Oestrogen & Progesterone
- During early development an embryo develops embryonic gonads that will either become ovaries in females or testes in males
- The factor that determines whether the embryonic gonads will develop into ovaries or testes is the presence or absence of a single gene known as the SRY gene
- The SRY gene is on the Y chromosome, so if the embryo has two X chromosomes the embryonic gonads will develop into ovaries
- This means testosterone will not be secreted by the developing embryo
- The two female hormones oestrogen and progesterone are present throughout pregnancy
- These hormones are secreted by the mother's ovaries and the placenta
- The absence of foetal testosterone and presence of maternal oestrogen and progesterone causes female reproductive organs to develop
- During female puberty, oestrogen and progesterone secretions increase.
- This leads to:
- The start of the menstrual cycle
- The development of female secondary sexual characteristics e.g. breast development
Secondary sexual characteristics of a human female