Every female goes through this process of menstruation but only some are aware of the physiology behind it. I believe that every individual should be aware of this process so that they can understand what their body is going through and they should be able to contribute positively to the life of their fellow human beings going through it, so let's understand this today.
WHAT IS MESNTRUATION?
It is a process in which a female body goes through hormonal changes and prepares the uterus(womb) by the formation of the functional layer in the uterus which is temporary for the possible pregnancy. But when fertilization doesn't occur the prepared uterus sheds its walls (functional layer) composed of blood and tissues and that’s why blood and clots come out of the vagina.
PHASES OF MENSTRUAL CYCLE:
Let's dive into further detail of it that how the uterus prepares itself and what other hormones and factors contribute to it. The two important hormones which are worth mentioning here are FSH and LH they mainly control this process and these two hormones themselves are controlled by the pituitary gland and hypothalamus. Before going into further detail there is brief information on the functions of the major hormones involved in the menstrual cycle.
•Follicular stimulating hormone: Helps in the development of the follicles and controls the menstrual cycle.
•Luteinizing hormone: Responsible for ovulation.
•Estrogen: Plays a role in ovulation and thickens the uterus wall.
•Progesterone: Thickens the uterus wall and maintains the pregnancy till the end.
The menstrual cycle is divided into four phases:
When a female child is born she has millions of primordial follicles in her ovaries, you can assume a primordial follicle as an immature egg. As she reaches puberty under the influence of hormones like FSH and LH some of these primordial follicle grows into the primary follicles, assuming the primary follicle is one step extra matured form of an egg.
During a monthly cycle of a female these primary follicles present in the ovaries 5 to 12 start undergoing further development due to the high level of follicle stimulation hormones, the low estrogen and progesterone hormones also favor their development, but as soon as the primary follicle starts to develop the growing follicle begin to release estrogen, estrogen, on the other hand, has an inhibitory effect on FSH and they decrease FSH secretion by the negative feedback mechanism.
As the FSH declines, the hormonal environment only favors the further maturation of 1 out of these 5-12 primary follicles and this enters the next phase of the Ovulation and rest of them usually degenerate but in rare cases, more than one of these follicles grow into mature eggs and ultimately leads to multiple pregnancies. This phase starts on the 5th day of the cycle and ends up around the 12th day, the first four days are of menstruation which is explained at the end, the duration of Follicular phase is variable and its duration decides the total length of the cycle.
Now, the hormonal environment of the ovary is such that there is low FSH and high estrogen and this environment favors the LH surge. LH surge is the release of luteinizing which results in Ovulation. What happens in ovulation is that the only follicle growing in the previous stage finally releases a mature egg.
This phase starts on the 13th day of the cycle. Generally, women experience libido changes during this phase and in the initial days of the luteal phase. During this period they are aroused easily and their sex drive increases and that makes sense because intercourse during these days will more likely to get them pregnant.
After the release of a mature egg, the remaining structure of the follicle forms a body called the corpus luteum. This corpus luteum becomes an endocrine organ because it releases progesterone and estrogen and they thicken the uterus wall in this stage of the menstrual cycle. It's like the hormones are preparing a bed for an egg and sperm to meet.
If fertilization occurs this corpus luteum enlarges and further increases its production of progesterone which is essential for the maintenance of pregnancy but if fertilization doesn't occur it degenerates. This phase starts around the 16th day of the monthly cycle and most women experience Premenstrual Syndrome (PMS) in the last days of this phase which continues till the menses cease.
The exact mechanism of PMS is unknown but it is believed that it is due to hormonal fluctuation. When fertilization doesn’t occur the level of estrogen and progesterone falls, this sudden decline in these hormones in the last stage of the menstrual cycle also affects the other hormones and neurotransmitters including dopamine and serotonin which are our mood regulators. These hormonal fluctuation manifests as mood swings, craving for specific foods, fatigue, and lack of motivation.
Typically this phase is defined as the first phase of the menstrual cycle but to make it understandable I am explaining it as the final stage of the menstrual cycle. Now all the preparation has been done by the uterus but if there is no entry of any sperm for the fertilization of the egg, the uterus sheds its walls resulting in the emission of blood and tissue particles from the vagina. The average duration of this phase is around 3 to 7 days.
Always remember that there is no fixed duration of the menstrual cycle. It can be as short as 21 days or can be as long as 35 days. I have explained the whole process by keeping in mind the average days of this cycle which are 28 days.
So this sums up my post, I have tried to keep it simple but still, I am open to questions and suggestions.