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Respiratory system

The respiratory system is the biological system of any organism that engages in gaseous exchange. Even trees have respiratory systems, taking in carbon dioxide and emitting oxygen.

The human respiratory system consists of:

The alveoli and bronchioles form the lungs. Air is moved in and out of the lungs by the movements of the rib cage and diaphragm, which expand the lungs to draw in air and compress the lungs to drive out air. A simple model of how the lungs are inflated can be built from a bell jar.

There are four basic measured lung volumes:

From these volumes, several important capacities are also calculated:

 TLC = IRV + TV + ERV + RV

The functional residual capacity (FRC): the amount of air that stays in the lungs during normal breathing.