Because of your height, giraffes call for scarily high blood pressures – yet they to escape the massive health difficulties that plague human being with hypertension. Exactly how do they perform it?

To most people, giraffes are simply adorable, long-necked animals that rank near the top of a zoo visit or a photo-safari bucket list. However to a cardiovascular physiologist, there"s even much more to love. Giraffes, it turns out, have actually solved a problem that kills millions of people every year: high blood pressure. Their solutions, just partly interpreted by researchers so far, involve pressurised organs, altered heart rhythms, blood warehouse – and the organic equivalent of assistance stockings.

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Giraffes have sky-high blood pressure since of their sky-high heads that, in adults, rise about 6m (19ft) above the ground – a long, long means for a heart to pump blood versus gravity. To have a blood pressure of 110/70 in ~ the mind – around normal because that a large mammal – giraffes require a blood press at the heart of about 220/180. The doesn"t faze the giraffes, but a pressure prefer that would cause all kinds of difficulties for people, from heart fail to kidney failure to puffy ankles and also legs.

In people, chronic high blood pressure reasons a thickening of the love muscles. The left ventricle of the love becomes stiffer and also less maybe to to fill again after every stroke, causing a disease known as diastolic heart failure, qualified by fatigue, shortness the breath and reduced capacity to exercise. This form of heart fail is responsible for nearly fifty percent of the 6.2 million heart failure instances in the us today.


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Giraffes keep extraordinarily high blood pressure, and also yet it doesn't seem to cause them health problems (Credit: C. Aalkjær & T. Wang / AR Physiology 2020)


When cardiologist and evolutionary biologist Barbara Natterson-Horowitz of Harvard and also UCLA check giraffes" hearts, she and her student discovered that their left ventricles did acquire thicker, yet without the stiffening, or fibrosis, that would occur in people. The researchers also found the giraffes have mutations in 5 genes regarded fibrosis. In keeping with that find, other researchers who examined the giraffe genome in 2016 discovered several giraffe-specific gene variants concerned cardiovascular advance and maintain of blood pressure and circulation. And also in march 2021, one more research team reported giraffe-specific variants in genes involved in fibrosis.


The giraffe has an additional trick to protect against heart failure: the electrical rhythm of its love differs from the of other mammals


And the giraffe has one more trick to prevent heart failure: the electrical rhythm that its heart differs from that of other mammals. In giraffes, the ventricular-filling step of the heartbeat is extended, Natterson-Horowitz found. (Neither of her studies has actually been published yet.) This permits the heart to pump much more blood v each stroke, permitting a giraffe to operation hard in spite of its thicker heart muscle. "All you have to do is look in ~ a photo of a fleeing giraffe," Natterson-Horowitz says, "and girlfriend realise that the giraffe has actually solved the problem."

Natterson-Horowitz is now turning her fist to an additional problem the giraffes seem to have actually solved: high blood pressure during pregnancy, a condition known together preeclampsia. In people, this have the right to lead to serious complications that include liver damage, kidney failure and also detachment of the placenta. However giraffes seem to fare just fine. Natterson-Horowitz and her team room hoping to examine the placentas of pregnant giraffes to watch if castle have unique adaptations that allow this. 

People who experience from hypertension are additionally prone come annoying ede in their legs and ankles due to the fact that the high pressure forces water out of blood vessels and also into the tissue. But you only need to look at the slender foot of a giraffe to recognize that they"ve fixed that problem, too. "Why don"t we check out giraffes through swollen legs? exactly how are lock protected versus the massive pressure under there?" asks Christian Aalkjær, a cardiovascular physiologist at Aarhus college in Denmark that wrote around giraffes" adaptations to high blood push in the 2021 annual Review of Physiology.


In part, at least, giraffes minimise swelling through the very same trick that registered nurses use on your patients: assistance stockings. In people, these are tight, elastic leggings that compress the foot tissues and prevent fluid from accumulating. Giraffes achieve the exact same thing through a tight pack of dense connective tissue. Aalkjær"s team experiment the result of this by injecting a tiny amount that saline systems beneath the wrapping into the foot of four giraffes that had been anesthetised for various other reasons. Successful injection forced much much more pressure in the reduced leg 보다 a comparable injection in the neck, the team found, indicating the the wrapping assisted resist leakage.


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One look at the slender legs of the giraffe reveals that they don't endure the fish eye swelling common in human beings with high blood press (Credit: Getty Images)


Giraffes also have thick-walled arteries near their knee that can act as circulation restrictors, Aalkjær and others have found. This can lower the blood press in the reduced legs, much as a kink in a garden hose causes water push to drop past the kink. It continues to be unclear, however, whether giraffes open and also close the arteries to control lower-leg pressure as needed. "It would be funny to imagine that as soon as the giraffe is was standing still the end there, it"s closing off that sphincter simply beneath the knee," claims Aalkjær. "But us don"t know."

Aalkjær has one an ext question about these amazing animals. Once a giraffe raises its head after ~ bending under for a drink, blood push to the mind should drop precipitately – a much more severe version of the dizziness that many human being experience when they wake up suddenly. Why don"t giraffes faint?

At least part of the answer seems to be that giraffes deserve to buffer this sudden alters in blood pressure. In anesthetised giraffes whose heads could be raised and lowered through ropes and pulleys, Aalkjær has uncovered that blood pools in the huge veins the the neck when the head is down. This stores much more than a litre (0.2 gallons) the blood, temporarily reducing the quantity of blood returning to the heart. With much less blood available, the heart generates less pressure with each win while the head is down. As the head is elevated again, the save blood rushes suddenly earlier to the heart, i m sorry responds v a vigorous, high-pressure stroke the helps pump blood up to the brain.

It"s no yet clean whether this is what happens in awake, easily moving animals, despite Aalkjær"s team has actually recently tape-recorded blood pressure and flow indigenous sensors implanted in free-moving giraffes and he wishes to have solution soon.

So – can we learn medical lessons native giraffes? nobody of the insights have yet gave in a details clinical therapy. But that doesn"t typical they won"t, says Natterson-Horowitz. Also though several of the adaptations are most likely not appropriate for hypertension in humans, they may aid biomedical researchers think around the difficulty in brand-new ways and also find novel approaches to this far-too-common disease.

* This article originally appeared in Knowable Magazine, and also is republished under a creative Commons licence.

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