Physical Development in Infancy Questions What is neoteny?
Physical Development in Infancy Questions What is neoteny? What are the basic patterns of physical growth in infancy? How do genes and environment influence growth? What are the differences between individual and group growth curves? List some major milestones and range of age of acquisition What are some differences in the ordering of these
milestones Principles of Physical Development Directionality: follows several characteristic directions Cephalocaudal Cephalocaudal Cephalocaudal development
Principles of Physical Development Proximodistal: development from inside out Mass-to-specific: gross motor skills (large muscles) develops first followed by fine motor (small muscles) skills Principle of Hierarchical Integration: simple skills develop independently and are later integrated into more complex skills. Independence of Systems Principle of Independence of Systems
Infancy is a period of rapid, decelerating physical growth. Rapid, decelerating growth characterizes Head circumference Body length Weight Rapid, decelerating growth: Head circumference 6 mos.. 17
Birth 13.75 12 mos. 18 24 mos. 19 Head circumference An index of brain size but not necessarily meaningful for individuals concern below 3rd percentile or above 97th Can be used as a predictor of early outcome in
premature infants at birth and at one month or later corrected age Its staying the course that its important allowing for catch-up growth reach growth channel by 12 - 14 months Babies have big heads Newborn head is 25% of own body length Head length is 40% of mature length at birth Adult head is only ~15% of body length
Why? Why such large heads? Why such rapid, early growth in head size? Neonteny:Mickey has a baby face Flat with small nose and cheekbones Small lower jaw Big cranium and forehead
Neoteny: Holding on to infantlike characteristics Neoteny characterizes human body form Big heads and faces Large eyes Smaller muzzle Spine attached at base of skull Brain continues growth after birth Essential constraint in human evolution Neoteny characterizes human behavior
Late sexual reproduction Play and curiosity throughout life span Cultural flexibility Head growth allows brain growth Rapid, decelerating growth At birth, 1 lb. 15% of total body birthweight 25% of final (adults) brain weight At 6 months
50% of final (adults) brain weight At the same time - Myelinization Fatty sheaths develop and insulate neurons Dramatically speeding up neural conduction Allowing neural control of body General increase in first 3 years is likely related to speedier motor and cognitive functioning allowing activities like standing and walking Endangered by prenatal lead exposure
Infancy is a period of rapid, decelerating physical growth. Rapid, decelerating growth characterizes Head circumference Body length Weight Height and Weight Growth During the First Two Years Height 105 41.3
15 33.1 100 39.4 14 30.9
95 37.4 13 90 28.7 Boys
12 85 33.5 11 24.3 80
31.5 10 22.0 75 29.5 9
19.8 75 27.6 8 17.6 26.5
25.6 7 60 23.6 6 55
21.7 5 11.0 50 19.7 4
8.8 45 17.7 3 6.6 40
15.7 12 15 18 21 24 2 4.4 12 15 18 21 24 Girls 0
3 6 9 Age in Months Girls 15.4
13.2 0 3 6 9 Age in Months
Pounds 65 Kilograms 35.4 Boys Inches
Centimeters Weight Genes and environment Body size influenced by multiple genes each has a small effect some do not function until after birth when individual differences emerge Body size influenced by environment nutrition
uterus can also constrain or promote growth Genes and environment example Japanese-American infants Smaller than European-American infants genetics But larger than Japanese national infants dietary differences Higher socioeconomic status Taller, heavier kids who grow faster
Professional 3 year olds: 1/2 taller In England Historical increase in body size Mean height of schoolchildren increased by 0.70 cm per decade independent of race, sex, and age. decrease in short children (<10th percentile) Rapid, decelerating growth: Length
Birth length 20 add 10 by one year add 5 more by 2 years Two year height approximately 1/2 adult height B o y
s Rapid, decelerating growth: Weight Newborn girl (7.25 lbs.) Gain 1.3 pounds per month for the first 6 months 100% bigger Double birth weight Then 1 pound per month through 12 months
50% bigger Triple birth weight Then less than a half a pound per month through 36 months G i r l s
Group curves Large samples Many children at a given age (e.g., 3 months) Find median (50th %ile), %s e.g. at 17 months, only 5% < 75 cm. Longitudinal data may have been collected but at monthly intervals What does individual growth in length look like?
