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Adolescence I
By peace | February 15, 2006
The period of life between childhood and maturity is adolescence, which biologically extends from the age of 10 to the age of 19. The most important event in adolescence, as far as the girl and her mother are concerned, is the onset of menstruation, whihc may occur at any time between the ages of 10 and 16. The time of onset of menstruation is called the menarche. For some reason, which may be concerned with better nutrition, the age of the onset of menstruation ahs become earlier.
The menarche is only the culminating change in a sequence of events which change the girl into a young woman. These changes are due to a series of interactions between several glands in the body. The controlling gland is a special part of the brain called the hypothalamus, which, working with the pituitary gland, controls the subsequent events. For reasons which are not clear, the hypothalamus begins to secrete substances called releasing hormones about four years before the menarche.
The releasing hormones pass down the blood vessels connecting the hypothalamus to the pituitary, where they cause the release of several hormones. One of these hormones is the growth hormone which causes the spurt of growth that precedes the menarche. The girl begins to grow about four years before the menarche, and the rate of growth is greatest in the first two years, slowing down as the menarche approaches.
About the age of 12, another releasing hormone, the gonadotrophin releasing hormone (GnRH) begins to be secreted by the pituitary gland in surges which occur every 90 minutes. These surges of GnRH have a profuound effect on the girl’s sexual maturity. The hormone reaches the pituitary gland where it causes certain specialized cells to produce two hormones which act on the girl’s ovaries.
The average age at which various changes occur:
age 9-10 : The bony pelvis begins to grow and to attain a female shape. Fat begins to be deposited, commencing the changes in shape to that of a woman. The nipples bud.
age 10-11 : The nipples increase in size. Hair begins to appear over the pubis.
age 11-13 : The area beneath the nipples develops. The internal and external genitals grow and develop. The vaginal wall thickens, and vaginal secretions may appear.
age 12-14 : The breasts develop further, and the nipples become darker in colour.
age 13-15 : Hair increases over the pubis, and appears in the armpits. Acne appears on the face of about half the girls. The menarche occurs, but the first few periods occur at irregular intervals.
age 15-17 : Increased fatty deposition occurs on the hips and the breasts. The periods become more regular.
age 16-18 : Growth of the skeleton ceases. The girl has now reached her maximum height.
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