menstrual cycle

• how long does a woman's menstrual cycle last for?

  28 days
• how is the start of the menstrual cycle marked?

  menstruation for 5 days
• what is menstruation?

  the lining of the uterus is shed through the vagina.
• what happens during the menstrual cycle?

  1. an egg starts to develop
  2. the egg is released
  3. the egg travels along the oviduct
  4. the unfertilised egg reaches the uterus
• what is FSH released by?

  pituitary gland
• what is the purpose of FSH in the menstrual cycle?

  causes a follicle (an egg and its surrounding cells) to mature in one of the ovaries, which stimulates oestrogen production.
• what is the purpose of oestrogen in the menstrual cycle?

  causes the lining of the uterus to thicken and grow. A high level stimulates an LH surge (a rapid increase).
• what is LH released by?

  pituitary gland
• what is the purpose of LH in the menstrual cycle?

  the LH surge stimulates ovulation at day 14, the follicle ruptures and the egg is released. It stimulates the remains of the follicle to develop into a structure called a corpus luteum, which secretes progesterone.
• what is progesterone released by?

  corpus luteum after ovulation
• what is the purpose of progesterone in the menstrual cycle?

  It maintains the lining of the uterus and inhibits the release of FSH and LH. When the level of progesterone falls, and there's a low oestrogen level, the uterus lining breaks down.
• what happens on days 4-14 of the menstrual cycle?

  the uterus lining repairs until it becomes a thick, spongy layer full of blood vessels ready for a fertilised egg to implant there.
• what happens if no fertilised egg has landed on the uterus?

  the spongy lining starts to break down again and the whole cycle starts over.
• how long is the lining maintained for?

  for about 14 days (from day 14-28)
• where is the egg released from?

  Ovary
• the menstrual cycle is controlled by what 4 hormones from the endocrine system?

  • FSH (follicle stimulating hormone)
  • oestrogen
  • LH (luteinising hormone)
  • progesterone
• what is FSH released by?

  pituitary gland
• what is the purpose of FSH?

  • causes an egg in the ovary to mature
  • stimulates the production of oestrogen
• where is oestrogen produced from?

  the ovaries
• what is the purpose of oestrogen?

  • causes the development of the thick, spongy uterus lining
  • stimulates the production of LH
  • inhibits the production of FSH
• what is LH produced by?

  the pituitary gland
• what is the purpose of LH?

  stimulates the release of a mature egg on day 14 of the menstrual cycle (ovulation).
• where is progesterone produced?

  in the ovaries after ovulation.
• what is the purpose of ovulation?

  • maintains the lining of the uterus during days 14-28
  • when progesterone levels drop, this triggers the breakdown of the lining, marking day 1 of the cycle
  • also inhibits the release of LH and FSH
• how do menstrual hormones affect the production of one another?

  FSH stimulates the production of oestrogen and oestrogen inhibits the production of FSH.
• what is the first stage of the menstrual cycle (days 1-4)?

  the uterus lining breaks down, resulting in a period.
• what is the second stage of the menstrual cycle (days 4-14)?

  the uterus lining starts to build up again into a thick, spongy layer full of blood vessels.
• what is the third stage of the menstrual cycle (day 14)?

  ovulation happens. This is when an egg is released from one of the ovaries.
• what is the fourth stage of the menstrual cycle (days 15-28)?

  the uterus lining is maintained, which means it is now ready for the arrival of a fertilised egg. If no fertilised egg is attatched to the uterus lining, the lining breaks down and the cycle begins again.
• what hormone controls the release of FSH?

  GnRH. Lower levels of GnRH means less FSH.
• which hormone inhibits the release of GnRH as the levels of it rise?

  oestrogen
• gonadotroph adenomas are a rare type of what?

  pituitary gland tumour.
• what are the symptoms of a gonadotroph adenomas?

  • menstrual irregularity
  • headaches
  • weight loss
• which hormone inhibits the release of LH and FSH?

  progesterone
• what would an increase in blood oestrogen levels cause?

  • decrease in GnRH
  • decrease in FSH
  • rise in LH
• what effect do oestrogen and progesterone have on the lining of the uterus?

  increase in thickness