Infants, Children, and Adolescents (6th Edition)

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CHAPTER 5 PHYSICAL DEVELOPMENT in INFANCY and TODDLERHOOD I. BODY GROWTH A. Physical growth occurs rapidly during the first 2 years of life. The transition from infancy to toddlerhood-the period that spans the second year of life-is marked by the infant's switch from crawling to walking. B. Changes in Body Size 1. During the first 2 years, the body grows more rapidly than at any time after birth. 2. By the end of the first year the infant's length is 50 percent greater than it was at birth, and by 2 years of age it is 75 percent greater. 3. Birth weight has doubled by 5 months of age, tripled by I year, and quadrupled at 2 years. 4. Research indicates that these height and weight gains occur in little growth spurts. 5. In infancy, girls are slightly shorter and lighter than boys. C. Changes in Body Proportions 1. The cephalocaudal trend is an organized pattern of physical growth and motor control that proceeds from head to tail; growth of the head and chest occurs before that of the trunk and legs. 2. The proximodistal trend is a pattern of physical growth and motor control that proceeds from the center of the body outward; growth of the arms and legs occurs before that of the hands and feet. D. Changes in Muscle-Fat Makeup 1. Body fat, which helps the infant maintain a constant body temperature, increases after birth and peaks around 9 months of age. 2. Toddlers become more slender, a trend that continues into middle childhood. 3. Muscle tissue increases very slowly and does not peak until adolescence. 4. Girls have a higher ratio of fat to muscle than boys. E. Early Skeletal Growth 1. Current body size is not an accurate indication of physical maturity. 2. General Skeletal Growth a. The best way to estimate a child's physical maturity is to use skeletal age, a measure of the body's bone development. b. The epiphyses are the growth centers in the bones where new cartilage cells are produced and gradually harden. c. As growth continues, the epiphyses thin and disappear and no more growth of the bone is possible. d. Girls are considerably ahead of boys in skeletal age. 3. Growth of the Skull a. Because of the large increases in brain size, skull growth during the first 2 years is very rapid. b. At birth, the bones of the skull are separated by six gaps called fontanels. F. Appearance of Teeth
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1. An infant's first tooth usually appears between 4 to 6 months of age. By age 2, the child has 20 teeth. 2. A child who gets her teeth early is likely to be advanced in physical maturity. II. BRAIN DEVELOPMENT A. At birth, the brain is nearer to its adult size than any other physical structure. B. Development of Neurons 1. The human brain has 100 to 200 billion neurons-nerve cells that store and transmit information.
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