Your heart is not where you think it is – Human Anatomy | Kenhub

Your heart is not where you think it is – Human Anatomy | Kenhub

January 5, 2020 48 By Bertrand Dibbert


This is your heart. During the Pledge of Allegiance or the National
Anthem, Americans – ah, some Americans – put their hands over their hearts. And this isn’t just in the U.S. too. People around the world automatically put
their right hand over the left side of their chest just under the shoulder level with the
armpit, because that’s where the heart is, right? No. There, you’re actually covering your left
lung, not your heart. Despite what you see depicted on t.v. in the
media, your heart isn’t quite where they say it is. Yes, you do feel your heart beat more on the
left side of your chest which adds to this perception but I’ll soon explain why that
is. So, the heart is a muscular organ with four
chambers – right atrium, right ventricle, left atrium and left ventricle. It’s about two hundred and fifty to three
hundred and fifty grams about the size of a fist and it pumps blood through the blood
vessels of the circulatory system. The right atrium collects the deoxygenated
blood which passes to the right ventricle then pumped to the lungs to receive oxygen. The newly oxygenated blood returns to the
heart and at the left atrium passes through the left ventricle before finally being pumped
out to the rest of the body. Now, you can see the heart is not on the left
or the right side. It’s actually located in the center of the
chest bound by the sternum and ribs, the spine closely behind it with both ventricles lying
on the diaphragm. It’s enclosed in a protective sac called the
pericardium and it’s wedged between the two lungs. But note, it’s not symmetrical. There’s a tilt which makes it seem like it’s
more to the left than it actually is. The heart is cone-shaped with the narrow end
or apex pointing roughly to the left hip and the broader end or base – the base actually
being the upper part – pointing to the right shoulder. Here, the muscle wall surrounding the left
heart specifically the left ventricle is much thicker than the right. Here’s a view from the back. This causes the heart to offset slightly to
the left and along with being the largest of the four chambers, it gives that considerable
impression of being more to the left side. But why is this muscle mass uneven to start
with? Why isn’t the heart symmetrical? Well, there are actually many theories on
this but, in general, we can explain a lot just by sticking to one of the basic principles
of anatomy – form follows function. The reason why we’re symmetrical or roughly
symmetrical on the outside can be explained by locomotion – the way we move. For example, if we had asymmetric legs, as
a species, we wouldn’t get very far, literally and figuratively. Internally, it’s a different story. There isn’t that same requirement and as
such, you can see a whole lot of asymmetries specifically in the torso area. A symmetrical heart positioned perfectly in
the center of the chest which sure look nice but we know that the left and right sides
of the heart serve different functions. So it shouldn’t be a surprise that they also
looked different. The left ventricle needs the strength to generate
enough force to pump blood through the entire body whereas the right ventricle just needs
to pump blood to the lungs – that’s a much shorter distance. This also explains why you feel your heartbeat
more on the left side of the chest. The left ventricle generates the highest pressure. Now, another point to consider is space. During our evolution, nature had to fit complex
organs in the most efficient of ways in the tiny space of a human body. Some things have to go on the right, some
on the left, the center, some things tilted and thus the result, a lack of internal symmetry. The heart happens to be in the center but
with that slight offset, it leaves less room for the left lung. There’s a depression there known as the cardiac
notch where the surface of the lung rests against the heart. This makes our left lung smaller than our
right lung – one asymmetry leading to another. As for why the heart is located where it is
in the middle of the thoracic cavity, well, there, it’s nicely protected by the rib cage. Imagine if the heart was in a more vulnerable
part of the body, maybe, your leg or, say, your palm. You’d get angina every time you’d shake someone’s
hand. So, the heart in the center of the chest with
the left tilt is what most of us have. Most – that’s right. Not all of us share this alignment. There are cases where people have their hearts
more to the right side of the body. This is called dextrocardia, a rare congenital
disorder affecting approximately one in twelve thousand individuals. There’s also another rare condition called
situs inversus or oppositus where the major visceral organs of the individual are reversed
or mirrored from their normal positions. This makes the right atrium, now the left
atrium, and the left atrium, the right atrium, and the same with the ventricles. The deoxygenated blood would now be received
by the left atrium. It can be a little confusing. In the past, many people with situs inversus
went through life unaware of their unusual anatomy as they tended to live normal, healthy
lives without complications. Their organs were just in reverse – meaning,
oftentimes, the normal functioning relationship between the organs was maintained and unchanged. Interesting fact: Spanish singer-songwriter
Enrique Iglesias is one such notable case of someone with situs inversus. So far, we haven’t yet covered the most
extreme case of displacement of the heart which would be this. It’s a rare syndrome where the heart is located
outside the chest through a split sternum dangerously shielded by only a thin layer
of skin. This happens approximately once in two hundred
thousand births with only a few cases surviving through childhood. This girl has what’s called pentalogy of Cantrell
with ectopia cordis – no, I did not make that up. There’s a spectrum of anatomical locations
the heart can be with this condition, not just the outside chest but also the neck and
abdomen. For these latter cases, the heart really is
not where you think it is. As for the pledge or during the national anthem,
having your heart under the shoulder and level with the armpit sure isn’t as extreme in comparison
but considering even rare conditions, it’s never actually quite there. Perhaps, from now on, if you ever find yourself
in such a situation and wanting to be anatomically correct, you might want to consider moving
your hand closer to the center of the chest to where your heart really is. Thanks for watching. We hope you enjoyed this topic. Let us know your thoughts. Did you think the heart was on the left, the
center, maybe somewhere else – drop us a comment down below. Give this video a thumbs up, share it, and
if you want to learn more about the human heart, you can go ahead and check out the
unbeatable Kenhub website. Alright guys, I’ll see you next time.