Hormonal control of the menstrual cycle Grade 12 Life Sciences Notes with Activities Questions and Answers The menstrual cycle is a complex and vital process in the female reproductive system, governed by intricate hormonal mechanisms. Understanding these hormonal controls is essential for grasping the physiological dynamics of menstruation. In this Page, we’ll delve into Grade 12 Life Sciences notes on the hormonal regulation of the menstrual cycle, accompanied by activities, questions, and answers to reinforce comprehension.
Notes
Hormonal changes during the menstrual cycle
| Days | A | B | C | D |
|---|---|---|---|---|
| day 0–11 |
Pituitary gland produces FSH which stimulates development of the follicle. |
Follicle is developing to become a Graafian follicle containing an egg cell. | Oestrogen levels increase as the hormone is produced by the follicle. | Thickness of endometrium increases from day 7 (after menstruation has ended) as a result of oestrogen. |
| day 11– 17 | FSH and LH (produced by the pituitary gland) levels are highest around day 14. |
Follicle development is completed as a result of the influence of FSH by day 14. Ovulation is stimulated by high levels of FSH and LH on day 14. LH then stimulates the development of the corpus luteum. |
Oestrogen levels reach a maximum towards day 14 until ovulation takes place, but then start to decrease because the Graafian follicle stops functioning. | Endometrium thickens further. |
| day 17– 28 |
LH levels decrease and then remain constant to maintain the corpus luteum. |
Corpus luteum produces progesterone. Corpus luteum gradually disintegrates since fertilisation does not take place. |
Oestrogen levels increase again and then decrease towards the end of the cycle. Progesterone levels increase towards day 21. Progesterone levels decrease when corpus luteum disintegrates and stops functioning. |
Progesterone prepares endometrium fully for pregnancy. Decreased progesterone levels from around day 21 cause endometrium to shed after day 28 by menstruation since no fertilisation took place. |
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