The reproductive System 3 Flashcards
Regulation of Reproductive Hormone Secretion: Male reproductive System (6 steps)
- GnRH stimulates secretion of LH
and FSH from anterior pituitary - LH stimulates testosterone
secretion from Leydig Cells - FSH stimulates Sertoli cells to
increase spermatogenesis - Testosterone
- Stimulates Sertoli cells
- Development of reproductive
organs - Testosterone: negative effect on
Hypothalamus and Pituitay - Sertoli cells secrete inhibin –
negative feedback
What cycles are included in the female reproductive cycle?
- Ovarian cycle:
- series of ovarian events that precede and follow oocyte maturation
- controls oogenesis
- Uterine cycle
- Preparation of uterus to receive ovum
- Mediated by reproductive hormones
What are the stages of the female cycle?
mensus -> follicular phase -> ovulation -> luteal phase
brief overview the ovarian cycle
- During each ovarian cycle, up to 20 primordial follicles are
activated to begin the maturation process - usually only one reaches full maturity, the remainder regress
- The ovarian cycle can be divided into 3 phases:.
- Follicular phase
- Development of Graafian follicle.
- Ovulatory phase
- Release of mature follicle
- Luteal phase
- Formation of corpus luteum
Details what happens during the follicular phase?
- secondary follicles mature
- Granulosa cells secrete oestrogens
- Oestrogen: causes the epithelial cells of
the endometrium to divide rapidly. - endometrium thickens
Details what happens during the luteal phase?
- the corpus luteum begins to secrete
progesterone and smaller amounts of oestrogen. - Progesterone: causes the cells of the endometrium to become larger and to secrete a small amount of fluid.
- Fullest development of endometrium
- If no fertilisation – corpus luteum
degenerates – progesterone drops
What are the ovarian and endometrial cycle controlled by?
- Controlled by HPG axis
- FHS and LH (from anterior pituitary)
Overall feedback for oestrogen?
- Postive feedback before ovulation,
- resulting in increased LH and FSH secretion;
- Negative feedback (with progesterone) on the hypothalamus and anterior
pituitary after ovulation, resulting in decreased LH and FSH secretion
overall feedback for progesterone?
- Negative feedback (with oestrogen) on the hypothalamus and anterior
pituitary after ovulation, resulting in decreased LH and FSH secretion
follicular phase again
- Oestrogen (developing follicles)
stimulates GnRH secretion from
hypothalamus - GnRH triggers FSH and LH
- FSH stimulates oestrogen
secretion at an increasing rate
from the developing follicles. - This positive-feedback loop
produces a series of larger and
larger surges of FSH and LH
secretion
decsribe hormone levels + structure stuff for ovulation?
- Ovulation occurs in response to
the large increases in LH levels - about day 14 of the menstrual
cycle - This large increase in LH is also
responsible for the
development of the corpus
luteum
describe hormone changes in luteal phase + others
- Corpus luteum begins to
secrete progesterone and
oestrogen - Progesterone : cells of the
endometrium to become larger - Negative Feedback: Together,
progesterone and oestrogen act
on the hypothalamus and
anterior pituitary gland to
inhibit GnRH, LH, and FSH
secretion. - LH and FSH levels decline
- No stimulation of follicles
- Corpus luteum degenerates -
Lower progesterone
Describe hormone changes during mensus + structure stuff
- Oestrogen and progesterone
secretion is low - In response to declining
progesterone levels, the
endometrial lining of the uterus
sloughs off, resulting in menses - The rate of LH remains low, and
- the rate of FSH secretion
increases as progesterone levels
decline (negative feedback
released) - Stimulates development of
follicles - Start to release oestrogen
fertilisation?
- The egg lives for 12-24 hrs
- Takes 5 days to reach
Uterus - Fertilisation must occur in
uterine tube - Endometrial development
continues - Progesterone production
- hCG from pituitary and later placenta maintains corpus luteum
- Oestrogen and progesterone levels maintained
- Endometrium doesn’t break down
- Subsequently Placenta takes over progesterone and oestrogen
production
contraception..
Chemical Methods
* Synthetic oestrogen and progesterone in oral contraceptives
* among the most effective contraceptives - 99.9% effectiveness.
* Synthetic steroids can have more than one action
* Generally they reduce LH and FSH release from the anterior pituitary.
* Oestrogen and progesterone are present in high enough concentrations to
have a negative-feedback effect on the pituitary
* prevents the large increase in LH and FSH secretion that triggers ovulation
* Mini-pill
* contains only synthetic progesterone
* reduces and thickens the mucus of the cervix
* Prevents sperm cells from reaching the oocyte
