PUBERTY is the period of physical and hormonal development that prepares the body for reproduction.
In FEMALES: the pituitary gland releases FSH and LH → ovaries begin producing OESTROGEN.
Oestrogen causes female secondary sexual characteristics:
Breast development.
Widening of the pelvis.
Pubic and underarm hair growth.
Beginning of the menstrual cycle.
Growth spurt.
In MALES: the pituitary gland releases LH → testes begin producing TESTOSTERONE.
Testosterone causes male secondary sexual characteristics:
Enlargement of the penis and testes.
Voice breaking (larynx enlarges).
Facial, pubic and body hair growth.
Muscle mass increase.
Sperm production begins (spermatogenesis).
Growth spurt.
The Menstrual Cycle — Overview
The menstrual cycle is approximately 28 days long (varies between individuals).
It prepares the female reproductive system for potential pregnancy each month.
Day 1: MENSTRUATION begins — the uterus lining (endometrium) is shed as the lining breaks down.
Days 1–13: The uterus lining rebuilds and thickens — stimulated by oestrogen.
Day ~14: OVULATION — a mature egg is released from one of the ovaries.
Days 14–28: The uterus lining remains thick (prepared for implantation if fertilisation occurs) — maintained by progesterone.
If FERTILISATION occurs: the embryo implants in the uterus wall and pregnancy begins. Progesterone remains high.
If NO FERTILISATION: progesterone falls, the uterus lining breaks down → menstruation begins and the cycle repeats.
Hormones Controlling the Menstrual Cycle
Four hormones work together to control the menstrual cycle:
FSH (Follicle Stimulating Hormone) — from the PITUITARY GLAND:
Causes an egg inside a follicle to mature in the ovary.
Stimulates the ovaries to produce oestrogen.
OESTROGEN — from the OVARIES:
Repairs and thickens the uterus lining after menstruation.
At low levels: inhibits FSH production (prevents too many eggs maturing at once).
At HIGH levels (mid-cycle): triggers a surge in LH production.
LH (Luteinising Hormone) — from the PITUITARY GLAND:
The LH surge at approximately Day 14 triggers OVULATION — the egg is released from the follicle.
PROGESTERONE — from the CORPUS LUTEUM (the remains of the follicle after ovulation):
Maintains the thickened uterus lining during the second half of the cycle.
Inhibits FSH and LH production (negative feedback).
If no pregnancy: corpus luteum breaks down → progesterone falls → lining breaks down → menstruation begins.
⚠️ Common Mistake
FSH stimulates EGG MATURATION (not ovulation). LH triggers OVULATION. Oestrogen REBUILDS the uterus lining. Progesterone MAINTAINS the lining. The pituitary produces FSH and LH. The ovaries produce oestrogen and progesterone. Students often confuse which gland makes which hormone.
🎯 Matching Activity — Match the Reproductive Hormone
Match each hormone to its source and main function. — drag the symbols on the right to match the component names on the left.
FSH
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Oestrogen
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LH
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Progesterone
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Testosterone
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From testes — causes male secondary sexual characteristics and sperm production
From corpus luteum — maintains uterus lining in second half of cycle
From pituitary — causes egg to mature in follicle, stimulates oestrogen production
From ovaries — repairs uterus lining, triggers LH surge at high levels
From pituitary — surge at Day ~14 triggers ovulation
⭐ Higher Tier Only
The full hormonal control of the menstrual cycle: FSH (pituitary) → follicle development and oestrogen production. Low oestrogen → inhibits FSH (negative feedback). Rising oestrogen → triggers LH surge (positive feedback at high concentration). LH surge → ovulation at Day ~14. Corpus luteum → progesterone → maintains uterus lining, inhibits FSH and LH. No pregnancy → corpus luteum degenerates → progesterone falls → menstruation → FSH rises → new cycle.
🎯 Test Yourself
Question 1 of 3
1. Which hormone triggers ovulation?
2. What happens to progesterone levels if fertilisation does NOT occur?
3. What is the role of oestrogen in the menstrual cycle?
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