Science Week 2

• Menstrual cycle


  The monthly series of changes a woman's body goes through in preparation for the possibility of pregnancy
• Menstrual cycle


  1. Pituitary gland controls and starts the cycle

  2. Pituitary gland releases hormones that cause the egg in the ovary to mature

  3. Ovary releases estrogen which causes the uterine lining to increase in thickness

  4. Ovary releases an egg on day 14

  5. Egg moves through the oviduct and enters the uterus

  6. Uterine lining continues to thicken

  7. Egg has not been fertilized, so it will not attach to the uterus

  8. Thick uterine lining is no longer necessary, so the cells break off and leave the vagina (menstruation)

  9. After menstruation, the cycle starts again
• Follicle stimulating hormone (FSH)


  • Assists in the maturation of the follicles and causes the secretion of estrogen from the follicles
• Luteinizing hormone (LH)


  • Initiates the maturation of the follicles, converts ruptured follicles into corpus luteum and causes the secretion of progesterone
• High levels of estrogen


  Prevent the further production of FSH
• Estrogen


  Stimulates the release of luteinizing hormone (LH) from the pituitary gland, which in turn controls the production of progesterone
• High levels of progesterone


  Inhibit the further release of LH
• Feedback mechanism


  The process through which the level of one substance influences the level of another substance
• Negative feedback


  High levels of one hormone may inhibit the production of another hormone
• A feedback mechanism is the process through which the level of one substance influences the level of another substance
• A negative feedback affects the production of hormones in the menstrual cycle
• High levels of estrogen then prevent the further production of FSH
• Estrogen also stimulates the release of luteinizing hormone (LH) from the pituitary gland, which in turn controls the production of progesterone
• High levels of progesterone then inhibit the further release of LH
• The menstrual cycle is the monthly series of changes a woman's body goes through in preparation for the possibility of pregnancy
• Each month, one of the ovaries releases an egg — a process called ovulation
• At the same time, hormonal changes prepare the uterus for possible pregnancy
• The pituitary gland controls and starts the menstrual cycle
• The pituitary gland releases hormones that cause the egg in the ovary to mature
• The ovary itself releases a hormone called estrogen, which causes the uterine lining to increase in thickness
• The egg moves through the oviduct and enters the uterus
• The egg has not been fertilized, therefore, it will not attach to the uterus
• The thick uterine lining is no longer necessary, so the cells of the thickened uterine lining break off and leave the vagina. The unfertilized egg is lost and some blood is lost too. This loss of cells from the uterine lining, blood, and egg is called menstruation
• After menstruation, the cycle starts again