Women's Health Series: The Menstrual Cycle

In this four-part blog series we are highlighting four important topics that can have an impact on women's health and wellbeing: cervical cancer, the menstrual cycle, contraception and some interesting science about the female orgasm!

The menstrual cycle

The menstrual cycle is the releasing and disposal of an unfertilised egg. Levels of the hormone oestrogen start to rise which causes ovulation, which is when the ovaries release a developed egg.

As the egg is released, levels of oestrogen fall, whilst levels of another hormone, progesterone, rise. This hormone ensures the lining of the womb gets thicker in preparation for this egg to embed itself into it, if it has been fertilised. Once the levels of progesterone have fallen, the lining will disintegrate resulting in small levels of blood flowing from the women’s vagina, known as the menstrual flow or a period. Against popular belief, the egg is actually reabsorbed into the body rather than washed out amongst the lining of the womb.

On average, 3 to 5 tablespoons of blood are lost through a period, which can take place over 2 – 7 days. The average menstrual cycle, which is calculated from the start of one period to the start of the next, is 28 days.

All of the eggs that a female will use during her reproductive lifetime are already stored in her ovaries when she is born. She will start off with around 2 million eggs, but this reduces significantly to around 400,000 by puberty. Once released, each egg only lives for 24 hours. The chances of fertilisation are increased however by the life-span of the male sperm, which can survive after sex in the Fallopian tubes for up to 7 days.

The menstrual cycle evolves as the woman ages, too. The teenage years normally present heavier periods and the cycle length may be longer (38 days+), however lighter and more consistent cycles appear during the woman's 20s and 30s. The transition to menopause begins in the woman's 40s, causing significant changes to their regularity, length and how heavy the bleeding may be.

Women's health-related AnatomyStuff resources

Budget Pelvis Model with Organs and Pelvic Floor Muscles
Female Reproductive System Chart / Poster
RITA Reproductive Implant Training Arm
IUD Trainer


Further reading / sources

The ovaries
Menstrual cycle

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