Pulmonary Physiology

On the most basic level, the pulmonary system exists to promote gas exchange from air into the circulatory system. We inhale in oxygen, which diffuses into the blood for systemic circulation and eventually produces ATP for cellular energy, and we exhale carbon dioxide and other metabolic waste from the body. The respiratory tract organs, which comprise the nose, throat, larynx, trachea, bronchi, and lungs, aid in this process. The lungs are further divided into lobes, which are further subdivided into about 300 million alveoli. Gas exchange takes place mostly in the alveoli. The phrenic nerve innervates the diaphragm, which is the primary breathing muscle. It is innervated by the nerve roots of C3, C4, and C5. External intercostals are inspiratory muscles that are most commonly employed during exercise and respiratory distress. The pulmonary system is an important component of the integrated network that maintains blood gas balance. Its principal job is to guarantee that mixed venous blood is turned into arterial blood with proper partial pressures of O₂ and CO₂ in all physiologic states, including sleep, rest, and dynamic activity.