Common view Individual follows continuous growth curves Portrait of group is portrait of individual But parents report of growing by leaps and bounds growth spurts growing overnight were dismissed
One childs growth Saltatory growth Lampl measures length/height 3 samples of babies every two weeks, weekly, daily
same pattern in all groups re-measures for reliability Individual growth not a curve Growth jumps or spurts Growth occurs in spurts, jumps of almost a cm. (.9) separated by periods of no growth [stasis] of 2 to 15 days
Total growth is sum of spurts Longer stasis continues, more likelihood of a spurt but spurts aperiodic Saltatory growth is the rule prenatal
infant child adolescent Prenatal growth Postnatal growth Individual differences Practical consequences Fussiness and hunger during growth periods
Sleep patterns less before, more during? Growth in height and weight follows a very predictable trend unless there are extenuating factors, such as nutritional deficiencies, extreme stress, neglect, etc. Extreme neglect also affects brain development, as shown on right above. There is an interaction of biological factors and environmental factors in producing physical developmentfor example, effects of extremes on growth. Motor Development
Motor development influences and is influenced by other components of development Intelligence is dependent on sensorimotor activities, Piaget Institutionalized infants delayed motor skills Motor activities impact emotional development, fear of heights Motor development Overall patterns Individual differences
Individual development Norms versus Individual Differences Motor Milestones Pull self up to stand Lift head Remain sitting without assistance once up
Roll from stomach Birth 2 4 6
Pull up with assistance Push chest up with arms Walk well alone Walk holding on to furniture
8 10 12 Stand holding on to furniture Sit up without assistance
14 Walk backward Stand well alone 16 months Motor Development is Orderly Occurs in a specific sequence
Reflexive movements (First 3-4 months): involuntary, undirected movements Postural Reaction (approximately 2-3 months): the higher brain centers (cortex) begin functioning inhibits lower brain centers causes primitive reflexes to disappear coordinate movements of head, trunk and limbs so body can adjust its posture to environment Voluntary Motor Milestones Controlled by higher brain centers (cortex)
Overall Motor Milestones Individual differences WHO Motor Development Study: Windows of achievement for six gross motor development milestones. WHO MULTICENTRE GROWTH REFERENCE STUDY GROUP.Acta Pdiatrica, 2006; Suppl 450: 86/95 Individual variability in locomotion Bimodality http://www.youtube.co m/watch?v=bh_ABVxp BsQ
First Walk http://www.youtube.co m/watch?v=q0arqxWU 7R8 Thelen Stages in Infant Development and Feeding Birth through 6 months
Breast milk OR Iron-Fortified infant formula Breastfeeding Infant Reflexes Maternal Reflexes Breastfeeding
Colustrum Oxytocin The Advantages of Breastfeeding Advantages for Child (1) Protects against infectionless diarrhea (2) Enhances vaccine response (3) Reduced risk of otitis media and respiratory infections (4) Decreased risk of SIDS (5) Protection from allergies; less eczema (6) Higher IQs
(7) Less risk of childhood cancer, diabetes, etc. Breastfeeding Advantages for Mother (1) Delays fertility and menstruation (2) Reduces risk of breast cancer (Am J. of Epidemiology, 1986) Breast cancer could be reduced by up to 25% through breastfeeding. (3) Reduced risk of uterine, ovarian and endometrial cancers. (4) Greater emotional health (less anxiety; more mutuality) (5) Decreased osteoporosis (4 x greater in non-breastfeeders) (6) Promotes postpartum weight loss (especially in lower body fat) So, if the benefits of breastfeeding
outweigh formula, why arent all children breastfed? Inconvenient Some medications can be passed in breast milk Sleep patterns Exhaustion for mom Can be painful Social taboo Pumping Sleep Patterns
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