Simply put, the female body every month goes to moderate lengths to prepare for growing a child. When it realizes that nothing has been implanted in the uterus, then it will release the outer lining of the uterus so that a fresh new lining can be prepared for the next potential pregnancy.
Your period, also called menses, usually occurs on a cycle between 23-35 days. If its longer or shorter than this length of time it’s an indication of hormonal imbalances in your body.
Day 1-7: Menses – Estrogen and progesterone levels have plummeted stimulating the uterus to contract and shed its outer lining of blood.
Day 8-14: Follicular phase – Preparing for ovulation and thickening of the uterine lining. FSH stimulates your ovary to produce a mature egg and estrogen stimulates uterine cell proliferation and endometrial thickening.
Day 13-16: Ovulation – The mature egg is ejected from the ovary into the fallopian tube which will transport it to the uterus. This occurs when estrogen and LH rise. Estrogen also make the cervical mucous nice and thin so sperm can easily enter the cervix.
Day 14-28: Luteal phase – Preparing for implantation – Progesterone is released from the ovary which maintains the uterine lining (keeps the blood in there) and makes the cervical mucous thick and impenetrable to sperm.