1. The Female Menstrual Cycle
Biology 12

2. Definitions:
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

3. Parts (within the ovary):
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 released, main function = producing estrogen and progesterone

4. The menstrual cycle can be divided into 4 phases:
Flow Phase
Follicular Phase
Ovulation
Luteal Phase

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

6. 2. Follicular phase 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)

7. Inside an ovary:

8. 3. Ovulation 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

9. 4. Luteal phase 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

12. Menopause:
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

13. Birth Control Pill:
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)

14. To do: Video: Complete Menstrual Cycle Graphing
Complete Menstrual Cycle Graphing
Complete Human Development WS