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Menstruation. Estrus v. Menstruation Menstruation Evolution of menstruation Menstrual cycle overview Physiology of menstruation Menstrual symptoms Menstruation and the environment. I. Estrus v. Menstruation. Estrus = “frenzy”
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Menstruation • Estrus v. Menstruation • Menstruation • Evolution of menstruation • Menstrual cycle overview • Physiology of menstruation • Menstrual symptoms • Menstruation and the environment
I. Estrus v. Menstruation • Estrus = “frenzy” • Species with estrus cycles, females are generally only sexually active • Females of species with menstrual cycles
A. Phases of Estrus • Proestrus • one or several follicles of the ovary are starting to grow, • Estrus • ovarian follicles are maturing and estrogen secretions exert their maximal influence. The animal exhibits a sexually receptive behavior, a situation that may be signaled by visible physiologic changes. • Metestrus • Estrogen declines, and the corpus luteum starts to form • Diestrus
B. Hormonal control & variation in cycles: Time line specific for canines Species Estrus Cycle AVERAGE LENGTHS (days) OF ESTRUS AND ESTROUS CYCLES
The female on the left is in estrus: note the swelling around the top of the vagina and the presence of a small opening as well as the bright red color.
II. Menstruation • Myths http://news.bbc.co.uk/2/hi/south_asia/4250506.stm • http://www.mum.org/
A. Evolution of menstruation • Inflammatory response? Only humans & great apes exhibit menstrual cycles, in contrast to the estrus cycle of most mammalian species.
B. Menstrual cycle overview • Series of cyclic changes that the uterine endometrium undergoes each month in response to changing levels of hormones in the blood
C. Physiology of menstruation Remarkable events: • Dependant upon interrelationships between the brain, pituitary gland, ovaries & uterus • Preparation of egg for fertilization, preparation of uterus for pregnancy, evaluation of pregnancy status, reabsorption and excretion, begin again… • Phases:
Days 1-5 Ovarian hormones at lowest point, • Prostaglandin level is high in menstrual • By day 5,
Days 6-14, • Follicular phase
Days 15-28 • Endometrium • Rising levels of progesterone from corpus luteum act on endometrium causing changes
IF fertilization occurs – • Shortly after implantation,
No fertilization – • Days 24-28, Premenstrual phase • Degeneration of endometrium
E. Menstruation and the environment • Amenorrhea – • Oligomenorrhea – • Effect of exercise • 28% competitive females experience athletic amenorrhea or oligomenorrhea • Diet • Stress • Menstrual synchrony –