i am a study scientist at The college of Nottingham. My key area of study is cardiovascular biology and also I aid teach college students to become veterinary surgeons and scientists. Once I am not working, I carry out a many community and also charity work and love safety time with my family, consisting of my two grandchildren. I have actually three children. The youngest has just finished school and the older two have completed their levels at university.

ns am a Manchester-based scientific research communicator and also artist at this time researching exactly how art and games have the right to be offered as tools for science outreach, as component of a M.Sc. In ~ the college of Hull. Ns have worked in cooperation with researchers anywhere the world, creating interdisciplinary projects that are used to interact science to the public and also to inspire human being to get connected in STEM.

ns am a teacher and also have taught young world for end 20 years. Ns am additionally a experienced proofreader and also copy-editor and an ext recently I have written my an initial children’s novel. I have actually two children, Joshua and Erin, who love learning around animals and also science. In my spare time, I reap playing tennis to keep my heart fit and also healthy and also my passion for the theater and acting keeps my love racing, particularly on opening night.


i am an combine Professor the Anatomy and Developmental genetics at The college of Nottingham and also a 2019 British scientific research Association Media Fellow. Ns lead a team of study scientists investigate why people and animals endure from heart and also blood courage disorders, trying to find techniques to detect, prevent, and also cure. Once I am no working, i love to travel approximately the world, visit museums, and also write scientific research fiction. My boyfriend Andrew and also I go running to keep our mind healthy. *catrin.rutland

Young Reviewers

Age: 11

you re welcome boy that loves to play basketball and also be with his family.

Age: 15

Hi, my name is Bruna and I live in São Paulo.


We every take our hearts because that granted: the fascinating body organ inside everyone that beats repetitively to save blood pumping v our bodies. Blood circulation ensures that oxygen, nutrient from food, hormones, and waste assets get to the exactly cells. The heart is important for keeping humans and also most pets alive. Hearts room even much more interesting as soon as we examine what castle do, exactly how they look, how they work, and also the similarities and also differences in the hearts of species across the planet. Is a giraffe heart similar to a human being heart? Which animal survives regardless of having no heart? can a heart yes, really beat end 1,500 time a minute? from dinosaurs to insects, people to dogs, this document looks in ~ what is really happening ~ above the inside, exploring the civilization of love anatomy.

You are watching: Do any animals have two hearts

How countless Hearts perform We Have?

You surely know that humans and also giraffes have just one heart, together most pets do—but no all. Octopuses and also squids (animals referred to as cephalopods) have three hearts. 2 hearts pump blood to the gills to take it up oxygen, and also the various other pumps blood about the body (Figure 1). Worms are likewise unusual, with 5 structures dubbed aortic arches acting as an easy hearts. The hagfish, sometimes referred to as the slime eel, has actually one true heart plus three accessory pumps help the blood come move. Simply when you thought you had heard that all, some pets are heartless. Jellyfish, starfish, and even corals manage very well there is no hearts. Starfish do not also have blood, so this defines why no heart is required. Instead, they use small hair-like structures referred to as cilia to push seawater through their bodies and they extract oxygen from the water.

Figure 1 - The simple structures of pet hearts.Bird and also mammal mind have four chambers (two atria and two ventricles). A frog, i m sorry is one amphibian, has actually a heart with three chambers (one ventricle and two atria), and also fish hearts have two chambers (one atrium and also one ventricle). One octopus heart system contains three hearts—one key heart (H1) pumping blood come the body and also two various other hearts (H2 and H3) pumping blood to the gills. A, atrium; V, ventricle.

For Dr. Who fans, the fictitious Time Lords have two hearts, but real humans really rarely do. In exceptionally unusual cases, people with the an illness cardiomyopathy have actually a 2nd heart attached onto their own heart by doctors. The healthy and damaged hearts occupational together to share the load. Also, twins that are born connected to each other (conjoined twins) deserve to have 2 hearts naturally.

Mammal and also Bird Hearts

It is not just the number of hearts the can adjust between species. The basic structure that this an important organ deserve to be extremely different from one types to the next. Hearts mostly consist of muscle the contracts and also relaxes, causing blood to relocate through blood ship to and also from the lungs and around the human body (Figure 2)1. As mammals, us have 4 main parts to the heart, a left and a right atrium and also a left and also a ideal ventricle. This is called a four-chambered heart. Other mammals and birds all have four-chambered hearts. Other animal groups, such as reptiles, amphibians, fish, and insects, have hearts the look a small different (Figure 1).

