OPRFHS Science - Kara Bohne Kristen Stow - Honors Biology



Name:Date:Period:Menstrual CycleBackground: When a human female is born, her ovaries already contain all the immature eggs that will later mature and produce functional eggs during her lifetime. Eggs usually begin to mature between the ages of 12 and 14, when a release of hormones triggers puberty and a young woman reaches sexual maturity. Most commonly, eggs mature every 28 days or so. They usually mature one at a time, in alternating ovaries. This rhythmic maturation of eggs and the other chemical and physical events that accompany the process are called the menstrual cycle.As a reaction to increasing levels of hormone FSH (follicle stimulating hormone), eggs start to mature in a woman’s ovary. Each egg matures inside an egg sac, or follicle, near the surface of one of the ovaries. When the egg is fully mature, another hormone – LH (luteinizing hormone) – reaches peak level. As a reaction to these high hormone levels, the follicle bursts open and releases the egg. This process is called ovulation. Tiny microscopic hairs, called cilia, on the cells at the opening to the Fallopian tube or oviduct, sweep the egg into the tube which leads to the uterus.3146425129603500As a reaction to increasing levels of the hormone estrogen, the lining of the uterus has been prepared to receive a fertilized egg by building up its lining with nurturing tissues and blood vessels.After the egg is released from the follicle in the ovary, the remaining follicle tissue becomes a hormone secreting gland, the corpus luteum. The gland releases the hormone progesterone. High levels of progesterone help maintain the uterine in its build up, nurturing phase.If the released egg remains unfertilized, it does not important in the uterus lining. This triggers further hormonal changes. Both estrogen levels and progesterone levels drop. This causes the lining of the uterus to deteriorate. As a result both unfertilized egg and uterus lining are shed and pass out of the body. This periodic loss of tissues and fluids form the uterus is a normal function known as menstruation. Menstruation is considered the beginning of the monthly menstrual cycle.All of these changes are governed by coordinated hormones carried in the bloodstream from their releasing gland to their responding target cells. These hormones act through feedback mechanisms. The pituitary gland, at the base of the brain, secretes the two hormones that trigger the growth and development of the egg in the ovary – FSH and LH. In response, the ovary then secretes the two sex hormones that control development of the egg and uterus lining – estrogen and progesterone. When ovarian hormones reach low levels, this feedback mechanism stimulates the pituitary gland to once again secrete its hormones to stimulate the development of another egg for another cycle.Follicular Phase StudyWithin the ovaries are located many egg cells. Each egg is enclosed within a structure called a follicle. The follicle is aid to be immature. Under the influence of a hormone called FSH, the follicle matures.Prepare a line graph of the data in Table 1. Table 1: FSH Levels measured over a Menstrual CycleDay13579111315171921232527Units of FSH10121413131420109988810FSH is a hormone in the female body that causes a woman’s follicles to mature within the ovary. Using your graph, on which day of the cycle has the follicle reached maturity? Day ____What happens to the egg follicle in the ovary as FSH rises (during Days 1 – 12)?______________________________________________________________________________________________________________________________________________________If the picture below is illustrating a cell secreting FSH, then draw what the receptors would look like on the target cell in the ovary.Describe the overall trend of FSH over a menstrual cycle._________________________________________________________________________________________________________________________________________________________________________________________________________________________________Luteal Phase131318079121000Once a follicle is mature, it bursts open and the egg is released. This process is called ovulation. The egg passes into the oviduct where it may or may not become fertilized. Meanwhile, the mature follicle, once it loses its egg, forms a body within the ovary called the corpus luteum.A hormone called luteinizing hormone is responsible for ovulation. Table 2 shows data obtained from blood samples taken from a female and analyzed for the amount of LH present.What is the purpose of the corpus luteum?_________________________________________________________________________________________________________________________________________________________________________________________________________________________________Describe how an egg goes from immature to a mature-released egg.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Prepare a line graph of the data from Table 2. Table 2: LH Levels measured over a Menstrual CycleDay13579111315171921232527Units of FSH12141414141670121212121288Luteinizing hormone stimulates the follicle in the ovary to release an egg. Using your graph, on which day of the cycle will an egg be released? Day ____What gland secrets LH? _____________________________What happens to the egg in the ovary on Day 14 after LH levels reach their peak?______________________________________________________________________________________________________________________________________________________If the picture below is illustrating a cell secreting LH, then draw what the receptors would look like on the target cell in the uterus.Describe the overall trend of LH over a menstrual cycle._________________________________________________________________________________________________________________________________________________________________________________________________________________________________Changes in the UterusWhile the follicular and luteal stages are taking place in the ovaries, a series of changes is also occurring in the uterus. The uterus lining changes from being very thin to being very thick. This change in thickness occurs because the number of cells increases through rapid cell division. At one point, the uterus ceases to thicken. The buildup of cells begins to break apart. This breakdown of the uterine lining, both as tissue loss and bleeding, is called menstruation.Two hormones are responsible for the thickening of the uterus, estrogen and progesterone. The amount of these hormones in the bloodstream influences the changes just described.Prepare a line graph of the data from Table 3 on the next page. Table 3: Amount of Estrogen and Progesterone Presence Day of CycleUnits of Estrogen Present in BloodDay of CycleUnits of Progesterone Present in Blood15015350355505577575912595112251151320013101575154017100176019100191102110021150231002315025502510027502730Based on the graph, when do estrogen and progesterone reach their peaks?Estrogen ___Progesterone ___What gland secretes estrogen? __________________________What happens to the uterus lining during days 1 – 12, as estrogen is rising?