SEXUAL DEVELOPMENT © 2016 Paul Billiet ODWS
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
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
The SRY gene © 2016 Paul Billiet ODWS
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
THE HORMONAL CONTROL OF PUBERTY © 2016 Paul Billiet ODWS
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
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 11.5-12y 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