Sperm whale . Myoglobin, which stores oxygen in muscle tissue, is much more abundant than in terrestrial animals. The blood has a high density of red blood cells, which contain oxygen-carrying haemoglobin. The oxygenated blood can be directed towards only the brain and other essential organs when oxygen levels deplete. The spermaceti organ may also play a role by adjusting buoyancy (see below). The arterial retia mirabilia are extraordinarily well-developed. The complex arterial retia mirabilia of the sperm whale are more extensive and larger than those of any other cetacean. Atop the whale's skull is positioned a large complex of organs filled
Whale lungs can hold about 5,000 litres of air. Spout shapes differ among species, which facilitates identification. The heart of a whale weighs about 180–200 kg. It is 640 times bigger than a human heart. The heart of the blue whale is the largest of any animal, and the walls of the arteries in the heart have been described as being "as thick as an iPhone 6 Plus is long". All whales have a thick layer of blubber. In species that live near the poles, the blubber can be as thick as 11 inches. This blubber can help with buoyancy (which