Transcript of CHEMICAL REGULATION OF THE REPRODUCTIVE SYSTEM ANATOMY & PHYSIOLOGY 13-14.
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- CHEMICAL REGULATION OF THE REPRODUCTIVE SYSTEM ANATOMY &
PHYSIOLOGY 13-14
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- TABOO Derived from word tapua New Guinea natives believe that
menstrual blood causes madness and kills males
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- Menstruation By The Numbers Females have 7,000 ovum prior to
birth but only release 450-500 ovum The average woman will spend
3,500 days menstruating (~9.5 years) The modern, urban woman will
have 450-500 menstrual cycles. Agrarian women have only 1/3 rd as
many cycles Women are menstruating earlier and more often. In
prehistoric times, women had less than 50 menstrual cycles Only
three mammals stop having menstrual cycles:
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- Menstrual Cycle Key Events Loss of endometrium in uterus
Release of mature oocyte by ovary Passage of ovum to Fallopian
tubes Thickening of new uterine lining Cycles range from 15-31 days
with the average being 28 Controlled by ovary, midbrain and
uterus
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- Menstrual Cycle or Cycles? Menstrual cycle is actually two
cyclical series of events depending upon location Ovarian Cycle
Uterine Cycle
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- Menstruation First phase of uterine cycle (Day 1) Eumenorrhea =
normal loss of endometrium 2-5 days 10-80mL Molimina = normal
menstrual symptoms Cramping Mastalgia (breast pain) headaches
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- Follicular Phase & Proliferative Phase Follicular Phase
(ovarian cycle) Ovarian follicles mature into Graafian follicles
(completion of folliculogenesis) Controlled by Follicle Stimulating
Hormone (FSH), secreted by Anterior Pituitary Gland Proliferative
Phase (uterine cycle) New endometrium (uterine lining) and cervical
mucus develops Controlled by estradiol and estrogen secreted by the
ovarian follicles Does not start until 3-7 days after onset of
menses
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- Ovulation (~Day 14) Key Events: Graafian follicle is released
by right or left ovary (random) Follicle is swept by the fimbriae
into the fallopian tube where it may become fertilized Chemistry of
Ovulation: Surge in estradiol/estrogen from ovarian follicle Surge
triggers release of Gonaotropin-Releasing Hormone (GnRH) from
Hypothalamus GnRH in turn stimulates the production of Luteinizing
Hormone (LH) by Anterior Pituitary LH causes release of Graafian
follicle/ovum
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- Luteal Phase & Secretory Phase Luteal Phase (Ovarian Cycle)
Final phase of ovarian cycle (Day 15-28) FSH and LH (anterior
pituitary) cause remnants of released follicle to become the Corpus
Luteum Corpus Luteum released progesterone, which maintains the
endometrium. If ovum is not fertilized, progesterone drops and
menses is triggered Secretory Phase (Uterine Cycle) Progesterone
makes endometrium more receptive to fertilized ovum Reduced
contractions of uterine visceral muscle Raised body
temperature
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- Hormonal Contraception & Menstrual Cycle Progesterone based
contraception utilizes a negative feedback loop Excess progesterone
inhibits GnRH production in hypothalamus Inhibited GnRH in turn
inhibits LH and FSH production by the anterior pituitary Inhibition
of LH and FSH prevents follicular development/release The Pill
utilizes progesterone and estrogen to suppress follicular
release
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- Lactational Amenorrhea Suckling of infant causes production of
prolactin Prolactin increases progesterone production, inhibiting
release of follicles via Luteinizing Hormone Active for 2-42 months
post-partum
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- Menstruation and Age Menarche = onset of menstruation (U.S.
avg. 12.5 yrs) Perimenopause = period of time surrounding menopause
noted by infrequent cycles Menopause = cessation (U.S. avg. 52
yrs)
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- Menstrual Synchrony? Hypothesized process in which women who
begin living together in close proximity experience their menstrual
cycle onsets becoming closer together in time than previously Not
supported
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- Pseudocyesis False pregnancy Complex endocrine/psychological
disorder caused by accidental release of androgens and regulatory
hormones Causes distention of abdomen due to gas and amenorrhea
Also possible in men (Couvade Syndrome)
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- Spermatogenesis 200-300 million spermatozoa produced/day
Production and maturation of spermatozoa = 74 days Transport via
epididymis & Vas deferens = 16 days
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- Hormonal Control of Spermatogenesis Follicular Stimulating
Hormone (FSH) = released from anterior pituitary. Stimulates
maturation of spermatozoa Gonadotropic Releasing Hormone (GnRH) =
hypothalamic hormone stimulates production of Luteinizing Hormone
(LH) Luteinizing Hormone (LH) controls production of Testosterone
Testosterone Produced by interstitial Leydig Cells Must be 20-50x
higher in seminiferous tubules than in bloodstream
Estradiol/Inhibin = produced by Sertoli Cells. Turns off
spermatogenesis Androgen Binding Protein (ABP) = produced by
Sertoli cells. Causes testosterone to bind to seminiferous
tubules
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