The menstrual cycle

Menstrual cycle

It's always good to have an understanding of how our menstrual cycle works. It helps particularly knowing when we will experience hormonal changes (woah, this really effects your mood at times) so normal jabs and pains don't get mistaken for something else.

There are 4 main phases in the menstrual cycle:

  1. Menstruation
  2. The Follicular Phase
  3. Ovulation
  4. The Luteal Phase

Menstruation is the elimination of the thickened lining of the uterus from the body through the vagina. Also known as your wonderful period. Although you may think this is purely blood, it holds a combination of cells from the lining of the uterus called endometrial cells, mucus as well as blood.

The Follicular Phase begins on the first day of menstruation and ends with ovulation. With the stimulation from the Hypothalamus, the pituitary gland releases Follicle Stimulating Hormone. This hormone stimulates the ovary to produce five to twenty follicles.

Ovulation is the release of a mature egg from the ovary and occurs generally about two weeks before menstruation begins. During the follicular phase, the developing follicle causes a rise in the level of oestrogen. The hypothalamus in the brain recognises these rising levels and releases a chemical called gonadotrophin-releasing hormone (GnRH). This hormone prompts the pituitary gland to produce raised levels of luteinising hormone (LH) and FSH. This rise in LH triggers the release of the mature egg from the ovary into the fallopian tube towards the uterus. 

The Luteal Phase involves the left over follicle from the ovary during the release of the egg transforming in to the corpus luteum, which starts to release progesterone as well as small amounts of oestrogen. This is to maintain the thickened lining of the uterus waiting for the fertilised egg to stick (implant). If the egg successfully implants, it beings producing hormones that maintain the corpus luteum. One of these, which is used to detect pregnancy, is human chorionic gonadotropin (hCG).

Of course, if you do not get pregnant, the corpus luteum falls away therefore dropping levels of progesterone. This begins the cycle again and you have menstruation.

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