Female reproduction physiology Flashcards
What is the female gonad?
The ovary
What is the role of the female ovary?
To produce eggs and female hormones
What does the primordial follicle develop into?
A growing follicle –> Vesicular follicle
What does a vesicular follicle develop into? What is the role of this?
The mature Grafiaan (dominant) follicle which produces the oocyte (ovulation).
After ovulation the dominant follicle develops into the Corpus luteum
After ovulation what does the mature grafiaan (dominant) follicle develop into?
The corpus luteum
What is the role of the mature corpus luteum?
Synthesis of Estrogen and Progesterone
What does the corpus luteum regress into?
The Corpus albicans
How is Oestorgen produced in the ovaries?
Step 1:
1) Conversion of cholesterol to prenenolone by LH stimulating theca cells. (This can be converted to progesterone)
2) Pregnenolone converted to (Several steps) testosterone
Step 2)
1) FSH acts on granulosa cells stimulating aromatase.
2) Aromatase converts Testosterone to 17B-Estradiol.
What stimulates the theca cells to produce testosterone?
LH
Where is Androstenedione converted to Testosterone?
The granulosa cells
Which enzyme is used to convert Androstenedione to Testosterone (Female)?
17B-hydroxysteroid dehydrogenase within the granulosa cells.
Which enzyme converts testosterone to 17B-Estradiol, where does this occur?
Aromatase within the granulosa cells
Which hormone stimulates the activation of aromatase within the granulosa cells?
FSH acts of the granulosa cells stimulating the increased activity of aromatase and hence and increase in 17B-estradiol production.
What stimulates the release of FSH and LH from the anterior pituitary?
Pulsatile Gonadotropin releasing hormone (GnRH) from the hypothalamus
Where is follicle-stimulating hormone secreted from?
FSH is released from the anterior pituitary in response to GnRH.
Where is luteinising hormone secreted from?
LH is released from the anterior pituitary in response to GnRH.
What is the action of FSH and LH on the ovaries?
1) Steroidgenesis in the ovarian follicle and corpus luteum.
2) Follicular development past the antral stage
3) Ovulation
4) Luteinization
What is the action of GnRH?
Gonadotropin releasing hormone acts on the anterior pituitary stimulating the release of LH and FSH
What is the action of FSH (female)?
1) Stimulate follicular recruitment and development
2) Steroidgenesis - Activation of granulosa cells to increase aromatase activity –> Increase 17B-estradiol production
What is the action of LH (Female)?
1) Stimulates ovulation
2) Formation of the corpus luteum
3) Steroidgenesis - Acts on the theca cells to stimulate the conversation of cholesterol to pregnenolone –> Increase in progesterone and oestrogen as a result.
What are the actions of oestrogen?
1) Negative feedback control of GnRH, FSH and LH secretion. Except for late follicular phase where is has a positive control of a LH surge.
2) Proliferation and development of ovarian granulosa cells/endrometrium
3) Maintains pregnancy
4) Support secondary sexual characteristics and reproductive organs
5) Lowers the uterine threshold to contractile stimuli during pregnancy
6) Stimulates prolactin secretion but blocks action on the breast
7) Bone maturation and turnover
When does bleeding within menstruation occur?
Starts Day 0, continues throughout early follicular phase
Negative and positive feedback loops during menstrual cycle - Follicular?
Estrogen acts on the anterior pituitary as a negative feedback
Negative and positive feedback loops during menstrual cycle -Midcycle?
Estrogen acts on the anterior pituitary as a positive feedback inducing a LH surge - Day 14
When does the LH surge occur?
Day 14
What occurs at day 14?
LH surge inducing ovulation and the development of the corpus luteum
Negative and positive feedback loops during menstrual cycle - Luteal?
Estrogen and progesterone = Negative feedback on anterior pituitary
Actions of progesterone (female)?
1) Negative feedback on the anterior pituitary
2) Maintains secretory endometrium during the luteal phase
3) Maintains pregnancy
4) Raises the uterine threshold to contractile stimuli during pregnancy
5) Participates in the development of the breasts
What happens to body temperature throughout the menstrual cycle?
1) Colder in the follicular stage
2) Hotter in the luteal phase
When is progesterone highest during the menstrual cycle?
During the luteal phase
When is 17B-Estradial highest during the menstrual cycle?
Late follicular stage, Roughly days 10-14.
When is LH highest during the menstrual cycle?
Day 14 there is a surge
When is FSH highest during the menstrual cycle?
