Gas Exchange in humans

Gas exchange or respiration in humans is the means by which getting oxygen from air into the blood and carbon dioxide out of the blood into the air. Humans must exchange these gases with the environment because oxygen is essential for cells, which use this vital substance to release the energy needed for cellular activities. In addition to supplying oxygen, carbon dioxide needs to be removed in order to prevent the buildup of this waste …

…called the tidal volume. In adults the tidal volume is about 0.5 liters. The lungs can hold about ten times this volume if they are filled to capacity. This maximum amount which is called ''the vital capacity'' is generally about 4.8 liters in an adult male, but varies from one individual to the next. For example, athletes can have a vital capacity of as much as 5.7 liters. Therefore, the vital capacity is reached only during strenuous exercise.