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Question
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.
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Solution
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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RELATED QUESTIONS
Name and explain the role of the inner and middle walls of the human uterus.
Explain the events that occur in a graafian follicle at the time of ovulation and thereafter.
Explain the role of hormones during the menstrual cycle.
Give Technical Term:
The phase in the menstrual cycle in which the remnant of a follicle in the ovary turns to corpus luteum.
Answer the following type of question Assertion (A) and Reason (R).
(A) - Ovulation is the release of the ovum from the Graafian follicle.
(R) - It occurs during the follicular phase of the menstrual cycle.
Level of which hormones are at their highest during the luteal phase (second half of the cycle) of the menstrual cycle?
A biology student after studying the different levels of hormones during the menstrual cycle was comparing 2 subjects (Patients). A table was created after looking at the levels of hormones A and B for Subjects 1 and 2. Read the information in the table and answer the question that follows.
| HORMONE A | HORMONE B | |
| Subject 1 | Shows a peak on the 14th Day of the menstrual cycle. | Falls down during the luteal phase. |
| Subject 2 | Shows a peak on the 14th Day of the menstrual cycle. | The level is maintained high in the luteal phase. |
If the peak of Hormone A does not appear in the study for Subject 1, which of the following statement is true?
Given below is a group of terms. In the group, one pair indicates the relationship between the two terms. Rewrite and complete the second pair on a similar basis.
Follicular phase: 5-12 days:: Luteal phase : ______ days.
Complete the following table by writing the name of the structure or the function of the given structure:
| Structure | Function | ||
| 1. | Corpus luteum | 1. | ______ |
| 2. | ______ | 2. | Produces male gametes in mass |
| 3. | Leydig cells | 3. | ______ |
| 4. | ______ | 4. | Stores the sperms until they mature and become mobile |
| 5. | Umbilical cord | 5. | ______ |
| 6. | Fallopian tube | 6. | ______ |
Which of the following statements are correct regarding female reproductive cycle?
- In non-primate mammals cyclical changes during reproduction are called oestrus cycle.
- First menstrual cycle begins at puberty and is called menopause.
- Lack of menstruation may be indicative of pregnancy.
- Cyclic menstruation extends between menarche and menopause.
Choose the most appropriate answer from the options given below:
