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What if you had two hearts?
It's a silly and speculative question, I know but just stick with me here.
What if you did?
Where would they even be in your body?
What size would they need to be?
I mean, could one be larger than the other or they have to be the exact same size?
How would blood pressure be affected when you have two pumps just pushing blood throughout
your entire body?
I mean, could you make it so that each heart supplies a different aspect of your body?
I mean, again, these are silly but yet they are interesting questions.
So, let's figure it out.
[Intro]
The chest seems like the most logical place for a second heart considering the rib cage
and sternum are already there to provide protection.
Now, instinctually, I want to mirror the original heart with its side by side at the midline
projecting to the right but as you can see, there's not a lot of room in the thoracic
cavity and especially on the right side given that the right lung has three lobes.
So, one of those lobes would have to go away in order to make room for the heart just as
it did with the left lung which only has two lobes but that would mean a decrease in overall
respiratory function making it more difficult to get enough oxygen to all of the tissues.
The body would need to adapt to lower oxygen levels, meaning that it would likely increase
red blood cell count just as it does in higher elevations but the problem with that is that
you're contributing to a higher blood pressure plus, assuming both hearts are pumping into
the same vasculature, blood pressure is going to shoot through the roof.
This could be a huge problem for the smallest blood vessels in the body called capillaries
but especially those capillaries in close proximity to the hearts themselves.
With enough pressure, they would just explode causing blood loss throughout the body.
One option is to split up the vasculature essentially creating a binary circulatory
system.
So, for all my fellow nerds out there, this is how the doctor from Doctor Who does it
but you basically have two separate cardiovascular systems.
Now, you'd still have options though with those separate systems on how you want to
get and deliver the blood to the various tissues.
If we're aiming for redundancy, meaning if one heart goes down and the other takes over,
having both circulatory system travel the same pathways makes the most sense to me.
The body wouldn't need to reorganize the tissue that much to accommodate the new vessels although
I'm not so sure there be a balanced venous return to the respective hearts.
What I mean is veins only have 10% of the pressure that arteries do and rely heavily
on muscle contractions to return blood to the heart.
It's possible that your day to day activities would lean to one circulatory system more
than the other even if it's just at certain times and with certain activities.
So, unless both hearts are always contract and in unison, you're also going to have differing
flow rates in the blood vessels which would also affect the delivery and return of the
blood to the hearts.
Since we haven't increased the amount of fluid in the bloodstream, this could create some
dramatic imbalances which would likely have ripple effects on the working efficiency of
other organs and tissues in the body.
It's possible that having one heart pump while the other rest could help balance this out
though.
Essentially, you'd have a continuous delivery of blood to all of the tissues in the body.
If you did this, you wouldn't even need to have two circulatory systems.
Both hearts could pump into the same vessels although you still could have duplicate vasculature
if you wanted.
If that's the case, every tissue in the body would have to adapt to the steady flow of
blood allowing for proper nutrient and waste exchange which is an enormous task.
Every organ in your body operates within a contracting and resting phase in the cardiac
cycle.
Pretty much every organ and tissue would have to adapt which would be more difficult for
some than it is others but it's still going to be insane amount of work but I want to
really quickly think about what an increase in blood flow would do to some of these tissues.
The skeletal muscles stand again the most here, although it would take time for them
to fully adapt.
Considering they're able to utilize nutrients and oxygen at a much more consistent rate,
it seems that stamina and recovery would also increase assuming waste removal is sped up
as well.
For other organs, I don't know that a steady blood flow would actually help them all that
much though even over time.
Everything in your body is optimized for your current flow of blood.
Just because you're now providing a steady flow of nutrients and oxygen doesn't mean
necessarily that the organs are going to become more effective or efficient.
If anything, it's now more difficult for them considering they have to help manage this
new heart in your body.
You have to understand that every organ system in your body evolved alongside the other systems.
Changing one system doesn't mean the other systems will respond in kind.
We also need to consider heart rate.
So, while the hearts might be beating normally on their own, let's say about 80 to 100 beats
per minute, the combined heart rates would be 160 to 200 beats per minute at rest which
just sounds utterly exhausting.
Again, this is without exercise.
Another option is to split the duties of each heart.
So, while one heart is pumping to the internal organs of the body, the other heart might
be pumping to various tissues such as muscle, bone, and skin.
Now, personally, this option just makes the most sense to me.
Since we're not redundancy here, you could actually adjust the sizes of the hearts according
to what they supply.
So, the heart that's in charge of organ function could be smaller and as long as it's still
in the chest, it should be able to apply - or supply enough pressure to the brain in order
to continue normal function.
It's primary blood vessels could just be traveling vertically.
So, you'd have one coming off of the heart heading towards the head and neck and then
another one heading towards the chest and abdomen.
Then, you'd have all these offshoots branching off of it to supply the various organs with
blood.
And then, in to return blood back to that heart, you'd have all these small veins coming
off of the organs which would then filter into two larger primary veins that would then
enter in the heart.
Now, your heart already does this, so we know it works but now essentially, you've completed
the loop.
The other heart could be larger but it would still need to be smaller than the one we currently
have.
Now, this larger heart should also handle respiration on top of muscle, skin, and everything
else.
Meaning, it would send vessels to and from the lungs.
It would also need to apply that smaller heart with oxygenated blood since the smaller heart
isn't contributing to the lungs at all.
Now, you'd also have to have a vein that takes deoxygenated blood from that smaller heart
back to the bigger heart but that probably isn't too difficult to do but as much as this
layout makes sense to me, there's a pretty big problem here and that is how do you get
fresh nutrients as well as filter the blood in both of those circulatory systems.
Kidneys and liver are the only organs that need to connect to both circulatory systems,
otherwise uric acid is going to build up in the bloodstream and without nutrients, things
are going to get very bad very quickly.
As long as we have both systems converging at the renal artery which delivers unfiltered
blood to the kidney and then both systems splitting at the renal vein which returns
filtered blood to the bloodstream, we should be good in terms of filtering.
Then, once nutrients have been absorbed by the small intestine and processed by the liver,
the nutrient-rich blood can be given to both hearts, providing essential nutrition to the
cells supplied by each circulatory system.
In my eyes, this is your best bet and - and it is far from optimal.
I mean, this doesn't even take into account the endocrine system and how glands will get
hormones to all the various tissues but I think this is the best potential layout out
of all the potential layouts but what do you think?
Do you agree with me or did I get something wrong or maybe just forget about a whole bunch
of stuff altogether?
Let us know in the comments below because we'd really like to hear your feedback on
this one.
I wholeheartedly believe that this type of logical and scientific thinking is extraordinarily
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