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