ANATOMY

Detailed explanation-1: -During respiration we breathe in oxygen and breathe out carbon dioxide. The air which we breathe in consists of 21% oxygen by volume.

Detailed explanation-2: -The air in Earth’s atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen.

Detailed explanation-3: -The atmospheric air consists of 78% of nitrogen, 21% of oxygen, 0.04% of carbon dioxide and 0.93% of argon and other inert gases.

Detailed explanation-4: -The amount of inhaled air contains 21% of oxygen and 0.04% of carbon dioxide, while the air we breathe out contains 16.4% of oxygen and 4.4% of carbon dioxide.

Detailed explanation-5: -The percentage of oxygen in inhaled air is 21%.