Sex Hormones - Female Reproductive Function

?
  • Created by: LBCW0502
  • Created on: 15-10-19 10:53
State features of ovarian function (1)
Unlike males, females has a limited supply of gametes. Early stages of gametogenesis occur during development before birth. After puberty, adult female reproductive function is controlled by a hormonal cycle
1 of 53
State features of ovarian function (2)
And interactions between the ovary and the hypothalamus/pituitary
2 of 53
Describe features of the HPG axis (1)
Female reproductive function controlled by HPG axis. Hypothalamus and pituitary is the same in males and females - GnRH neurones, LH, FSH. Different function of LH and FSH (release of oestrogen/progesterone acts on ovaries, release oocyte)
3 of 53
Describe features of the HPG axis (2)
Negative feedback of oestrogen and progesterone on hypothalamus and pituitary
4 of 53
What are the effects of LH and FSH on female reproductive function?
LH controls reproductive cycle and ovulation, stimulates oestrogen. FSH stimulates growth and maturation of ovarian follicles
5 of 53
Describe the anatomy of female genitalia
Ovaries within abdomen, on either side of the uterus, fallopian tubes. Stoma tissue/blood supply, general cell types. Follicles - structure comprised of oocyte/egg cell (can be inactive/dormant) surrounded by follicular cells. Ovarian follicles
6 of 53
Which steroid hormones are involved in the female reproductive cycle?
Oestrogens (primary female reproductive hormones, in non-pregnant women naturally occurs as oestradiol, mainly synthesised from androgens/released by ovaries). Progesterone (derived from testosterone, involved in menstrual cycle/pregnancy)
7 of 53
What are the ratios of steroid hormones in males and females?
Both males and females have testosterone, oestrogen and progesterone. Males have more testosterone whereas females have more oestrogen and progesterone
8 of 53
Describe the process of oogenesis (1)
Migratory germ cells divide by mitosis to produce oogonia (starts week 4-8 of foetal development). Oogonia (diploid, 46 chromosomes) divide by asymmetric mitosis to produce one oogonia and one primary oocyte
9 of 53
Describe the process of oogenesis (2)
(starts week 10-20 of foetal development until birth). Oogonia (female equivalent of spermatocyte). Primary oocytes (diploid, 46 chromosomes) start meiosis, stop at prophase I, become dormant, halted
10 of 53
Describe features of primary oocytes (1)
Before birth (7 million eggs). At birth (2 million eggs). Puberty (0.4 million). Menopause (<1000 eggs). After birth no further primary oocytes can be generated. Limited number of oocytes (selective, no mutations/defects)
11 of 53
Describe features of primary oocytes (2)
Some oocyte stem cells may survive in adults (further oocytes might regenerated in adults) but the number of oocytes and oocyte stem cells is still low
12 of 53
Describe the development of an ovarian follicle - initial recruitment (1)
Primordial follicle (40 microns), immature dormant oocytes, surrounded by flat granulosa cells, can remain dormant for up to 50 years until initial recruitment
13 of 53
Describe the development of an ovarian follicle - initial recruitment (2)
Primary follicle (100 microns), oocyte genome activates, gene transcription, signalling between oocyte and follicle. Granulosa cells change form flat to cuboid structure. Oocyte and follicle grow in size. Zona pellucide form around oocyte
14 of 53
Describe the development of an ovarian follicle - initial recruitment (3)
Follicles develop FSH receptors (but not required yet). Secondary (200 microns)/antral follicle (4000 microns) - theca cells recruited by oocyte to form basal lamina around follicle. Basal lamina differentiates into two layers (theca externa/interca)
15 of 53
Describe the development of an ovarian follicle - initial recruitment (4)
Provide blood supply to follicle. Antrum (fluid filled cavity next to oocyte) forms. 300 days have passed since initial recruitment. Initial recruitment doesn't rely on hypothalamus/pituitary, no external factors/signals involved
16 of 53
Describe the development of an ovarian follicle - cyclic recruitment (1)
Requires external factors/signals involved, antral follicles enter cycle (start to be affected by HPG axis). Cannot grow further without external factors
17 of 53
Describe the development of an ovarian follicle - the ovarian cycle (1)
3 phases. Follicular phase (days 1-10), hormonal signals, 10-20 follicles grow (stimulated by LH and FSH), one oocyte selected, remainder become atretic. Ovulatory phase (days 11-14), oocyte undergoes cell division, follicle wall thins/ruptures
