3.7 understand the roles of oestrogen and progesterone in the menstrual cycle

3.7 •the menstrual cycle has 4 stages  

                •1. bleeding starts and the uterus lining breaks down for 4 days

                •2. uterus lining builds up again from day 4 to day 14 into a thick spongy layer full of blood vessels to receive a fertilised ovum 

                •3.an ovum develops and is released at day 14

                •4.the wall is then maintained for 14 days until day 28

                          •if no fertilised ovum has landed on the uterus by day 28, the lining breaks down and the process is repeated again 

 •oestrogen and progesterone  are produced in the ovaries 

              •oestrogen: •uterus lining to thickens and grows

                                 •stimulates the release of an ovum at day 14

                                           •LH stimulates actually stimulates ovum release but oestrogen

                                            stimulates the production of LH  

              •progesterone: •if a fertilised ovum implants in the uterus then the level of progesterone to maintain the lining of the uterus during pregnancy