female reproductive system Flashcards
what are the important facts about female cycles
human ≃ 28-day cycle, but variable - mensturation
A single mature egg (oocyte) is released from paired ovaries each month
Endometrium (lining of uterus) is specially prepared for implantation of the ovum, should fertilization occur
If fertilization does NOT occur, endometrium degenerates and maturation of a new follicle resumes
Cycle repeats…….unless…………….
If fertilization DOES occur, conceptus in uterus secretes Human Chorionic Gonadotropin (hCG) which “rescues” corpus luteum (CL) and maintains Progesterone secretion
=> maintains endometrium
=> blocks Follicle Stimulating Hormone (FSH)/ Luteinising Hormone (LH) secretion and ‘new’ follicle growth
what is the function of uterus
Hosts the developing fetus
Produces vaginal and uterine secretions
Passes the anatomically male sperm through to the fallopian tubes
what does ovaries do
Produce the anatomically female egg cells.
Produce and secrete estrogen and progesterone
what is the role of estradiol
Estradiol
Before birth: released by the gonads in female fetus and leads to development of female reproductive organs
At puberty: estrogens levels rise and are responsible for sexual maturation and development of female secondary sex characteristics
Also involved in regulation of menstrual cycle and ovulation
what is the role of progesterone
Progesterone
Prepares the uterus for pregnancy
If pregnancy occurs: helps maintain the pregnancy; prepares the mammary glands for lactation
Oestrogen (E) Synthesis during
the Follicular Phase
LH stimulates the synthesis of androgens (from cholesterol) in theca cells
Some androgen diffuses to nearby granulosa cells of follicle
FSH stimulates the conversion of androgens into oestrogens in granulosa cells
(P450aromatase = CYP19)
Referred to as the “Two hormone / two cell mechanism” of oestradiol biosynthesis in the ovary
what is the ovarian cycle
Cycle has 3 phases:
Follicular phase
follicles mature, oocyte is prepared for release
Ovulation (at mid-cycle)
rupture of follicle and release of oocyte
Luteal phase
luteinization of ruptured follicle, preparation of reproductive tract for pregnancy, should fertilization occur
initated at puberty.. ends at menopause
Regulation of Hypothalamic-Pituitary-Ovary
(H-P-O) Axis
Gonadotropin-releasing hormone (GnRH) (tropic peptide hormone synthesized and released from GnRH neurons in hypothalamus) stimulates release of LH and/or FSH from the anterior pituitary
LH and FSH promote increased ovarian secretion of progesterone (P), androgen (A) and oestrogen (E)
P and E combined have a negative feedback effect on the pituitary and hypothalamus, inhibiting both LH and FSH secretion
During luteal phase:- both P and E high
=> LH and FSH low
Inhibin (peptide produced by follicle granulosa cells and corpus luteum) has selective negative feedback action on FSH secretion
Providing P is low, high level of E (as occurs at end of follicular phase) has positive feedback action on Hypothalamus & Pituitary to promote the preovulatory surge of LH
=> OVULATION
The Uterine or Endometrial Cycle
Proliferative Phase
Oestrogens (E):
increase thickness of endometrium
increase growth of endometrial glands and blood vessels
promote secretion of thin ‘sperm-friendly’ mucus
Secretory phase
Progestogen (P):
causes endometrial swelling and secretory development
increases blood supply
increases lipid and glycogen deposition
Menstruation
Caused by sudden decrease of E and P at end of luteal phase
Loss of hormonal stimulation initiates necrosis in the endometrium
Aided by uterine prostaglandins
Follicular Phase Menstrual Cycle
FSH rise at start of cycle stimulates growth of 6-12 small antral follicles
By Day 6 in cycle one follicle has been “selected”
Referred to as the “Dominant follicle”
This single follicle grows rapidly into a preovulatory (Graffian) follicle
Other secondary follicles not selected undergo atresia (degenerate)
Ovulation triggered by a surge of LH released from Anterior Pituitary
what is Ovulation (at Mid-cycle)
Ovulation occurs within 24h of pre-ovulatory LH surge
home ovulation detection kits detect this LH surge in urine!
LH surge causes swelling of follicle and thinning of wall
Oocyte (+surrounding cumulus cells) released into peritoneal cavity, where it is drawn into opening of fallopian tube (Fimbria)
Remainder of follicle (theca and granulosa cells) develops into corpus luteum (which lasts for ~14 days of “LUTEAL PHASE” of cycle”)
what is menopause
Depletion of finite ‘ovarian reserve’ by ~age 50 (UK mean age of menopause is 51)
Follicle development and ovulation ceases
Menstrual cyclicity decreases and eventually
ceases
Decreased production of ovarian hormones
(oestrogen, progesterone, androgen, inhibin)
Raised FSH and LH (due to lack of –ve feedback)
Diagnosed clinically after 12 months’ amenorrhoea
Premature ovarian failure (1% women <40)
what are symptoms of menopause
night sweats
mood swings
sleep disturbances
hot flushes
gas
Oestrogen Hormone
Replacement Therapy HRT
examples and use
Tablets (e.g.Elleste®), patches (e.g. Estradot®) or topical therapy via application of gel to the skin (e.g.Oestrogel®)- used to treat:
Hot flushes (sudden strong feelings of heat and sweating) (also termed vasomotor instability) and mood swings in peri-menopausal women
Vaginal dryness, itching, atrophy
(start with moisturisers and lubricants)
Prevention of osteoporosis in postmenopausal women (but not if this is the only symptom-use bisphosphonates instead)
what are the considerations with HRT?
Side effects include breast tenderness, headaches, vaginal bleeding
HRT increases the risk of venous thromboembolism, stroke, coronary heart disease and, after some years of use, endometrial cancer (reduced by a progestogen), breast cancer, ovarian cancer.
The minimum effective dose should be used for the shortest duration
Treatment should be reviewed at least annually
For osteoporosis alternative treatments should be considered (e.g. bisphosphonates)
For hot flushes and mood swings, antidepressants are sometimes used as an alternative (e.g. the SNRI venlafaxine) (off-label use)
