Growth and Development PDF

Course Learning Outcome 3. Describe human growth and development including, developmental stages, growth in height and weight, velocity curves, bone mineral content, body proportions, puberty, sexual and ethnic differences, assessments of maturity, and influences affecting growth. (I) (LE, IC) Lea...

Course Learning Outcome 3. Describe human growth and development including, developmental stages, growth in height and weight, velocity curves, bone mineral content, body proportions, puberty, sexual and ethnic differences, assessments of maturity, and influences affecting growth. (I) (LE, IC) Learning Goals Develop a foundational knowledge of human growth and development including terminology, scientific methodology, influences and practical implications. Learning Outcomes - Define growth and describe why monitoring and studying growth and development is important. - Name and describe the stages of postnatal growth. - Define and differentiate between distance and velocity curves, longitudinal and cross- sectional data. - Sketch a typical velocity curve for growth in height for both males and females. Use the information in these curves to describe how males on average are taller. - Sketch a typical velocity curve for growth in weight for both males and females. - Describe the changes in human shape, including a definition of menarche. - Name and describe each of the indices of maturity. - Discuss the impacts that rates of maturity may have on sport performance, competition and development. - Discuss the factors that influence growth and maturation, including how the average height of Canadians has changed during the last century. I. Nature of Growth II. Stages of Postnatal Growth III. Growth in Height and Weight IV. Changes in Body Proportions and Composition. V. Indices of Maturity VI. Early and Late Maturing Children VII. Factors Influencing Growth and Maturation  I. Nature of Growth Growth - "the progressive development of a living being or part of an organism from its earliest stage to maturity, including the attendant increases in size". British Medical Dictionary (1961) Monitoring growth and development can help identify and diagnose problems in those who are not developing typically Studying growth and development can help create developmentally appropriate movement curricula and programming  I. Nature of Growth Growth involves a series of changes not just the addition of material to achieve an increase in size. These changes involve a differentiation of the various parts of the body to perform distinct functions. Human embryo 6 weeks old Human embryo 6 weeks old 10 days old Adult  I. Nature of Growth Not all parts of the human body grow at the same rate, nor do they all stop growing simultaneously. The body does not retain the same proportions throughout growth and the relative weights of given tissues and organs do not remain constant..  I. Nature of Growth For example, the brain at birth is about 24% of its adult weight, whereas the neonatal body is only about 6% of its adult weight.  I. Nature of Growth Extremely rapid growth of the brain continues, reaching 90% of its adult weight at 5 years old, whereas body weight is only 25% of adult weight.  I. Nature of Growth The reproductive organs remain at less than 10% of their final weight until the onset of puberty.  II. Stages of Postnatal Growth 5. Adulthood 4. Adolescence 3. Childhood 2. Infancy 1. Neonatal Period nursingcrib.com II. Stages of Postnatal Growth 1. Neonatal Period - extends from birth to the end of four weeks. 2. Infancy - extends from the end of the neonatal period at four weeks until two years of age. Infancy is characterized by tremendous growth, increased coordination, and mental development.  II. Stages of Postnatal Growth 3. Childhood - the period of growth and development extending from infancy (2 years) to adolescence, at which time puberty begins. - The chronological duration of childhood varies because puberty begins at different ages for different people. - Childhood years are a period of relatively steady growth until preadolescence when there is a growth spurt.  