journal

PHYSICAL DEVELOPMENT In

INFANCY and TODDLERHOOD

BODY GROWTH

• During the first 2 years, the body grows more rapidly than at any time after birth.

• 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.

• Birth weight has doubled by 5 months of age, tripled by 1 year, and quadrupled at 2 years.

BODY GROWTH

• Research indicates that these height and weight gains occur in little growth spurts.

• In infancy, girls are slightly shorter and lighter than boys. Ethnic differences in body size are apparent as well.

Changes in Muscle-Fat Makeup

• Body fat, which helps the infant maintain a constant body temperature, increases after birth and peaks around 9 months of age.

• Toddlers become more slender, a trend that continues into middle childhood.

Changes in Muscle-Fat Makeup

• Muscle tissue increases very slowly and does not peak until adolescence.

• Girls have a higher ratio of fat to muscle than boys.

Skeletal Growth

• Children of the same age differ in rate of physical growth.

• Current body size is not

an accurate indication of

physical maturity.

Upper Growth plate

Bone Shaft

Lower Growth plate

X-ray of a baby’s hand at18 months and comparing it

to the x-ray of an adult. Notice the spaces where

cartilage has not turn into bone and the bones

Growth of the Skull

• Because of the large increases in brain size, skull growth during the first 2 years is especially rapid.

• At birth, the bones of the skull are separated by six gaps called fontanels.

Growth of the Skull

Appearance of Teeth

• An infant’s first tooth usually appears between 4 to 6 months of age. By age 2, the average child has 20 teeth.

• A child who gets her teeth early is likely to be advanced in physical maturity.

• 65 percent of teething infants show no symptoms. – How often do infants find teething difficult and painful?

– If infants experience a difficult time teething parents usually know by the following: • Changes in eating and sleeping routines

• A low grade temperature

• Drooling to an excess

• Biting on things

BRAIN DEVELOPMENT

• The brain

continues to develop

at an astounding pace

during infancy and

toddlerhood.

Development of the Cerebral Cortex • The cerebral cortex is the largest structure of the human brain

and accounts for 85 percent of its weight.

• It contains the greatest number of neurons and synapses, and it is the last of the brain structures to stop growing.

Development of Neurons

• The human brain has 100 to 200 billion neurons- nerve cells that store and transmit information.

• Synapses are tiny gaps between neurons where fibers from different neurons come close together but do not touch.

• Neurons release chemicals that cross the synapse, thereby sending messages to one another.

Know the parts of the neuron

Development of Neurons

• Neurons that are stimulated by input from the surrounding environment continue to establish new synapses

• Myelinization is a process in which neural fibers are

coated with an insulating fatty sheath (myelin) that improves the efficiency of message transfer.

• Glial cells make up about half of the brain’s volume and

do not carry messages; their most important function is myelinization.

Changing States of Arousal

• During the first 2 years, the organization of sleep and wakefulness changes and fussiness and crying also decline. • Over time, infants remain awake for longer daytime

periods and need fewer naps. • Although brain maturation is largely responsible for

changes in sleep and wakefulness, the social environment also contributes. By the middle of the first year, melatonin secretion in the brain is greater at night.

Changing States of Arousal

• The practice of isolating infants to promote sleep is rare outside of the United States and other Western nations.

• Even after infants sleep through the night, they continue to wake occasionally for the next few years.

Operant Conditioning

Berk, L. E., (2016). Infants, Children, and Adolescents.

Boston, MA: Pearson. EIGHTH EDITION