Figure 2 - hearts have adapted differently to finest suit every animal.(A) The giraffe has a very big left ventricle so the the heart muscle deserve to pump blood come the body and all the means up the long neck come the head. The giraffe’s right ventricle is smaller, together it only pumps blood to the lungs. Microscope photos of the love muscle the a chick (B) and also a dog (C) are also shown. The chick is young and also therefore only has one ventricle and one atrium. Later, the chick love will end up being four-chambered, with two atria and two ventricles.

Reptile and Dinosaur Hearts

Reptile hearts have three chambers, two atria and also one ventricle (Figure 1). The exemption is crocodilians, which have actually four-chambered hearts, as with mammals and also birds. However, there is a hole in the crocodile chamber wall, so even if it is there room three or four heart chambers is up because that debate. Human being often wonder whether dinosaurs evolved from bird or reptiles. Finding a dinosaur love is very rare because, unequal bone, the love is a soft tissue, so it is not often preserved. One potentially fossilized heart appeared to present that dinosaurs had 4 heart chambers, an ext like birds 보다 reptiles. Sadly, together this specimen to be investigated more using much more advanced scientific technology, it was discovered not to it is in dinosaur tissue, so us still carry out not know enough about dinosaur hearts to predict which pets dinosaurs evolved from <2>.

Amphibian Hearts

Amphibians space an exciting group, as their hearts vary greatly. Living on land and also in water, countless get oxygen utilizing their lungs, but additionally take it up via their skin. Many amphibians, consisting of frogs and toads, have actually three-chambered hearts, with two atria and one ventricle (Figure 1). However, lungless salamanders perform not have a structure called a septum to divide the atrium right into two separate parts, so this pet has just one atrium and also one ventricle. Some lesser known amphibians seem to have actually a septum in in between their ventricles, for this reason perhaps old amphibians had four-chambered hearts, favor mammals and birds.

Fish and also Insect Hearts

Fish hearts have just two chambers, an atrium and a ventricle (Figure 1). Insects often have just a tube that pumps hemolymph (the name for the insect indistinguishable of blood) freely around the whole body, through a courage to aid it move. Cockroaches, however, have 13 heart chambers!

How large is her Heart?

It goes there is no saying the heart size varies in different animals. After all, a whale could not make it through with a mouse-sized heart. One adult human being heart weighs around 0.6 lbs. If you do a fist, the is around the size of her heart. The giraffe heart is a hefty 26 lbs, however the blue whale really tips the scale at 400 lbs. The world’s smallest heart belongs to the fairyfly. This tiny animal is just 0.2 mm long, and also a microscopic lense is required to watch its heart.

Hearts are normally about 0.6% of an animal’s human body mass. Dogs and also wolves have actually relatively big hearts in comparison through their weight, at 0.8%. Meanwhile, the cat love is just 0.35% that a cat’s human body weight. Hopefully, family member heart size and also the amount of love animals feel room not related. If they were, the world’s the smallest mammal, the Etruscan shrew, would have a most love come give! The mouse-like shrew weighs a small 2 g and also is approximately 4 centimeter long, but its heart renders up 1.2% of its body weight <3>. Scientists additionally found the the shrew heart have the right to shrink in cold weather. This shrinkage helps shrews endure harsh climates, by reducing the amount of food the needs. This tiny mammal eats double its body weight in food every day, so hibernation is no an option. They rarely also sleep.

Swift and also Sluggish heart Rates

The method animals’ hearts work varies between species, too. The heart rate, measure up in beats per minute (bpm), varies in various species. Generally, larger animals have slow heart rates. A huge slug has a heart rate of approximately 55 bpm, while smaller slug varieties are in the 90s. Countless whales have actually heart rates of 10–30 bpm, giraffes space 40–90, and cats are around 150. In even smaller animals, the number increases: an adult chicken has actually a heart rate of 259 bpm, a chick is 400 (Video 1), and also the hamster love beats away at 450 bpm. The tiny Etruscan shrew clocks 835 bpm, an ext than 12 times higher than a person. The greatest recorded shrew rate was 1,511 bpm, a human being record because that a warm-blooded animal <3>.

People have heart rates of about 60–100 bpm, but children regularly have slightly higher rates. At 1 month old, 70–190 is relatively normal, 80–120 because that 3–4-years-olds, and also 60–100 by the time a son is 10 years old. A farming baby within its mom starts in ~ 80 bpm in week 5, 155–195 in ~ 9 weeks old, and around 130 just before it is born. Interestingly, the person heart starts as a pipe in the 19–20-days-old embryo, rather favor a fish, but gradually rotates, develops, and also separates into 4 chambers over the next 6 weeks.

