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Reproduction > Fertilization > Flashcards

Fertilization Flashcards

1
Q

What does seminal fluid consist of?

A

→ Prostatic and seminal vesicle secretions

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2
Q

What is the function of seminal fluid?

A

→ It coagulates to prevent loss and later liquefies

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3
Q

What is the function of the cervical mucus?

A

→ To remove seminal fluid

→ removing morphologically abnormal sperm and cellular debris

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4
Q

When is cervical mucus less viscous and why?

A

→ in the absence of progesterone

→ allows sperm to pass

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5
Q

What forms a reservoir of sperm in the female?

A

→ Cervical crypts

→some evidence of thermotaxis

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6
Q

When does fertilisation occur within?

A

→ 24-48 hours

→ sperm have been found alive after 5 days

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7
Q

What attracts the sperm to the egg?

A

→ Chemoattractants released from the oocyte cumulus complex

→ Sperm become hyperactivated near the egg

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8
Q

How do sperm become hyperactivated near the egg?

A

→ Forceful tail beats with increased frequency and amplitude

→ mediated by Ca2+ influx via CatSper channels

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9
Q

How is capacitation achieved?

A

→ Removing the sperm from the seminal fluid

→ uterine or tubal fluid may contain factors which promote capacitation

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10
Q

What must occur to the sperm before the acrosome reaction?

A

→ Biochemical rearrangement of the surface glycoprotein

→ changes in membrane composition

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11
Q

What time does capacitation occur?

A

→ 4-16 hours

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12
Q

Where does the acrosome reaction occur?

A

→ within the zona-cumulus complex

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13
Q

How does the acrosome reaction occur?

A

→ Acrosomal membrane on the sperm fuses
→ releases enzymes that cut through the zona-cumulus complex

→ acrosin bound to the inner acrosomal membrane digests the zona pellucida so sperm can enter

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14
Q

What causes the oocyte to undergo meiosis?

A

→ LH spike

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15
Q

What does the LH spike make the oocyte change into?

A

→ Primary oocyte becomes seconday oocyte + 1st polar body

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16
Q

What does the corpus luteum produce?

A

→ Progesterone

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17
Q

What does progesterone do to the endometrium?

A

→ Makes it secretory and receptive to implantation

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18
Q

What does progesterone do to the cilia?

A

→ Suppresses cilia in uterine tubes once the oocyte has passed
→Increase in tortosity of arterium

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19
Q

What does progesterone do the the cervical mucus?

A

→ It makes it viscous to prevent further sperm penetration

20
Q

What is the function of estrogen in the luteal phase?

A

→ Maintains the endometrium- causes proliferation of follicular phase

21
Q

What causes the LH spike?

A

→ sustained levels of estrogen produced by the dominant follicle

22
Q

After ovulation what happens to the follicle?

A

→ it becomes the corpus luteum

23
Q

What does progesterone do in the secretory phase?

A

→ Makes the stratum functionalis thicker

→ uterine glands become more secretory

24
Q

What causes the proliferative phase?

A

→ Estrogen from the follicular phase

25
Q

What is the life span of the CL?

A

→ 14 days

26
Q

What causes the inter cycle rise of FSH?

A

→ the fall in CL derived steroids

27
Q

What does the CL becomes when it dies?

A

→ Corpus albicans

28
Q

What happens to the CL in pregnancy?

A

→ It is rescued by the HcG from the embryo binding to the LH receptors
→ it continues to produce progesterone and maintain the endometrium

29
Q

What does the menstrual cycle achieve?

A

→ Selection of a single follicle and oocyte
→ Correct number of chromosomes in the oocyte

→ Changes in cervix and uterine tubes to enable egg transport and sperm access
→ Preparation of the endometrium
→ Support of the implanting embryo

30
Q

What are cumulus cells?

A

→ Remnants of the granulosa cells

31
Q

What is the corona radiata?

A

→ innermost granulosa cells(cumulus)

→in contact with the ZP. →Formed by granulosa cells adhering to the oocyte before it leaves the ovarian follicle

32
Q

What is the zona pellucida made from?

A

→ Matrix of proteins which are secreted from the egg

33
Q

What is a polar body?

A

→ The other half of cell division without the cytoplasm

34
Q

What does the first polar body mean?

A

→ That meiosis I has occurred

35
Q

When is meiosis triggered to finish?

A

→ By LH at ovulation

36
Q

Where does the acrosome reaction occur?

A

→ In contact with the zona-cumulus complex

37
Q

Describe sperm binding

A

1) Sperm penetrates the cumulus and bind to the ZP
2) Sperm enzymes cut through the ZP with ZP3 and the sperm fuses with the plasma membrane

3) Sperm are taken in by phagocytosis
4) Phospholipase Zeta is activated by basal Ca2+ inside the egg
PIP2 → DAG + IP3 which causes intracellular release of Ca2+ leading to a large Ca2+ spike
5) Cortical reaction as a wave of Ca2+ sweeps over the egg

38
Q

What is the cortical reaction?

A

→ Releases proteases, peroxides and hyaline which prevents polyspermy

39
Q

After meiosis I how many chromosomes does the oocyte have?

A

→ 23

→ 2 copies of each chromosomes are arranged as a sister chromatid

40
Q

What does entry of the sperm into the egg cause?

A

→ increase in Ca2+

41
Q

What does Ca2+ cause in the egg?

A

→ Completion of Meiosis II

42
Q

Describe syngamy

A

1) entry of sperm causes an increase in Ca2+ which causes the completion of meiosis II expelling the second polar body
2) Sperm nuclear membrane breaks down and chromatin decondenses and chromosomes separate

3) 4-7 hours after fusion the two sets of haploid chromosomes become surrounded by distinct membranes forming pro nuclei
4) the haploid structures synthesize DNA in preparation for the first mitotic division
5) pro nuclei fuse and mitotic metaphase spindle forms
6) mitosis occurs and one cell zygote becomes a two cell embryo

43
Q

What happens after primary oocyte is converted to secondary oocyte in LH spike?

A

→Basement membrane breaks so blood pours into the middle.
→Oocyte cumulus complex extruded out and caught by fimbrae of uterine tube
→Theca and granulosa become mixed and the empty follicle is known as the corpus luteum

44
Q

What is the cause of the removal of the negative feedback on the hypothalamus if pregnancy doe not occur?

A

When CL dies, it stops producing progesterone resulting in removal of negative feedback on hypothalamus
→Results in rise of FSH and LH- inter cycle rise of FSH

45
Q

How can you differentiate an egg at fertilization and an egg at ovulation?

A

ovulation has one polar body so has completed meiosis I.

→At fertilization there will be two polar bodies

46
Q

What must happen to the egg before implantation?

A

embryo comes out of zona pellucida

47
Q

What is the complex called 5 days after fertilization?

A

→blastocyst which differentiates into into inner cell mass, blastocoel and trophoblast.

Reproduction (12 decks)

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