Adjustments of the Infant at Birth

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Adjustments of the Infant at Birth Chase Carr Biology 333 Human Anatomy and Physiology Dr. Mian Ashraf February 12, 2012 ABSTRACT During pregnancy, the embryo is totally dependent on the mother for its existence. The mother supplies the fetus with oxygen and nutrients, eliminates its carbon dioxide and other wastes, protects it against shocks and temperature changes, and provides antibodies that confer protection against certain harmful microbes. At birth, physiologically mature baby becomes much more self-supporting, and the newborns body systems must make various adjustments. The most dramatic changes occur in the respiratory and cardiovascular systems. The reason that the fetus depends entirely on the mother for obtaining oxygen and eliminating carbon dioxide is that the fetal lungs are either collapsed or partially filled with amniotic fluid. The production of surfactant begins by the end of the sixth month of development. Because the respiratory system is fairly well developed at least two months before birth, premature babies delivered at seven months are able to breathe and cry. After delivery, the baby’s supply of oxygen from the mother ceases, and any amniotic fluid in the fetal lungs is absorbed. Because carbon dioxide is no longer being removed, it builds up in the blood. A rising carbon dioxide level stimulates the respiratory center in the medulla oblongata, causing the respiratory muscles to contract, and the baby to draw his or her first breath. Because the first inspiration is unusually deep, as the lungs contain no air, the baby also exhales vigorously and naturally cries. A full-term baby may breathe 45 minutes for the first 2 weeks after birth. Breathing rate gradually declines until it approaches a normal rat of 12 breaths per minute. INTRODUCTION After the baby’s first insipiration, the cardiovascular system

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