Day 14 there is a surge, not as high as LH though
Which days of the cycle does the follicular stage occur?
Days 0-14
Which days of the cycle does ovulation occur?
Day 14
Which days of the cycle does the luteal phase occur?
Days 14-28
Which days of the cycle does menses occur?
Days 0-4
What occurs throughout the follicular stage (Days 0-14) of the menstrual cycle?
> A primordial follicle develops to the Graafian stage (Dominant follicle).
Neighbouring follicles undergo atresia
Oestorgen levels rise and cause proliferation of the uterus
FSH and LH levels are suppressed by negative feedback of oestrogen
Why does ovulation occur at day 14?
1) A burst of Estrodial production at late follicular stage has a positive feedback action on FSH and LH release.
2) Surge of LH induces ovulation
What happens to the cervical mucus after Day 14, why?
Increase in quantity and decreased viscosity of the cervical mucus allows increased penetrance of the sperm
What happens during the luteal phase (Days 14-28)?
1) The corpus luteum develops and synthesises oestrogen and progesterone
2) Increased vascularity and secretory activity of the endometrium in preparation to receive a fertilised egg.
3) Increase in progesterone leads to a rise in the basal body temperature.
4) If fertilisation does not occur the corpus luteum rapidly regresses. Hence a rapid decrease in the oestrogen and progesterone levels inducing menses.
Why is the basal body temperature higher during the luteal phase?
Due to the increase in progesterone levels.
What happens during menses (Days 0-4), why does this occur?
The endometrium is sloughed because an abrupt withdrawal of estradiol and progesterone.
How does oestrogen make a woman feel?
> Good
Better skin
Higher sexual arousal
How does progesterone make a woman feel?
> Bad
Mood swings
Reduced sexual desire
By age 35 what percentage of eggs are left in a woman?
Only 5%, it is after this stage that is can become difficult to get pregnant.
What is released during meiosis of oocytes?
Polar bodies
How many round of meiosis of the oocyte is there?
Two rounds
When there is an LH surge what occurs to the daughter cell?
1) Mitotic division
2) Primary oocyte undergoes meiotic division and release of polar body.
3) Second meiotic division and release of the polar body occurs when the secondary oocyte is completed after sperm unites.
When does oogonia division (mitosis) occur?
From the second to the seventh month of gestation to from roughly 7 million germ lines.
What happens to oogonia after the seventh month?
> Most oogonia die
Remaining enter meiotic division, called primary oocytes, they progress through prophase until the diplotene stage, at which point they are maintained until puberty.
In which meiotic stage are the primary oocytes maintained until puberty?
Diplotene
How many primary oocytes are there at birth?
2 million
How many of the 2 million primary oocytes at birth will mature and ovulate?
Roughly 400
For a primary oocyte to be capable of fertilisation what must first occur?
Meiosis to produce a secondary oocyte which is capable of fertilisation.
Then is the optimal fertility time?
Between 18 to 31 years of age
When does fertility begin to decrease?
Roughly 31 with a dramatic decrease after 37
When is there usually loss of fertility?
41 years old
When is there usually the start of irregular cycles preceding menopause?
45-51 years old
What are the components of the female reproduction jigsaw?
1) HPO (Hypothalamus-pituitary-ovarian) axis
2) Hormones
3) Menstrual cycle
4) Ovarian cycle
What are the components of the female reproduction jigsaw - hormones in female reproduction?
1) GnRH - Gonadotrophin releasing hormone
2) Gonadotrophins - FSH (Follicle stimulating hormone). and LH (Leutinising hormone)
3) Steroid hormones - Oestrogen (Estradiol, estrange, estriol), progesterone, testosterone
What are the components of the female reproduction jigsaw - Hypothalamus-pituitary-ovarian (HPO)axis?
1) Hypothalamus = GnRH
2) Anterior pituitary = FSH & LH
3) Ovaries = Ova, progesterone and oestrogen.
What is the difference between the menstrual cycle and ovarian cycle?
Although interlinked the menstrual cycle describes the changes in the endometrium whilst the ovarian cycle describes the maturation of the follicles
What is the aim of the menstrual cycle?
1) Release a mature ovum every month
2) Prepare the uterine lining for pregnancy
3) Pregnancy can result if the egg is fertilised
4) Menstruation if no pregnancy established.
What is a fertilised egg referred to as?
A zygote
What is amenorrhoea?
No periods
Causes of amenorrhoea?
1) Problems regulating hormones
2) Problems with ovarian function
3) Problems with uterus or outflow tract
