperm has traveled through the zona pellucida?

A

the head moved into the vitelline space and contracts the vitelline membrane. Sperm tail propells sperm into vitelline space, rotating the vitelline membrane within the zona pellucida

71
Q

What is the vitelline membrane covered with?

A

dense microvilli

72
Q

What happens to the surface of the equatorial region of the sperm head?

A

it is incorporated into the plasma membrane of the ovum

73
Q

What happens when the cortical granules release their content?

A

causes extensive reorganization of zona pellucida and/or vitelline surface

74
Q

What does the cortical reaction result in?

A

release of enzymes that cause hardening of zona pellucida/inactivation of sperm receptors

75
Q

How do zygotes attain a ratio (nuclear to cytoplasmic) similar to somatic cells?

A

Through cleavage: cell divisions occur without increasing the mass

76
Q

What happens to the nucleus and cytoplasm during cleavage?

A

Cytoplasm amount decreases and the nucleus amount increases

77
Q

How does the egg receive metabolic support during early pregnancy?

A

By oviductal and uterine secretions

78
Q

What are the daughter cells of cleavage called?

A

blastomeres

79
Q

What sequence does cleavage follow in terms of the number of blastomeres?

A

A doubling sequence

80
Q

What type of division is cleavage?

A

Mitotic division with each daughter cell receiving the full assortment of chromosomes

81
Q

What does totipotent mean?

A

the cell can give rise to anything

82
Q

What is a morula?

A

When the embryo has formed 9-16 blastomeres

83
Q

What is compaction?

A

The combined process of flattening of the blastomeres and polarization

84
Q

When do tight junctions form between the blastomeres?

A

when the blostomeres are in close apposition during the process of compaction

85
Q

What do the tight junctions allow?

A
  • provides a permeability seal that allows fluid to move from the outside to the inside of the blastocyst without substantial leakage
  • important role in separating cells from contact with the maternal environment, thereby allowing the blastocyst to positionally differentiate into two populations of cells
86
Q

What do the two populations of a blastocyst give rise to?

A
  • Inner cell mass gives rise to the embryo proper

- outer cell mass gives rise to the trophectoderm or trophoblast which forms the chorion

87
Q

What forms during gastrulation?

A

The ectoderm, mesoderm and endoderm

88
Q

What do the microvilli on the outside of the trophoblast do?

A

contact and adhere to the maternal uterine epithelium for placental attachment and nutrient uptake

89
Q

Following the hatching from the zona pellucida, the trophectoderm will become lined with what? why?

A

mesoderm which expands out from the inner cell mass to form the outer membrane of the placenta

90
Q

What is the chorion?

A

the outer membrane of the placenta formed by the mesoderm

91
Q

When does bloastocyst hatching occur? Where?

A

Where: uterine lumen
When: 4-8 days post-ovulation

92
Q

What stretches the zona of the blastocyst during hatching?

A

physical and enzymatic actions in the form of rhythmic expansion and contraction of the blastocyst causing the zona to stretch. Involves cellular hyperplasia and increased fluid accumulation in the blastocoele

93
Q

What does hatching and fluid movement within the blastocyst seem to involve?

A

prostaglandin synthesis (Especially prostaglandin E)

94
Q

What causes softening of the zona matrix?

A

activation of enzymes such as plasmin and trypsin

95
Q

What is the conceptus?

A

embryo and its extraembryonic membranes

APBI 411 Reproductive physiology and technology (10 decks)

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