*Explain and give examples of how physical development changes during conception, infancy, childhood, adolescence, and adulthood.
Physical growth in humans is an ongoing process that most of us are blessed to witness. The earliest stage of development seems to be the germinal period, the first two weeks of conception. During this period the embryo and the zygote have started to form. The embryonic period, also known as the prenatal period, follows two to eight weeks after conception. The respiratory and digestive systems form at this time also. The middle layer of cells, called the mesoderm, will become the circulatory system, bones, muscle, excretory system, and reproductive system. The outer layer of cells, the ectoderm, will become the nervous system, the sensory receptors (eyes, nose, ears), and skin. The placenta, the umbilical cord and the amnion (fluid-filled sac) develop along with the embryo. The final developmental stage during conception would be the fetal period. It begins two months after conception, lasting an average of seven months. Three months after conception the fetus becomes active, moving its arms and legs, opening and closing its mouth, and moving its head. The face, forehead, eyelids, nose, and chin are all distinguishable, as are the arms, hands and legs. At four months, a growth spurt occurs in the fetus' lower parts. By the end of the fifth month the toenails and fingernails have formed and the fetus is more active. By the end of the sixth month the eyes and eyelids have completely formed, a grasping reflex is present and irregular breathing occurs. (1)
Infancy has now come into effect. The cephalocaudal, the first growth pattern in infants, will make the infants head look enormous. During this spurt the head takes up a fourth of the body while the legs take up a third. (7) One of my sons is almost two years old. He is still in the "big head-little body" stage. His shirts scarcely fit over his head, but are just right for his...
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