______________________________________________________________________________________________________________________________________________________If the picture below is illustrating a cell secreting estrogen, then draw what the receptors would look like on the target cell in the uterus.Describe the overall trend of estrogen over a menstrual cycle._________________________________________________________________________________________________________________________________________________________________________________________________________________________________On day 14 the egg is released (ovulation). After that the corpus luteum forms in the remaining follicle and it starts releasing progesterone. On what day does the progesterone reach its peak concentration? ____While progesterone stays at a high level what happens to the lining of the uterus?______________________________________________________________________________________________________________________________________________________If the woman does not get pregnant, then the corpus luteum breaks down and the level of progesterone starts declining. Once progesterone decreases what happens to the lining of the uterus?______________________________________________________________________________________________________________________________________________________Figure 1Answer the following questions using Tables 1, 2, 3, Graphs 1, 2, 3, and Figure 1.After a follicle has released an egg it turns into a corpus luteum. This in turn releases estrogen and progesterone, which cause the uterine lining to thicken and prepare to receive a fertilized egg. On which day would the uterine lining be the thickest? Day____Look at the LH graph. How much time passes from the time the egg is released until when the uterine lining is the thickest? ____ DaysWhat might account for this? (Hint: Where does egg start and where is the uterus?)______________________________________________________________________________________________________________________________________________________If an egg is not fertilized, estrogen and progesterone levels ___________. When this occurs, the thick lining of the uterus falls off and is released. This causes menstrual flow, or the menstrual period. During which days in the cycle does menstruation occur? Days ____If an egg is fertilized, it will attach to the thick __________________ wall and estrogen and progesterone will continue to be released. What two things do these hormones prevent from happening?__________________________________________________________________________There are four stages/phases in a given menstrual cycle. Match these stages/phases with the days below. Draw a line connecting the stages/phases and their corresponding days.Follicular Phase (follicle is developing)~Day 14Ovulation (egg is released)~Day 1-5Luteal Phase (corpus luteum releases E and P)~Day 15-28Menstrual Period (excess uterine lining and egg released)~Day 6-13How might one trick the female body into thinking it was pregnant?______________________________________________________________________________________________________________________________________________________After an egg implants on the thick uterine lining, the egg releases a hormone called hCG, or human chorionic gonadotrophin (home pregnancy kits test for this hormone). What might be the purpose of this hormone?______________________________________________________________________________________________________________________________________________________Under which situations/conditions would the menstrual cycle stop?______________________________________________________________________________________________________________________________________________________Why would the menstrual cycle stop during pregnancy?______________________________________________________________________________________________________________________________________________________Is it possible to become pregnant during menstruation? Why or why not?______________________________________________________________________________________________________________________________________________________If you miss your period, does that mean that you are pregnant? Explain._________________________________________________________________________________________________________________________________________________________________________________________________________________________________In Figure 1 Events in Lining of Uterus chart, what process is occurring between Days 3 – 6?______________________________________________________________________________________________________________________________________________________Describe the changes that take place during the menstrual cycle from Day 5 – 13 to the following:Unfertilized egg in ovary ___________________________________________________________________________________________________________________________Uterus lining _____________________________________________________________________________________________________________________________________Describe what happens to the egg during the menstrual cycle on Day 14.______________________________________________________________________________________________________________________________________________________Describe the changes that take place to the an egg:From Day 15 – 28, if no fertilization occurs ________________________________________________________________________________________________________________________________________________________________________________________From Day 15 – 21, if fertilization occurs __________________________________________________________________________________________________________________________________________________________________________________________From Day 21 – 26, if fertilization does occur _______________________________________________________________________________________________________________________________________________________________________________________Explain why the female needs a thick uterus lining if fertilization does occur. __________________________________________________________________________________________________________________________________________________________________At what time during a woman’s menstrual cycle is it easiest to become pregnant?______________________________________________________________________________________________________________________________________________________No Fertilization of EggCut out individual boxes and place on the appropriate empty date on the accompanying calendar labeled “Figure 2B Day by Day Changes in the Menstrual Cycle: No Fertilization of Egg”. Note: Do not paste over the days with writing in them. Paste into the empty day next to the correct description.Fertilization of EggCut out individual boxes and place on the appropriate empty date on the accompanying calendar labeled, “Figure 3B Day by Day Changes in the Menstrual Cycle: Fertilization of Egg”. Note: Do not paste over the days with writing in them. Paste into the empty day next to the correct description. ................
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