Growth curve : A growth curve is an empirical model of the evolution of a quantity over time. Growth curves are typically displayed on a set of axes where the x-axis is time and the y-axis quantifies the phenomenon in question.
In developmental biology, growth curve is a graphical representation which reveals growth pattern of different parts and tissues of the body during different phases of life. It is explained below :
General body growth : It is rapid during the fetal life, first one or two years of postnatal life and also during puberty. In the intervening years of mid-childhood, somatic growth velocity is relatively slowed down. The classic growth curve, is divided into four phases, in order of their appearance: (1) lag phase; (2) log (logarithmic), or exponential, phase; (3) stationary phase; and (4) death, or decline, phase.
Brain growth : Brain enlarges rapidly during the later months of fetal life and early months of post natal life. Head reaches 90 parent of the adult head size by the age of two years.
Growth of gonads : Gonadal growth is dormant during childhood. It becomes conspicuous during puberty.
Lymphoid growth : It is most notable during mid-childhood. Children between 4 and 8 years of age often have hypertrophied tonsils and large lymph nodes. It reaches its maximum amount before adolescence and during adult phase. It regresses to some extent probably due to influence of sex hormones.
Growth of subcutaneous fat : Subcutaneous fat begins to be laid down in the fetus at about 34 weeks until about 9 months of fetal life after which it decreases until age of 7 years, when it begins to increase once again. The decrease is less in girls than boys, so that at the age of 7 years, girls come to have more fat than boys.The increase from age of 7 years occurs in both sexes in both limbs fat and body fat. At adolescence however, the limb-fat in boys decreases and is not gained back until the age of about 20 years. In girls there is a slight halting of the limb fat increase, but no loss and the trunk-fat shows steady rise.