Our heart – why pressure makes the difference

Our heart  – why pressure makes the difference

Hi and welcome to BrainSnacks episode
full of hearts. No, not these kind of hearts! These kind of hearts. I’m not a
physician, I see things with the engineer eyes, so
our heart is basically a pump and generally spoken, the purpose of a pump
is to move fluid and increase the pressure of it. Here we have an air pump
for example. You can fill the pump with fluid which in this case is air then you
move the piston compressing the air and therefore increasing the pressure and
then you can pump it into the bicycle tire through the valve stem. Another
example is a water pump for a garden hose. If the water pump is off, no fluid
is flowing because without a pressure difference the fluid won’t move. If the
water pump is on, it creates a greater pressure than here on the outside and the
water flows. This cool pump aka heart pumps and therefore increases the
pressure from very special fluid, blood. The question arising is why do we need
to pump in our body? Our heart is part of the cardiovascular system which permits
blood to circulate through our body and transport essential substances like
oxygen and nutrients and pick up carbon dioxide and other waste materials. The
blood flows through a network of blood vessels that have diameters from 0.02 millimeters to 32 millimeters. The smaller they are, the
higher their resistance, meaning that it’s more difficult for the blood to
flow through them. A flow resistance causes a pressure drop, consequently the
pressure of the blood decreases on the way from the heart through the body.
Remember a pressure difference is a driving force for a flow; a fluid always
moves from high pressure to low pressure. In order to have a continuous flow of
blood in our circulatory system our heart needs to create a pressure
difference permanently and it does so by pumping the blood. So to answer the
question is that a pump in our body is just essential for our life. As an engineer
you’re always very curious to know facts about the performances of technical
devices. I know our heart is not a technical device, but here are some facts
and numbers. The performance of a pump is influenced by two factors: How much fluid
can the pump pump in a certain amount of time and how high is the pressure
difference it can create? Our heartbeats on average 70 times per
minute and at pump 0.08 litters per beat. That means that it pumps 5.6 liters a
minute 336 litters an hour and 8,064 liters a day. The volume flow rate and
the heart rate can of course vary depending on factors like physical
activity. On average a human being has four to five liters of blood that means
that approximately every minute the whole blood in our body passes through
our heart. Wow, that’s impressive! The difference between the pressure
before and after the heart is called the arterialvenous pressure difference and
that is what keeps our cardiovascular system going. The pressure before the
heart if you look at it in the direction of the blood flow it’s the one in the
blood vessel entering the heart which is called the vena cava and it is
approximately three millimeter mercury. The pressure downstream the heart so
where the blood exits is the one in the blood vessel called the aorta and it is
100 millimeter mercury on average. That makes the arterial venous pressure
difference 97 millimeter mercury on average. Millimeter mercury is one of the
really weird non SI units but it’s widely used in the
medical world. 97 of those millimeter mercury correspond to 0.13 atm. That might not seem a lot but that is the pressure
difference that makes the difference and that keep those in our feet. Thank you
very much for watching! I hope now you understand this or get a little bit
better and from the bottom of my blood pump, I wish you a great day! 😉

9 Replies to “Our heart – why pressure makes the difference”

  1. Love your videos can you do one with the sound of your heart beat it would be so relaxing and cool !!!

  2. Really interesting and I love the humour you put in your videos, it makes it fun to watch and easier to understand! Looking forward to seeing and learning more 🙂

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