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The Menstrual Cycle

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The menstrual cycle occurs in the uterus and the ovary as a part of making sexual reproduction possible. The menstrual cycle is a monthly occurrence and happens so the ovary can produce eggs and the uterus can get ready for an egg becoming fertilized. (Wikipedia) The menstrual cycle is a complex cycle and is controlled by hormones produced by many different glands. The hypothalamus causes the pituitary gland to produces chemicals which then cause the ovaries to produce the sex hormones oestrogen and progesterone. Each gland and structure is affected by the activity of another which is a biofeedback . The menstrual cycle has been assumed to last around 28 days and happens in four stages, the menstrual phase (day 1-5), follicular phase (day 1-13), ovulation phase (day 14) and the luteal phase (day 15-28). The day count for the menstrual cycle starts on the first day that the blood comes out of the vagina. (Women’s Health)

Puberty is the time in a person’s life when the body begins to sexually mature; the hormone oestrodiol is produced by females. Puberty is initiated by hormonal signals that go to the brain then to the gonads, ovaries in female. (NHS Choices Puberty) A hormone is the produced by the gonads that stimulates the growth, function and transformation of the brain, skin, hormones, breast and sexual organs. During puberty it causes severally different changes, the physical changes are breast development, pubic hair, body shape (hips get wider), vagina and uterus, menstruation and body odour. (Wikipedia)

The first phase, menstrual phase, also known as the period, begins on the first day of menstruation which last for five days. During this phase the uterus shed it inner lining of blood vessels and soft tissues which leave ...

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...erone, oestrogen and inhibin, to decrease so the uterus can get ready to get shed the tissues that were produce for the fertilized egg. (Wikipedia)

A fertilized egg cell, zygote, is produced when two gamete cells, male and female gamete, fuse by sexual reproduction. After sexual reproduction, a single sperm cell can live between 48-72 hours. The sperm cells begin to swim towards the fallopian tubes to fertilize the egg cell waiting in the fallopian tube. Fertilization takes around 24hours; once the sperm cell penetrates the oocyte it leaves the plasma behind and the egg cell changes its surface so that another sperm cell cannot penetrate the egg cell. After the sperm cell entering the egg it finishes it second meiotic division, which forms an ovum and a second polar body. Within 24-48 hours after fertilization early signs of pregnancy can be detected. (Chronolab)
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