The Human Menstrual Cycle Name: The female human s menstrual cycle is broken into two phases: the Follicular Phase and the Luteal Phase. These two phases are separated by an event called ovulation. (1) During the Follicular Phase, a few follicles are stimulated to grow under FSH (Follicle Stimulation Hormone) but only one achieves a full maturity as a tertiary follicle. This follicle forms a thin-walled blister on the surface of the ovary. The primary oocyte will complete its first meiotic division during the follicular phase to form the secondary oocyte and a polar body. The secondary oocyte continues to the second meiotic division but is stopped during metaphase II. It will be released in this state during the process of ovulation. (2)Ovulation occurs when a follicle bursts, releasing the secondary oocyte where it moves down the fallopian tube, brushed gently along by ciliated epithelial cells. Only if it is fertilized with meiosis complete where it fuses with the sperm forming a diploid zygote. (3) The Luteal phase occurs when hormones trigger the empty Graafian follicle to develop into a structure called the corpus luteum ( Yellow Body ). This body releases estridiol and progesterone. The high levels of these hormones cause a negative feedback which inhibits the production of FSH and LH. These hormones act as a natural contraceptive and make sure that more follicles do not rupture and stops ovulation. Estridiol triggers the formation of the endometrium (uterine lining) This can be called the proliferative phase. During this period the lining becomes much more glandular and enriched with glycogen. If fertilization does not take place, the corpus leuteum regresses by secreting hormones (estridiol and progesterone) that stop the secretion of LH, the hormone needed for the survival of the corpus leuteum. The disappearance of the corpus leuteum leads to the decline of estridiol and progesterone. This triggers the shedding of the endometrial lining, a process called menstruation. In the case of fertilization, the corpus leuteum s demise is stopped by the small embryo. The embryo secretes a hormone called Human chorionic gonadotrophin (hcg). This is the hormone all pregnancy tests check for as it can only be produced by an embryo. What to Do: 1. Graph the data on both Graph 1 and Graph 2. Graph 1 includes FSH and LH and Graph 2 includes Estrogen (Estradiol is the major form of this)
Day FSH LH Estrogen Progesterone 1 9 9 30 0.6 2 11 12 40 0.8 3 13 16 50 1.0 4 14 18 70 1.0 5 15 19 80 1.0 6 14 16 100 1.0 7 14 12 130 1.2 8 15 19 140 1.2 9 13 15 180 1.3 10 11 16 200 1.5 11 9 20 220 1.5 12 18 30 230 1.6 13 13 75 220 1.8 14 9 57 200 2.0 15 9 30 180 2.3 16 8 14 150 3.7 17 8 10 120 5.8 18 8 9 100 8.3 19 8 7 50 10.4 20 7 5 30 12.0 21 7 3 25 12.0 22 6 3 25 11.8 23 5 2 25 10.3 24 5 3 25 7.2 25 6 3 20 4.0 26 7 4 20 3.0 27 7 5 25 1.5 28 8 7 25 0.8 1. (Continued) (a) Connect points representing FSH in a Blue Line. Connect points representing LH in a Green Line. (b) Connect points representing Estrogen in a Red line. Connect points representing Progesterone in a Purple line. (c) Place a vertical dotted black line on Day 14 and label this line Ovulation (d) Place a vertical solid black line on Day 28 and label this line Menstrual Phase. 2. Answer the analysis Questions
Analysis 1. On what day does FSH reach its peak concentration? What is happening in the menstrual cycle at this point? 2. Explain what happens to the follicle during the first 14 days of the cycle. You will need your class notes for this! 3. Which hormones are at their maximum during ovulation? 4. (a) When is progesterone at its peak concentration? (b) What does progesterone do during the menstrual cycle? (c) Why would progesterone and estrogen be used in birth control pills (oral contraceptives)? 5. Looking at the four hormones we plotted, which hormone triggers change between Day 1 and Day 14 to prepare for ovulation? Explain your suggestion.
6. On each Graph label the Follicular Phase and Luteal Phase by shading the numbers of the day. 7. What is the difference between the Follicular Phase and the Luteal Phase? 8. If a woman were to become pregnant, how would these plots change? How is this connected to the Corpus Leutum?
Concentration of FSH (unit/ml blood) Biology 12 Unit 2: Reproduction 11/1/2015 Graph 1 Concentration of LH (unit / ml blood) 20 15 10 5 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Day of Cycle 80 70 60 50 40 30 20 10 0
Concentration of Estrogen (unit/ ml Blood) Biology 12 Unit 2: Reproduction 11/1/2015 Graph 2 Concentration of Progesterone (unit / ml blood) 250 200 150 100 50 0 0 5 10 15 20 25 30 Day 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0