The respiratory system of the horse is well adapted to athletic exercise, with unrestricted upper airway diameters, and a large lung capacity afforded by 18 ribs. These combine to enable air intakes of up to 1800 litres per minute in a galloping horse. Volumes of up to 300 litres of blood are pumped at high pressure through small lung capillaries surrounding 10 million air sacs to take up and deliver over 70 litres of oxygen per minute to the working muscles at the gallop.
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