What is Menstrual Cycle and Ovarian Cycle?

What is menstrual cycle and ovarian cycle?

ILLUSTRATED BY JORGE MUNIZ, PA-C

Alot of women have questions which they hasitate to ask anyone or thier doctors about. I have tried my level best to cover those questions with short and simple answers. I would like you to go thru if you have one of those and if you dont want to read whole article you can use Page of Content to read what you feel good for you.

  1. Is menstrual cycle in females responsible for reproduction?
  2. Is menstrual cycle and reproductive cycle one and the same thing?
  3. Is the reproductive capability of a woman dependent on her menstrual cycle?

Know Your Menstrual Cycle and Ovarian Cycle in Detail here and get to know all the biological secrets behind why you bleed so much every month.

The cyclic changes in females which take place in a span of about 28 days in the ovary, vagina & endometrium, under the influence of the hormones (FSH, LH, estrogen, progesterone) is known as a female reproductive cycle or the menstrual cycle.

It is a cycle of reproductive physiology in females. It is also called an ovarian cycle in biological terms.

 

What is menstrual cycle and ovarian cycle?

 

Your menstrual cycle is made up of four phases. These four phases of the menstrual cycle are as follows:

 

Menstrual phase (day 1-5)

Illustrated by menstrupedia

1. Menstrual Phase:

Menstrual Phase lasts for 3 to 4 days on an average in a woman’s entire menstrual cycle. However, in certain cases, the duration of the menstrual phase may last for 5 days too.

Hormonal Changes :

Sudden changes take place in the woman’s body during the menstrual phase. The levels of several hormones that are responsible for a woman’s menstrual cycle change considerably during the actual menstrual phase.
The secretion of follicle-stimulating hormone (FSH), estrogen and progesterone by the respective hormonal glands decreases to a great extent for the period of menstrual phase. Thus, the levels of Follicle Stimulating Hormone (FSH), Estrogen and Progesterone become extremely low in a woman’s body compared to the levels in other phases of the menstrual cycle.

Endometrial Changes :

The innermost layer of skin of the uterus, i.e. the endometrium, is literally sloughed off and the well-developed mucus glands and spiral arteries are ruptured, which causes bleeding through the vaginal opening in the menstrual phase.

The discharge of blood from the vagina occurring in the menses consists mainly of a mixture of the damaged epithelium, blood clots, blood, and mucus. This process of discharge coming out of he vaginal opening in a woman is called ‘MENSTRUATION’. It can be described as ‘uterus crying for lack of baby’!

Most of the women are under the presumption that they lose a lot of blood during their periods. However, you will be surprised to know that actually the average amount of blood that is lost during one cycle of periods in a woman is about only 50 ml to 70 ml. The rest of the content of the vaginal discharge in periods consists of other material like endometrial wall, mucus, etc and not the actual blood!!

However, although not often, there are also women in whom the amount of blood loss is about 70 ml to 100 ml. If the blood loss in a woman is more than 80 – 90 ml, she should better undergo a treatment to lessen her menstrual flow.

Ovarian Changes :

The ovary also undergoes sudden fast changes. ‘Corpus Luteum’, an endocrine structure in the ovary responsible for secreting progesterone(required to maintain pregnancy), is degenerated almost entirely.
At the end of the menstrual phase, when the flow of blood of periods becomes less, the development of the new ‘female egg’ or the ‘Primordial Follicle’ begins in the ovary.

 

Follicular phase (day 1-13)

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2. Proliferative Phase (Follicular Phase):

Proliferative Phase lasts for about 10 days on an average in a woman’s entire menstrual cycle. It starts from day 4 or day 5 after the menses (periods) have started and lasts till the day 14 of the entire cycle. Gradual changes take place in the woman’s body during the proliferative phase.

Hormonal Changes :

The levels of several hormones that are responsible for a woman’s menstrual cycle change gradually as the proliferative phase progresses.

The levels of ‘Follicle Stimulating Hormone’ (FSH) secreted by the anterior part of the pituitary gland increase gradually through the proliferative phase. The follicular development in the ovary is stimulated due to the increased concentration of the FSH.

The developing follicle secretes estrogen which helps to make the endometrium wall of the uterus soft, thick and vascular with a lot of mucus glands.

The anterior part of the pituitary gland also secretes Luteinizing hormone in small quantities throughout the proliferative phase.

However, the dominating hormones of the proliferative phase are mainly FSH and Estrogen.

Ovarian Changes :

Numbers of follicles start developing in the ovary with the initiation of the proliferative phase.

Although many follicles develop in the proliferative phase, there is only one follicle that develops and enlarges to the greatest extent and thus gets developed into the ‘Graafian Follicle’.

Endometrial Changes :

The endometrial lining undergoes repair & it increases in thickness over the period of proliferative phase by about 2 to 3 mm by the process of growth.

The uterine mucus glands become well developed.

