KNSS 307 physical growth maturation and aging
prenatal development
Early development is controlled by genes.
Normal development
Inherited abnormal development
The embryo or fetus is sensitive to extrinsic factors.
Positive effects
Negative effects
embyonic development
Conception to 8 weeks
Differentiation of cells to form specific tissues and
organs
Limbs formed at 4 weeks
Human form noticeable at 8 weeks
Fetal Development
8 weeks to birth
Continued growth by hyperplasia (cell number) and hypertrophy (cell size)
Cephalocaudal (head to toe) and proximodistal (near to far)
Plasticity (capability of taking on a new function)
complications in prenatal
- Oxygen and nutrients diffuse between fetal and maternal blood in the placenta.
- Poor maternal health status can affect the fetus.
- The source of abnormal development can be genetic
or external.
- Congenital defects (present at birth) can derive from a genetic or external source.
GENETIC CAUSES OF ABNORMAL
DEVELOPMENT
Can be caused by dominant disorders (defective gene from one parent) or recessive disorders (defective gene from each parent).
Can result from mutation of a gene.
Effects on growth and maturation are variable.
external causes of abnormal development
- External factors can affect the fetus through nourishment or physical environment.
- Teratogens delivered through the nourishment system act as malformation-producing agents.
- Some teratogenic effects result from too much of a substance, some from too little
-The placenta screens some substances (e.g., large viruses) but not all harmful ones.
- Harmful environmental factors include pressure, temperature, X rays and gamma rays, oxygen-
deficient atmospheres, pollutants.
- Tissues undergoing rapid development at time of exposure are most vulnerable.
postnatal development
- Overall growth follows a sigmoid (S-shaped) pattern.
- The timing of spurts and steady periods can vary among individuals.
- Timing differs between the sexes.
weight
- Weight follows a sigmoid pattern.
- It is susceptible to extrinsic factors, especially dietand exercise.
- People grow up and then fill out. Peak weight velocity follows peak height velocity (by 2.5–5 months in boys, 3.5–10.5 months in girls).
height
Height follows a sigmoid pattern.
Girls
Peak height velocity occurs at 11.5 to 12 years.
Growth in height tapers off around 14, ends around 16. Boys
Peak height velocity occurs at 13.5 to 14 years.
Growth in height tapers off around 17, ends around 18.
The long growth period of males contributes to
absolute height differences.
assesment of extent and rate postnatal growth
-Distance curves show extent of growth.
-Velocity curves show rate of growth.
-Peaks on velocity curves show ages at which rate of growth changes from faster to slower.
relative growth
- The body as a whole follows a sigmoid pattern; specific parts, tissues, and organs have different
growth rates.
- Body proportions change from head-heavy, short- legged form at birth to adult proportions.
- In adolescence, boys increase in shoulder breadth.
physiological maturation
As children and youth become older, they grow in
size and mature.
Children vary in maturation rate.
It is difficult to infer maturity from age alone, size alone, or age and size
together.
Secondary sex characteristics
Characteristics appear as a function of maturation.
They appear at a younger age in early maturers.
extrinsic influences on postnatal growth
Individuals are especially sensitive during periods of rapid growth.
Catch-up growth demonstrates extrinsic influences.
Adulthood and aging
Height is stable in adulthood but may decrease in older adulthood.
Compression of cartilage pads
Osteoporosis
The average adult starts gaining weight in the 20s.
Diet and exercise
Consider loss of muscle mass (see following graph)