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RED > L04: Ovarian Function > Flashcards

L04: Ovarian Function Flashcards

1
Q

Is the first 7 weeks of embryonic development different in females and male

A

No

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2
Q

When do PGCs arise

A

Week 3

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3
Q

Where do PGCs arise from

A

Epithelium of yolk sac

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4
Q

What happens between week 3 and 7

A

PGCs migrate to gonadal ridges and undergo mitosis (proliferation)

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5
Q

What is migration of PGCs mediated by

A

Chemotaxis: TGF-beta

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6
Q

Where are chemotaxis from

A

Gonadal ridges that attract the PGCs

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7
Q

From week 7 onwards what determines if the embryo is male or female

A

SRY gene that is expressed on the Y chromosome for males

Absence of Y chromosome develops female gonads

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8
Q

What are the female gonads

A

Ovary

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9
Q

Describe the process of ovary formation when PGCs migrate

A

1) Sex cord cells do not penetrate deeply and cluster around the PCGS to from primordial follicles
2) Sex cord cells then from granulosa cells (i.e Sertoli cells like in male)
3) Mesonephric cells that migrate from the vasculature to form theca cells in families (i.e leydig cells in males)

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10
Q

Is there any endocrine activity in ovarian development unlike the male foetus

A

No

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11
Q

What is turners syndrome

A

When individuals only have one X chromosome so they cannot develop an ovary which requires 2 X chromosomes

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12
Q

What is the role of a ovary after puberty

A

Produce eggs

Produce hormones

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13
Q

What is the male equivalent of primordial germ cells

A

Primordial germ cells

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14
Q

When PGCs are at the gonadal ridges what are PCGS termed as

A

Oogonium

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15
Q

What is the male equivalently oogonium

A

Spermatogonia

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16
Q

What is the female equivalent of primary spermatocytes

A

Primary oocyte

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17
Q

What is the female equivalent of secondary spermatocytes

A

Secondary oocyte

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18
Q

What has to occur to go from primary oocyte to secondary occyte

A

Meiosis

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19
Q

Which is the female equivalent of spermatozoa

A

Mature oocyte

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20
Q

What do secondary oocyte undergo to become haploid

A

2nd meiotic division

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21
Q

What is the difference between the the timing of spermatogonesis and Oogenesis

A

Males undergo meiosis post puberty

Females enter meiosis during fetal development

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22
Q

Which gene in females controls the entry of meiosis in

A

STRA8

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23
Q

What is this gene regulated by

A

Retinoic acid

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24
Q

Why doesn’t meiosis occurs in the male embryo

A

The embryo testis expresses cytochrome p450 that is mediated by breaking retinoic acid therefore we do no get a build up of retinoic acid in males

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25
Q

What is the difference between oogenesis and spermatogenesis in terms of being continuous

A

Males: spermatogenesis is continous when it starts after puberty
Females: 1st meiotic block just before ovulation, 2nd meiotic block after ovulation, meiosis completes post fertilisation.

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26
Q

Which oocyte is at rest in the 1st meiotic block

A

Primary oocyte at prophase 1

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27
Q

Which oocyte is in the 2nd meiotic block

A

Secondary oocyte at metaphase 2

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28
Q

If the primary oocyte remains in the 1st meiotic block what are they prone to

A

Damage

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29
Q

What is the difference with the number of sperm and egg produced

A

Males: have as spermatogonia (stem cells) that self renew so they produce sperm until end of life

Females: all oogonia enter meiosis before birth and there are no ovarian stem cells. A girl is born with the number of eggs she will have for the rest of her life.

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30
Q

What is the difference in number of eggs at different stages of life

A

Female germ cells undergo proliferation and then atresia (reduction) before birth

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31
Q

What is menopause a consequence of

A

Depletion of oocyte reservoir

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32
Q

What is climacteric

A

A period of reproductive changes that precedes menopause

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33
Q

What are the symptoms women can experience before menopause

A

Oligomennorhea
Mood changes
Loss of libido
Hot flushes

34
Q

What is the definition of menopause

A

12 months without period if over 50
Or
24 months without periods if under 50

35
Q

What happens to the levels of oestrogen during menopause

A

Decrease

36
Q

What are the consequences of oestrogen withdrawal

A

Loss of anti-PTH: osteoporosis
Change in lipid ratio: coronary thrombosis
Reduction in vaginal lubrication: painful intercourse
Mood changes

37
Q

How do we treat menopausal symptoms

A

Hormone replacement therapy

38
Q

In hormonal replacement therapy what hormones do we give

A

Oestrogen

Progesterone

39
Q

Why can you not give oestrogen without progesterone

A

It will lead to endometrial hyperplasia (endometrial cancer)

40
Q

What is the difference in male and female meiotic division

A

They are asymmetrical

41
Q

What 2 products does the 2nd meiosis of the secondary oocyte in females results in