The spiral arteries of the uterine mucosa become long and branched.

The vaginal mucosa also becomes thick as the proliferative advances.

 

Ovulation phase (day 14)

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3. Ovulatory Phase:

Ovulatory Phase is the shortest phase in the menstrual cycle of a woman. It lasts only for about 24 hours (1day). Ovulatory Phase appears approximately on the 14th or the 15th day of a woman’s cycle.

Ovarian Changes :

In this period of 24 hours, the Graafian Follicle that is developed by the end of the Proliferative Phase is burst due to the increased pressure of liquor follicle.

The female egg which is hidden inside the Graafian Follicle escapes from the surface of one of the ovaries.

This escape of the egg from the ovary during the ovulatory phase of the menstrual cycle is called ‘ovulation’.

The fingers like the structure of the uterus, ‘Fimbriae’ become active.

The ciliary action produces a current of fluid due to which the egg enters in the fallopian tube. This phenomenon of the menstrual cycle is also described as if the egg is caught by the fimbriae as soon as it is released from the ovary.

The egg is in the secondary oocyte stage at the time of ovulation.

Hormonal Changes :

Very drastic and sudden changes in the hormonal levels occur during the ovulatory phase of the menstrual cycle.

The levels of follicle-stimulating hormone (FSH) drops down suddenly.

Also, the level of Luteinizing Hormone (LH) shoots up suddenly in the ovulatory phase. The level of Luteinizing Hormone in the ovulation phase is the highest as compared to the other phases of the menstrual cycle. It is this hormone, LH, which is mainly responsible for the ovulation in the cycle.

Thus, Luteinizing Hormone is the most dominant hormone of the Ovulatory Phase.

 

Luteal phase (day 15-28)

Illustrated by menstrupedia

4. Secretory Phase (Luteal Phase):

The secretory phase is also called the Luteal Phase. It lasts for approximately 14 days on an average in a woman’s entire menstrual cycle. It starts after ovulation on approximately the 15th day and lasts up to the 28th day of the cycle in a woman.

Endometrial Changes :

The uterine lining that has developed during the Proliferative phase further continues to develop more during the Secretory Phase.

It becomes thicker of about 4 mm to 5 mm, glandular and vascular to form a comfortable cushion-like structure for the implantation of the early embryo.

The glands become cork-screw shaped.

The arteries in the wall of the uterus become extremely branched during the Secretory Phase of the menstrual cycle.

The cells of the uterus become rich in glycogen.

The endometrium of the uterus reaches its maximum development around the 20th day of the menstrual cycle.

Thus, in the secretory phase, the endometrium is made ready for implantation and nourishment of the early embryo.

In the absence of fertilization of the female egg in the immediate days after the ovulation, the endometrium starts the regressive changes.

In the last 8 days of the menstrual cycle, the endometrium shows the degenerative changes.

These degenerative changes of the endometrium ultimately lead to the menstrual flow of the periods/menstruation.

Ovarian Changes :

The follicle ruptured in the ovary during the ovulatory phase changes into a yellow colored body called corpus luteum in the secretory phase.

This corpus luteum exists in the ovary for about 8 days of the secretory phase and later it starts degenerating. And thus the follicular development is stopped.

Hormonal Changes :

The Corpus luteum that is produced in the ovary in the secretory phase of the menstrual cycle produces two main hormones, progesterone and estrogen.

These two hormones are necessary for the development and the maintenance of the endometrium.
Progesterone is necessary for implantation.

The levels of Luteinizing Hormone and the follicle-stimulating Hormone are very low in the secretory phase.
In the last 8 days of the menstrual cycle, the levels of progesterone and estrogen are also dropped down due to the degenerating corpus luteum.

The most dominating hormone of the secretory phase is progesterone.

At the end of the secretory phase, the menstrual phase begins leading to the blood flow through the vaginal opening and thus the menstrual cycle continues.

Significance of the Menstrual Cycle:

The most important significance of the menstrual cycle is that it is responsible for female fertility (ovulation).

The onset of the menstrual cycle in a girl indicates puberty (menarche), while the stoppage of cycle indicates the termination of the reproductive life of a woman (menopause).

In the secretory phase of the menstrual cycle, the endometrium is made ready for implantation and nourishment of early embryo.

The menstrual flow during the menses of the menstrual cycle ensures removal of damaged endometrial and vaginal lining if there is no fertilization.

Menarche: It is the start of the menstrual cycle (menses) in women around the age of 13 to 14 years. It symbolizes puberty of a girl, thereby resulting in the physical maturity of the girl. A girl’s sexual organs get fully developed when she achieves the puberty stage; thus making the girl capable of reproduction.

Menopause: It is the stoppage of the menstrual cycle (menses) in women around the age of 45 to 50 years.

The duration between menarche and menopause is the reproductive life of a woman. After menopause, the sexual organs of the lady are turned dysfunctional, making the lady incapable of reproduction.