At puberty testosterone and oestrogen bring about the changes that make the body able to reproduce. In females a monthly cycle then repeats: an egg matures and is released while the lining of the uterus is built up and, if no embryo arrives, broken down. Where the hormones are made and how FSH, LH, oestrogen and progesterone control the cycle and pregnancy are Extended content.
Testosterone (from the testes) and oestrogen (from the ovaries) cause the development of secondary sexual characteristics at puberty. In the menstrual cycle, of about 28 days, the uterus lining breaks down (menstruation), then repairs and thickens while an egg matures in a follicle; the egg is released at ovulation, about day 14, and the lining is kept thick ready for an embryo. Extended: FSH and LH come from the pituitary gland; oestrogen is made by the ovary (follicle), progesterone by the corpus luteum and, in pregnancy, by the placenta.
In the reproductive systems tab, switch between female and male and read the puberty box under the parts list.
| Testosterone (males) | Oestrogen (females) | |
|---|---|---|
| Made in | testes | ovaries |
| Secondary sexual characteristics | voice deepens; facial, pubic and body hair grows; muscles develop; testes and penis grow; sperm production starts | breasts develop; hips widen; pubic and underarm hair grows; menstrual cycle starts |
Secondary sexual characteristics develop at puberty. They are not the reproductive organs themselves, which are present from birth (primary sexual characteristics).
Drag the day slider (or the day line on the graph) from day 1 to 28, or press Play. Watch the follicle and corpus luteum in the ovary and the thickness of the uterus lining.
| Days (approx.) | In the ovary | In the uterus lining |
|---|---|---|
| 1 to 5 | a new follicle starts to develop | menstruation: the lining breaks down and is lost with some blood through the vagina |
| 6 to 13 | an egg matures inside a follicle | lining repairs and thickens |
| about 14 | ovulation: the egg is released into the oviduct | lining thick |
| 15 to 28 | the empty follicle becomes the corpus luteum, which later breaks down if there is no pregnancy | lining kept thick, ready for an embryo; if none implants it starts to break down |
Four quick checks. Each correct answer earns XP and records this skill on your profile.
In the reproductive systems tab, which hormone does the puberty box say causes the voice to deepen?
In the menstrual cycle tab, what happens to the uterus lining on days 1 to 5?
On about which day does the sim show ovulation?
Extended: with Pregnancy ticked, what happens to the progesterone level after day 21?
Extended. Four hormones control the cycle. Go back to the menstrual cycle tab, watch the hormone graph, then tick Pregnancy to see what changes when an embryo implants.
| Hormone | Made by | Role |
|---|---|---|
| FSH | pituitary gland | stimulates a follicle (and its egg) to develop in the ovary, and the follicle to secrete oestrogen |
| Oestrogen | ovary (the developing follicle) | makes the uterus lining repair and thicken; a high level triggers the LH surge |
| LH | pituitary gland | a surge triggers ovulation and the change of the follicle into the corpus luteum |
| Progesterone | corpus luteum; in pregnancy, the placenta | maintains the thick uterus lining; with oestrogen, stops FSH and LH being released |
FSH and LH come from the pituitary gland, not the ovary. Oestrogen and progesterone come from the ovary (follicle and corpus luteum), and later in pregnancy from the placenta.
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Which is a secondary sexual characteristic caused by oestrogen?
Extended: where is progesterone produced during the second half of a menstrual cycle?
Extended: which hormone triggers ovulation?
Extended: why does menstruation not occur during pregnancy?
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