Why don’t whales get the bends?
Xiao Tsai
Any scuba diver is aware of the dangers of decompression. When you dive deep in high-pressure water, the air which you breathe from your tank will have the same pressure that the water is exerting. If this weren’t the case then the air wouldn’t come out of your tank. At a depth of ten metres the air pressure is twice that of atmospheric air pressure on land. High-pressure nitrogen from this air dissolves in your bloodstream and the water in your body. Anyone who’s unscrewed a lid on a shaken fizzy drink bottle knows that bubbles start to fizz up due to the lessening of pressure.
The same effect happens to the nitrogen in the bloodstream of a diver if they ascend too quickly.
How do whales and other marine mammals handle this tremendous pressure increase? They’ve adapted to collapse their thoracic cavity, lungs and alveolar sacs. Whales have very weak and flexible rib cages. While diving, the thoracic cavity is collapsed so no air can get in. When this collapse occurs, there’s still air with high nitrogen levels present in the alveolar sac, which is the site of gas exchange. Marine mammals have adapted to this by creating a cartilage buildup in the bronchioles. This allows for alveolar collapse and storage of the air in the bronchioles. This is important because nitrogen is no longer at the site of gas exchange and cannot be absorbed into the body. The nitrogen will not fizz in the bloodstream upon ascent, therefore making them effectively immune to the bends.