Largest lungs

The world's largest lungs are those of the blue whale Balaeonoptera musculus. Its two lungs have a combined, total capacity of approximately 5,000 litres of air. Extremely efficient, its enormous lungs can transfer up to 90% of their inhaled air into the whale's bloodstream. By comparison, the equivalent figure on average for humans is a mere 15%.

Like other whales, instead of possessing nostrils the blue whale has blow-holes – on top of its head. Some species only possess a single blow-hole, but the blue whale has twin blow-holes, which are protected by a special splash guard, preventing water from splashing inside them. For as the blow-holes are linked directly to the lungs, a whale could theoretically drown if too much water splashed inside them. When underwater, it closes its blow-holes and holds its breath, having taken a deep breath before submerging, because like all mammals it cannot breathe underwater.