Because of their height, giraffes require scarily high blood pressure – however they escape the huge health troubles that plague human being with hypertension. How do they execute it?

To many people, giraffes are merely adorable, long-necked animals that rank close to the height of a zoo visit or a photo-safari bucket list. However to a cardiovascular physiologist, there"s even more to love. Giraffes, it transforms out, have actually solved a difficulty that death millions of human being every year: high blood pressure. Your solutions, just partly construed by scientists so far, indicate pressurised organs, transformed heart rhythms, blood warehouse – and also the organic equivalent of assistance stockings.

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Giraffes have actually sky-high blood pressure due to the fact that of your sky-high heads that, in adults, rise around 6m (19ft) over the ground – a long, long method for a love to pump blood versus gravity. To have a blood press of 110/70 at the mind – about normal for a huge mammal – giraffes need a blood press at the heart of about 220/180. The doesn"t faze the giraffes, however a pressure like that would reason all species of difficulties for people, native heart fail to kidney failure to swollen ankles and also legs.

In people, chronic high blood pressure causes a thickening of the love muscles. The left ventricle the the heart becomes stiffer and less maybe to to fill again after every stroke, causing a disease known as diastolic heart failure, qualified by fatigue, shortness the breath and also reduced capability to exercise. This form of heart failure is responsible because that nearly half of the 6.2 million love failure cases in the united state today.


Giraffes preserve extraordinarily high blood pressure, and yet the doesn't it seems to be ~ to cause them health problems (Credit: C. Aalkjær & T. Wang / AR Physiology 2020)

When cardiologist and evolutionary biologist Barbara Natterson-Horowitz that Harvard and also UCLA check giraffes" hearts, she and her student uncovered that your left ventricles did get thicker, but without the stiffening, or fibrosis, that would happen in people. The researchers additionally found that giraffes have actually mutations in 5 genes concerned fibrosis. In maintaining with that find, various other researchers that examined the giraffe genome in 2016 discovered several giraffe-specific gene variants concerned cardiovascular advancement and maintain of blood pressure and circulation. And in march 2021, another research group reported giraffe-specific variants in genes involved in fibrosis.

The giraffe has one more trick to protect against heart failure: the electrical rhythm that its heart differs from that of other mammals

And the giraffe has an additional trick to protect against heart failure: the electric rhythm of its heart differs from the of other mammals. In giraffes, the ventricular-filling step of the heartbeat is extended, Natterson-Horowitz found. (Neither of she studies has actually been published yet.) This permits the heart to pump more blood through each stroke, enabling a giraffe to run hard in spite of its thicker heart muscle. "All you have to do is look at a snapshot of a fleeing giraffe," Natterson-Horowitz says, "and girlfriend realise the the giraffe has solved the problem."

Natterson-Horowitz is now turning her fist to an additional problem that giraffes it seems ~ to have actually solved: high blood pressure throughout pregnancy, a problem known as preeclampsia. In people, this deserve to lead to significant complications that incorporate liver damage, kidney failure and also detachment of the placenta. Yet giraffes seem come fare simply fine. Natterson-Horowitz and also her team are hoping to research the placentas that pregnant giraffes to see if castle have distinctive adaptations that allow this. 

People who endure from hypertension are also prone come annoying swelling in their legs and ankles because 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 know that they"ve fixed that problem, too. "Why don"t we see giraffes v swollen legs? just how are they protected against the enormous pressure under there?" asks Christian Aalkjær, a cardiovascular physiologist at Aarhus college in Denmark who wrote about giraffes" adaptations to high blood push in the 2021 annual Review that Physiology.

In part, in ~ least, giraffes minimise swelling with the exact same trick that registered nurses use on your patients: support stockings. In people, these room tight, elastic leggings the compress the leg tissues and prevent fluid from accumulating. Giraffes attain the very same thing v a tight pack of dense connective tissue. Aalkjær"s team tested the effect of this through injecting a tiny amount that saline solution beneath the wrapping right into the foot of 4 giraffes that had been anesthetised for other reasons. Effective injection forced much much more pressure in the lower leg 보다 a equivalent injection in the neck, the team found, indicating the the wrapping assisted resist leakage.


One look at the slender foot of the giraffe reveals that they don't suffer the ankle swelling usual in people with high blood push (Credit: Getty Images)

Giraffes additionally have thick-walled arteries near their knee that could act as circulation restrictors, Aalkjær and also others have actually found. This can lower the blood pressure in the reduced legs, lot as a kink in a garden hose causes water pressure to drop past the kink. It stays unclear, however, even if it is giraffes open and also close the arteries to regulate lower-leg press as needed. "It would certainly be funny to imagine that when the giraffe is stand still out there, it"s closing off the sphincter just beneath the knee," claims Aalkjær. "But us don"t know."

Aalkjær has actually one more question about these exceptional animals. As soon as a giraffe raises that is head ~ bending down for a drink, blood pressure to the mind should fall precipitately – a an ext severe variation of the dizziness the many world experience as soon as they wake up suddenly. Why don"t giraffes faint?

At least part of the answer appears to be the giraffes deserve to buffer these sudden alters in blood pressure. In anesthetised giraffes whose heads can be raised and lowered v ropes and pulleys, Aalkjær has discovered that blood pools in the large veins the the neck as soon as the head is down. This stores an ext than a litre (0.2 gallons) the blood, temporarily reducing the lot of blood returning to the heart. With less blood available, the love generates less pressure through each win while the head is down. Together the head is raised again, the save on computer blood rushes suddenly back to the heart, which responds v a vigorous, high-pressure stroke the helps pump blood up to the brain.

It"s not yet clean whether this is what wake up in awake, freely moving animals, though Aalkjær"s team has actually recently tape-recorded blood pressure and also flow native sensors implanted in free-moving giraffes and also he wishes to have solution soon.

So – can we learn medical lessons from giraffes? nobody of the insights have actually yet succumbed a details clinical therapy. Yet that doesn"t median they won"t, says Natterson-Horowitz. Also though several of the adaptations are probably not appropriate for hypertension in humans, they may assist biomedical scientists think about the difficulty in brand-new ways and also find novel philosophies to this far-too-common disease.

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


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