Menstrual Cycle: Menstruation, Phases, Menstrual Hormones

Ans: The differences between the Follicular Phase and Luteal Phase are given below: 

Ans: After the ovulatory phase (ovulation), the luteal phase starts. In the Luteal phase, the remaining parts of the ruptured Graafian follicle transform as corpus luteum. The corpus luteum secretes a large amount of progesterone which is very important for the maintenance of the endometrium. When the fertilization does not take place, the corpus luteum degenerates causing disintegration of endometrium leading to menstruation.

Ans: Gonadotropins i.e. the level of LH and FSH increase gradually during the follicular phase and secretory phase respectively. FSH regulates follicular development and secretion of estrogens by the growing follicles, while LH stimulates the corpus luteum to secrete progesterone. Both LH and FSH attain a peak level in the middle of the cycle, i.e. about the 14th day of the menstrual cycle.

Ans: Menstrual cycle in females is under hormonal control in the following ways:

1. The follicular phase is under the influence of FSH from the anterior pituitary.
2. The follicular cells of the mature follicles secrete estrogens, which control the growth and maintenance of the secondary sex organs like the uterus, Fallopian tube, etc.
3. FSH and LH reach their peak level in the middle of the cycle. The peak level of LH surge causes the rupture of the Graafian follicle and release of the ovum.
4. LH influences the remaining parts of the Graafian follicle to transform into the corpus luteum.
5. The Corpus luteum secretes a large quantity of progesterone in the luteal phase. Progesterone is required for the growth and maintenance of the endometrium of the uterus for implantation.
6. In the absence of fertilization, the high levels of progesterone exert a negative impact on the pituitary. This stops the secretion of LH and corpus luteum degenerates leading to menstruation.

Ans: The source of gonadotropins in females is the anterior pituitary.

The menstrual cycle is a rhythmic change in the reproductive organs of females. The first menstruation begins at puberty and is called menarche. Average interval of menstruation in females is about 28-29 days. The cycle starts from one menstruation till the next one constitutes the menstrual cycle. 

The changes that are brought in the ovary by the hormones during the different phases of the menstrual cycle are classified below: 

1. Menstrual phase: The levels of hormones LH, FDH, estrogen and progesterone are very less in this phase. It results in the breakdown of the endometrial lining of the uterus.
2. Follicular phase: In this phase, the levels of pituitary hormones FSH and LH increase which releases the ovarian hormone estrogen. FSH controls the follicular phase, it stimulates the growth of follicles. Both FSH and LH reach their peak level in the middle of the cycle.
3. Ovulatory phase: The level of LH hormones reaches its peak in this phase. It induces the ruptures of mature Graafian follicles and thereby release of ovum
4. Luteal phase: The LH and FSH hormones begin to decline. After ovulation, the follicle ruptures and transforms into the corpus luteum which secretes large quantities of progesterone.

Ans: The menstrual cycle is described as the sequence of events that occur in the females’ body to prepare for the possibility of pregnancy. It comprises four phases which are regulated by both pituitary and ovarian hormones that affect ovaries and uterus, respectively.

The events occurring in a menstrual cycle are:

Menstrual Phase: It is initiated by the reduction in the secretion of LH and progesterone and estrogen. The endometrium breaks down and blood along with unfertilized ovum constitute menstrual flow. 

Follicular Phase: The FSH secreted by the anterior pituitary gland regulates the ovarian follicles to secrete estrogen. These estrogens stimulate the proliferation of uterine walls as a result of which endometrium gets thickened. 

Ovulatory Phase: Pituitary Hormones LH and FSH reach the highest level in the middle of the cycle. The rapid secretion of LH causes ovulation, thus indicating rupture of Graafian follicle and release of ovum and secondary oocyte. 

Luteal Phase: In this phase, the pituitary hormone LH stimulates the remaining cells of ovarian follicles to develop corpus luteum. This corpus luteum secretes a large amount of progesterone necessary for the maintenance of the endometrium as such endometrium is required for implantation of fertilized ovum and pregnancy. 

In the absence of fertilization, the levels of the hormone are reduced and endometrium disintegrates and another menstrual cycle starts. 

Ans: There are four phases in a menstrual cycle- menstrual phase, follicular phase, ovulatory phase and luteal phase. In terms of the luteinizing hormone (LH) surge, the ovulatory phase is most important. During the follicular phase, the follicle develops at the beginning of the menstrual cycle. This cycle begins with the shedding of the uterine lining. This shedding cleanses the lining of the uterus for ovulation during the ovulatory phase.

Ans: (a) During this phase, primary follicles transform into Graafian follicles under FSH stimulation. Graafian follicles secrete estrogens and regulate the enlargement of the Endometrium of the uterus.

(b) During this phase, the Corpus luteum is fully formed and secretes a large quantity of Progesterone.

Ans: The ovary produces around 5 to 20 follicles (cysts or tiny nodules) followed by hormonal stimulation, which bead on the surface. Each follicle comprises an immature egg. Among these only one follicle matures into an egg. Finally, from one of the two ovaries, a mature egg follicle releases an egg. For a possible pregnancy, the follicular growth also stimulates the lining of the uterus and helps it to thicken.

Ans: Menstruation is an important phase in the life cycle of a Woman till menopause. In this phase, the lining of the endometrium or uterus is shed. The endometrium prepares itself to nourish a fetus with each monthly cycle. If fertilization does not occur, the progesterone starts to decline in the last stage disrupting the endometrium leading to periods in females. The endometrium, along with mucus and blood from the cervix and vagina make up the menstrual fluid that comes out through the vagina during the period.

Ans: The cycle of menstruation in a girl initiates from the age of 10 to 15 when she reaches puberty. This starting point of menstruation is referred to as menarche. At the age range of 50, the ending of menstruation takes place and is known as menopause.

The first day of a menstrual cycle is marked as the first day of bleeding and the time period from one menstrual cycle takes 28 to 30 days to reach the other.

Ans: An average menstrual cycle for a menstruating woman lasts 28 days. It ends with the first day of the next menstrual period and initiates with the first day of the last period. Women may have cycles as long as 45 days during the first few years or as short as 21 days. However, the time period ranging outside this may require medical attention.