The major physiologic problems of the child beyond the neonatal period are related to special metabolic needs for growth, which have been fully covered in the sections of this book on metabolism and endocrinology.
Figure 83-8 shows the changes in heights of boys and girls from the time of birth until the age of 20 years. Note especially that these parallel each other almost exactly until the end of the first decade of life. Between the ages of 11 and 13 years, the female estrogens begin to be formed and cause rapid growth in height but early uniting of the epiphyses of the long bones at about the 14th to 16th year of life, so that growth in height then ceases. This contrasts with the effect of testosterone in the male, which causes extra growth at a slightly later age—mainly between ages 13 and 17 years. The male, however, undergoes much more prolonged growth because of much delayed uniting of the epiphyses, so that his final height is considerably greater than that of the female.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.