Exercise, Temperature and Hibernation All adjust Heart Rate

Heart rate alters in most working out animals. To run giraffes can reach 170 bpm and also humans have the right to hit 220, yet ideally it should be a tiny less. A crocodile heart price at 10° C is 1–8 bpm, at 28° C it hits 24–40, and once the reaches end 40° C, the love can come to be damaged. Young swifts (birds) lower their love rates when in the nest, to avoid starvation. Hibernating pets can likewise lower their heart rates. Grizzly bears normally clock 84 bpm, i beg your pardon lowers to 19 bpm throughout hibernation; a human being heart would usually stop working if that went the low. Emotions, such together fear, love, and also excitement, and also hormone levels, sickness, oxygen levels, and other determinants both inside and outside the the body can change the love rate.

Mending a damaged Heart

In our previous Frontiers because that Young Minds record “Mending a broken Heart,” us looked at addressing failing mind <4, 5>. The zebrafish has actually a really important ability: it have the right to regenerate (regrow), for this reason if that gets hurt or that is heart has a problem, the can frequently repair itself. Human being bodies are fantastic, and also they continuously try to replace heart cells and also repair love tissue, however the zebrafish is a real experienced at mending a damaged heart.


In this article, us looked at several of the similarities and differences in between the hearts of various species. Mammals and birds have very similar hearts due to evolution, if reptiles, fish, insects, and other pets evolved mind that are slightly in different ways from those of mammals. The environment both inside and outside that each pet helps control the heart’s structure and function, yet lifestyle choices, such as exercise and also food, can have large impacts on your heart’s health. Your friends’ hearts are an ext similar to yours than to a giraffe’s because that example, and also even much more similar than to a frog or spider heart, however every person’s love is unique. Your heart is continually adapting come the situations you space in, reaction to food, exercise, emotions, and illness. Uneven a squid, you only have actually one heart, and it will certainly beat roughly 2.21 billion times in her life, so that is worth maintaining it healthy.


Cephalopods: pets without backbones, including squids, octopi, and also nautiluses. Cephalopods have symmetrical bodies, influential heads, and tentacles.

Atrium: The top chamber or chambers that the heart. The many is atria: for example, you deserve to have one atrium or two atria.

Ventricle: The lower chamber or chambers the the heart.

Amphibian: pets with backbones that need water or wet settings to survive. Amphibians encompass toads, frogs, salamanders, and also caecilians (amphibians without legs or limbs).

Hemolymph: Fluid, comparable to blood, that some an easy animals have to move nutrients and also oxygen approximately their bodies.

Heart Rate: The variety of times every minute that a love beats.

Video 1: beforehand on, when a chick is farming in one egg, that heart can be watched on the exterior of that is body. Over time, the love will relocate inside the body. This video shows a chick’s heart beating once it is just a few days old. The love is quiet a pipe containing two chambers, a ventricle and also an atrium, but as it grow it will at some point have 4 chambers. You have the right to see the blood pumping with the heart chambers.

Conflict that Interest

The authors declare the the research study was conducted in the absence of any commercial or financial relationship that could be interpreted as a potential problem of interest.


The writer would prefer to say thanks to our young reviewers, Erin and also Joshua Rutland. Component of this work-related was made possible due to capital from the Anatomical culture with a publicly Engagement and also Outreach grant to Catrin titled Anatomy because that ALL—Making Anatomy Accessible. We would also like to say thanks to the British scientific research Association and also University the Nottingham because that awarding Catrin v a BSA Media Fellowship 2019.


1. check out the file “Blood vessels Under the Microscope” for information about blood <1>.

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<1> Machado, M., Mitchell, C., Franklin, J., Thorpe, A., and also Rutland, C. S. 2020. Blood ship under the microscope. Front. Young minds 8:151. Doi: 10.3389/frym.2019.00151

<2> Cleland, T., Stoskopf, M., and Schweitzer, M. 2011. Histological, chemical, and also morphological reexamination of the “heart” the a tiny Late Cretaceous Thescelosaurus. Naturwissenschaften. 98, 203–211. Doi: 10.1007/s00114-010-0760-1

<3> Jurgens, K. D., Fons, R., Peters, T., and also Sender, S. 1996. Heart and respiratory rates and their significance for convective oxygen transport rates in the the smallest mammal, the Etruscan shrew Suncus etruscus. J. Exp. Biol. 199:2579–84.

<4> Clark, N., Alibhai, A., and also Rutland, C. S. 2018. Repair a damaged heart—the genetics of love disease. Front. Young mental 6:19. Doi: 10.3389/frym.2018.00019

<5> Simpson, S., Rutland, P., and Rutland, C. S. 2017. Genomic insights into cardiomyopathies: a comparative cross-species review. Vet. Sci. 4:19. Doi: 10.3390/vetsci4010019