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Embryology > Fertilization > Flashcards

Fertilization Flashcards

1
Q

Sequence of events:

A

1.) Attraction and Activation of sperm
2.) Contact and recognition between sperm and egg
3.) Sperm entry
4.) Preventing Polyspermy (and polyploidy)
5.) Fusion of egg and sperm (nuclear fusion)

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2
Q

What is the average size of sperm?

A

5.1um by 3.1um and the flagellum is 50um (flagellum is the longest part)

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3
Q

Sperm can survive and are capable of fertilization up to______ days?

A

7

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4
Q

What is the motion time for sperm?

A

1-3mm per minute

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5
Q

Sperm ejaculation stats

A

1.5-5ml per ejaculation

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6
Q

Sperm per milliliter

A

20-150 million

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7
Q

Where are sperm released in the vaginal canal?

A

Cervix

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8
Q

Within how many hours can the sperm reach the oviduct?

A

1/2 to 2 hours

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9
Q

Prep Sperm for environment and encounter with egg

A

1.) The sperm are immobile until they reach the epididymis
2.) Seminal fluids add + strip of carbohydrates and proteins at the head of the sperm because with all of these materials attached to the sperm it will not be able to fertilize an egg
3.) The female reproductive tract contains enzymes and lower pH levels that also help to strip off the sperm’s surface glycoproteins

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10
Q

The sperm are immobile until they reach which structure?

A

Epididymis

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11
Q

Why do seminal fluids add + strip of carbohydrates and proteins at the head of the sperm?

A

Because with all of these materials attached to the sperm, it will not be able to fertilize an egg

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12
Q

The female reproductive tract contains enzymes and ______ pH levels that also help to strip off the sperm’s surface glycoproteins

A

Lower; acidic

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13
Q

What is the average size of an egg?

A

0.1mm

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14
Q

Egg mobility

A

“floating” to and thru oviduct

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15
Q

Egg viability

A

within 12-24 hours after ovulation

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16
Q

Where is the egg fertilized?

A

Within oviduct

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17
Q

What is the protective layer of the egg?

A

Zona Pellucida (Vitelline Membrane)
- glycoproteins
- increase surface area

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18
Q

________ cells cover and accompany the egg

A

Granular cells

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19
Q

The egg is covered with_________

A

Microvilli

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20
Q

Approximately how many eggs lost each month?

A

1000

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21
Q

Role of microvilli

A

Increases surface area and receptors (they do not move though)

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22
Q

Approach of sperm to egg for what?

A

FUSION (union)

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23
Q

Human sperm travel in this order

A

cervix –> uterus –> oviduct

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24
Q

Positive retroactive response

A

sperm in the oviduct have to orient themselves against the ciliated current

(swimming upstream)

25
Q

Capacitation

A

Enhancement of sperm to allow penetration of the egg’s membrane

26
Q

Fertilization occurs within what part of the oviduct?

A

Upper 1/3 of oviduct

27
Q

Gametes– haploid + haploid

A

= diploid

28
Q

Species gene barrier

A

Sperm will only fertilize with its own species
- genetic material has to match receptors

29
Q

Life span of gametes

A

Females: shorter, roughly 12-24 hours

Males: longer lived, typically 1-2 days

30
Q

Sperm released

A

ejaculated

31
Q

Chemoattraction

A

Sperm find the egg by detection of soluble chemoattractant
- immune cells releasing chemical sirens and communicating via chemical signals

32
Q

What happens during chemoattraction?

A
  • human sperm are activated and attracted by fluids in the female reproductive tract
  • follicular fluid
  • Corona Radiata - Granular cells
  • “Sperm Chemotropic Factors”
33
Q

What is the fluid called that attracts the sperm?

