CHEMICAL REGULATION OF THE REPRODUCTIVE SYSTEM ANATOMY & PHYSIOLOGY 13-14

TABOO Derived from word “tapua” New Guinea natives believe that menstrual blood causes madness and kills males

Menstruation By The Numbers Females have 7,000 ovum prior to birth but only release ovum The average woman will spend 3,500 days menstruating (~9.5 years) The modern, urban woman will have 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:

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 days with the average being 28 Controlled by ovary, midbrain and uterus

Menstrual Cycle or Cycles? Menstrual cycle is actually two cyclical series of events depending upon location Ovarian Cycle Uterine Cycle

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

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

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

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

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

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

Menstruation and Age Menarche = onset of menstruation (U.S. avg yrs) Perimenopause = period of time surrounding menopause noted by infrequent cycles Menopause = cessation (U.S. avg. 52 yrs)

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

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)

Spermatogenesis million spermatozoa produced/day Production and maturation of spermatozoa = 74 days Transport via epididymis & Vas deferens = 16 days

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