Hormones of the female reproductive system Flashcards
what are the female gonads?
the ovaries
what do the overaries produce?
haploid oocytes
what 3 hormones are produced and released by the ovaries?
- oestrogen
- progesterone
- inhibin
how many oocytes does a female have at birth?
1,000,000 +
how many oocytes does a female have once they reach puberty?
300,000
what do the developing follicles secrete?
oestrogen
what is the function of the outer cortex?
storage and maturation of the female gametes (oocytes)
what are the 2 reproductive cycles in women?
- ovarian cycle
- uterine cycle
how does the female body prepare for the first menstual cycle?
- hypothalamus releases pulses of goadotropin-releasing hormone (GnRH) in pulses
- this stimulates the anterior pituitary to release FSH and LH
- variations in FSH and LH produce the ovarian cycle
what is the term that means first mentrual cycle?
menarche
when does the typical person in the UK have their first period?
11-12 years old
what age does the typical woman reach menopause in the UK?
51 years
what are the 7 stages of follicle development?
- primordial follicle
- primary follicle
- secondary follicle
- antral follicle
- mature follicle
- corpus luteum
- corpus albicans
what are the 4 primary oocytes?
- primordial follicle
- primary follicle
- secondary follicle
- antral follicle
what is the 1 secondary oocyte?
mature follicle
which follicle first appears in the fetal period?
primordial
what are the characteristics of the primordial follicle?
single layer of flattened follicuular cells surround an oocyte
what are the characteristics of the primary follicle?
single layer of cuboidal granulose cells surround an oocyte
what are the characteristics of the secondary follicle?
many layers of granulosa cells + small antrum in layers of granulosa cells
what are the characteristics of the antral follicle?
many layers of granulosa cells surround the oocyte and a very large antrum
what are the characteristics of the mature follicle?
multiple layers of granulosa cells surround the oocyte
what are the characteristics of the corpus luteum?
yellowish, collapsed folds of granulosa cells
what are the characteristics of the corpus albicans?
whitish connective tissue scar: degenerated corpus luteum
how many primordial oocytes are there at birth?
1,000,000
how are primordial follicles changed into mature follicles?
- FSH promotes the development of a few primordial to form primary
- begin to increase in size
- supporting cells produce oestrogen becoming secondary follicles
- secondary follicles produce more oestrogen and become antral follicles
- one follicle will continue to a mature follicle
when is the mature follicle released?
ovulation
what are the 3 phases in the ovarian cycle?
- follicular phase
- ovulation
- luteal phase
how long is the follicular phase?
13 days (approx.)
day 1-day 13
where are FSH and LH released from? what is there function?
- released from anterior pituitary
- stimulate up to 20 primordial follicles into primary follicles
what hormone is released by the follicles as they develop? what is its function?
- inhibin
- helps futher FSH secretion by anterior pituitary
what happens after the primary follicles are matured?
some primary follicle mature into secondary follicles
what happens in the follicular phase?
typically only one secondary follicle in an ovary matures into a vesicular follicle
what does the influence of LH cause to the vesicular follicle?
- the volume of fluid increases within the antrum of this follicle
- the oocyte is forced toward one side of the follicle, where it is surrounded by the cumulus oophorus.
what is the innermost layer of the cumulus oophorus cells called?
corona radiata
as the secondary follicle matures into a vesicular follicle, its primary oocyte finishes what?
finishes meiosis I: so two cells form….
what is the functions of the 2 cells from meiosis I
- One of these cells receives a minimal amount of cytoplasm and forms a polar body, which is a non-functional cell that later regresses.
- The other cell receives the bulk of the cytoplasm and becomes the secondary oocyte
what happens to the secondary oocyte after it is formed?
- Continues to develop and reaches metaphase II of meiosis.
- This secondary oocyte will not complete meiosis unless it is fertilized by a mature sperm.
- If the oocyte is not fertilized, it breaks down about 24 hours later.
what day does ovulation occur?
approx. day 14
what happens at ovulation?
At Ovulation, the secondary oocyte is released from a vesicular follicle
what is needed to induce ovulation?
a peak in LH secretion
how is the secondary oocyte released from the vesicular follicle?
- As the time of ovulation approaches, the follicle cells in the vesicular follicle increase their rate of fluid secretion, forming a larger antrum and causing further swelling within the follicle.
- The edge of the follicle that continues to expand at the ovarian surface becomes thin and eventually ruptures, expelling the secondary oocyte.
when does the luteal phase occur?
approx. days 15-28
what is the most consistant phase in duration?
the luteal phase (14 days duration)
what forms the corpus luteum?
