1. SEXUAL DEVELOPMENT
© 2016 Paul Billiet ODWS

2. Female: the default sex
Syndrome
Klinefelter
Turner
Karyotype
47, XXY
45, X
General appearance
Male
Female
Genitals
Abnormally small, sterile testes
Rudimentary, sterile ovaries
Genital ducts
Female but poorly developed
2ndry sexual characteristics
Develop breasts, wide hips and shoulders
Little or no development
© 2016 Paul Billiet ODWS

3. Sex-determining Region Y
The SRY gene is found on the Y chromosome
The SRY codes for the testis determining factor
This protein activates genes involved in testes formation
Testes tissues secrete testosterone
Testosterone stimulates the development of the rest of male genital system.
© 2016 Paul Billiet ODWS

4. The SRY gene
© 2016 Paul Billiet ODWS

5. Development of the female embryo
If the SRY gene is not expressed the embryo becomes female
A different embryological pathway is taken
Development of the ovary then the uterus and fallopian tubes.
© 2016 Paul Billiet ODWS

6. THE HORMONAL CONTROL OF PUBERTY
© 2016 Paul Billiet ODWS

7. GIRLS BOYS Brain Pituitary Gland FSH LH Ovaries Oestrogens
e.g. Oestradiol
Brain
Pituitary Gland
FSH LH
Testes
Androgens
e.g. Testosterone
© 2016 Paul Billiet ODWS

8. GIRLS BOYS Oestrogens Androgens e.g. Oestradiol e.g. Testosterone
Secondary Sexual Characteristics
Appear from 10.5y
Breast growth
Fat distribution (hips, breasts)
Bone maturation (complete in 2y)
Pubic hair
Uterus growth
Secondary Sexual Characteristics
Appear from y
Axillary (arm pit) hair
Acne
Bone maturation
Beard growth & body hair
Pubic hair
Menarch, the first menstrual bleed at 12.5–13y
First ovulation 6-9 months after menarch
Spermarch, the first sperm produced about14y
Rise in progesterone levels
© 2016 Paul Billiet ODWS