The average giraffe is about as tall as a house and weighs almost as much as a Toyota Camry, so it's not too much of an understatement to say that there's something special about giraffe anatomy. But these majestic creatures, which hail from the African savanna grasslands, aren't unique just by being the world's tallest mammals. Their bodies have evolved a number of other special biological features that help them thrive – but can be deadly to humans and other animals. One example? For giraffes, extremely high blood pressure is actually a sign of good health, and low blood pressure can be a life-threatening event. While the reasons for this are not yet fully understood, scientists are investigating the beneficial aspects of high blood pressure in giraffes and are making interesting findings that may have future implications for our own health. Biological adaptations that allow giraffes to avoid the harmful effects of high blood pressure are now giving scientists ideas for treating hypertension in humans.
Why exactly do giraffes have high blood pressure?
Like us, giraffes rely on the constant flow of blood around their bodies to deliver oxygen and nutrients to their brains and hearts. But unlike us, giraffes' brains and hearts can be 10 feet apart—a long distance for the animals' hearts to pump the blood they need to reach their brains. Blood in a giraffe's circulatory system endures an uphill battle to travel up its legs and long neck to its head. So giraffes actually need high blood pressure to fight gravity and propel their blood up that high.
Normal blood pressure for humans is about 120/80 mmHg, but normal blood pressure for a giraffe is a much higher 280/180 mmHg. Despite the advantages of high blood pressure, giraffes still have similar vascular, connective and visceral tissues to most other mammals. Long-term high blood pressure, or hypertension, commonly damages these structures and organs. Nevertheless, giraffes have special adaptations that help them withstand the pressure of their own blood.
Giraffes have a special heart
Fluid under pressure can be hard enough to scrub surfaces and sharp enough to cut objects. While high blood pressure doesn't have the same effect as a pressure washer sprayed on our internal organs, in humans, hypertension causes the walls of organs to thicken and eventually harden—a process called fibrosis, which can prevent these body structures from functioning properly. . Hypertension-induced fibrosis is one of the main causes of heart failure in humans. The same harmful process can also occur in the kidneys of people who live with hypertension. Both conditions can be life-threatening and life-changing.
Giraffes do not have this type of organ failure from hypertension. A study of 136 giraffes that died of natural causes revealed that each animal had a cluster of five specialized genes that changed their heart tissue. The giraffes' hearts were thicker on one side, the first sign of wear and tear caused by hypertension. Yet none of their hearts developed the stiffening that is associated with fibrosis. Three of these specialized genes found in giraffes promote the formation of fibrosis, and the other two genes block the formation of fibrosis in organs.
The exact effect of these genes is still under investigation, but scientists hypothesize that the combined, opposing effect of the genes reshapes the giraffe's heart so that it can enlarge in response to long-term exposure to high blood pressure. There may be a mechanism in the genes that stops giraffe hearts from developing fibrosis and pressure damage. As scientists learn more about giraffe genes, there is hope that these biological markers can be isolated and potentially incorporated into medicines for humans.
And their feet are also unique.
One of the more common symptoms of hypertension in humans is swelling of the lower extremities. Blood under high pressure can force water out of the cells, and it collects in the surrounding tissues, causing them to swell. Compression stockings can help alleviate this hypertension-related problem by preventing fluid from accumulating in the body's tissues.
Another interesting aspect of giraffe anatomy? They have built in compression stockings - sort of. The connective tissue around their feet is naturally much harder and stronger than their tissue elsewhere. The researchers discovered this tissue when injecting giraffes who were receiving the treatment. Injecting giraffes in their legs requires significantly more pressure than any other part of the animals' bodies because the connective tissue forms a sort of wall to prevent swelling that might otherwise occur due to their high blood pressure.
Scientists are also studying a special type of thickened arteries that giraffes have around their knees. More research is needed, but scientists believe that giraffes can control the rate at which blood flows to their legs by voluntarily constricting these arteries. High blood pressure that flows in a smaller volume is much easier for their body to handle.
How can giraffes help people with high blood pressure?
Currently, much of the focus in treating hypertension in humans is on lowering blood pressure using lifestyle changes and medications such as ACE inhibitors, beta blockers, and vasodilators. Some people with hypertension must take lifelong medications in increasing doses to manage their high blood pressure, and these medications can have troubling side effects.
Some people develop hypertension at an early age or regardless of diet and lifestyle choices, so diet and exercise do not always lead to improvement. Some of the most serious pregnancy complications include uncontrolled hypertension, and the treatment methods can be dangerous for pregnant people. Often, the safest method of treatment is to induce premature labor, which is a high risk for both parents and baby.
A drug that could prevent some of the harmful health effects of hypertension could be life-changing, especially for people whose high blood pressure has no underlying cause. There is hope that drugs made from giraffe genes could treat the effects of hypertension; giraffe genes allow the animals' hearts to withstand high blood pressure without being damaged, and a similar kind of drug could prevent the gradual effects of organ failure in humans.
Biomimetics researchers also hope to create new medical devices based on the arteries and connective tissues of giraffes. Devices that could strengthen or support the connective tissue inside a person's leg could amplify the positive effect of support stockings. Just as science already has shunts and stents to help our circulatory systems work better, scientists may be able to create devices that can strengthen and strategically narrow specific arteries that are most susceptible to damage from hypertension. These innovations could extend the lives of people whose bodies have already been damaged by high blood pressure.
The natural world is full of living wonders, and giraffes are certainly no exception. Although the scientific community is uncertain about what the future may hold in terms of effective human treatments based on giraffe biology, it is increasingly clear that we can learn a lot from these evolutionary marvels.
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