A

Follicular fluid

34
Q

Contact and Recognition between sperm and egg

A

a.) Docking
b.) Acrosome Bursting

35
Q

Docking (Specific Recognition)

A
  • “lock and key” idea for it to activate
  • the sperm bind to a glycoprotein (ZP2) found on the zona pellucida (ZP1-ZP4)
36
Q

Acrosome bursting

A

ZP3 binding and Ca++ surge in sperm initiates acrosome rupture and allows for next cellular process to begin

37
Q

Acrosome projecting

A

cytoskeleton within the sperm is synthesized and pushes acrosome and sperm into the ovum

38
Q

The exocytosed acrosome enzymes drill through the egg’s_______

A

zona pellucida

39
Q

Within acrosome =

A

Hydrolytic enzymes

40
Q

Acrosome enzymes triggers_______

A

sperm tail to whip faster pushing into the egg’s Zona Pellucida
- many sperm attach but only one makes it in!

41
Q

Sperm entry

A

1.) Acrosome reacts with Zona Pellucida space
2.) Sperm membrane fuses with egg membrane
3.) membrane fusion and Calcium surge triggers egg to complete Meiosis II and is now mature Oocyte (and polar body)
4.) A fertilization cone powered by the ovum’s actin filaments rise up out of the egg engulfing sperm
5.) Cortical Granules fuse with egg membrane which renders the Zona Pellucida impenetrable to OTHER sperm

42
Q

What happens when acrosome reacts with Zona Pellucida space?

A

Encounters more egg proteins

43
Q

Sperm specific protein

A

IZUMO1

44
Q

Egg specific protein

A

JUNO

45
Q

IZUMO1 and JUNO_____

A

bind

46
Q

Calcium surge

A

Triggers egg to complete Meiosis II and is now mature oocyte (and polar body)

47
Q

A ______ ______ powered by the ovum’s actin filaments rise up out of the egg engulfing sperm

A

fertilization cone

48
Q

______ fuse with egg membrane which renders the Zona Pellucida impenetrable to OTHER sperm

A

Cortical Granules

49
Q

Preventing Polyspermy (and polyploidy)

A

a.) Fast block
b.) Slow block

50
Q

The FAST block (1-3 seconds)

A
  • Slam the door!
  • Sperm entry causes the egg membrane to depolarize by opening sodium channels and Na+ is pumped into the egg cell
  • The electrical potential of a cell swings from negative -70mV to positive +20mV
  • This only lasts one to two minutes but long enough to prevent sperm binding
  • The sperm ZP2 receptor proteins change shape and detaches the other sperm
51
Q

The electrical potential of a cell swings from________ to _________

A

Negative -70mV to positive +20mV

52
Q

The Slow block (30 sec to 1 minute)

A
  • lock and bolt the door!
  • sperm entry triggers a intercellular wave of calcium ions to radiate over egg membrane (Calcium tsunami)
  • *Cortical Granules Reaction
53
Q

Calcium tsunami releases what?

A

1000s cortical granules

54
Q

Cortical Granules Reaction

A

Granules beneath cell membrane “pop” and release their contents into the space between the plasma membrane an the next outmost layer
- cortical proteases digest other partially attached sperm
- HydroPHILIC (loving) mucopolysaccharides (+ water) push away the outer layer creating a FERTILIZATION ENVELOPE that sperm cannot cross (increases volume) and pushes out other sperm!

55
Q

Fertilization envelope

A

Sperm cannot cross

56
Q

What initiates the cortical granule reaction?

A

A wave of calcium ions that begins where the single sperm has entered the egg; this calcium wave flowing across the egg takes on average about 30 seconds (slow block)

57
Q

Nuclear fusion of sperm and egg

A

1.) The sperm nucleus breaks down
2.) Chromatin is unwound and exposed to the maternal cytoplasm
3.) Microtubules extending of the male and female pronuclei together
4.) All chromosomes unite and lineup right away for the first mitotic division
- 1 cell = zygote
- 23+23 = 46 chromosomes
- Onward to the 1st cell division

58
Q

Generalized acrosomal process

A

1.) sperm makes contact with egg
2.) Acrosome reacts with zona pellucida
3.) Acroome reacts with perivitelline space
4.) Plasma membranes of sperm and egg fuse
5.) Sperm nucleus enters egg
6.) Cortical granules fuse with egg plasma membrane, which renders the vitelline layer impenetrable to sperm

Embryology (13 decks)

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