KEY CONCEPT Physical development continues through adolescence and declines with age.

Birth occurs in three stages. Stage one of birth is the dilation of the cervix. contractions push cervix open if cervix dilates too little, C-section done STAGE 1 As regular, strong contractions occur, the cervix dilates and the baby turns.

Stage two is the emergence of the baby. baby usually born headfirst oxytocin stimulates milk production STAGE 2 The baby is pushed through the cervix and out of the vaginal canal.

Stage three is the expulsion of the placenta. placenta detaches from uterine wall contractions helps control bleeding STAGE 3 Contractions continue, expelling the placenta and helping to control bleeding.

Human growth and aging also occur in stages. Genetics, hormones, lifestyle, environment affect all stages. during infancy, growth is rapid during childhood, motor and language skills develop

Genetics, hormones, lifestyle, environment affect all stages. during puberty, sexually maturity begins during adolescence, growth is rapid and the brain rewired adulthood marks the peak of skills and independence

Aging is also affected by genetics, hormones, lifestyle, environment. Effects of aging can be reduced with good diet, exercise, and continued learning. Jerry Peel at age 1 1/2 Jerry Peel at age 17 Jerry Peel at age 71