18 of 53
Describe the development of an ovarian follicle - the ovarian cycle (2)
Oocyte enters abdominal cavity near fimbrae of fallopian. Luteal phase (days 14-28), progesterone levels increase, egg travels through fallopian tube towards uterus
19 of 53
Describe the changes in the hormone levels during the follicular phase (days 1-10) - 1
Antral follicles become dependent on FSH to continue growing and enter oestrus cycle. Levels of FSH are high from the end of the previous cycle. Low levels of oestrogen and progesterone
20 of 53
Describe the changes in the hormone levels during the follicular phase (days 1-10) - 2
FSH stimulates growth of follicle (~20 mm) to form mature follicle. Causes release of inhibin from granulosa cell (negative feedback effect on FSH). Follicles compete for limited FSH. Competition causes weaker follicles to be destroyed
21 of 53
Describe the changes in the hormone levels during the follicular phase (days 1-10) - 3
(atresis, reduction to single follicle/single oocyte). Continues until one dominant follicle remains
22 of 53
Describe the changes in the hormone levels during the follicular phase (days 1-10) - 4)
LH stimulates theca cells to produce androgens. Granulosa cells convert androgens to oestradiol. As follicles grow, oestradiol levels increase
23 of 53
Describe the changes in the hormone levels during the ovulatory phase (days 11-14) - 1
Normally oestradiol has a negative feedback effect on LH release. At high concentrations, oestradiol has a positive feedback effect on LH/FSH/GnRH (causes LH surge). LH surge triggers ovulation - release of oocyte from follicle into fallopian tube
24 of 53
Describe the changes in the hormone levels during the ovulatory phase (days 11-14) - 2
Just before ovulation, oocyte complete meiosis I. Forms one secondary oocyte (23 chromosomes), has all cytoplasm/is released. Remaining DNA forms polar body (degenerates). Secondary oocyte immediately starts meiosis II but stops at metaphase II
25 of 53
Describe the changes in the hormone levels during the luteal phase (days 15-28) - 1
With oocyte released the follicle collapses and becomes corpus luteum. Theca cells become small luteal cells (androgens and progesterone). Granulosa cells become large luteal cells (oestrogen, progesterone)
26 of 53
Describe the changes in the hormone levels during the luteal phase (days 15-28) - 2
Corpus luteum releases oestradiol and progesterone. After 14 days corpus luteum degenerates. Progesterone and oestradiol levels fall. Falling oestradiol and progesterone levels remove negative feedback on FSH which increases
27 of 53
What happens if there is no fertilisation?
After 14 days, corpus luteum degenerates, progesterone/oestradiol levels fall (removal of negative feedback on LH and FSH, leads to increased LH and FSH, high for start of cycle again)
28 of 53
Summarise the ovarian cycle and the HPG axis (1)
Follicular phase (high FSH, proliferation of granulosa cells, increased oestradiol/follicles grow, negative feedback causes FSH to fall). Ovulatory phase (high oestradiol causes positive feedback on LH/surge)
29 of 53
Summarise the ovarian cycle and the HPG axis (2)
Luteal phase (follicle collapses, oestradiol levels fall, negative feedback on LH/FSH, follicle becomes corpus luteum, release oestradiol/progesterone, LH/FSH suppressed)
30 of 53
Summarise the ovarian cycle and the HPG axis (3)
End of luteal phase (corpus luteum degenerates, oestradiol/progesterone levels fall, LH/FSH rise, cycle starts again)
31 of 53
What is the menstrual cycle?
Changes in the uterus across the ovarian cycle. Series of changes in endometrium in response to changes in hormone levels
32 of 53
What are the phases of the menstrual cycle?
Proliferative phase, late proliferative phase, secretory phase, menstrual phase
33 of 53
Describe features of the proliferative phase (day 5-13)
Starts halfway through follicular phase/end of ovulatory phase. Endometrium (uterus lining) beings to proliferate/thicken, tubular glands/arteries form. Stimulation of progesterone receptors synthesis in endometrial cells
34 of 53
Describe features of the late proliferative phase (day 13-14)
Glands are long and tortuous due to active growth. Stroma is gradually becoming oedematous
35 of 53
Describe features of the secretory phase (15-22)
Enlargement of tubular glands which being secretory mucus and glycogen in preparation for implantation of fertilised ovum
