The menstrual cycle

• Luteinising Hormone, secreted by the pituitary gland, stimulates ovulation.
• Oestrogen is a female sex hormone produced in the ovaries, which is responsible for puberty in girls and the regulation of the menstrual cycle.
• Progesterone is a sex hormone produced by the ovaries and placenta that maintains the uterine lining.
• The menstrual cycle lasts for approximately 28 days and can be followed using graphs to track changes in hormone levels during this process.
• During days 1 to 12 of the menstrual cycle, oestrogen gradually increases and peaks approximately on the 12th day.
• Progesterone, which stays approximately at the same level and begins to increase slightly from around day 12, mirrors this shape and also has a second lower peak at about day 21.
• The pituitary gland produces FSH which causes the development of a follicle in the ovary.
• As the egg develops inside the follicle, the follicle produces the hormone oestrogen.
• The oestrogen causes growth and repair of the lining of the uterus.
• When oestrogen rises to a high enough level it causes a surge in LH from the pituitary which causes ovulation.
• LH (luteinising hormone) is produced by the pituitary gland and triggers ovulation (the release of a mature egg).
• Oestrogen repairs, thickens and maintains the uterus lining.
• If a woman becomes pregnant, the placenta produces progesterone which maintains the lining of the uterus during pregnancy and prevents menstruation.
• FSH (follicle stimulating hormone) is produced by the pituitary gland and causes an egg to mature in an ovary.
• The follicle becomes the corpus luteum after it has released an ovum (egg) into the fallopian tube.
• The process of releasing an egg from an ovary is known as ovulation.
• This causes menstruation, where the uterus lining breaks down - this is known as having a period.
• Oestrogen inhibits FSH.
• Progesterone maintains the uterus lining (the thickness of the uterus wall).
• The corpus luteum secretes hormones involved in the menstrual cycle and this produces oestrogen and progesterone which inhibit FSH and LH production by the pituitary.
• If the egg has not been fertilised, the corpus luteum dies and progesterone levels drop.
• Oestrogen is produced by the ovaries and stops FSH being produced (so that only one egg matures in a cycle).
• Progesterone is produced by the ovaries and maintains the lining of the uterus during the latter part of the menstrual cycle and during pregnancy.
• Negative feedback is a mechanism to lower raised levels of something, and to raise reduced levels of something.
• The fertilised egg (ovum) develops in the wall of the uterus.