How canine and human hearts differ, and what they have in common

The heart is of course one of the body’s most vital internal organs; a compromised or improperly formed heart can lead to a wide range of acute and serious health problems, and various health conditions like heart disease can also have potentially serious implications for your dog’s longevity and quality of life.

The hearts of all mammals – including humans and dogs – have more in common with each other than they do apart, in terms of their functions and structures, but there are also a number of notable differences too, in terms of the construction and normal functions of the hearts of humans versus dogs.

Developing a basic understanding of how the dog’s heart works, and how it differs from our human hearts can provide insights into the canine anatomy that can help you to appreciate the core functions of the dog’s body, and in some cases, allow you to recognise and identify any anomalies or problems that arise early on.

In this article, we will examine how the canine heart and the human heart differs in terms of function and construction, and the things we have in common too. Read on to learn more.

What does the heart do?

The main function of the heart is to pump blood throughout the body, serving all of the major organs and forming the core of the circulatory system. The heart oxygenates the blood and pumps this oxygenated bright red blood back out of the heart through the arteries, and once blood has completed a circuit of the body, it becomes darker in colour due to the lack of oxygen within it, and returns to the heart via the veins to be re-oxygenated and restart the journey once again.

Heart size and shape

The size of the heart in any given dog is determined by the dog’s own size – and so there is a wide range of variance between say, a Yorkshire terrier and a Siberian husky, due to their respective sizes. Very large dog breeds might well have a heart that is around the size of that of a human heart, or even larger – but the shape of your dog’s heart is very similar to that of our own human hearts.

The chambers of the heart

Both human and canine hearts have four chambers, arranged in a cross-sectional layout of two up two down, on the left and right side of the heart respectively.

In the top half of the heart are the right and left atriums, and the body’s two largest veins feed into the right atrium, while the pulmonary artery exits from the left atrium.

In the lower half of the heart you can find the left and right ventricles, and the pulmonary artery exits from the right ventricle, while the aorta exits from the left ventricle.

The veins

The pulmonary veins move oxygenated blood from the lungs to the heart, where the heart then goes on to pump this blood out through the rest of the body on its circuit. The number of pulmonary veins that both dogs and people may possess can be variable, even within the same species – human hearts are served by four or five pulmonary veins, while for dogs, there is even more scope for differences between different animals, with the number ranging from four to eight.

The vena cava vein moves deoxygenated blood from the body’s lower extremities back through the heart’s right atrium, and in humans, this vein is more or less vertical in position, but for dogs, it has a more horizontal position within the anatomy of the heart – which reflects the differences in the normal posture of dogs and humans, as humans walk upright whilst dogs walk on all fours.

Heart rate differences

When it comes to the heart rate – the number of times the heart beats and pumps blood per minute – the difference between dogs and humans is quite acute. For humans, the usual resting heart rate ranges between sixty to one hundred beats per minute (BPM), while for dogs, the range of variance is much greater, ranging from sixty to one hundred and sixty beats per minute at rest.

The size of the dog itself goes a great way towards determining the heart rate – the larger the dog, the slower the heart rate. This means that small and toy dog breeds will tend to have a heart rate towards the higher end of the spectrum, whilst large and giant breeds will be much lower.

This holds true across the animal kingdom as a whole, where mammals are concerned – the smaller the animal, the faster their heart rate. Tiny pets like hamsters and even rabbits have such a fast heart rate that it can be virtually impossible to even count the beats unless you are very experienced at doing so!

Younger dogs too tend to have a faster heart rate than adult dogs, and if you monitor your dog’s heart rate from when they are a puppy, you will even be able to measure the change as they grow towards maturity.