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प्रश्न
Explain the changes that occur in the ovary and uterus during menstrual cycle in human females. Mention the influence of pituitary and ovarian hormones in bringing these changes.
उत्तर
Menstrual phase (1-5)
Endometrium breaks down the cell of endometrium secretions unfertilised ovum constitute menstrual flow. Progesteron production is reduced
Follicular Phase (6-13 days)
Endometrium rebuilds, FSH and oestrogen secretion is increased.
Ovulatory Phase (14-16 days)
Both LH and FSH attain peak level. Estrogen level is also high. It leads to ovulation.
Luteal Phase (16-28 days)
In absence of fertilisation corpus luteum secretes progesterone. Endometrium thickens and uterine glands become secretary.
The menstrual cycle starts with the menstrual phase, when menstrual flow occurs and it lasts for 3-5 days. It results due to breakdown of endometrial lining of the uterus and its blood vessels.
Follicular Phase The menstrual phase is followed by the follicular phase.
During this phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle and simultaneously the endometrium of uterus regenerates through proliferation. These changes in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones.
The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase and stimulates follicular development as well as secretion of estrogens by the growing follicles. Both LH and FSH attain a peak level in the middle of cycle (about 14th day).
Rapid secreation of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation). The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the Graafian follicle transform as the corpus luteum. The corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium.
Such an endometrium is necessary for implantation of the ferillised ovum and other events of pregnancy. In the absence of fertilisation, the corpus luteum degenerates.
This causes disintegration of the endometrium leading to menstruation.
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संबंधित प्रश्न
The human female gonads are ovaries. A maturing egg in the ovary is present in a sac of cells called ______ (1). As the egg grows larger, the follicle enlarges and gets filled with a fluid and is now called the ______ (2) follicle. The process of releasing the egg from the ovary is called ______ (3). The ovum is picked up by the oviducal funnel and fertilization takes place in the ______ (4). In about a weak the blastocyst gets fixed in the endometrium of the uterus and this process is called ______ (5).
Mention one significant difference between Hormones of ovulatory phase and hormones of luteal phase
How many pairs of testis are present in human male?
Explain the importance of cleanliness during the time of menstrual cycle in girls.
If the corpus luteum is present in the ovary even after 72 hours after ovulationit indicates that ______.
Immediately after ovulation, the mammalian egg is covered by a membrane known as ______.
Which one of the following statements is incorrect about menstruation?
Menstrual flow occurs due to lack of ______.
Given below is the diagram depicting the menstrual cycle in human beings. Study it carefully and answer the questions that follow.
- Which phases are indicated by ‘C’ and ‘D’?
- Name the structures labelled ‘F’. What is its role?
- Explain the changes in the level of progesterone during phases ‘C’ and ‘D’.
- Which hormone present in the urine confirms pregnancy in human beings?
- Identify the structure labelled ‘E’. Name the hormone released by it.
Give a reason for the following:
The second half of the menstrual cycle is called the luteal phase as well as the secretory phase.
