The air that enters the nasal cavity flows down the trachea. The trachea has a number of adaptations: cartilage rings in the walls of the trachea help to keep it open ciliated epithelium and ...

Limewater can be used to detect carbon dioxide. Breathing in through the mouthpiece draws air from the atmosphere in through tube A. Breathing out through the mouthpiece bubbles exhaled air ...

Now, scientists have discovered a fourth: breathing. The pupil is smallest around inhalation onset and largest during exhalation. "This mechanism is unique in that it is cyclical, ever-present and ...

Seals may be able to directly sense oxygen levels in their blood, an ability humans don't possess. A Scottish study reveals ...

These parallels could be “a very tidy example of convergent evolution, where you have humans that have developed this kind of neural mechanism for speech, and these parrots have developed a kind ...