: Gases must dissolve in liquid before they can diffuse across a membrane, meaning respiratory organs must remain moist to function.
Respiratory organs are specialized biological structures designed to facilitate gas exchange—primarily the uptake of oxygen ( O2cap O sub 2 ) and the release of carbon dioxide ( CO2cap C cap O sub 2
: Millions of tiny structures (like alveoli in humans or filaments in fish) maximize the area available for gas to cross into the blood.
: Respiratory surfaces consist of incredibly thin, squamous epithelial cells. This "air-blood barrier" must be as thin as possible to allow for rapid diffusion.
). While humans rely on lungs, the animal kingdom features a wide variety of respiratory systems adapted to diverse environments, from the deep ocean to high altitudes. Primary Features of Respiratory Organs
Depending on an organism's habitat and metabolic needs, the form of the respiratory organ varies significantly: Respiratory Organ‐on‐a‐Chip for Disease Modeling
To function efficiently, all specialized respiratory organs across species share several key physical characteristics: