Menstrual Cycle

• Menstruation


  • is a process where blood from the uterus is discharged through the vagina every month
  • the uterine lining and unfertilised egg break down and are shed with some blood
  • days 1 to 5
• After menstruation

  • The ovaries produce a hormone called oestrogen
  • oestrogen causes the uterine lining to repair and thicken
  • high oestrogen concentration leads to ovulation
  • days 6 to 9
• Ovulation


  • on the day 14, an ovary releases and egg into the oviduct through ovulation
  • the two ovaries take turns to release an egg
  • days 10 to 15 are the fertile period, where the uterine lining grows and thickens
• After ovulation


  • the ovaries produce a hormone called progesterone
  • progesterone prevents ovulation and further development of eggs. It also causes the uterine lining to thicken further, preparing the uterus for implantation and growth of the embryo
  • oestrogen production decreases
  • if fertilisation occurs progesterone production decreases
  • the uterine lining breaks down and the menstrual cycle repeats
  • days 16 to 28
• If no fertilisation occurs

  • the egg breaks down
  • blood progesterone level decreases, without progesterone, the uterine lining begins to break down and menstruation begins after the day 28
• If fertilisation occurs

  • the fertilized egg becomes a zygote that develops into an eembryo
  • the ovary secretes progesterone and oestrogen for the maintenance and thickening of the uterine lining for the implantation of the embryo
  • the embryo embeds itself in the uterine lining until the placenta is formed
  • the ovary continues to secrete progesterone and oestrogen until the placenta can take over the production of hormones
• Fertile and Infertile Periods

  • the egg can survive in the oviduct for up to 24 hours
  • sperm can survive in the female reproductive system for about 3 to 5 days
  • the fertile period is during days 10 to 15