36 of 53
Describe features of the late secretory phase (23-28)
If fertilisation doesn't occur, corpus luteum degenerates, progesterone levels fall, endometrium degenerates. Uterine glands are wide. Arteries begin contracting and capillary beds begin leaking blood into endometrium and uterus
37 of 53
Describe features of the menstrual phase (1-5)
Uterine lining sloughs off and is removed from the body. Once uterine lining is removed, endometrium starts to proliferate again
38 of 53
What happens if there is fertilisation? (1)
Acrosome reaction (sperm-oocyte contact, ZP3 proteins, enzymes to break down egg coating). Causes secondary oocyte to complete meiosis II. Another polar body formed/degenerates. Sperm cell chromosomes fuse with remaining oocyte chromosomes
39 of 53
What happens if there is fertilisation? (2)
Formation of a dipoloid zygote (46 chromosomes)
40 of 53
What happens if there is fertilisation? (3)
Zygote travels down fallopian tube towards uterus and divides (8-16 cells when reaching uterus). Zygote forms a blastocyst after 5 days (inner cell mass will become embryo, trophoblast surrounding inner mass will become placenta, blastocoele/fluid)
41 of 53
Describe features of implantation
Trophoblast layer attaches to surface of endometrium. Blastocyst invades endometrium. Trophoblast cells release human chrionic gonadotropin which maintains the corpus luteum during early pregnancy
42 of 53
What is the function of trophoblast cells?
Develops into the placenta - responsible for supporting growing foetus as releases a wide range of hormones into maternal blood
43 of 53
Give two examples of disturbances in ovarian function at the genetic level (1)
Triple X syndrome (female has *** chromosomes, 47 instead of 46, effects vary, may not have symptoms, can result in under-developed ovaries/reduced fertility/CV issues, not as serious, affects 1:1000 females)
44 of 53
Give two examples of disturbances in ovarian function at the genetic level (2)
Turner syndrome (has X chromosome, 45 instead of 46, majority of embryos abort or are stillborn, results in health issues, non-functional ovaries, lack of reproductive function)
45 of 53
Give an example of disturbances in ovarian function at the hypothalamic level
Kallman syndrome (GnRH neurons failing to migrate)
46 of 53
Give an example of disturbances in ovarian function at the pituitary level
Hyperprolactinaemia - suppresses reproductive function
47 of 53
Give an example of disturbances in ovarian function at the ovary level (1)
Polycystic ovary syndrome - unclear cause (genetic). Some follicles at early antral stage halt development and release excess androgens. Effects vary, slightly irregular cycles to infertility, hirsutism, susceptible to other diseases (diabetes)
48 of 53
Give an example of disturbances in ovarian function at the ovary level (2)
Most common female endocrine disorder, affects 5-10% of females
49 of 53
Give an example of disturbances in ovarian function at the tissue level (1)
Congenital adrenal hyperplasia (21-hydroxylase deficiency) - mutation leading to inactive of enzyme 21-hydroxylase (responsible for cortisol synthesis). Adrenal gland cannot produce cortisol and instead produces an excess of androgens
50 of 53
Give an example of disturbances in ovarian function at the tissue level (2)
Excess androgens in females cause male physical development/external male genitalia or ambiguous genitalia (inappropriate levels of testosterone but individuals can have normal ovary/uterus due to not depending on testosterone)
51 of 53
Summarise features of female reproductive function (1)
Development of ovarian follicles is an ongoing process from embryo to menopause. Control of ovarian and menstrual cycle is mainly via interaction between ovary and pituitary
52 of 53
Summarise features of female reproductive function (2)
Disturbance of female reproductive function can occur at genetic, hypothalamic, pituitary or organ level
53 of 53

Other cards in this set

Card 2

Front

State features of ovarian function (2)

Back

And interactions between the ovary and the hypothalamus/pituitary

Card 3

Front

Describe features of the HPG axis (1)

Back

Preview of the front of card 3

Card 4

Front

Describe features of the HPG axis (2)

Back

Preview of the front of card 4

Card 5

Front

What are the effects of LH and FSH on female reproductive function?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Pharmacy resources:

See all Pharmacy resources »See all Sex Hormones - Female Reproductive Function resources »