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Genes and early embryology > Gametogenesis, fertilization and the blastocyst > Flashcards

Gametogenesis, fertilization and the blastocyst Flashcards

1
Q

Once eggs are released from ovary, where do they go through and what do they go to

A

Go through fimbrae to fallopian tube

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2
Q

What are the parts of the Fallopian tube starting from the fimbrae

A

1) infundibulum
2) Ampulla
3) Isthmus
4) interstitial

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3
Q

Where does fertilization happen

A

Ampulla

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4
Q

What is the first entity that is present in female gametogenesis

A

Primary follicle

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5
Q

What is the primary follicle

A

Primary oocyte is surrounded by a single layer of follicular cells

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6
Q

What do primary follicles begin to develop into

-when does this happen

A

5-12 primary follicles develop and become growing follicles

-happens at the beginning of each monthly cycle

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7
Q

What happens to the primary follicles after they become growing follicles

A

Follicular cells multiply and become several layered

-Also become separated from the ovum by a layer called the Septum Pellucidum

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8
Q

What is the septum pellucidum

A

Layer that separates follicular cells from the ovum

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9
Q

What do all but one of the growing follicles degenerate to become

A

Corpus atreticum/scar

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10
Q

After all but one of the growing follicles becomes a corpus attreticum, what happens

A

The follicular cells of the remaining growing follicle secrete a fluid which produces a fluid-filled Antrum within the follicle

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11
Q

What is the thecal layer of the growing follicle made from?

A

Made from the ovarian non-gamete cells surrounding the follicle

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12
Q

What is the thecal layer divided into

A
  • Vascular theca interna

- Avascular inactive theca externa

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13
Q

What does the theca interna do

A

Produce oestrogen

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14
Q

What is the mature follicle callled

A

Graafian follicle

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15
Q

In the graafian follicle (mature follicle), what do the majority of the follicular cells form

A

Stratum granulosum

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16
Q

What does the stratum granulosum produce

A

Progesterone

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17
Q

What do the remaining of the follicular cells do

A

Remainder surround oocyte as the cumulus oophorus

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18
Q

What is a secondary oocyte

A
  • majority of the follicular cells have now formed the stratum granulosum
  • The remainder of the follicular cells surround the oocyte as the cumulus oophorus
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19
Q

What is formed after a graafian follicle

A

Secondary oocyte

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20
Q

What happens after a secondary oocyte is produced

A

Mature follicle ruptures and releases an ovum

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21
Q

What does the released ovum still have

A

Retains a covering of follicular cells which form the corona radiata

22
Q

What happens to the septum pellucidum after ovum is released

A

Septum pellucidum expands to become the zone pellucida

23
Q

What forms the corpus luteum

A

Cells of the theca interna and the stratum granulosum enlarge and become yellowish to form the corpus luteum

24
Q

What does the corpus luteum do?

-what did it do before ovulation

A

Secretes a large amount of progesterone

-THe follicle produced mainly oestrogen

25
Q

What is the life span of the corpus luteum is fertilization does not occur

A

12 days

26
Q

What degenerates if fertilization does not occur

A

Corpus luteum degenerates into the corpus albicans

- the cessation of its hormonal output leads to menstruation

27
Q

What happens if fertilization does occur

A

The corpus luteum is sustained by the HCG produced bu the conceptus and form a large corpus luteum of pregnancy

28
Q

What does a corpus luteum of pregnancy eventually form

A

Corpus albican

29
Q

In a sperm, what does the head consist of

A

Largely of a nucleus with a sparse cytoplasmic covering

30
Q

What is the acrosomal cap derived from

A

Golgi

31
Q

What does the acrosomal cap do

A

contain enzymes which help in the penetration of the ovum

32
Q

Main difference between spermatogenesis and oogenesis

A

spermatogenesis has mitosis followed by meiosis

-oogenesis has meiosis in ovaries and no mitosis

33
Q

What is the cytoplasmic:nuclear ratio in spermatogenesis vs in oogenesis

A

Spermatogenesis
Low cytoplasmic:nuclear ratio
Oogenesis
High cytoplasmic:nuclear ratio

34
Q

How is the abdominal cavity different in males and females

A

Abdominal cavity is closed in males but it communicates with the exterior in females
(vagina->Fallopian tube->abdominal cavity)

35
Q

After being in the cervix, where does the sperm go and what happens to it

A

sperm reaches the isthmus and becomes less motile

36
Q

What makes the sperm motile again? Where are these released from

A

Chemoattractants released from cumulus cells

37
Q

What does sperm require in the female reproductive tract

A

Requires capacitation

-during which acrosomal region loses glycoprotein coat

38
Q

What is fertilization 1

A

Shed secondary oocyte halted part way through 2nd meiotic division

39
Q

What is fertilization 2

A

Mature ovum- penetration by spermatozoon prompts completion of 2nd meiotic division

40
Q

What do acrosomal enzymes do

A

Help disperse corona radiata and aid penetration of zone pellucida. Plasma membranes of gametes fuse and male nucleus is ‘injected’

41
Q

What is fertilization 3

A

Fertilized ovum is diploid again and the permeability of the zone pellucida is altered to prevent further penetration

42
Q

What is done to stop more sperm entering fertilized ovum?

A

Zona reaction- permeability of zone pellucida is altered to prevent further penetration

43
Q

Where are enzymes released from to digest sperm receptor proteins on ovum so they can no longer bind sperm

A

Enzymes released by cortical granules

44
Q

What is the circumvitelline space

A

Ovum has shrunk and there is a ‘gap’ between the zona pellucida and the ovum

45
Q

How are blastomeres formed

A

Mitosis

46
Q

What happens when there is further cleavage

-what is DNA and protein synthesis like

A

Cells continue to cleave to form progressively smaller blastomeres. There is DNA synthesis but virtually no protein made

47
Q

What is a morula

A

New solid balls of cells. Cytoplasmic:nuclear ration is now normal

48
Q

What is the zone pellucida like in a morula and why

A

Still persists to stop implantation

49
Q

What do morula cells undergo

-What happens to the zone pellucida

A

COmpaction- establishment of tight junctions between surface cells
-the zone pellucida starts to split

50
Q

When does the blastocyst form

A

5 days after fertilization

51
Q

What does a blastocyst look like

A

Has an inner cell mass and a trophoblast

52
Q

When are 2 daughter cells (blastomeres) formed by mitosis

A

30h post fertilisation

Genes and early embryology (12 decks)

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