Menstrual Cycle

• The menstrual cycle is a process that prepares the uterus lining for a fertilised egg.
• If an egg is fertilised, it can implant itself in the prepared uterus lining.
• If an egg is not fertilised, the lining of the uterus breaks down and is lost from the body, this is known as menstruation or a period.
• Assisted Reproductive Technology (ART) uses hormones and other techniques to increase the chance of pregnancy.
• Clomifene therapy is useful for women who rarely or never release an egg cell during their menstrual cycles.
• Clomifene is a drug that helps to increase the concentration of FSH and LH in the blood.
• In Vitro Fertilisation (IVF) is another Assisted Reproductive Technology (ART) technique.
• Stage 1: Days 1-5 - Menstruation, when the uterus lining breaks down and is lost with the unfertilised egg cell.
• Stage 2: Days 6-12 - The follicle starts to develop/mature, the lining of the uterus begins to build up again around day 11.
• Stage 3: Day 14 - An egg cell is released from an ovary, this is called ovulation.
• Stage 4: Days 16-28 - The uterus lining continues to thicken, if a fertilised egg does not implant into the uterus lining then the cycle begins again.
• The menstrual cycle is controlled by hormones, there are 4 hormones involved in the cycle: FSH (follicle stimulating hormone), LH (Luteinizing Hormone), both released from the pituitary gland.
• Oestrogen and Progesterone are both released from the ovaries.
• Oestrogen stimulates the growth and maturation of an egg.
• Progesterone causes the release of oestrogen.
• Follicle Stimulating Hormone (FSH) is secreted by the pituitary gland and stimulates the maturation of a follicle, also stimulating the production of oestrogen.
• Oestrogen levels increase, inhibiting the production of FSH.
• An increase in oestrogen causes a surge in LH around day 14, leading to ovulation (release of the egg).
• Once the egg is released, the follicle becomes a corpus luteum and releases progesterone.
• Increase in progesterone allows the uterus lining to thicken and maintains this, it also inhibits the production of both FSH and LH.
• If fertilisation has occurred, progesterone continues to be released, maintaining the uterus lining.
• If no fertilisation took place, the levels of progesterone and decrease which leads to the uterus lining shedding/breaking down.
• Usually one egg cell is released from one ovary during ovulation.
• Sometimes two or more egg cells are released though.
• If all egg cells are fertilised, this can lead to non-identical twins, triplets, etc.
• Contraception is the prevention of fertilisation and therefore pregnancy.
• The male condom is placed over the erect penis, preventing sperm entering the vagina.
• The diaphragm or cap is placed over the cervix, preventing sperm in the vagina entering the uterus.
• The hormone pill or implant is placed under the skin, releasing hormones to prevent ovulation and thickening mucus at the cervix, making it difficult for sperm cells to pass through.
• Assisted Reproductive Technology (ART) is used by some couples who are unable to have a child.