When a whale swims, it moves its tail up and down, which causes a wave of increased blood pressure to travel from the tail to the head. However, a network of veins in the animal's body diverts the blood away from the brain in order to protect it.
The complex network of blood arteries that surrounds and protects the brains of whales and other cetaceans.
It is possible that the complex network of blood veins found in whale brains protects these animals from the harm that would otherwise be caused by the intense pulses of blood pressure that are generated during swimming.
Whales navigate by waving their tail up and down in the water, which, when combined with holding their breath, causes a wave of pressure to travel from the tail to the head of the animal. In most animals, this would result in damage to the brain; however, whales are able to avoid this type of harm.
According to Robert Shadwick, who teaches at the University of British Columbia in British Columbia, Canada, “the squeezing activities cause pressure pulses which can flow through the blood through veins or arteries.” “[Whales] are unable to ease the locomotion-induced pulses by expelling air like a sprinting animal would,” says the article.
The webs of blood vessels known as retia mirabilia, which is Latin for “beautiful nets,” were originally identified by researchers in the 1600s in deep-diving whales. However, the function of these webs was not well understood until recently. As part of their investigation, Shadwick's team developed a computer model that recreates the shifting pressures that occur within the body of a whale as it swims. The morphological traits of 11 different cetaceans, ranging from bottlenose dolphins to baleen whales, served as the basis for their model.
According to the findings of their research, retia mirabilia play a role in helping to keep the blood pressure in the brain at a constant level without reducing the force of the pulsations or the power of the tail movement.
The surge of pressure is redirected from the arteries that are entering the brain to the veins that are exiting the brain via the network of blood vessels. Cetacean brains are so shielded from fluctuations in pressure, and this defence mechanism has no effect on the circulation of blood in the rest of the body.
According to Shadwick, the simulations demonstrated that the retia (also known as the mirabilia) might prevent more than 90 percent of the deleterious effect of locomotion-induced pulses by using this transfer mechanism. “It came as quite a shock when the simulations reached their conclusion.”
This research also contributes to our understanding of the absence of retia mirabilia in other marine species, such as seals and sea lions. Because these creatures swim by undulating from side to side, they prevent a potentially harmful pressure pulse from being sent to the brain, which reduces the requirement for retia mirabilia.