The human menstrual cycle

Describe the main stages and events of the menstrual cycle, and state its approximate duration.
Explain how the menstrual cycle prepares the lining of the uterus for potential pregnancy.
Define contraception and describe how condoms and The Pill work to prevent pregnancy, noting whether they offer protection against STIs.

The menstrual cycle is a sequence of changes in the female reproductive system, controlled by hormones. It generally lasts around 28 days, though it can vary from person to person.
The main stages of the menstrual cycle are:
- Day 1: If the egg has not been fertilised, the body detects this and the uterus lining breaks down, and bleeding begins. This is known as a period, or menstruation. Most girls start experiencing during puberty. Blood and tissue from this lining leave the body through the vagina. Each period usually lasts from three to seven days.
- Days 1-5: The lining of the uterus starts to grow back, becoming thicker and spongy to prepare for a possible pregnancy.
- Day 14: An egg is released from one of the ovaries in a process called ovulation. The egg travels down the oviduct toward the uterus.
- Day 28: If the egg isn’t fertilised, the uterus lining will break down again, and the cycle will restart.

Contraception refers to methods used to prevent pregnancy. Two common forms of contraception are:
- Condoms: Thin latex barriers worn on the penis during intercourse, preventing sperm from reaching the egg. They also help protect against sexually transmitted infections (STIs).
- The Pill: A daily tablet that contains hormones to stop ovulation, making it harder for a pregnancy to happen. While effective at preventing pregnancy, the pill does not protect against STIs.

Menstrual cycle: A monthly sequence of hormone-controlled changes in the female reproductive system.
Hormones: Chemical messengers that control the timing and events of the menstrual cycle.
Uterus lining: The inner layer of the uterus that thickens in preparation for pregnancy and is shed during menstruation.
Period (Menstruation): The shedding of the uterus lining, accompanied by bleeding, which occurs if an egg is not fertilised.
Ovulation: The release of an egg cell from one of the ovaries, usually around the middle of the menstrual cycle.
Contraception: Methods or devices used to prevent pregnancy.
Condoms: A barrier method of contraception worn on the penis that prevents sperm from entering the vagina and also helps protect against STIs.
The Pill: A daily tablet containing hormones that primarily works by stopping ovulation to prevent pregnancy.
STIs (Sexually Transmitted Infections): Infections that can be passed from person to person through sexual contact.

Research other methods of contraception beyond condoms and The Pill, explaining how each method works to prevent pregnancy.
Investigate the specific roles of the key hormones (FSH, LH, oestrogen, and progesterone) in controlling the different stages and events of the menstrual cycle.