Final answer:
The first breath a newborn takes at birth inflates the lungs and alters the circulatory system by closing the three shunts that direct oxygenated blood away from the lungs.
Step-by-step explanation:
The newborn's first breath alters the circulatory pattern by closing the three shunts that direct oxygenated blood away from the lungs and liver during fetal life. This allows for the opening of the pulmonary alveoli and filling of alveolar capillaries with blood. The lungs take over the task of the placenta in exchanging carbon dioxide for oxygen through respiration.
The first breath typically occurs within 10 seconds of birth, after the mucus in the infant's mouth and nose is aspirated. This breath inflates the lungs to nearly full capacity, decreasing lung pressure and resistance to blood flow.
Nasal breathing is generally considered superior to mouth breathing because it filters particles out of the air, warms and moistens the air, and creates greater pressure in the lungs during exhalation, allowing for more efficient oxygen extraction.