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Menstrual cycle

Lecture 2

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Objectives

• To list the phases of the menstrual cycle• To describe the hormonal changes during

each phase• To describe the hormonal changes behind

ovulation• To point the source and control of the

hormones involved in the menstrual cycle

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What is a menstrual cycle?

• The menstrual cycle is the series of changes a woman's body goes through to prepare for a pregnancy.

• About once a month, the uterus grows a new lining (endometrium) to get ready for a fertilized egg.

• When there is no fertilized egg to start a pregnancy, the uterus sheds its lining.

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• This is the monthly menstrual bleeding (also called menstrual period) that women have from their early teen years until menopause, around age 50.

• The menstrual cycle is from Day 1 of bleeding to Day 1 of the next time of bleeding. Although the average cycle is 28 days, it is normal to have a cycle that is shorter or longer.

What is a menstrual cycle?

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NORMAL MENSTRUAL CYCLE

What is the mean duration of the MC? Mean 28 days (only 15% of )♀ Range 21-36What is the average duration of menses? 3-7daysWhat is the normal estimated blood loss? Approximately 20 – 80 mlWhen does ovulation occur? Usually day 14 10 -- 12 hrs after the onset of mid-cycle LH surge.How many have women menstrual cycle with life time? 300—400 How many oocyte at birth female has? 2 million

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What controls the menstrual cycle?

• Hypothalamus and pituitary gland send hormone signals back and forth with your ovaries. These signals get the ovaries and uterus ready for a pregnancy.

• The hormones estrogen and progesterone play the biggest roles in how the uterus changes during each cycle.

• Estrogen builds up the lining of the uterus. • Progesterone increases after an ovary releases an

egg (ovulation)

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Symptoms of painful periods

1. Pains in the abdomen 2. Pain in the vagina 3. Feeling nauseous and generally unwell 4. Diarrhoea 5. Sweating 6. Fatigue

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Related Terms

• Oligomenorrhoea : Irregular, infrequent periods• Menarche: is the age of the first menstrual cycle and

culminates at the age of Puberty.• Dysmenorrhea - painful menstruation

– Possible cause - prostaglandins• Amenorrhea - absence of menstruation

– Primary amenorrhea - when girl has not.• Mittelschmerz - middle pain; cramping in lower abdomen that occurs during ovulation.• Menopause is cessation of regular menstrual cycle.

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Factors effect of menarche starts

1. Genetics 2. Geographical location.3. Nutrition 4. Weight 5. Psychological factors

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Menstrual Cycle Consists of:

1. Ovarian Cycle

2. Endometrial Cycle

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The Phases of the Menstrual Cycle

The menstrual cycle has 4 phases:1. Follicular phase - proliferative phase orPre ovulatory phase2. Ovulation3. Luteal phase - secretory phase or postovulatory phase4. Menstruation

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1. Follicular phase :• high levels of FSH secreted– Function is to stimulate follicles in the ovaries One follicle begins to mature and brings an eggto maturity 1- 14day

– Follicle secretes estrogen– Increase level of estrogen secreted by maturating follicle that effect on

the endometrial proliferation.

2. Ovulation phase• Follicle ruptures open and releases the mature egg 14 day promoted by LH

surge • Decrease level of estrogen• Life span of ovum is 24 hrs.

The Phases of the ovarian Cycle

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3. Luteal phase after releasing an egg, the follicle turns into the corpus

luteum15 -28day• The corpus luteum secrets progesterone toPrepare

endometruim for implantation and to secret glycogen and mucus.

• The absence of fertilization the corpus luteum begins to degenerate that will lead Estrogen and Progesterone decrease.

4. Menstruation - shedding of the inner lining of the uterus 28 day.

The Phases of the Menstrual Cycle

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Endometrial cycle

1.Proliferative phase • Start in day 5• Start endometrial proliferates in response of estrogen• Increase thickness dramatically from 0.5 – 5mm.• Cervical mucus becomes thin and clear and more alkaline 2. Secretory phase : • begins at ovulation • progesterone secreted by the corpus luteum stimulates

the glands of the endometrium to start secreting the nourishing substances preparation of implantation.

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Endometrial cycle

3. Ischemic phase • If fertilization does not occur, the ischemic phase begins.• Estrogens and progesterone level drop • Corpus luteum degenerate.• Spasm of arterioles and lead of shedding of the

endometrium. 4. menstrual phase : • Rupture of spiral arteries • The beginning of menstrual flow marks the end of one

menstrual cycle

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Changes in the Uterus:

Stage 1- Day 1-5 menstruation

Stage 2 Day 5- 13 pre-ovulatory stage Stage 3 Day 14

Ovulation

Stage 4 Day 15-28 post-ovulatory stage

Ovarian Hormones

Days 1-14

Triggers uterine lining th ickening

ProducesEstrogen & Ovum

Triggers form ation of theFollicle

W ith in th e o va ry

ProducesFSH

F o llic le S tim u la tin g H o rm o ne

PituitaryG land

Days 14 - 28

C ontinues uterine lining thickening

ProducesProgesterone

Triggers O vulationand the form ation of the

Corpus LutiumW ith in th e ovary

ProducesLH

L u tin iz in g H orm on e

PituitaryG land

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Fluctuations in Mood

• Premenstrual syndrome - PMS• PMS is a combination of severe physicaland psychological symptoms, such as depression

and irritability, occurring just before menstruation

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Fluctuations in Performance

• Research on intellectual or athletic performance generally shows no fluctuations over the cycle

• Research on academic performance, problem solving, memory, or creativethinking shows no fluctuations over thecycle

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What Causes the Fluctuations in Mood

• Biological factors– Fluctuations in levels of hormones• Environmental factors– Menstrual taboos and cultural expectations

• 12 months of amenorrhea (no menses)• Average age 51• Derived from the Greek words “men” (month) and

“pausis” (cessation)• Primary ovarian function stops• Marks the permanent end of fertility

What is Menopause?

• Hot flashes• Sleep disturbances• Vaginal dryness• Mood changes• Difficulty concentrating• Memory impairment• Bladder irritability/urgency• Changes in balance• Decreased interest in sex, possibly decreased response to

sexual stimulation

Menopausal Symptoms

Other Causes to Consider

• Thyroid disorders• Pheochromocytoma• Leukemia• Cancer• Infection

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References

• http://www.ux1.eiu.edu/~cfjcd/Menstrual_Cycle.

• http://members.optushome.com.au/medstuff/Menstrual%20cycle.pdf

• http://www.drugs.com/cg/menstruation.html