Humans inhale air that is rich in oxygen and exhale air that is rich in carbon dioxide. The pathway that air takes in the human body begins with the nose and ends with the alveoli in the lungs. More » Science Human Anatomy

The air that makes up Earth's atmosphere contains 20.9 percent oxygen. This is true up to about 70,000 feet above sea level. However, above 10,000 feet, the atmosphere becomes too thin to support human life, even though ... More » Science Earth Science Atmosphere

In dry air that does not contain pollution, the predominant gas is nitrogen, which makes up 78 percent of the atmosphere. The next two most voluminous gases are oxygen (21 percent) and argon (1 percent). Other gases appe... More » Science Earth Science Atmosphere
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During gas exchange, oxygen from the air breathed in diffuses into the bloodstream, and carbon dioxide from the bloodstream diffuses into the air in the alveoli. This gas exchange occurs through the thin wall of the alve... More » Science Human Anatomy

Humans exhale oxygen, carbon dioxide and nitrogen. Humans inhale these same gases, though in different proportions to exhalation; that is, oxygen is exchanged for carbon dioxide during breathing. More » Science Human Anatomy

The purpose of respiration is to supply the body with oxygen and eliminate carbon dioxide. Oxygen is essential for cellular respiration as cells cannot exist in the absence of it. More » Science Human Anatomy

The primary function of the respiratory system is to provide oxygen to every part of the body through the process of inhaling oxygen and exhaling carbon dioxide. The respiratory system consists of tissues and organs insi... More » Science Human Anatomy