Integrated Scince M3 Menstrual cycle

REVIEW & QUIZREVIEW & QUIZOBJECTIVESOBJECTIVESINTRODUCTIONINTRODUCTION The Menstrual CycleThe Menstrual Cycle OvulationOvulation

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Integrated Science, Module 3 Unit 7 Lesson 8

I hope I don’t get any backaches and

nausea this month!My belly is so

bloated and I’m so tired.

Females are saying ...

Great! My period came. I’m so relieved Tom. I’m

NOT pregnant! I just wasn’t ready for a second child right now.


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A female is born with all the eggs she will ever produce already in her ovaries, but they are in an immature stage.

These eggs do not start to mature until she enters puberty and reaches menarche, or the start of her monthly menstrual cycles.

The various processes occurring during each menstrual cycle prepare the female’s body to mature an egg each month and also prepare her womb for a possible pregnancy.

If no fertilization and pregnancy occurs, her body stops the processes, gets rid of the prepared cell and uterine tissues and starts the processes over again.

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On completing this slide presentation, you should be able to: describe the stages of the menstrual cyclestate the role/s of the hormones oestrogens, luteininizing hormone, follicle stimulating hormone and progesterone in the menstrual cycle.calculate the stages in the menstrual cycle on a calendar.distinguish between menstruation, ovulation and fertilization.

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Normal, healthy females in this class should be ‘having a period’ each month. What is a ‘period’? Why does it happen?

A period is the shedding of the lining of the endometrium of the uterus.

It happens because fertilization and subsequent pregnancy did not occur after the body had prepared for them.

All of these events are part of the menstrual cycle.

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A menstrual cycle normally spans between 21 to 28 days. For some females, it may last 31 days and can even go to 35 days in total.

The first day of a female’s period marks the first day (Day 1) of menstruation.

The events occurring during the cycle are all controlled by hormones, so, let’s look at the hormones involved and what they do.

The hormones are: FSH, LH, progesterone, oestrogens. GnRH is also involved.

Do your recall the full name for FSH and LH?

Check the diagram on the next slide!5


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Note that a feedback mechanism is involved to trigger the secretion of the various hormones.

Source of image - http://www.britannica.com/EBchecked/topic/436140/ovulation6


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http://www.chancesofconceiving.com/not_conceiving/hormones-of-the-female-reproductive-system7

Copyright © 2011 CHANCES OF CONCEIVING


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Starting from day 1 of the cycle, the pituitary gland secretes FSH.

This causes a Graafian follicle to develop. As the follicle develops in the ovary, the

follicle secretes oestrogen. Oestrogen causes the endometrium, on the

inner wall of the uterus, to grow more tissues and gradually become filled with blood and fluid.

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At about day 14 another pituitary hormone, LH is secreted.

LH causes the Graafian follicle to rupture releasing the egg from the follicle in the ovary. This is ovulation.

The egg is caught by the finger-like fimbriae of an oviduct and starts to travel down the oviduct/Fallopian tube.

LH also causes the remains of the follicle to be converted to the corpus luteum or yellow body.

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1. Click and look at the diagram of an ovary in which the egg is developing up to and after ovulation at http://www.biog1105-1106.org/demos/105/unit8/ovaryplacenta.html

2. On the next slide, follow the increase and decrease of the various hormones. Note the increase in the blood concentration of LH which triggers ovulation.

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The corpus luteum secretes the hormone progesterone/progestins. It maintains the thickness of the lining of the uterus.Progesterone is called ‘pregnancy hormone’. Why? Well, that is because progesterone: 1.causes the breasts to enlarge and become tender. 2.causes water retention which is responsible for the bloating associated with periods. 3.might cause the female to experience various changes such as: cravings for specific foods, tiredness, headaches, sensitivity and becoming easily emotional with sudden mood swings.

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Try the short Quiz at http://wps.prenhall.com/esm_krogh_biology_3/17/4448/1138823.cw/index.html

Click the button Submit Answers for Submit Answers for Grading Grading to see if you were correct.

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After the menarche, each month throughout a female’s adult life, normally one egg reaches maturity, and is capable of being fertilized.

When the female reaches mid-life, she enters a phase called menopause, in which the production of certain hormones gradually slows down then ceases, and her menstrual cycle becomes irregular then finally ceases.

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Day of Cycle What happens in the reproductive system

1 – 5Menstrual bleeding occurs. Several egg follicles each containing an egg each begin to ripen under control of FSH.

6 – 14Uterus wall begins to thicken, preparing for a possible pregnancy. Oestrogen causes the cervical mucus to become more fluid, stretchy and less acidic. Eggs maturing.

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Ovulation of a mature egg occurs, triggered by increased LH. (Fertilization is possible if sperm are ejaculated into the vagina and travel up into the Fallopian tubes.)

15 – 28

Progesterone continues to prepare the uterine wall by developing extra blood vessels, in preparation for a possible pregnancy. If fertilization occurs, the zygote starts to divide by mitosis while it travels down into the uterus. The ball of cells called a blastula borrows into the uterine wall – i.e. implantation occurs. If no ferilization, the menses flow.

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1. Watch the video on Ovulation at

http://www.news-medical.net/health/Ovulation-What-is-Ovulation.aspx

2. List the possible occurrences after ovulation.

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1. The uterus wall becomes thickened in preparation for possible implantation of an embryo and a possible pregnancy to result.

2. The egg can live for just about 24 hours after ovulations, if sexual intercourse occurs within the female’s fertile period fertilization/fusion of gametes can occur resulting in a zygote.

3. That zygote would immediately start to divide by mitosis to form a ball of cells while continuing down the Fallopian tube.

4. The ball of cells would implant/embed itself into the thickened uterine wall and continue its development into an embryo.

5. If no fertilization occurs, the egg dies.

6. The progesterone level then falls and the uterus wall breaks down and passes out of the vagina as a period with small clumps of the lining and bloody fluid.


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Reflect on what has been discussed so far in this lesson, then,

discuss the stages of the menstrual cycle

with a partner.

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Gloria told her friend Francine that she has a 28 day cycle and that last month she had two menstrual periods in the same month.

Francine said “That’s impossible!”

Use the calendar below to explain to Francine how Gloria had two periods in the same month. Type your answer in the box below.

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Day of Cycle What happens during the 31 days month

2nd – 6th Menstrual bleeding occurs.

7th – 15th Uterus wall begins to thicken, preparing for a possible pregnancy. Oestrogen causes the cervical mucus to become more fluid, stretchy and less acidic. Eggs maturing.

15th Ovulation of a mature egg occurs. No sexual intercourse occurred during this fertile period.

16th – 29th

30th – 31st to 5th of next month

Progesterone continues to prepare the uterine wall by developing extra blood vessels, in preparation for a possible pregnancy. But NO FERTILIZARTION.

Menstrual bleeding starts again


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Write the answers to the questions in the worksheet at the site below:

http://ubykotex.co.nz/pdfs/worksheet3_menstrual-cycle.pdf

Make sure you write your answers BEFORE you check for accuracy!

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The credits for photos used in this The credits for photos used in this presentation are below each photo.presentation are below each photo.

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Education

Integrated Scince M3 Menstrual cycle