A

Mature oocyte

Polar body

42
Q

What is the polar body

A

Excess genetic material

43
Q

How many polar body is released for each 2 meiosis

A

2 polar bodies in total

44
Q

What are granulosa cells in females equivalent to in females

A

Sertoli cells

45
Q

What are theca cells equivalent to in males

A

Leydig cells

46
Q

What is the development of ovary follicles called

A

By folliculogenesis

47
Q

What does sex cord cells cluttering around PGCs form

A

Primordial follicles

48
Q

Until what stage does primordial follicles remains

A

Puberty

49
Q

What happens during puberty to the primordial follicles

A

Grow each dayt

50
Q

As primordial follicles grow what do they become

A

Primary follicle

51
Q

What happens to the granulosa cells within the primordial follicle to become primary follicle

A

Granulosa cells become cuboidal

52
Q

What happens to the outer layer of the egg during primary follicle development

A

Zona pellucida forms

53
Q

How does the primary follicle form into the secondary follicle

A

Granulosa cells proliferate

Theca cells form 2 layers outside: theca interna and theca externa

54
Q

What is the development of theca interna and theca externa dependent on

A

FSH signal

55
Q

What happens when secondary follicle forms the tertiary follicle

A

1) Granulosa cells secrete follicular fluid
2) Follicle fluid fills the antrum (space around oocyte)
3) egg becomes surrounded by granulosa cells and fluid= Corona radiata
4) outside the corona radiata we have the cumulus cells (specialised granulosa cells)

56
Q

At puberty when GNRH acts on the anterior pituitary gland what hormone is releases

A

LH

FSH

57
Q

What receptor does FSH act on

A

FSHR

58
Q

What does FSH stimulate

A

Follicle development

59
Q

What receptor does LH act on

A

LHCGR

60
Q

What does LH stimulate

A

Follicle maturation
Ovulation
Development of corpus luteum

61
Q

What are the 3 hormones produced by the ovaries

A

Oestrogen
Progesterone
Cytokine: inhibin

62
Q

What is progesterone produced by

A

Corpus luteum after ovulation

63
Q

What is the role of progesterone

A

Preparation and maintenance endometrium for pregnancy

64
Q

What is the role of estrogen

A

Development of secondary sex characteristic
Thinking of endometrium
Follicle maturation

65
Q

What hormone is the 2 cell hypothesis

A

Oestrogen

66
Q

Describe the 2 cell hypothesis

A

1) Theca cells release testosterone
2) testesterone diffuses into the follicle to become taken up by granulosa cells
3) granulosa cells express enzyme called aromatase
4) aromatase converts testerone to estorgen
5) LH acts on theca cells to increase cholesterol and produce testosterone
6) FSH acts on granulosa cells to increase aromatase enzyme

67
Q

What are the 3 phases of the menstrual cycle

A

Proliferative/follicular
Ovulation
Secretory/luteal

68
Q

Describe the process that occurs in the follicular/proliferative phase

A

1) hypothalamus secretes GNRH
2) GNRH acts on anterior pituitary gland so cause release of FSH
3) FSH rescues 15 follicles
4) in the growing follicles granulosa and theca cells develop to produce oestrogen
5) oestrogen that is produced at moderate level, suppresses FSH so you end with one dominant follicle
6) granulosa cells in the dominant follicle work with theca cells to produce more oestrogen and cause expression of LHCGR
7) high levels of oestrogen cause LH release from anterior pituitary gland
8) LH surge leads to ovulation

69
Q

Describe the process that occurs in ovulation

A

1) LH sry gene leads to completion of meiosis 1
2) so secondary oocyte enters meiosis 2 but is at arrest at metaphase until fertilisation
3) there is an increase in follicular fluid and granulosa cells
4) follicle wall weakens
5) everything ruptures due to increased pressure
12) cumulus- oocyte complex ovulates and is picked up by fimbrae.

70
Q

What happens at the luteal/secretory phase

A

1) corpus luteum (remain of follicle) undergo changes called lutenaisation
2) granulosa cells become large lutein cells and secrete progesterone and oestrogen
3) theca cells become small lutein cells and also secrete progesterone and oestrogen
16) under action of progesterone the endometrium becomes secretory to receive a fertilised egg if there is one
17) high levels of progesterone and oestrogen create a negative feedback so FSH/LH levels are low

71
Q

What hormone is produced if fertilisation has occurred and there is pregnancY

A

HCG

72
Q

Where does HCG act on

A

LHCGR on lutein cells to maintain corpus luteum

73
Q

Why is it important to maintain the corpus luteum

A

Corpus luteum produces progesterone and oestrogen

74
Q

What do high levels of progesterone and oestrogen do

A

Suppress ovulation

75
Q

What happens after 6 weeks to the corpus luteum

A

Degenerates to from corpus albicans

76
Q

Why does the corpus luteum degenate after week 6 of pregnancy

A

Placenta takes over

77
Q

If there is no pregnancy what happens to the corpus luteum

A

Degenerates into the corpus Albicans

78
Q

What happens to the progesterone and oestrogen levels if there is no pregnancy

A

Decrease

79
Q

What does a fall in progesterone and oestrogen do

A

Remove Negative feedback and cycle continous

80
Q

What does loss of progesterone cause

A

Menstruration

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