The Processes of the Respiratory System

Pulmonary ventilation, or breathing, is driven by pressure differences between the lungs and the atmosphere, as described by Boyle's Law. During inspiration, the contraction of the diaphragm and external intercostals increases thoracic volume, which decreases pressure and draws air in. Expiration occurs passively when these muscles relax and the lungs recoil, increasing internal pressure to force air out.

The system facilitates gas exchange through four stages: external respiration (alveoli to blood), transport of gases via the bloodstream, internal respiration (blood to tissues), and cellular respiration (converting glucose to ATP). Oxygen binds to hemoglobin for delivery, while carbon dioxide is transported back to the lungs—mostly through plasma—to be exhaled.

Respiratory rate is governed by the brain's medulla oblongata, which monitors carbon dioxide levels and blood pH. Conditions like Chronic Obstructive Pulmonary Disease (COPD) and sleep apnea illustrate respiratory system malfunctions; COPD involves chronic inflammation and loss of alveolar elasticity, while sleep apnea entails periodic breathing cessation due to airway obstruction or failure of the brain's respiratory center.