Menstrual Cycle

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mikaaylaa

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  • Females are born with approximately 2 million immature eggs in their ovaries. By the time they reach their first menstrual cycle they have around 400,000 left.
  • Each monthly menstrual cycle, between 20-30 eggs are selected to become a possible candidate for release. Usually, only one egg is released per cycle.
  • The menstrual cycle is the body’s way of preparing for pregnancy.
  • It is controlled by chemicals called hormones.
  • follicle stimulating hormone (FSH) causes the maturation of an egg in the ovary.
    • luteinising hormone (LH) stimulates the release of the egg.
  • oestrogen is involved in repairing and thickening the uterus lining
  • Progesterone maintains the uterus lining
  • The cycle lasts an average of 28 days but may vary between 21 and 35 days.
    • First menstrual period: Menarche
  • The menstrual cycle often begins at puberty between the ages of 8 and 15 (average age of 12).
  • The average blood loss during normal menstruation is about 35 ml, with arange of 10 to 80 ml.
  •  Menstruation – uterus lining breaks down, blood and cells are lost.
  • Proliferation – repair of the uterus lining.
  • Ovulation – release of an egg from the ovary – day 14
  • PHASE 1 The elimination of the internal lining of the uterine wall along with other secretions from the body through the vagina.
  • PHASE 2 Starts on the first day of menstruation and ends with ovulation. A follicle (cyst) stimulating hormone produces 10 to 20 follicles in the ovary and each follicle houses an immature egg.
  • PHASE 3 Ovulation occurs 12 to 16 days before the following menstrual period but not necessarily in the middle of the cycle
  • Ovulation is when a mature egg is released from the ovary, pushed down the fallopian tube, and is available to be fertilized. 
  • cervical mucus (discharge)
  • PHASE 4 THE LUTEAL PHASE empty follicle changes to a yellow colour, becomes corpus luteum
  • If pregnant, embryo will release hormones to preserve corpus luteum
  • If fertilization does NOT occur, the yellow body degrades and progesterone levels decrease, leaving the lining unstable. The lining then falls away and a new menstrual cycle period begins.
  • Fertilization is when a sperm cell joins with an egg cell. It is important because this is how reproduction occurs in most living things including humans