The Human Gas Exchange System

Humans like other mammals are aerobic organisms that need a constant supply of oxygen and need carbon dioxide constantly removed from the body as the accumulation of carbon dioxide in the body would be harmful.They are relatively large organisms with a small surface area to volume ratio. They have a high metabolic rate and also need to maintain their body temperature.As a result the lungs of mammals are adapted to meet the high oxygen demand.The lungs are located inside the body because air is not dense enough to support the delicate alveoli and because too much water would be lost from the surface if they were outside the body.The lungs are protected and supported by the ribcage and ventilated by moving the ribcage and diaphragm using muscles between the ribcage called intercostal muscles.Ventilation ensures that a steep concentration gradient is maintained.