the menstrual cycle

• this is a reoccurring process that takes around 28 days. here, the lining of the uterus is prepared for pregnancy. if the implantation of a fertilised egg into the uterus does not take place the lining is shed (menstruation)
• stage 1 (day 1) the menstruation starts and the lining of the uterus breaks down and is released causing a period
• stage 2 (day 4-14) the uterus lining builds up until it becomes a thick spongy layer full of blood vessels are ready for a fertilised egg to implant there.
• stage 3 (day 14) the egg develops and is released from the ovary, ovulation
• stage 4 (day 14-28) the lining of the uterus is maintained and if a fertilised egg is not implanted, the spongy lining starts to break down again and the whole cycle starts again
• the hormones that control the menstrual cycle are oestrogen, progesterone, LH and FSH. the changes in levels if these hormones cause each stag of the menstrual cycle
• firstly, oestrogen is released by the ovaries and this stimulates the lining of the uterus to build up.
• secondly, progesterone is released by the corpus luteum after ovulation to maintain the lining of the uterus . when progesterone levels fall and there is a lows oestrogen level the uterus lining breaks down
• thirdly, LH which spikes at day 14 is released by the pituitary gland and triggers ovulation
• lastly, FSH is released by the pituitary gland and stimulates the growth and maturation of an egg follicle