II. Stages of Postnatal Growth 4. Adolescence - the period of growth and development between childhood and adulthood. It begins around the age of nine in girls and the age of eleven years in boys. The end of adolescence is approximately 17-18 years, but it is not clearly delineated. In Latin, adolescere meaning "to grow up” II. Stages of Postnatal Growth 5. Adulthood - the period of life beyond adolescence. An adult has reached maximum physical stature as determined by genetic, nutritional, and environmental factors. III. Growth In Height and Weight A. Growth Curves B. Growth in Height C. Growth in Weight D. Bone Mineral Content in Adolescence as Related to Osteoporosis in the Elderly  A. Growth Curves Distance curve Height vs. time measurements taken at intervals are plotted against time to produce a graph of progress. Velocity curve Change in Height / year vs. time increments in growth are plotted against time to show the variation in the rate of growth with time. A. Growth Curves Data for Growth Curves collected in two ways – Longitudinal data – Cross-sectional data Longitudinal data - growth curve is derived from a single individual or from repeated measurements on the same group of individuals over a period of many years. A. Growth Curves Cross-sectional data - measurements are made of several children in each age group these are then combined to form a cross-sectional picture of the various age groups in the community at the time of the investigation.  B. Growth In Height If measurements from several children are combined on the same graph, the adolescent spurt is smoothed out and becomes less dramatic because the spurt occurs at different times in different children. longitudinal cross sectional B. Growth In Height From birth to maturity, the most important difference between boys and girls is in the rate of maturity.  B. Growth In Height Girls grow up faster than boys – Girls reach 50 percent of their adult height at an earlier age (1.75 vs. 2.0 years), enter puberty earlier, and cease growing earlier – Half way through the fetal period, the skeleton is already three weeks more advanced in girls; – at birth, the difference is four to six weeks of maturation; – at puberty, the difference is two years.  B. Growth In Height Before the adolescent growth spurt, there is little difference between the average height of boys and girls. The mean growth takeoff age (ie,the onset of growth acceleration) in children in North America growing at an average rate is approximately 9 ± 1 year in girls 11 ± 1.5 years in boys Because the spurt begins earlier in girls, there is an age (~ 9-10 years) at which girls become taller and heavier than boys of the same age. The age at growth takeoff correlates highly with pubertal stage. B. Growth In Height During the spurt, boys gain about 20 cm. in height while girls gain about 16 cm. in height. mostly growth of the trunk Peak height velocity in boys ~ 13.5 years Peak height velocity in girls ~ 11.5 years  B. Growth In Height Since the peak height velocity may occur as much as two years earlier or later than the average within each sex, a six year difference in the event between an early maturing girl and a late maturing boy is quite possible. – PHV in Girls 11.5 ± 2 yrs Earliest 9.5 yrs; Latest 13.5 yrs – PHV in Boys 13.5 ± 2 yrs Earliest 11.5 yrs; Latest 15.5 yrs The conclusion of the growth spurt is followed by a rapid slowing of growth. B. Growth In Height In USA cross-sectional studies, boys with a mean takeoff age of 11 years reached their final heights by 17-18 years of age, and girls with a mean takeoff age of 9 years reached their final heights by 14-15 years of age. However, there is a wide variation around these means - plus or minus two years. B. Growth In Height Boys end up being taller than girls because they have two more years of growth before the growth spurt. During these two extra years of prepubertal growth in boys, the legs are growing relatively faster than the trunk. – Thus the average male has relatively longer legs than the average female. Peak growth rate also a bit higher on average C. Growth In Weight Weight of ovum (0.005 mg) -> birth - 3 X 109 fold increase Birth (~7.5 lb.) ---> maturity (20 years) - 20 fold increase Birth ---> 2 years - 4 fold increase then steady increase of 2 - 3 kg/yr until growth spurt. C. Growth In Weight During the growth spurt, boys may add 20 kg. to their weight, and girls 16 kg. The peak velocity for the spurt in weight lags behind the peak velocity for height by about 3 months - child shoots up and fills out later. BMI BMI D. Bone Mineral Content in Adolescence as Related to Osteoporosis in the Elderly Osteoporosis – a condition of the bones where they become thin and brittle due to decreased mineral content, which makes them susceptible to fracture. D. Bone Mineral Content in Adolescence as Related to Osteoporosis in the Elderly For all bone sites in both boys and girls, peak velocity in bone mineral content occurs approximately one year after peak height velocity. This suggests that there could be a transient period of relatively long bone weakening during the adolescent growth spurt, resulting in an increased fracture risk following peak height velocity. Requires adequate calcium and vitamin D D. Bone Mineral Content in Adolescence as Related to Osteoporosis in the Elderly As much bone mineral will be laid down during the four