The cycle is divided into 4 phases/stages:
Here are the 4 phases (in order):
- MENSTRUAL PHASE
The menstrual cycle begins (day 1 is) from the start of menstruation.
Menstruation takes place when there is no fertilisation, so the thick lining of the uterus breaks down.
The menstrual phase ends when menstruation ends.
Then the follicular phase begins.
- FOLLICULAR PHASE
In this phase, the ovary gets its internal system ready to release the egg.
The egg sits inside a follicle inside the ovary.
So the ovary develops the follicle so that the follicle becomes prepared to release the egg.
As the follicle develops, it gets bigger.
When the follicle reaches full size , the follicular stage ends.
Then the ovulation phase starts.
This phase consists of all the days when it is possible that the ovary could release the egg into the oviduct.
When the egg is released during this period varies from person to person.
But the egg is released sometime during this period when the ovary gets a high shot of Lieutinising Hormone from the pituitary gland.
The follicle in the ovary bursts open and the egg is released into the oviduct.
After ovulation, the luteal phase begins, which ends at the start of menstruation.
- LUTEAL PHASE
During this phase, the body thickens the lining of the uterus to prepare for implantation of a zygote in case fertilisation happens.
This is done via some hormones, most prominently progesterone which is secreted in large amounts by the burst ovarian follicle that released the egg, which is now called the corpus luteum .
The follicle continues to secrete progesterone until menstruation and then dies off.
AND then all of it starts all over again.
The whole menstrual cycle takes 28 days.
Well that was very much it.
Following are some significant details which tie in to the various stages.
Here is an overview with all the important hormones:
Notice how Lieutinising Hormone levels rise during ovulation and how much the burst follicle ( corpus luteum ) secretes progesterone after ovulation.
Here you can see the thickness change of the uterus lining throughout the cycle:
Notice how much of the thickness is related to the amount of progesterone secreted (spoiler: a lot!)