The remaining follicle cells in the ruptured vesicular follicle within the ovary become an important endocrine structure: the corpus luteum
how is the corpus luteum a temporary endocrine gland?
secretes progesterone and oestrogen that stabilize and build up the uterine lining and prepare for possible implantation of a fertilized oocyte.
what is the lifespan of the corpus luteum?
10-13 days (if the oocyte is not fertillised)
what does the corpus luteum regress into?
corpus albican
what causes menstruation?
- the corpus luteum regresses
- its levels of secreted progesterone and oestrogen drop
- causing the uterine lining to be shed in a process called menstruation.
what marks the end of the luteal phase?
menstruation
what is the primary source of gonadotropin releasing hormone (GnRH)?
hypothalmus
what are the effects from gonadotropin releasing hormone (GnRH)?
stimulates anterior pituitary to produce and secrete FSH and LH
what is the primary source of FSH?
anterior pituitary
what are the effects of FSH?
stimulates growth of ovarian follicles
what is the primary source of LH?
anterior pituitary
what are the effects of LH?
stimulates ovulation (where there is a peak in LH)
what are the 3 primary sources of oestrogen?
- ovarian follicles (before ovulation)
- corpus luteum (after ovulation)
- placenta (during pregnancy)
what are the 2 primary sources of progesterone?
- corpus luteum
- placenta (during pregnancy)
what are the effects of oestrogen?
initiates and maintains growth of the functional layer of the endometrium
what are the effects of progesterone?
primary hormone responsible for functional layer growth after ovulation; causes increases in:
- uterine blood vessel distribution
- uterine gland size
- nutrient production
what is the primary source of inhibin?
ovarian follicles
what are the effects of inibin?
inhibits FSH secretion to prevent excessive follicular development
what hormone is released from the hypothalamus?
GnRH
what 2 hormones are released from the anterior pituitary?
FSH & LH
what 3 hormones are released from the ovaries?
- oestrogen
- progesterone
- inhibin
how is GnRH released from the hypothalumus?
in pulses
- the size and frequency of pulses regulate LH & FSH secretion
what increases the frequency of GnRH pulses pre-ovulation?
oestrogen
what decreases the frequency of GnRH pulses post-ovulation?
oestrogen and progesterone together
what is an alternative name for GnRH?
Luteinising Hormone Releasing Hormone (LHRH)
when is FSH most active?
pre-ovulation phase (follicular phase)
what 2 things does FSH stimulate?
- stimulates maturation of ovarian follicle
- stimulates follicles to secrete oestrogen
why is FSH inhibited after ovulation?
to prevent futher follicles maturing
what 3 hormones are increased by oestrogen via a positive feedback system?
FSH, LH & GnRH
when does the peak of LH occur? what is it’s alternative name?
- once the oestrogen threshold is reached
- LH burst
what does the LH burst trigger?
ovulation
LH burst converts the __________ in the ovary into a ________________
LH burst converts the now empty follicle in the ovary into a corpus luteum
what happens to the hormones post-ovulation?
- Corpus luteum secretes progesterone, a little oestrogen & inhibin
- Oestrogen and progesterone together suppress FSH and LH, preventing further follicles maturing
- Inhibin also supresses the release of FSH from the anterior pituitary
what happens if the oocyte is fertilised?
it travels to the uterus and implants
what hormone does the embryo produce?
human chorionic gonadotrophin (hCG)
what is the basis of hCG?
mimics LH and acts on the corpus luteum to maintain progesterone (and oestrogen) levels for 3-4 months (morning sickness?) until the placenta takes over hCG production
why are there high progesterone and oestrogen levels during pregnancy?
inhibits the hypothalamus to prevent FSH rising and prevent further follicles maturing
what are the 3 phases of the uterine cycle?
- Menstrual phase: (d1-d5)
- Proliferative phase: (d5-d14)
- Secretory phase: (d14-d28)
what happens in the menstrual phase of the uterine cycle?
If no pregnancy occurs the thickened lining of endometrium is shed, due to the drop in progesterone levels
what happens in the proliferation phase of the uterine cycle?
- Oestrogen [from developing follicles in the ovary] stimulates proliferation of the endometrium (thickening) pre-ovulation, ready for fertilised ovum.
- Uterine lining becomes highly vascular and rich in mucus-secreting glands.
what happens in the secretory phase of the uterine cycle?
- Corpus luteum (empty follicle within the ovary) secretes progesterone to thicken the endometrium further - ready for possible pregnancy
- Uterus becomes oedematous with watery secretions
- Corpus luteum degrades after ~10 -16 days leading to drop in progesterone and subsequent endometrium degradation (starts menstrual phase again)