adolescent years surrounding peak height velocity as most people lose mineralization during all of adult life. Peak bone mineral density of the lumbar spine and hip is achieved in the early to late twenties Anatomy and Physiology: OpenStax I. Nature of Growth II. Stages of Postnatal Growth III. Growth in Height and Weight IV. Changes in Body Proportions and Composition. V. Indices of Maturity VI. Early and Late Maturing Children VII. Factors Influencing Growth and Maturation IV Changes in Body Proportions and Composition The relationship between one part and another of the growing body is not a consistent one, but changes with age. A. Shape of the Infant B. Changes in Shape With Growth C. Puberty - Males vs. Females A. Shape of the Infant Large head - ratio of head height to total height equals 1:4 in the infant, 1:7.5 in the adult. Lower limbs are much less well developed at birth than upper limbs - ratio of leg length to total height equals 1:3 in infant, 1:2 in adult. B. Changes in Shape With Growth At all ages the dimensions of the head are in advance of those of the trunk, and at all ages more peripheral parts of the limbs are in advance of the more central parts – foot --> calf--> thigh. In the later stages of the adolescent spurt, there is laterality of growth rather than linearity. B. Changes in Shape With Growth The bones of the face grow faster than those of the cranial vault - "at adolescence the face emerges from underneath the skull". C. Puberty - Males vs. Females Puberty - refers to the period at which the testes, prostate gland, and seminal vesicles or the breasts, uterus and vagina, suddenly enlarge. This is the time of greatest sex differentiation since the early intra- uterine months – sexual dimorphism.  C. Puberty - Males vs. Females There are changes in reproductive organs and secondary sex characteristics, in body size and shape, and in relative proportions of muscle, fat, and bone. __ C. Puberty - Males vs. Females Menarche - refers to the onset of menstruation. It occurs relatively late in puberty. The average age of occurrence in North America is 12.2-13 years – There is a standard deviation of plus or minus one year. The 95 percent range is 11.0 - 15.0 years.  C. Puberty - Males vs. Females Menstruation begins when the height velocity is falling The development of mature ova follows menarche by as much as two years; puberty is not complete in females until sexual maturity has been attained.  V. Indices of Maturity It is important to be able to assess how far an individual child has progressed towards maturity. The chronological age of a child is an unreliable guide since children mature at very different rates and measurements of height and weight are only partially useful. A. Radiological (Skeletal) Age B. Dental Age C. Growth Curves D. Sexual Age E. Neural Age  A. Radiological (Skeletal) Age During growth, every bone goes through a series of changes which can be recorded radiographically. The times of appearance of primary and secondary centers of ossification can be observed and the progressive enlargement of the ossified portion of an epiphysis can be followed in detail. The wrist and hand are most commonly used for this purpose because, in this region, there is a large number of centers of ossification. At every chronological age up to full maturity, the radiological age of girls is in advance of that of boys by a factor of about 20 percent or more. 3 year old 5 year old 14 year old B. Dental Age The deciduous dentition erupts from six months to two years of age and can be used during that period. The permanent dentition provides a measure from six to 13 years of age. However, skeletal maturity and dental maturity are not closely related in the individual. C. Growth Curves The timing of the peak height velocity and the peak weight velocity are useful maturity indicators. D. Sexual Age The secondary sex characteristics can be used as a method of rating maturational development. Ratings can be made of stages in pubic hair development, stages in breast development, and stages of genital development. These indicators have limited applicability over the growth span, in contrast to skeletal maturation, which can be monitored from infancy into young adulthood.  