VMBO Year 3 · Reproduction and sexuality · Section 2.3

Changes during puberty

Primary and secondary sexual characteristics

Primary sexual characteristics are reproductive structures already present at birth, such as the penis or vulva. During puberty, hormones cause further changes called secondary sexual characteristics. Typical examples include:

• A deeper voice, increased muscle mass and facial hair in boys.
• Breast development, wider hips and changes in body-fat distribution in girls.
• Different patterns in some intersex people, depending on their particular variation in sexual development.

The timing and extent of these changes vary between individuals.

The role of hormones

Hormones from the pituitary gland stimulate the testes and ovaries to produce more sex hormones. Testosterone contributes to changes such as a deeper voice and greater muscle mass. Oestrogens help bring about breast development and changes in the uterine lining. Sex hormones also regulate the menstrual cycle.

The menstrual cycle

The menstrual cycle starts on the first day of menstruation. Part of the uterine lining, together with blood, leaves the body through the vagina. A cycle is often described as 28 days, but its length varies, especially during the first years after menstruation begins.

From follicle to menstruation

In the first part of the cycle, a follicle develops in an ovary. At ovulation, the follicle opens and releases an egg. In a textbook 28-day cycle this happens around day 14, but the actual timing varies. The remaining follicle becomes the corpus luteum, which produces hormones maintaining the uterine lining. If pregnancy does not become established, the corpus luteum breaks down and hormone levels fall. The lining is shed and a new cycle begins.