PH1124 - Reproductive Hormones 3 Flashcards

1
Q

what is oogenesis and what does it start with? (2)

A
  • oogenesis is the formation of the female gameteovum (egg) cell from precursor cells in the ovaries
  • oogenesis actually begins in ovaries prior to birth where precursor germ cells (oogonia) are found in foetal ovary
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2
Q

when does production of egg cells span?

A
  • production of egg cells spans pre-reproductive & reproductive life
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3
Q

what happens in oogenesis? (3)

A
  • initial mitosis of the germ cells (oogonia) occurs in the foetal ovary
  • early meiosis of primary oocyte that completes after puberty (before ovulation)
  • late meiosis of secondary oocyte that completes after ovulation if there is fertilization, giving the mature ovum
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4
Q

what does the reproductive cycle consist of? (2)- ovarian cycles

A
  • ovarian cycles

- uterine cycles

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5
Q

what is the ovarian cycle? (2)

A
  • controls stages of oogenesis in the ovary

- comprises events in the ovary that precede and follow oocyte maturation and ovulation

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6
Q

what is the uterine cycle?

A
  • the preparation of the uterus to receive the ovum
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7
Q

what are the reproductive cycles regulated by?

A
  • hormonally regulated by the HPG axis and reproductive hormones
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8
Q

how does the HPG axis help the hormonal control of the female reproductive cycle?

A
  • synthesis and secretion of LH and FSH
  • LH promotes follicle development, androgen production and triggers ovulation and development of corpus luteum
  • FSH initiates follicle development and growth, conversion of androgens to oestrogens
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9
Q

what is the corpus luteum?

A
  • the corpus luteum develops from a ruptured follicle in the ovary and secretes estrogen and progesterone
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10
Q

how does the reproductive hormone oestrogen help the hormonal control of the female reproductive cycle? (2)

A
  • controls ovarian/follicular function

- feeds back onto hypothal/pit to control GnRH, FSH and LH

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11
Q

how does the reproductive hormone progesterone help the hormonal control of the female reproductive cycle? (2)

A
  • regulates preparation of uterine endometrium for potential implantation
  • feeds back onto hypothal/pit to control GnRH, FSH and LH
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12
Q

how does the reproductive hormone inhibin help the hormonal control of the female reproductive cycle? (2)

A
  • protein hormones made by ovarian granulosa cells in response to high FSH/oestrogen
  • feeds back to inhibit FSH release from pituitary
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13
Q

what are the phases of the ovarian cycle? (3)

A
  • follicular phase up to day 14; development of graafian follicle and its oocyte
  • ovulatory phase at day 14; release of secondary oocyte from follicle
  • luteal phase after day 14 to day 28; formation of corpus luteum
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14
Q

what happens in the follicular phase over the first 14 days? (3)

A
  • primary follicle growth
  • secondary follicle growth
  • graafian follicle stage
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15
Q

what happens in the primary follicle growth stage of (the follicular phase)?

A
  • involves thickening of follicular epithelium (granulosa cells) round the primary oocyte by proliferation
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16
Q

what happens in the secondary follicle stage of (the follicular phase)? (3)

A
  • theca cells round the follicles develop and secrete androgens which granulosa cells use to make oestrogen
  • granulosa also secretes nutrient fluid into cavity (antrum)
  • one follicle and its oocyte becomes dominant
17
Q

what happens in the graafian follicle stage of (the follicular phase)? (2)

A
  • early meiotic division to produce secondary oocyte completes just before ovulation at day 14
  • the mature graafian follicle has large antrum with this secondary oocyte
18
Q

what happens in the ovulatory phase at day 14? (3)

A
  • mature graafian follicle bulges from the wall of ovary
  • ovarian wall ruptures and expels the secondary oocyte into uterine tube
  • wound healing of ovarian surface epithelium after rupture
19
Q

what happens in the luteal phase after day 14 to day 28? (2)

A
  • granulosa cells of empty graafian follicle proliferate forming the corpus luteum which secretes progesterone
  • progesterone prepares uterus endometrium for implantation
20
Q

what happens in the uterine (menstrual) cycle?

A
  • cyclical changes also occur in the endometrium of the uterus over the 28 day cycle
  • occur in response to the changing levels of ovarian reproductive hormones (oestrogen and progesterone) during the ovarian cycle
  • comprised of three phases that correlate with the ovarian cycle - uterine changes ensure endometrium is most receptive to potential implantation of a fertilised ovum after ovulation
  • the ovarian cycle thus not only promotes oogenesis but also helps prepare the endometrium for pregnancy
21
Q

what are the phases of the urterine (menstrual) cycle? (3)

A
  • menstrural phase (days 1 to 5)
  • proliferative phase (days 6 to 14)
  • secretory phase (days 15 to 28)
22
Q

what happens in the menstrual phase of the uterine (menstrual) cycle?

A
  • muscular layer of endometrium is detached from uterine wall and expelled
23
Q

what happens in the proliferative phase of the uterine (menstrual) cycle? (3)

A
  • endometrium proliferates and thickens
  • synthesis of progesterone receptor (PR) in the endometrial cells
  • ovulation occurs at the end of this phase at day 14
24
Q

what happens in the secretory phase of the uterine (menstrual) cycle? (3)

A
  • progesterone (from corpus luteum) stimulates endometrial lining via PR
  • in absence of fertilisation endometrium progressively degenerates
  • cycle starts again with day 1 of the next menstrual cycle
25
Q

what is the luteal phase?

A
  • after ovulation LH promotes transformation of the ruptured graafian follicle into the corpus luteum which contains luteal cells
26
Q

what does LH stimulate the luteal cells to secrete?

A
  • substantial progesterone and some oestrogen; progesterone maintains and stimulates the thickened endometrium in its secretory phase
27
Q

what is oestrogen and progesterone secreted by?

A
  • corpus luteum negatively feedback onto the anterior pituitary inhibiting FSH and LH production in order to prevent development of any new follicles