1. Biology 12 THE FEMALE MENSTRUAL CYCLE

2.  The menstrual cycle is the term for the physiological changes that can occur in fertile women for the purposes of sexual reproduction and fertilization  The menstrual cycle is regulated by hormones.  Menstruation is the shedding of the lining of the uterus (endometrium) accompanied by bleeding.  Menstruation starts during puberty and stops permanently at menopause  Does not occur during pregnancy DEFINITIONS:

3.  Follicles: structures in the ovaries that contain the egg and secrete estrogen  Corpus luteum: mass of follicle cells that form within the ovary after the egg is release, main function = producing estrogen and progesterone PARTS (WITHIN THE OVARY):

4. 1.Flow Phase 2.Follicular Phase 3.Ovulation 4.Luteal Phase THE MENSTRUAL CYCLE CAN BE DIVIDED INTO 4 PHASES:

5.  Marks the beginning of the cycle  Characterized by the shedding of the endometrium.  Lasts about 5 days  Triggered by decreasing progesterone and estrogen levels 1.FLOW PHASE

6.  Started by an increase in FSH  The follicle develops within the ovary  Follicle cells produce estrogen which promotes the thickening of the endometrium.  Usually only one follicle matures during each cycle  Occurs approx during days 6-13 of the cycle (lasts about 10 days) 2. FOLLICULAR PHASE

7. INSIDE AN OVARY:

8.  Sharp increase in LH and small inc in FSH  Around day 14  The oocyte bursts from follicle  The remaining follicle cells become the corpus luteum 3. OVULATION

9.  Development and maturation of corpus luteum occurs  The corpus luteum begins secreting progesterone.  Progesterone  maintains the endometrium  strengthens the uterus  inhibits further ovulation  prevents uterine contractions  If pregnancy does not occur, the conc of progesterone declines which triggers uterine contractions and the shedding of the endometrium 4. LUTEAL PHASE

12.  Is the permanent stopping of the primary functions of the human ovaries  Due to a 90% decrease in estrogen  The transition from reproductive to non- reproductive is the result of a reduction in female hormonal production by the ovaries MENOPAUSE:

13.  Birth control pills contain hormones that suppress ovulation.  Without ovulation there is no egg to be fertilized and pregnancy cannot occur.  There are 2 types of birth control pills  Combined pill (contains both estrogen and progesterone)  Mini pill (contains only progesterone) BIRTH CONTROL PILL:

14.  Video:  http://www.youtube.com/watch?v=WGJsrGmWeKE http://www.youtube.com/watch?v=WGJsrGmWeKE  Complete Menstrual Cycle Graphing  Complete Human Development WS TO DO: