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The physical changes which take place at puberty in both sexes may be classified under the following headings: (1) Morphological . The rate of growth increases but this acceleration is greater in some dimensions than others so that the overall shape of the body changes, i.e. the rate of change in both size and shape alters. (2) Body composition . There are changes in the relative amounts of bone, muscle and fat. (3) Physiological . There are changes, particularly in the circulatory and respiratory systems, altering the ability to carry out prolonged muscular work. (4) Sex specific . The secondary sex characters develop and reproductive capacity is attained. (5) Endocrine . The above changes result from alterations in the quantities of various hormones released into the blood stream by the endocrine glands, especially the pituitary, the gonads (ovaries in female and testes in male), and the adrenal cortex. The endocrine changes must precede the morphological or other effects which they produce, but will be more readily understood if we examine their effects first.
W. A. Marshall (Thu,) studied this question.