This key facts covers The 28-Day Menstrual Cycle within Contraception for GCSE Biology. Topic 9: Contraception It is section 2 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
📌 The 28-Day Menstrual Cycle
- Days 1-5: Menstruation — uterus lining breaks down (period)
- Days 6-13: Uterus lining rebuilds; egg matures (FSH + oestrogen)
- Day 14: Ovulation — egg released (LH surge)
- Days 15-28: Uterus lining maintained by progesterone
- If no fertilisation, progesterone drops and cycle restarts
📊 Visual: The Menstrual Cycle — Hormones, Ovary & Uterus Lining
📌 Remember: FSH → egg matures | Oestrogen → repairs lining, triggers LH | LH → ovulation (day 14) | Progesterone → maintains lining. Examiners often ask you to link a hormone to its biological event — LH triggers ovulation, progesterone maintains the lining, the lining sheds if progesterone drops.
Practice questions for Contraception
Which hormone triggers the release of an egg from the ovary (ovulation)?
Explain the role of oestrogen in the menstrual cycle.
Quick recall flashcards
How does the contraceptive pill work?
The pill contains synthetic oestrogen and/or progesterone. These keep hormone levels high, which inhibits FSH release from the pituitary — preventing egg maturation and ovulation.
What is contraception?
Contraception is any method used to prevent pregnancy by stopping fertilisation or implantation of an egg. Methods can be hormonal, barrier, or other approaches.