This document discusses physical development from conception through adolescence. It notes that the principal changes occur during this period, with critical growth needed in muscles, bones and the nervous system during infancy in order to meet milestones like sitting and walking. The document also mentions the decrease in pressure in parts of the heart and lungs as blood is received.

19. Set priorities as in giving care.

23. ;
However the period in which the principal changes occur is from
conception to the end of adolescence.

27. For example: for an infant muscle, bones and
nervous system must grow to a certain point before the
infant is able to sit up or walk.

42. As the lungs receive blood, the pressure in the right atrium, right
ventricle and pulmonary artery decrease