Reproductive Cycle Ch. 28-3

Female Reproductive Cycle Ovarian Cycle – events in the ovaries that occur during and after the maturation of an oocyte Menstrual Cycle – changes in the endometrium (lining) of the uterus to prepare for the arrival of a fertilized ovum that will develop until birth Female reproductive cycle includes both of these

Hormones of Cycles Gonadotropin-releasing hormone (GnRH) Estrogens Secreted by hypothalamus Stimulates release of FSH and LH Stimulate release of egg from ovaries Estrogens Secreted by ovaries Promote development of sex characteristics Progesterone Prepare and maintain endometrium for implantation Prepare mammary glands for milk secretion

Hormones of Cycles Relaxin Inhibin Relaxes the uterus by inhibiting contractions Increases flexibility of pubic symphysis Helps dilate cervix Inhibin Secreted after ovulation Inhibits secretion of FSH and LH

Tortora & Grabowski 9/e 2000 JWS Hormonal Changes Tortora & Grabowski 9/e 2000 JWS

Summary Cycle is counted from 1st day of last period Menstruation lasts 4-5 days Proliferative phase (13 days) Endometrium fills will tissue and blood Ovulation occurs around day 14 Secretory phase (10 days) If egg is fertilized, tissue stays to care for fetus If egg is not, menstrual phase begins again

Birth Control Oral contraceptives (the pill) – inhibits FSH and LH from being released, ovulation doesn’t occur, no egg for fertilization – close to 100% effective “morning-after-pill” – causes shedding of lining (induces period) to prevent implantation IUD – prevent implantation in uterus by changing lining Spermicides – kill sperm, more effective with use of condom or diaphragm

Birth Control Barrier methods – prevent sperm from getting into uterus (condoms, diaphragm); also helps protect against STD’s Periodic Abstinence – couple learns “cycle” and abstains during that time