Puberty
Puberty is the phase of sexual development by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads (the ovaries and testes). In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of brain, bones, muscle, skin, breasts, and reproductive organs.
The age at which puberty begins can vary widely between individuals and between populations. Age of puberty is affected by both genetic factors and by environmental factors such as nutritional state or social circumstances. Timing may also be affected by environmental factors (exogenous hormones and environmental substances with hormone-like effects) and there is even evidence that life experiences may play a role as well. On average, puberty is typically from around age 9 to 14 in girls and from around age 10 to 17 for boys.
Growth and change of body proportions
Growth accelerates in the first half of puberty and stops at the completion of puberty. Before puberty, body differences between boys and girls are almost entirely restricted to the genitalia. During puberty, major differences of size, shape, composition, and function develop in many body structures and systems. The most obvious of these are referred to as secondary sex characteristics (such as body and facial hair, stature, shoulder width, hip width, location of fat deposits, waist-to-hip ratio, muscle mass and strength, and voice).
Specific terms
- prepubescent - a child before puberty
- pubescent - a child during puberty
- postpubescent - a child/adult after puberty
- gonadarche - beginning of gonadal changes (testicular/ovarian growth)
- menarche - beginning of menstrual bleeding in females
- thelarche - beginning of breast development in females
- pubarche - beginning of pubic hair growth
Historical shift
The age at which puberty occurs has dropped significantly since the 1840s. Researchers refer to this drop as the 'secular trend'. From 1840 through 1950, in each decade there was a drop of four months in the average age of menarche among Western European female samples. In Norway, girls born in 1840 had their first menarche at average 17 years. In France in 1840 the average was 15.3 years. In England the 1840 average was 16.5 years for girls. In Japan the decline happened later and was then more rapid: from 1945 to 1975 in Japan there was a drop of 11 months per decade.
See also
- More information is available at [ Wikipedia:Puberty ]
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