Editing Cetacea (section)

=== Respiration ===
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Cetaceans have lungs, meaning they breathe air. An individual can last without a breath from a few minutes to over two hours depending on the species. Cetacea are deliberate breathers who must be awake to inhale and exhale. When stale air, warmed from the lungs, is exhaled, it condenses as it meets colder external air. As with a terrestrial mammal breathing out on a cold day, a small cloud of 'steam' appears. This is called the 'spout' and varies across species in shape, angle and height. Species can be identified at a distance using this characteristic.

The structure of the [[respiratory system|respiratory]] and [[circulatory system]]s is of particular importance for the life of [[marine mammals]]. The oxygen balance is effective. Each breath can replace up to 90% of the total lung volume. For land mammals, in comparison, this value is usually about 15%. During inhalation, about twice as much oxygen is absorbed by the lung tissue as in a land mammal. As with all mammals, the oxygen is stored in the blood and the lungs, but in cetaceans, it is also stored in various tissues, mainly in the muscles. The muscle pigment, [[myoglobin]], provides an effective bond. This additional oxygen storage is vital for deep diving, since beyond a depth around {{convert|100|m|ft|abbr=on}}, the lung tissue is almost completely compressed by the water pressure.