The importance of growth studies Can be evaluated in the light of proper understanding of concepts of human growth and interpretation of patterns of growth with the help of various growth curves. Growth refers to changes in size and dimension including differentiation and alterations in form that an organism undergoes with advancing age. Maturity or development is an increase in fun .tional ability. The three elements increases in size, differentiation of structure and alteration of form, together constitute not only growth but also development.
| Collectively, growth and development refer to a series of orderly and irreversible changes that every organism undergoes during its life span. A significant portion “of biological variation evident among adults in any population has its origin during the years of growth and maturation including the prenatal period. Thus, growth, maturation and development are the processes that lead to adulthood |
These processes are quite plastic and can be influenced by a variety of environmental factors like nutritional intake, diseases, pattern of physical activity and other environmental stresses which interact with the individual’s genetic potential for growth and maturation. Individuals not only vary considerably in size but also in tempo of growth i.e. the speed at which they reach maturity. The understanding of growth and its quantification at individual and population level requires the integration of data from a range of sources and the employment of a broad set of methods and techniques. We can measure growth using primarily anthropometric techniques and external dimensions of body such as height, weight, circumferencesand measures of subcutaneous fat. The study of growth and maturation involves the measurement and observation of the outcome of these processes e.g. .size attained, level of fatness, level of maturity or the extent to which an individual has progressed to adulthood. Growth curves plotted from the mean values provided in the tables of body dimensions are ordinarily presented by chronological age. In the construction of curves or tables, children are grouped into age categories, but there may be variation in methods of grouping children into age categories e.g. in earlier studies children labelled all 6 years were grouped between 5.50 – 6.49 years but in more recent years age groups are defined in terms of the whole year (i.e. 6.00-6.99 years) so the average age of the group is 6.5 years. Although age is often taken for granted, care must be taken in interpretation. Age is quite important in making comparisons among groups in evaluating the growth of individual children. e.g., if the two groups of 6 years old children described previously are compared, the taller (6.0 to 6.99 years) is on average about 0.5 years older than the former (5.50 -6.49 years) and would probably be taller and heavier. The method of growing children by age thus has implications for comparisons.
The amount of growth achieved obviously depends on the time for which growth proceeds and on the speed of growth per unit time. Measurements taken on a single individual atintervals can be plotted against time to produce a graph of progress whether they are derived from the whole body or from one of its component parts. A graph of this sort is called a “distance curve”, since any point on it iadicates the distance travelled along the road to maturity. The curve flattens out to a plateau as growth ceases. Another way of presenting the same data, is in which the increments of growth (the amounts added in specific time intervals) are plotted against time (Sinclair and Dangerfield, 1998). Such a curve shows the variation in the rate of growth with time, and is therefore known as a “velocity curve”. The curve tends to zero as ‘growth ceases. Most skeletal and muscular dimensions follow approximately the growth curve of height and weight, (general curve) so also do the dimensions of organs such as the liver, spleen and kidneys. However, there are other tissues and organs which have curves sufficiently different and therefore need elaborate description. These are the brain and skull, the reproductive organs, the lymphoid tissues and the subcutaneous fat. All these curves were first of all explained by Scammon and are known as Scammon’s curves. In this unit, you will be explained the concept and importance of Scammon’s growth curves i.e., distance and velocity curves with special reference to the interpretation of growth data of various bodily dimensions. You will also understand the Scammon’s growth curves of different tissues and organs which do not follow the general curve and exhibit characteristic growth curves. This knowledge will help you in understanding how different body dimensions, tissues and organs grow at any point . of time and how different individuals vary in their timing and rate of growth with respect to different dimensions, tissues and organs.