Describe the changes that occur in ovaries and uterus in human female during the reproductive cycle.
Menstrual cycle is the reproductive cycle in all primates and begins at puberty (menarche).
In human females, menstruation occurs once in 28 to 29 days. The cycle of events starting from one menstruation till the next one is called the menstrual cycle. These changes are brought about by ovarian and pituitary hormones.
The changes occurring in the ovaries are as follows:
- The cycle starts with the menstrual phase, where menstruation occurs. This is followed by the follicular phase. In this phase, the primary follicles mature into the Graffian follicles and the release of gonadotropins (LH and FSH) also increases. This causes follicular growth and the growing follicles produce oestrogen.
- The LH and FSH are at their peak in the middle of the cycle (14th day), and cause the rupture of the Graffian follicles to release ovum. This phase is called the ovulatory phase.
- The remains of the Graffian follicles get converted into the corpus luteum that secretes progesterone for the maintenance of the endometrium.
- In the absence of fertilisation, the corpus luteum degenerates, thereby causing the disintegration of the endometrium and the start of a new cycle.
The changes occurring in the uterus are as follows:
- In the absence of fertilisation, during the menstruation phase, the endometrium of the uterus breaks down. Blood vessels in liquid state are discharged.
- During the follicular phase, the action of the gonadotrophins (LH and FSH) causes the regeneration of the endometrium to receive the fertilised egg.
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