D. Sexual Age The “Tanner” stages of sexual maturity were developed in 1962 and are used as the universal standard for classifying sexual maturity. Stages I through V for Female Breast development, Male Testes and scrotum development and; Female/Male pubic hair development Stage I (P1) - prepubertal, lanugo may be present in genital area but it is fine and downy Stage II (P2) - sparse growth of pubic hair in the midline, mainly at the base of the penis or along the labia majora Stage III (P3) - more hair grows so that it is visible from several feet, along with coarsening and increased pigmentation in some people Stage IV (P4) - hair now makes a triangle over the pubis Stage V (P5) - adult; hair is outside of triangle, extending up the abdomen and down the thighs D. Sexual Age The age at which menarche occurs is an important indicator of maturation status in females. Menarche is more closely related to radiological age(12 - 14.5 years) than to chronological age (10 - 16 years). E. Neural Age In spite of the large size of the central nervous system at birth, much of it is incompletely functional and requires considerable time to develop to the stage at which it can be fully utilized. Girls are ahead of boys throughout the phase of motor and sensory development – on the average, girls learn to – walk earlier – control their bladders earlier – are ahead in the use and understanding of speech. – They are also first in the development of skills which need fine movements and coordination, such as tying shoes. VI. Early and Late Maturing Children Five types of skeletal development have been recognized. (1) Average maturation and adult height (2) Early maturation - tall in childhood but not as adults (3) Early maturation and genetically tall (4) Late maturation - small in childhood, average as adults (5) Late maturation and genetically short VI. Early and Late Maturing Children There is good evidence that, in European and North American school systems, children who are physically advanced towards maturity score, on average, slightly higher on most tests of mental ability than children of the same age who are less physically mature. It is very likely that mental and psychological development are much more closely related with radiological age than with chronological age.  VI. Early and Late Maturing Children Boys with muscle dominant physiques, tend to mature earlier than others and have an early adolescent growth spurt. Late maturing boys are greatly handicapped in competition with early maturing boys. Late maturing boys may be deselected from age-class sports early Early maturing boys may develop unrealistic expectations and have difficulty adjusting to their loss of sports advantage when their late maturing peers catch up. VIII. Factors Influencing Growth and Maturation A. Genetic Control B. Nutrition C. Secular Trends D. Season and Climate E. Differences between Races A. Genetic Control Both genetic and environmental factors influence growth, and the progress of any given child is the result of a complex interaction of many different factors. Studies of twins have shown that body shape and size, deposition of fat, and patterns of growth are all more closely related to nature (genetics) than to nurture (environment). Heredity affects not only the end result of growth, but also the rate of progress toward it. B. Nutrition Malnutrition delays growth. Children subjected to an episode of acute starvation recover more or less completely provided that the adverse conditions are not too severe and do not last too long. Adult size is affected by a less severe level of under-nutrition than adult body proportion (ie) leg length versus trunk length, etc. C. Secular Trends Between 1880 and 1950, the average height of American and West European children between the ages of five and seven years increased by more than 1 cm / decade for a total of more than 10 cm. Children are now growing faster and stopping growing earlier. There has been an upward trend in adult height of one centimeter per decade since 1880. The causes of these trends are probably multiple – better nutrition, lessening of disease, some degree of dominance of height genes? CBC News - Canadians still getting taller, but not as fast as others July 26, 2016 D. Season and Climate Studies done on West European children indicate that season of the year may exert a considerable influence on velocity of growth. The children grew faster in height in spring and summer than in autumn and winter. Weight gain was faster in the autumn than in the spring. E. Differences Between Races Populations differ slightly in their average – Adult size – Tempo of growth – Body Proportions (limb vs torso length, shoulder to hip width ) Tempo of growth - Asiatic and African children are slightly ahead, on average, of European children in skeletal age, dental maturity and age of menarche. A research study involving 4,131 American boys, reported in the November 2012 issue of “Pediatrics”, indicated that the average African American boy is one year ahead in pubertal development compared to the average Caucasian boy. This knowledge may be important to consider when monitoring a child for developmental disorders. CBC News - Canadians still getting taller, but not as fast as others July 26, 2016