Reproductive cells and the menstrual cylce

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Which hormones control the menstrual cycle?

The two main hormones that control the menstrual cycle are progesterone and oestrogen.

What are the stages in the menstrual cyle?

The mestrual cycle had 4 stages.

1. Day one is when menustration starts. The lining of the uterus breaks down and is released.

2. From day 4 to 14, the lining of the uterus begins to build up again into a thick, spongy layer of blood vessels ready to for a fertilised egg to be implanted.

3. Around day 14, ovulation occurs- an egg is released from the ovaries.

4. The lining is maintained for about 14 days, until day 28. If no fertilised egg has landed on the uterus wall by day 28, the uterus lining begins to break down and the cylce begins again.

Why is the uterus lining maintained if fertilisation occurs?

The thickened lining is maintained so the embroyo can be implanted and begin to develop,

What are the other hormones involved in the menstrual cycle?

The hormones in the menstrual cycle are: progesterone, oestrogen, FSH (follicle stimulating hormone) and LH (luteinising hormone).

What is the role of FSH?

FSH is secreted by the pituitary gland. It causes a follicle to mature which stimulates oestrogen production.

What is the role of oestrogen?

Oestrogen causes the lining of the uterus to thicken and grow. A high level stimilates an LH surge.

What is the role of LH?

The LH surge at around day 14 stimulates ovulation. LH also stimulates the remains of the follicle to develop into a corpus luteum- which secrets progesterone.

What is the role of progesterone?

Progesterone maintains the lining of the uterus. Inhibits the production of FSH and LH. When the level of progesterone falls, it causes a fall in oestrogen and the uterus lining breaks down, A low progesterone level allows FSH to increase, and the cycle begins all over again.

What happens to progesterone levels during pregnancy?

If fertilisation occurs, the corpus luteum continues to secrete progesterone, therefore the progesterone levels remain high.

How is the menstrual cycle controlled by


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