 In 1959 , the heart of a 22 metric tons ( 24 short tons ) male taken by whalers was measured to be 116 kilograms ( 256 lb ) , about 0 @.@ 5 % of its total mass . The circulatory system has a number of specific adaptations for the aquatic environment . The diameter of the aortic arch increases as it leaves the heart . This bulbous expansion acts as a windkessel , ensuring a steady blood flow as the heart rate slows during diving . The arteries that leave the aortic arch are positioned symmetrically . There is no costocervical artery . There is no direct connection between the internal carotid artery and the vessels of the brain . Their circulatory system has adapted to dive at great depths , as much as 2 @,@ 250 metres ( 7 @,@ 382 ft ) . 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 . 
