Summary
Highlights
The lungs serve to remove carbon dioxide, a metabolic waste product, while replenishing the body with oxygen. This process is supported by the heart, which pumps deoxygenated blood to the lungs via the pulmonary artery for oxygenation before returning fresh blood to the body through the pulmonary vein.
Air travels through the upper respiratory system into the trachea, branching at the carina into primary, secondary, and tertiary bronchi. These further divide into bronchioles, eventually reaching the alveolar ducts and sacs where gas exchange occurs.
The right lung consists of three lobes, while the left lung has two. The lungs are protected by two layers: the visceral layer, which adheres to the lung organ, and the parietal layer, with serous fluid in between to prevent friction during breathing cycles.
Breathing is driven by the diaphragm and accessory muscles; contraction of the diaphragm creates negative pressure for inhalation, while relaxation forces air out for exhalation.
At the alveolar-capillary interface, an assembly-line process occurs where carbon dioxide is released from red blood cells and oxygen is absorbed, allowing freshly oxygenated blood to return to the heart for systemic distribution.