Transcript Maturation PowerPoint

Prenatal Development
 Nerve growth begins
when a sheet of cells on
the back of the embryo
folds in the middle to
form the future spinal
cord. At one end, the
tube enlarges to form the
brain’s major sections.
Prenatal Development
Fetal Development
 First responses are reflexes.
 Touch develops early, as early as 7-1/2 weeks.
 By 15 weeks, fetus can grasp, frown, squint, grimace.
 At 20 weeks nerve-cell production slows, existing cells
grow larger and make more complex connections. Taste
and smell formed.
 Around 24 weeks fetus can feel movement and may
respond to sound.
Final Stages of Fetal
Development
 Age of viability – About 25 weeks, if
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born about 50% chance of survival.
25 weeks – nerve supply to ear
complete
26 weeks – response to touch
27 weeks – response to light
29 weeks – eyes open in womb
32 weeks – start of ‘awareness’ neural
circuits advanced as a newborn’s
35 weeks – fetus begins to develop
daily activity cycles
Birth rate: # of live births per 1000 people
Infant Mortality: # of infant deaths under 1 year of age per 1000 live
births
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Birth Rate
U.S.
14
Afghanistan
47
Australia
12
Canada
10
China
13
Iraq
32.5
Japan
9.5
Infant Mortality
6.37
163.0
4.57
4.63
24.2
50.3
2.8
Some Principles of Development
 Rules of Maturation
 Follows an orderly sequence
 Rate is not uniform
 Follows physiological gradients
 Cephalocaudal
 250,000 neurons per min.
 60% adult size at birth
 Proximodistal
 Principle of motor primacy – neuromuscular structures of
the body must reach certain levels of maturation before
they can respond to stimulation